Purpose of the work: to study various kinematic diagrams of the overhead crane lifting mechanism.
2.1 Quest
Table 1.1
Initial data
|
Option No. |
Carrying capacity, t |
Lifting height, m |
Lifting speed, m / min |
operating mode |
The multiplicity of the chain hoist |
Number ex. blocks |
2.2 Instructions for the task
An indispensable and most critical element of any PMG is the lifting mechanism.
Depending on the lifting capacity and operating conditions, lifting mechanisms with a manual or machine drive are used.
The machine drive can be individual (each PTM mechanism has its own motor) or group (all PTM mechanisms are driven by one engine).
Figure 2.1 shows the kinematic diagram of the overhead crane lifting mechanism. The mechanism consists of a motor 1, a coupling with a brake pulley 2, on which a brake is mounted 3. The coupling is used to connect the ends of the shafts of the motor and the gearbox 4. Coupling 5 connects the end of the gearbox shaft and the drum 6. A rope 7 is wound on the drum, which bends Block 8. A hook suspension is used to connect the load to the overhead crane.
When calculating the lifting mechanism, the following tasks are solved:
Determination of the breaking force of the rope and selection of the standard rope;
Drum selection and calculation of its parameters;
Determination of engine power and selection of engine type;
Gearbox selection;
Choice of couplings;
Determination of the required braking torque and selection of the brake type.
Figure 2.1. Kinematic diagram of the lifting mechanism
In most cases, a steel wire rope is used as a flexible body for hanging loads.
In accordance with the requirements of the international standard ISO 4301/1, steel ropes are selected according to the breaking strength:
where F 0 - breaking force of the rope as a whole N, taken according to the certificate;
S is the maximum tension of the rope branch, determined when lifting the rated load, taking into account losses on the pulley blocks and on bypass blocks, but without taking into account dynamic loads;
Z p - minimum rope utilization factor (minimum rope safety factor), determined according to tables 2 and 3.
The greatest tension of the rope branch is determined by the formula:
where a - the number of rope branches wound on the drum;
η bl - unit efficiency; you can take: the efficiency of the unit mounted on rolling bearings 0.98; on plain bearings 0.96;
i n is the frequency of the chain hoist;
n is the number of guide blocks.
Having determined the breaking force and given the ultimate strength of the steel wire, the rope is selected according to the reference tables. The most widespread are ropes of the type LK-O, LK-R, TLK, TLK-O. Having chosen the rope, set its diameter d.
The design of the entire drum unit further depends on the choice of the installation scheme for the cargo drum. There are several drum installation schemes:
a) the output shaft of the gearbox is connected to the drum shaft using a general coupling (a rigid compensating coupling is recommended) (Figure 2.2, a). The advantages of this scheme are: simplicity of design, ease of installation and maintenance. Disadvantages: significant dimensions; the need to use a shaft (for installing a drum), loaded with twisting and bending moments.
b) the drum is connected to the gearbox by means of a gear transmission (Figure 2.2, b). The driven gear wheel is rigidly attached to the drum flange (detachable or non-detachable connection), thus, the drum is installed on the axle, unloaded from torque, which is an advantage of this scheme. The disadvantage is the presence of an open gear train to be calculated. This scheme is used in the event that, as a result of the calculation, it is not possible to select a gearbox with a standard gear ratio.
c) the drum shaft and the gearbox output shaft are combined in one design (Figure 2.2, c). The advantages of this circuit are small dimensions and simplicity of design. Disadvantages: the presence of a three-bearing shaft (accurate installation in the supports is difficult), the need to jointly mount the gearbox and the drum.
Figure 2.2. Drums installation schemes.
d) the output shaft of the gearbox is connected to the drum using a special toothed coupling built into the drum (Figure 2.2, d). This scheme requires the use of special crane gearboxes, the output shaft of which has a gear flange. Circuit advantages: compactness; installation of a drum on an axle, which is unloaded from torque. Disadvantages: difficult access to the gear coupling during installation and repair; it is necessary to match the dimensions of the gearbox and the drum.
During the calculation, the geometric parameters of the drum are determined - the drum diameter and its length. The drum diameter, measured at the centers of the section of the rope turn (Figure 3), is determined:
where h 1 is the coefficient of selection of the drum diameter, determined according to table 5.
Having taken the diameter of the drum, you should find the diameter of the drum along the bottom of the groove:
Figure 2.3. Drum parameters
The resulting value should be rounded up to the value from the normal range of sizes: 160, 200, 250, 320, 400, 450, 560, 630, 710, 800, 900, 1000. Then the value of D 1 should be specified.
If a connection diagram of a drum with a gearbox is used, using a built-in gear coupling, then the minimum drum diameter is taken to be 400 and then specified when assembling the mechanism.
The length of the cutting drum is determined by the formulas:
when working with a single pulley block, mm:
when working with a double pulley block, mm:
where L 1 is the length of the rifled part of the drum, determined by the formula, mm:
,
(2.7)
where t is the cutting step, t ≈ (1,1… .1,23) d, while the resulting value should be rounded to a multiple of 0.5;
L 2 is the distance from the ends of the drum to the beginning of cutting, L 2 \u003d L 3 \u003d (2 ÷ 3) t;
L 4 - distance between cutting sections, L 4 \u003d 120 ÷ 200 mm.
The length of a smooth drum is determined, mm:
where n is the number of rope turns laid along the entire length of the drum;
z is the number of layers of rope winding on the drum;
γ - coefficient of unevenness of the rope laying, γ \u003d 1.05.
The number of rope turns laid along the entire length of the drum:
The required power of the lifting mechanism engine is determined by the formula, kW:
where η is the overall efficiency of the mechanism, η \u003d η m × η b × η p;
η m - efficiency of the transmission mechanism;
η b - efficiency, taking into account the power loss on the drum;
η p - the efficiency of the chain hoist.
For preliminary design calculations, you can take the efficiency of the mechanism 0.8 ÷ 0.85 or take: η m \u003d 094 ÷ 0.96; η b \u003d 0.94 ÷ 0.96; η p \u003d 0.85 ÷ 0.9.
Based on the power received, a standard MT (MTF) type electric motor is selected - with a phase rotor or MTK (MTKF) type - with a squirrel cage rotor. As an exception, we can recommend general purpose motors - type AO.
Having chosen the engine, write out from the literature, the following parameters necessary for the further calculation of the mechanism:
N dv - rated power of the engine, kW;
n dv - engine rotor speed, rpm;
d dv - diameter of the outlet end of the engine rotor.
The kinematic calculation of the mechanism consists in determining the gear ratio of the mechanism, according to which a standard gearbox is selected:
where n b - drum rotation frequency
For this gear ratio, the standard gearbox is selected according to the literature. Two-stage horizontal gear reducers of the C2 crane type are most widely used in lifting mechanisms. When choosing a gearbox, the conditions regarding the strength, durability and kinematics of the gearbox must be checked:
a) the selected gear ratio of the gearbox should not differ from the calculated one by more than 15%;
b) the rotational speed of the high-speed shaft of the gearbox must not be less than the rotational speed of the motor shaft.
Having chosen a gearbox from the catalog, they write out the parameters necessary for the calculation:
U p - actual gear ratio;
d 1, d 2 - diameters of the output ends of the high-speed and low-speed shafts of the gearbox.
Using couplings, the motor shaft is connected to the input shaft of the gearbox, as well as (in some drum installation schemes) the output shaft of the gearbox to the drum shaft. One of the half of the drive clutch usually serves as a brake pulley for the brake, which is also installed on the drive shaft. This design is called a brake pulley clutch.
Special couplings with a brake pulley are made in two versions - on the basis of an elastic sleeve-finger coupling (MUVP) and on the basis of a gear coupling (MZ),.
In some cases, a toothed clutch can be made with an intermediate shaft-insert, and then it includes: a clutch with a brake pulley, a conventional toothed clutch and an insert connecting them to the shaft, the length of which is set structurally. Such a solution is used when it is structurally impossible to install the gearbox next to the engine or when there is a question about a more even distribution of weight loads from the mechanisms on the running wheels.
A standard (rigid compensating) coupling is used as a coupling mounted on the drum shaft.
The choice of couplings is made according to the diameters of the connected shafts, then the selected coupling is checked by the torque.
Torque on the motor shaft, N ∙ m:
Torque on the drum shaft N ∙ m:
where η B - drum efficiency, η B \u003d 0.99;
η p - gearbox efficiency, η p \u003d 0.92.
The calculated value of the moment is determined, N ∙ m:
where k 1 is the coefficient taking into account the operating mode (light duty - 1.1; medium - 1.2; heavy - 1.3).
The selected coupling must satisfy the condition: T p ≤ T table (T table is the maximum allowable torque value specified in the reference books).
In most cases, the brake in hoist mechanisms is mounted on the drive shaft, with the brake pulley, which is one of the drive coupling halves, facing the gearbox. The most common are shoe brakes: two-shoe brakes with an alternating current electromagnet of the TKT type and with electro-hydraulic pushers of the TT and TKG type. TKT brakes are structurally simpler; therefore, their use is preferable for brake pulley diameters up to 300 mm and braking torques up to 500 Nm. The advantages of TT and TKG brakes are smooth operation and the ability to implement large braking torques. When using direct current, TKP type brakes are used.
The braking torque is determined, N ∙ m:
The brake selection is based on the braking torque:
where β is the braking safety factor (light duty - 1.5; medium duty - 1.75; heavy duty - 2).
According to the obtained value of the braking torque and the operating mode, a standard brake is selected, having selected a brake, it is necessary to check that the diameter of the brake pulley of the brake coincides with the diameter of the brake clutch.
THESIS PROJECT
Improving the maintenance of the mechanism for lifting the cargo of the railway crane KZhDE-161
THE TASK
Project topic: Improving the maintenance of the mechanism for lifting the cargo of the KZhDE-161 railway crane
Initial data for the project (special instructions for the project)
a) Technical and economic indicators of the enterprise and analysis of existing structures
b) Reference information on railway cranes
c) Reference books for design calculations
1. Analysis of the existing structure
2. Design calculations of mechanisms
3. Strength calculations of units of mechanisms
4. Maintenance and repair of the crane
5. Labor protection
6. Economic part
5 List of graphic material (with exact indication of required drawings)
1. Railway crane (General view).
2. Kinematic diagrams of crane mechanisms
3. Load lifting mechanism
4. Boom lifting mechanism
5. Cargo drum
6. Technical and economic performance of the equipment
INTRODUCTION
The KZhDE-161 universal full-revolving self-propelled jib crane on a railway track is used in the cargo sector of the UGZhDT and is a means of mechanizing loading and unloading operations with various loads. This crane is manufactured with a diesel-electric drive.
Diesel - electric crane KZhDE-161 is equipped with a main 15-meter boom with a hook and, on request, can have additional equipment: a 5-meter insert for extending the boom up to 20 m, a grab for a forest or a grab with a set of ropes, a cargo electromagnet with a motor-generator station for its power supply. The crane units are maximally unified with the KZhDE-251 crane units, up to 80% of the parts are the same.
The crane's power source is a diesel engine that rotates a generator set, which supplies individual electric motors of all actuators with 380 V alternating current. It is possible to operate the crane with power from an external network via a flexible cable.
The aim of the diploma project is to modernize the lifting mechanism and improve its maintenance. The modernization consists in changing the scheme of the mechanism from a single drum to a double drum scheme. The two-drum scheme provides lifting or lowering of the load with one drum or two at the same time, since the gearbox is paired. When working with two drums, the lifting speed is doubled, since the chain hoist will work as a double one and its multiplicity will not be six, but three. When working with a two-rope grab, one drum is used as a lifting drum, and the other as a closing drum.
1. ANALYSIS OF THE EXISTING STRUCTURE
The technical characteristics of the crane in question are given below:
Carrying capacity, t
With the smallest departure 25
With the greatest departure 4.9
Boom length, m 15
Speed, m / min
Lifting load 8.8: 17.5
Movement 175
Rotational speed of the rotary part, rpm 2
Boom full lift time, min 0.62
Crane weight in working order 52.5
The KZhDE-161 crane has a running platform, a turntable with a body and mechanisms installed on it, a slewing support, a boom and a hook clip.
The undercarriage is the base of the crane and consists of a welded frame, the pockets of which are filled with ballast, and standard biaxial rolling-bearing bogies. Under the running frame there are two movement mechanisms, including electric motors and gearboxes, the driven shafts of which are the axles of the running wheels (wheel pairs). Outrigger brackets are welded to the outer frame beams. Outriggers increase the stability of the crane by increasing the support base. The outriggers are brought to the transport position by turning them relative to the axis by 90 0 along the turntable. The outriggers are made of screw.
The swing frame of the KZhDE-161 crane is a welded structure of longitudinal and transverse beams with a deck welded to them. Two pairs of inclined posts are pivotally attached to the longitudinal beams, forming the portal supports; boom supports are fixed in front of the frame. A diesel engine and a generator are installed in the tail section of the swing frame on a special cast-iron plate, which serves simultaneously as a counterweight. The fuel tank and radiator are located nearby. There are also mechanisms for lifting the load, changing the boom reach, turning and the driver's cab with a control panel.
When the crane is operating with an electromagnet, a direct current is provided by a motor - a generating station installed on top of the body. A control panel and a magnetic controller are mounted inside the body.
The slewing bearing of the crane has a double-row ball slewing ring consisting of three rings. The outer cage consists of two rings: the upper one, which is bolted to the swing frame, and the lower one, which is bolted to the upper one. The inner cage is at the same time a gear ring of the rotation; the cage is fastened with bolts to the chassis frame. The outer and inner race has treadmills for two rows of balls. Rolling surfaces are hardened with high currents. The slewing ring takes the load from the mass of the slewing part with the mechanisms located on it, as well as the overturning moment during the lifting of the load.
The lifting mechanism is located in the central part of the turntable.
The kinematic diagram of the lifting mechanism is shown in Figure 1.
On a special welded frame, it is planned to place two electric motors 1, a double two-stage gearbox 4, two brakes 3 and two drums 5. The rotor shaft of the electric motor is connected to the drive shaft of the gearbox by a coupling 2, one of the half-couplings of which is the brake pulley of the shoe brake.
The two gearboxes are housed in one housing, separated by a baffle that supports the ball bearings of the shafts.
Lip seals are installed in the through bearing caps to prevent dirt and dust from entering the gearbox and oil leakage from the gearbox. Along the plane of the connector, the cover is placed on the body on oil varnish. The gearbox has inspection windows for checking the oil level and a drain hole with a plug.
a) kinematic diagram: 1 - electric motor, 2 - connecting clutch, 3 - brake, 4- gearbox, 5- drum; b) diagram of the storage of the cargo rope
Figure 1 - The mechanism of lifting the cargo of the KZhDE -161 crane
The driven shafts of the gearbox end with gear rims, which are half-couplings of gear couplings that connect the shafts to the drums. The second half-couplings are made in the form of plug-in hubs with internal engagement, installed on the axes of the drums and engaging with the gear rims of the driven shafts.
The drum axis with one end rests on a spherical ball bearing mounted in the rack, and at the other end on the same bearing mounted in the bore of the gearbox driven shaft.
The drums are grooved for laying ropes. The ends of the ropes are fastened with wedges. The double-drum lifting mechanism provides lifting or lowering of the load with one drum or two simultaneously. In this case, the lifting speed is doubled, since the pulley block (Figure 1b) will work as a double one and its multiplicity will not be six, but three. When working with a grab, one drum is used as a closing drum.
The boom lifting mechanism has distinctive features, namely: the presence of a worm gearbox, as well as an open gear transmission between the gearbox and the drum. The electric motor of the mechanism of communication with the gearbox by means of a connecting elastic sleeve-finger clutch, which is simultaneously a brake pulley of a brake with an electric hydraulic pusher. The drums rotate on an axle fixed in brackets. An open gear gear is installed on the output shaft of the reducer, and the gear wheel is simultaneously the crown of the drum. The drum is threaded with side flanges, the rope is attached to the drum with a steel wedge.
The open drum transmission is shielded by a casing. The boom chain hoist is made sixfold and consists of a movable and fixed clips. The fixed frame is connected with the axis of the portal bipedal post. The movable yoke is suspended from the boom head using cable ties. A deflection block is installed on the portal axis.
The swing mechanism has a bevel-helical gearbox. At the lower end of the vertical output shaft of the reducer, an open gear gear is attached, which meshes with the ring gear of the slewing ring. To stop the mechanism, it is provided to install a shoe brake on the drive shaft.
The movement mechanism is made with a separate drive. The crane has two movement mechanisms, so one of the axles of the bogies is the leading one. The movement mechanism is made according to the traditional scheme with a horizontal arrangement of the gearbox.
2. DESIGN CALCULATION OF MECHANISMS
2.1 Calculation of the lifting mechanism
2.1.1 Single-drum operation
Initial data.
m - maximum carrying capacity, t 25;
H - lifting height of the load, m 14.2;
V is the speed of lifting the load, 8.8 m / min (one drum);
(two reels) 17.6;
Working mode group 4M
The initial data correspond to the operation of a crane with a 15 m long boom with a hook or with an electromagnet with plates and blanks. The choice of the scheme of the mechanism for lifting the load and the scheme of the cargo chain hoist was already made earlier. We accept the drum installation with a toothed clutch built into it as the most compact and reliable design.
A steel wire rope is taken as a flexible lifting of the organ. According to the "Rules for the Construction and Safety of Operation of Cranes", the steel rope is selected according to the breaking strength:
where S is the maximum rope tension, H;
Z P - safety factor of the rope; Z P \u003d 5.6 5, table 2
The maximum rope tension is determined by formula 2:
where m is the carrying capacity in kt; m \u003d 25t \u003d 25000kt;
Kpd block; \u003d 0.98 - for blocks on rolling bearings;
a - the number of ropes wound on the drum; a \u003d 1;
i n - the frequency of the chain hoist; i n \u003d 6 (according to the adopted scheme);
n is the number of guide blocks, n \u003d 1.
F \u003d 43904.45.6 \u003d 245864.65 H \u003d 245.864 kN.
Taking into account the possible multilayer winding of ropes onto a drum from 1, Table 5.2.3, we select a double lay steel wire rope LK-RO 6Ch36 + 1 o.with GOST 7668-80. Rope diameter d \u003d 22.5 mm, breaking force F times \u003d 251 kN with a marking group of 1568 MPa.
We make a geometric calculation of the cargo drum. The drum is made with two flanges.
Drum diameter along the middle line of the rope turn:
where h 1 is an empirical coefficient, taken depending on the mode group and the type of crane; h1 \u003d 20 5, table 5
D122.520 \u003d 450 mm.
To reduce the length of the drum, we take its diameter large. The diameter of the drum along the bottom of the groove is assigned from the normal range of values, i.e. D1o \u003d 630mm. Estimated drum diameter:
D1 \u003d D1о + d к \u003d 630 + 22.5 \u003d 625.5 mm.
Cutting drum length when working with a single chain hoist
L b \u003d L 1 + L 2 + L 3, (4)
where L 1 is the length of the threaded part of the drum, mm;
L 2 L 3 - distance from the ends of the drum to the beginning of cutting, mm.
where n in - the number of turns of the rope, laid on the drum;
t - cutting step, mm;
t \u003d d k + 23mm \u003d 22.5 + 3 \u003d 25.5mm;
The coefficient of unevenness of the laying of the ropes, \u003d 1.05.
where Z is the number of layers of rope winding on the drum; set Z \u003d 2.
We accept n in \u003d 20.
L 1 \u003d 2025.51.05 \u003d 535.5mm
Length of sections:
L 2 \u003d L 3 \u003d (23) t \u003d 225.5 \u003d 51mm
Full drum length:
L b \u003d 535.5 + 51 + 51 \u003d 637.5mm
The required power of the hoist motor is found according to formula 2:
where is the overall efficiency of the mechanism, defined as
where m \u003d - efficiency of the transmission mechanism for a two-stage gearbox;
b \u003d 0.96 - efficiency of the drum, for a drum on rolling bearings;
n is the efficiency of the pulley block.
General efficiency of the mechanism: \u003d 0.960.960.933 \u003d 0.86
We choose from 1, Table 2.1.11, an AC crane electric motor with a wound rotor MTF 412-6.
Engine power N dv \u003d 43 kW at duty cycle 25%,
shaft speed n dv \u003d 955 rpm
maximum moment T max \u003d 638 Nm,
the moment of inertia of the rotor J p \u003d 0.5 kgm 2,
diameter of the motor shaft end d dv \u003d 65mm.
Gear ratio of the mechanism
where n b - drum rotation frequency, rpm
As a reducer, we choose a cylindrical two-stage coupled reducer for the possibility of working with a grab. The reducer has two input and two output shaft ends and is used in KDE-251 railway cranes. The output end of the shaft is made in the form of a gear half-coupling.
To connect the end of the motor shaft and the high-speed shaft of the gearbox, it uses an elastic sleeve-pin coupling, one of the half-couplings of which is a brake pulley and is installed on the gearbox side.
By the size of the ends of the connected shafts (mm) from 1, table. 5.2.41 select a clutch according to OST 24.848.03-79 with a rated torque T k \u003d 2000 Nm, providing a connection of the shafts 65h75mm, brake pulley diameter Dt \u003d 400mm, coupling moment of inertia, Jm \u003d 4.8kgm 2
The selected coupling must satisfy condition 2
T calc T k
where T calculated is the calculated value of the moment, Nm.
Torque on the motor shaft:
T calc \u003d K 1 T s, (11)
where K 1 \u003d 1.2 is the operating mode coefficient; for medium duty 2
T cal \u003d 1.2419.1 \u003d 503 Nm
T calc \u003d 503 Nm T k \u003d 2000 Nm
The brake is matched to the braking torque:
T t \u003d T c t, (12)
where \u003d 1.75 braking safety factor; adopted for medium operating mode 2;
T with t - the torque on the motor shaft during the braking period, Nm
T t \u003d 1.75310 \u003d 542 Nm
According to the diameter of the brake pulley Dt \u003d 400mm and the value of Tt \u003d 542 Nm from 1, Table 5.2.23, we select a two-shoe brake driven by an electro-hydraulic pusher. Brake type: ТКГ-400, braking torque Тт \u003d 1400Nm
We check the electric motor according to the starting conditions:
a) The engine power must be sufficient to ensure the acceleration of the load with a given acceleration not exceeding the permissible values;
b) When operating in intermittent mode, the engine should not overheat.
The first check condition is written: j j
where j is the estimated acceleration of the load during the launch period, m / s 2;
j \u003d 0.20.6 m / s 2 - permissible value for general purpose cranes.
where t n is the start time of the load lifting mechanism, s.
where T p.av is the average starting torque of the electric motor, Nm;
J 1 is the total moment of inertia of the parts installed on the drive shaft of the mechanism, ktm 2.
J 1 \u003d J p + J m \u003d 0.5 + 4.8 \u003d 5.3 ktm 2;
k \u003d 1.11.2 is a coefficient that takes into account the influence of other rotating parts of the mechanism.
For AC motor with wound rotor, average starting torque
T p.av \u003d T nom (16)
where T is the nominal torque of the engine, Nm;
Multiplicity by maximum torque.
T nom \u003d 9550,
Start time:
Start acceleration:
The check condition is met.
We do not check the electric motor for heating, since the motor power is greater than the calculated value.
2.1.2 Two-drum operation
The double-drum lifting mechanism provides lifting and lowering of the load not only with one drum, but also with two simultaneously. In this case, each drum is brought into vision from its electric motor when the brake is released. The speed of lifting the load when working with two drums simultaneously increases 2 times, since the chain hoist will now work as a double one and its multiplicity is: j n \u003d.
Lifting speed: V \u003d 8.82 \u003d 17.6 m / min.
The calculation of the mechanism consists in checking the suitability of the previously selected elements for the case of operation with two drums simultaneously, the maximum rope tension from the condition of uniform distribution of the load between the two drives is found by the formula (2)
In fact, the safety factor of the rope according to the formula (1):
Z P ф \u003d 6 Z P \u003d 5.6 - this means that the previously selected rope is suitable.
The power required to lift a load with two drives according to the formula (7):
The required power of each of the two motors:
N 1 \u003d N 2 \u003d 0.5N \u003d 0.583.6 \u003d 41.8 kW.
Power of the selected engine: N motor \u003d 43 kW N 1 \u003d N 2 \u003d 41.8 kW.
Since the lifting speed increased 2 times, and the frequency of the chain hoist, respectively, decreased 2 times, the value of the required gear ratio of the mechanism, torque and braking torque, did not change.
Consequently, we leave the gearbox, coupling and brake the same.
The starting time of the mechanism according to the formula (15) at:
Acceleration of cargo during the launch period:
The previously selected motor meets the start condition.
2.1.3 Case of working with grab
Initial data are taken from the technical characteristics of the crane:
grab weight, t - 1.9;
bulk density of the material, t / m 3 - 1.1;
grab lifting speed, m / min - 53;
grab capacity, m 3 - 1.5
Material weight in grapple:
m m \u003d V \u003d 1.5 1.1 \u003d 1.65t \u003d 1650kg.
Total mass of grab with material
m \u003d m gr + m m \u003d 1.9 + 1.65 \u003d 3.55t \u003d 3550kg.
The ropes are calculated for the case of lifting a loaded grab on the assumption that the weight of the grab is evenly distributed over the closing and hoisting ropes with a safety factor Z P \u003d 6.
Estimated force in one rope of two rope grab:
S \u003d 0.5 m g (17)
S \u003d 0.535509.81 \u003d 17413 H \u003d 17.413kN.
In fact, the safety factor:
The lifting and closing ropes are assumed to be the same in design and diameter.
The total installed power of the winch with independent drums when working with a grab is:
Each of the two engines is selected according to power:
N 1 \u003d N 2 \u003d 0.6N \u003d 0.642.898 \u003d 25.74kW
Power of the previously selected motor: N motor \u003d 43 kW N 1 \u003d N 2 \u003d 25.74 kW, therefore, the motor is suitable.
2.2 Calculating the departure change mechanism
The existing diagram of the boom winch is shown in Figure 2.
In the existing design of the winch, a cylindrical gear is mounted on the output shaft of the gearbox, which is in constant engagement with the toothed ring 5, which is attached to the drum.
The proposed modernization aims to get rid of the open gear, which in itself is a disadvantage, as it requires constant inspection and control; Lubricating such a transmission with grease is a constant source of contamination and dust on the turntable frame. In addition, to increase the productivity of the crane, we will reduce the time for changing the outreach from 0.62 min to 0.5 min, focusing on similar designs. At the same time, the multiplicity of the boom chain hoist does not change and remains equal to 6.
1-electric motor; 2-coupling coupling; 3-brake; 4 - worm gear; 5-open gear transmission; 6 - rope drum.
Figure 2 - Kinematic diagram of the boom winch:
Since the lifting characteristics of the crane do not change, that is, the lifting capacity is 25 tons at a minimum outreach of 4.8 meters, the jib rope remains the same. According to the operating manual, the type of boom rope is the same as that of the cargo winch, that is, LK-RO 6Ch36 + 1 o.s. GOST 7688-80, rope diameter 22.5 mm, breaking force 251 kN, marking group 1568 MPa, mode group work 4M (medium).
We check the suitability of the engine installed in the boom winch at a new speed of departure change, determined by the formula:
where DL is the change in the crane outreach when lifting the boom, m;
t \u003d 0.5 s - departure time change.
Required engine power, kW:
where s \u003d 0.96 is the efficiency of the mechanism;
S MAX - maximum rope tension, N.
For an average operating mode at Z P \u003d 5.5 we have by the formula (1) at F TIME \u003d 251 kN:
From 1, tab. II.1.11 we choose an MTF 411-6 crane electric motor with a power of 15 kW at an duty cycle of 25%, a shaft speed of 935 rpm, a rotor moment of inertia of 0.225 kg · m 2, a shaft end diameter of 70 mm, a maximum motor torque of 314 Nm.
The gear ratio of the mechanism is found by the formula (9).
Boom drum speed:
where D B is the diameter of the boom drum, m, we take equal to 0.5 m.
From we choose a cylindrical two-stage gearbox Ts5-500 with a gear ratio of 16, a torque on the low-speed shaft of 17.5 kN · m, a diameter of the end of the high-speed shaft of the gearbox of 60 mm, with the design of the end of the low-speed shaft - a ring gear.
To connect the gearbox shaft to the motor shaft, we provide for the installation of an elastic sleeve-finger coupling with a brake pulley. Torque on the motor shaft, Nm:
The design moment of the coupling, with a safety factor K 1 \u003d 1.2, will be equal to:
T P \u003d 1.2 969.32 \u003d 1163.18 Nm.
From we choose with a nominal torque of 1000 Nm, providing a connection of shafts with a diameter of 50 ÷ 60 mm, a coupling moment of inertia of 1.5 kg · m 2, a brake pulley diameter of 300 mm.
The calculated braking torque is found by formula (12) with a braking safety factor of 1.5.
Torque on the brake shaft during braking, Nm:
From we choose the TKG-300 brake with a braking torque of 900 Nm, a brake pulley diameter of 300 mm.
3. STRENGTH CALCULATIONS
3.1 Calculation of the drum assembly of the lifting mechanism
We draw up a design diagram of the drum unit (Figure 3).
Figure 3 - Scheme for calculating the drum axis
When a drum is operating with a single chain hoist, the position of the rope is considered alternately under each hub, since when winding onto the drum, the rope moves along the length of the drum.
1 POSITION. The rope is located under the left drum hub. We take the lengths of the sections constructively, focusing on the length of the drum.
Bending moment in section under the left hub:
2 POSITION. The rope is located above the right drum hub.
Bending moment under the right hub:
Calculation of the drum axis is reduced to determining the diameters of the trunnions d c and hubs d c from the condition of the axle bending in a symmetric cycle:
where М И - bending moment in the design section, Nm;
W And - the moment of resistance of the design section in bending, m 3;
Allowable bending stress, MPa, with a symmetrical cycle.
Since the moment of resistance of the axle section under the hub is W I \u003d 0.1d c 3, substituting this expression into formula (19), we first find the diameter of the axle under the hub:
The permissible bending stress for a symmetric cycle is determined by the formula:
where -1 is the endurance limit of the axle material, MPa;
k 0 - coefficient taking into account the design of the part, for shafts and axles is taken 22.8;
n is the permissible safety factor; for the group of the 3m mechanism operation mode, n \u003d 1.4 is taken.
She chooses 45 s steel as the axle material,
We take k 0 \u003d 2.8.
Axle diameter under the hub:
From the condition of placing the axle bearing inside the bore of the output end of the gearbox, we take d c \u003d 0.115 m. The diameter of the axle trunnions for the bearing d c \u003d 90 mm.
Let's make a more accurate calculation of the drum axis. With a dangerous section, the middle section of the axis (between the hubs), the diameter of which is taken:
d \u003d d c -15 mm \u003d 115 - 15 \u003d 100 mm.
Safety margin for fatigue resistance in the considered section:
where -1 is the endurance limit of the axle material at symmetric bending cycles, MPa;
K b - effective coefficient of stress concentration during bending;
Coefficient that takes into account the effect of surface roughness;
Scale factor of normal stresses;
a is the amplitude of normal stress cycles, MPa.
Previously, steel 45 was used as the drum axis material, having h \u003d 600 MPa.
For carbon steel endurance limit:
K value \u003d 2.13 for steel shafts with fillets 6, table 11.2; scale factor E \u003d 0.7 6, table 11.6 for carbon steel and shaft diameter d \u003d 100 mm.
Amplitude of normal stress cycles according to the formula (19)
The strength in the section under consideration is ensured, since the smallest allowable safety margin for the S axis \u003d 1.6.
To connect the toothed half-coupling, made in the form of a flange, we apply a pin connection to the drum itself. The material of the bolts is steel 45, with a yield point of t \u003d 353 MPa.
We install the pins on a circle D okr \u003d 300 mm \u003d 0.3 m.
Circumferential shear force on the pins:
Allowable pin shear stress:
where t is the yield point of the material of the pins;
k 1 \u003d 1.3 - safety factor for the lifting mechanism;
k 2 \u003d 1.1 - load factor for the 4M 4 operating mode group.
The diameter of the pin is determined by the formula 4:
where P env is the force acting on the circumference of the installation of the pins, N;
m / \u003d 0.75m is the estimated number of pins, here m is the number of installed pins (m \u003d 68);
Permissible shear stress, Pa.
We take the number of pins m \u003d 6, then m 1 \u003d 0.756 \u003d 4.5.
We choose 6 pins 16GCH50 GOST 3128-80.
We calculate the strength of the drum wall. Compression analysis is the main design calculation, bending and torsion calculations are optional.
As the material of the drum, we take the gray cast iron SCH18, the permissible compressive stress of which is sr \u003d 88.3 MPa.
Wall thickness of cast iron drum for rope operation 4:
0,02D1 + (610mm), (28)
where - D1 is substituted in mm
0.02652.5 + (610mm) \u003d 19.05 23.05 mm
Finally, we accept \u003d 20mm.
Compression stresses
compression \u003d 86.087 MPa compression \u003d 88.3 MPa.
The strength condition is met.
We do not check the drum wall for bending and torsion, since the ratio of the drum length to its diameter L / D1< 34.
We do not calculate the fastening of the end of the rope on the drum, since a steel wedge is used as a clamping device, installed in a nest performed when the drum is ebbing.
3.2 Selection of bearings
We choose double-row radial spherical ball bearings as support bearings according to GOST 5721-75. The number of bearings is 2. Bearing number 3618, inner diameter d \u003d 90 mm, outer diameter D \u003d 140 mm, ring width B \u003d 64 mm. Dynamic load capacity C \u003d 400000 N \u003d 400 kN, static load capacity C 0 \u003d 300000 N \u003d 300 kN. We check the selected bearing for durability in accordance with 6. Nominal durability in hours:
where n is the frequency of rotation of the bearing ring, rpm;
n \u003d n b \u003d 25.95 rpm;
С - dynamic carrying capacity, kN;
p - exponent (for roller bearings p \u003d 10/3).
where F r \u003d 194148N \u003d 19.415kN - radial load on the bearing, kN;
V \u003d 1 - coefficient of rotation, when the inner ring rotates;
K b \u003d 1.31.5 - coefficient of working conditions for cranes 6, table 12.27;
К Т \u003d 1.05 - temperature coefficient for the bearing operating temperature 125 0 С.
4. ELECTRICAL PART
The drum of the cargo winch is driven by the M13 and M15 motors. Motor control is separate, using the S1 and S2 command controllers, which, with their contacts, turn on the stator and rotor contactors KM9-KM17.
Command controllers have seven fixed positions: three - "Rise"; three - "Descent" and one - neutral.
On "Rise" stator contactors KM13 and KM14 are switched on, and on "Descent" contactors KM110 and KM15. When the load is lowered by the left drum in the dynamic braking mode, the KM9 contactor is switched on.
The rotor circuits of engines M13 and M15 include ballast resistors R18 and R19. At the first positions of the controllers, all resistances are introduced into the rotor winding of each motor. When working with loads of more than 3-4 tons and a grab, these positions correspond to the minimum speed for ascent and maximum speed for descent. At the third positions of the command controllers, the resistances are completely removed from the rotor circuits of the electric motors, which corresponds to the maximum speed for ascent and minimum - for descent.
The output from the rotor circuits of the electric motors of the resistance stages is carried out by the acceleration contactors KM11, KM12, KM16 and KM17.
The left drum engine M13 has two modes of operation for lowering the load:
Power descent;
Descent in dynamic braking mode.
Switching of operating modes is performed by the SA21 batch switch located on the control panel. The SA21 switch must always be in the "Normal descent" position, and only when it is required to lower the load at low speed, it is transferred to the "Dynamic braking" position.
In this case, the stator winding of the M13 motor is disconnected from the 380V alternating current network by the KM10 and KM13 contactors. The contactor KM9 is switched on, and a direct current flows through the transformer T4 and the rectifier block of diodes VD18 to the two phases of the stator winding of the M13 motor.
The KA8 minimum current relay monitors the presence of current in the stator circuit and, in the event of a sharp decrease in current due to the failure of the FU5 or FU6 fuses, it turns off the power from the KM8 starter coil, turns off the M12 electric pusher motor, i.e. the drum pulley is braked.
Resistors R20, R21, R22 and switch SA24 are designed for stepwise regulation of the current in the stator winding. Depending on the current value, the braking torque of the motor and the speed of lowering the load change.
The electro-hydraulic pusher M1 of the brake receives power through the contacts of the KM8 starter. The KM8 coil receives power through the closing block contacts of the KM10 or KM13 contactors in the power mode of operation or through the KM9 and the KA8 relay in the operating mode or through the KM9 and the KA8 relay in the dynamic braking mode.
In the clamshell operation of the crane, to improve the scooping of bulk goods, the KM8 starter is switched on when the M13 engine is not running, using the SA19 pedal.
In the hook mode of operation, the KM8 starter from the SA19 pedal will not turn on, since the contact of the SQ6 limit switch is turned on in series with the SA19 pedal, the opening contact of which will be opened when the hook is loaded with the rope.
The electro-hydraulic pusher M14 of the right drum is connected directly to the stator of the M15 engine and has no separate control.
Protection of motors against overcurrent is carried out by relays KA6 and KA7, which disconnect the line contactor.
Limit switches SQ7 and SQ11 are introduced to turn off the motors of the cargo winch at the moment when there are two turns of the rope on the drum.
The SQ8 limit switch is designed to limit the lifting height of the lifting device.
In the grab operation mode of the crane, when lowering the grab, in order to avoid loosening the cables, the limit switches SQ6 and SQ124 are installed in the hook mode, they are shunted by the SA22 packet switch. The SA22 switch is installed on the control panel and has two positions: "Grab" and "Hook".
The crane is protected from overloads in terms of the load moment by load moment limiters, the circuit of which includes the coils of the KM13 and KM14 contactors. When the load torque limiters are triggered, the load winch motors can only operate for lowering and the lifting circuit will be open.
Limit switches SQ9 and SQ10 limit the winding of the rope onto the drum and turn off the motors when the third layer of rope starts to wind on the drum.
5. SPECIAL PART
5.1 Organization of maintenance
During the operation of the crane, there is a loss of its performance and destruction of its individual parts. In order to maintain the quality indicators stipulated by the regulatory documentation at the appropriate level, and to ensure trouble-free operation of the crane, a set of interrelated provisions, norms and preventive measures are provided for, included in the system of technical maintenance and repair of equipment.
The essence of the system is that after the crane has worked a certain number of hours, they carry out maintenance and repairs.
Crane maintenance includes the following types of work: shift maintenance, maintenance No. 1 (TO-1), maintenance No. 2 (TO-2), and maintenance No. 3 (TO-3). Maintenance is performed at intervals and in the amount established in this manual, regardless of the technical condition of the crane at the time of the start of maintenance.
shift maintenance;
maintenance # 1 - after 100 hours of work;
maintenance # 2 - after 600 hours. work;
maintenance # 3 - after 3000 hours. work;
When carrying out maintenance and repairs of cranes, it is necessary to strictly observe the basic requirements of safety, labor protection and fire safety.
All maintenance work is entrusted to the drivers: cleaning, lubrication, fastening, adjustment, elimination of minor faults.
The admission of drivers to the maintenance and repair of the electrical equipment of the crane can be carried out only with the permission of the chief power engineer of the enterprise in the manner established by the "Rules for the technical operation of electrical installations of consumers";
Some limited maintenance work is assigned to the machinists: the cleaning part of the lubricants. The rest of the work - changing the lubricant in gearboxes, fastening, regulating and eliminating malfunctions of mechanisms - is assigned to mechanics and electricians;
There is no maintenance obligation on the driver, and all maintenance is done by fitters and electricians.
The possibility of using each of the above schemes is determined by the operating conditions of the crane and, in particular, by its loading in time.
For the correct maintenance of the cranes, the administration of the enterprise is obliged to provide the operating personnel with instructions that determine their rights and obligations.
Before starting work, the crane operator must perform a shift maintenance of the crane, for which the administration of the enterprise should allocate appropriate time.
Maintenance of cranes should be based on a planned preventive system, i.e. after a certain number of hours, the crane must be inspected, checked, and adjusted without fail, regardless of its technical condition, with the elimination of the detected faults.
When carrying out maintenance of the crane, it is necessary to use this operating manual, the operating instructions for the diesel generator set, the installation and operation instructions for ECC series synchronous generators and other instructions supplied with the crane.
When carrying out a shift maintenance, it is necessary:
Carry out an external examination of the mechanisms and assemblies of the crane in order to check the absence of visible damage. The following items are subject to inspection: undercarriage, swing frame, undercarriages, movement mechanisms, safety devices for movement mechanisms, automatic coupler, swing mechanism, load and boom winches, boom, portal, outriggers, power plant, control panel.
Check the lubricant level in the gearboxes, make sure there is no leakage. If the lubricant level falls below the permissible level, top up the lubricant. Take measures to eliminate leakage.
Carry out work on the daily maintenance of the diesel generator in accordance with the diesel operating instructions.
Check the condition of the ropes and block guards, make sure there are no unacceptable damages, the correct position of the ropes in the block streams.
Check the wedge fasteners of the ropes on the boom head and at the movable cross-beam of the boom chain hoist to check that there is no visible damage on the wedge bushings and that there are clamps at the ends of the rope.
Run the diesel generator for further maintenance.
Make sure that the instrumentation, lighting and alarms are in good working order by alternately examining them or turning them on.
Check the crane at idle operation by alternately switching on and braking all mechanisms.
Make sure the safety devices are in good working order:
Hook lifting height limiter - by lifting the hook block until the limiter is triggered and the lifting winch is turned off;
The limiter for the minimum number of turns on the drum of the cargo winch - by setting the boom to the minimum reach and lowering the hook until the limiter is triggered and the cargo winch is turned off for descent (in this case, at least one and a half turns of the rope should remain on the drum);
Load limiter - by checking the presence of a seal on the limiter;
Load indicator and fire extinguisher - visually.
When carrying out maintenance No. 1 (TO-1), it is necessary to carry out work on a shift basis and, in addition:
Carry out maintenance work No. 1 of the diesel generator in accordance with the diesel operating instructions.
Carry out maintenance work on batteries according to the instructions.
Inspect undercarriages, spring suspension, axle boxes, wheelsets, check the condition of the undercarriage, the correctness of the suspension of the frames of the movement mechanism on articulated rods.
Check the fastening of the diesel generator, electrical devices, panels, resistors, fuel tank, removable counterweight.
Make sure that there is no visible damage to the metal structure of the portal, movable and fixed traverse-boom chain hoist.
Check the slewing ring bolts for tightness. The bolts connecting the slewing bearing to the chassis and slewing frames must be tightened with a force that creates a torque of 115-125 kgcm.
Check the fastening of the gearbox of the mechanisms of movement, turning, the lifting winch, the fastening of the electric motors of these mechanisms to the frames.
Check the attachment and correct adjustment of the electro-hydraulic brakes of the load and boom winches, movement and swing mechanisms.
Check the condition of the pantograph, the stabilizing device of the generator, clean the slip rings of the rotor from brush dust, tighten the loose contact connections.
Lubricate according to the lubrication table.
Check the oil level in the outrigger hydraulic reservoir and top up if necessary.
Eliminate the faults identified during the maintenance process.
When carrying out maintenance No. 2 (TO-2), it is necessary to carry out maintenance work No. 1 and, in addition:
Carry out maintenance work No. 2 of the diesel generator in accordance with the diesel operating instructions.
Inspect gearboxes through inspection hatches. The gearing must work the entire surface (the minimum contact patch is allowed 40% in height 50% in length). Check the alignment of the machine couplings.
Check the adjustment of the mechanism brakes, add oil to the hydraulic pushers.
Inspect all elements of the metal structure, paying special attention to the condition of the welded joints of the boom, portal, welding of the frames of mechanisms to the swing frame, to the absence of cracks and residual deformations.
Inspect the condition of blocks, guide rollers, boom and cargo ropes, guy ropes, wedge fasteners of the ropes.
Inspect the replacement boom equipment.
Change oil in all gearboxes.
Eliminate the faults identified during the maintenance process.
When carrying out maintenance No. 3 (TO-3), it is necessary to carry out maintenance work No. 2 and, in addition:
Carry out maintenance work No. 3 of the diesel generator in accordance with the diesel operating instructions.
Carry out maintenance work on the running platform: inspect the outriggers, automatic couplers, rail grips, spring switches, auto-brake equipment; clean the undercarriage from dirt and check for cracks in the frame beam, paying special attention to the center, pivot, longitudinal and central, outrigger and slewing bearing attachment points.
Carry out maintenance work on the swing frame; clean the rotary frame of dirt and oil and check the frame beam for cracks, paying particular attention to the center beams, the beam with the lugs for the boom, the gantry support boom attachment points, the slewing bearing, the welding of the mechanism frames.
Carry out maintenance work on the slewing ring; inspect, replace torn bolts and fix loose ones, adjust the gap between the rings.
Carry out maintenance work on the outriggers: inspect the outrigger hydraulic system, repair the leak, check the hydraulic system oil for cleanliness and replace if necessary.
Carry out maintenance work on the cargo and boom winches: inspect all bearings and gearbox seals with the cover removed, inspect drums and their guards, cargo drum pressure roller, replace excessively worn brake linings.
Carry out maintenance work on the slewing mechanism: inspect all bearings and gearbox seals with the cover removed, inspect the open gear train (connection between the mechanism and the slewing bearing), replace excessively worn brake linings.
Carry out maintenance work on the movement mechanisms: inspect all bearings and gearbox seals with the covers removed, as well as the axial bearing, replace excessively worn brake linings, check the integrity of the frame suspension on hinged rods, clean the wheelsets from dirt and check the wheel profile.
Carry out maintenance work on the portal and the load limiter: check the condition of the portal's construction, lugs, portal axis, fixed traverse; check the condition of the load limiter cam, torsion shaft, adjusting screws and levers, microswitches, thrust; check that the capacity limiter is adjusted correctly.
Carry out maintenance work on the crane body: inspect and repair the locks of the doors and body doors that come off, check the sealing of hatches, braces and portal struts.
Carry out maintenance work on the hook frame: inspect the thrust bearing of the hook, the crosshead and the hook, paying particular attention to the transition of the threaded part of the shank to a smooth one and wear of the hook support surface.
Carry out maintenance work on the counterweight: inspect and tighten loose counterweight bolts.
Carry out maintenance work on the crane boom: inspect the boom head, the attachment points of the boom to the swing frame, the grab damper, the rope weakening limiter, the joints of the boom sections.
Carry out maintenance work on the driver's cab: inspect the control panel, paying special attention to the control levers and their reliable fixation in extreme and intermediate positions, check all stops and interlocks.
Carry out maintenance work on electrical equipment in accordance with the instructions in subsection 6.8. of this manual.
5.2 Repair of cranes
Repair of cranes is carried out in a planned manner, depending on their technical condition. Unscheduled repairs are caused by a crane failure, and this type of repair is not provided for in the annual repair plans.
Repair of cranes is divided into current, medium and major.
During routine repairs, by replacing or restoring worn parts and adjusting mechanisms, they provide or restore the crane's performance.
Medium repairs are performed to restore the crane's resource; at this time, partial disassembly of the crane, overhaul of individual small assembly units, replacement and restoration of the main worn parts are carried out.
Overhaul is carried out to restore serviceability and full or close to full restoration of the crane resource. The repair includes the complete development of the crane, replacement of all worn out assembly units and parts, including the base ones.
Based on the experience of operating diesel-electric cranes, the following types of scheduled repairs and the approximate timing of their implementation have been established.
Routine repairs are carried out as soon as the malfunctions found in the course of technical maintenance are revealed, and, as a rule, is combined with maintenance No. 3.
Medium repairs are carried out after 13,000 hours of work. In case of medium repairs, they revise the slewing bearing, all gearboxes with the replacement, if necessary, of gear elements, bearings, replacement of blocks, drums, ropes, weld metal structures of frames and booms.
Overhaul is carried out after 26,000 hours of work. In this case, the repair of the chassis and swing frames, technical documentation is carried out. When changing the working fluid, oil should be poured through a metal mesh to prevent foreign matter from entering the pusher chamber.
The hydraulic pusher is filled with oil in the vertical position of the hydraulic pusher body. In this case, it is necessary to ensure the removal of air from under the piston and from the electric motor. For this, 5 minutes after filling the hydraulic pusher with oil to the upper level, the hydraulic pusher is switched on 10 times. These inclusions will speed up the removal of air from the oil. When pouring oil into electric hydraulic pushers, the level must be strictly observed. The oil must be filled before it appears in the filler tube. Overfilling with oil can lead to overpressure in operation, which can destroy the terminal block. If there is less oil than the norm, the pusher may work in an unstable mode or will not work at all.
Before the first start-up of pushers filled with transformer oil at a temperature of -10 ° C and below with PES 3D liquid at a temperature of -40 ° C, it is necessary to warm up the pusher by several short-term starts. Duration of inclusion 10 -20 with an interval of 1-2 minutes.
More detailed instructions on maintenance, possible malfunctions and methods of their elimination, repair of brakes with electro-hydraulic pushers are given in the brake passports attached to the crane documentation.
During operation, irregularities are formed on the friction surface of the brake pulley rim.
If the depth of irregularities is more than 0.5 mm, the surface must be reground. The size of regrinding is allowed not more than 30 of the initial thickness of the rim. After grinding, the surface of the pulley must be heat treated to the required hardness.
The working surface of the pulley is also allowed to be restored by vibroblast or manual surfacing followed by grinding and heat treatment.
Brake pulleys are not allowed to run out due to uneven wear, more than 0.002 of the pulley diameter, as well as cracks and loose fit on the shafts or loose fit of the keys.
For brake springs, cracks, broken coils, permanent deformation are a rejection feature.
In the articulated joints of the levers, wear of more than 5% of the original diameter and ovality of more than 0.5 mm, as well as the presence of cracks in the levers, are not allowed. Worn holes of the levers' eyes are repaired by reaming to a new (larger) repair size, and the rollers are made with a corresponding increased diameter. The limiting increase in diameter is 7-10% of the initial one. It is advisable to increase the wear resistance of the rollers by chemical-heat treatment to a hardness of HRC 54-62, as well as to press heat-treated bushings with a high hardness of the working surface into the holes of the levers.
When repairing and replacing brakes, the following requirements for installing the brake must be observed
The diameter of the brake pulley should be no more than 300 mm (-0.32) for the TG-300 brake and 200 mm (-0.29mm) for the TG-200 brake. Runout, taper and ovality of the working surface of the pulley are not allowed more than 0.05 mm. The working surface of the pulley must have a hardness HB of at least 280 and a roughness of at least 1.25 in accordance with GOST 2308-79;
when installing, the center of the brake must coincide with the center of the pulley (the permissible deviation must not exceed 1 mm);
the non-parallelism of the shoes relative to the pulley surface should not exceed 0.3 mm per 100 mm of the shoe width;
in the pusher motor, check the insulation resistance of the winding relative to the case, make sure there is no possible phase failure. The smallest permissible cold insulation resistance must be at least 20 megohms. If the insulation resistance is lower, the stator winding must be dried. During drying, the temperature of the winding should not exceed 70 ° C.
5.3 Rope maintenance
Ropes maintenance includes cleaning, visual inspection, lubrication and checking of the rope fastening.
The ropes are cleaned manually using metal brushes or by passing through the knob at a speed of 0.25-0.4 m / s with dies, the inner surface of which in diameter and shape corresponds to the surface of the rope. Fixtures of other designs can also be used.
An external examination to check the condition of the rope is carried out after cleaning it. The rope should be inspected along its entire length. The areas of the most probable wear and tear of the wires (areas wound on the drum and bending on the blocks) are inspected with special care. The condition of the rope is assessed by the number of broken wires, the degree of their wear and the breakage of strands.
Rejection rates for steel ropes are regulated by the Rules for the Construction and Safe Operation of Cranes.
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The most common electric bridge, slewing, jib, metallurgical and other cranes have much in common in the lubrication system, but depending on different operating conditions, they also have their own characteristics.
Lubrication of crane gearboxes of the lifting mechanism and the mechanisms of movement of the bridge and bogie is usually carried out by means of an oil bath. Since the gears in crane gearboxes work in harsh conditions, with shock loads, frequent switching on and off, they use more viscous and oily oils compared to conventional machine tool gearboxes. When filling crane gearboxes with oil, it is recommended to follow the instructions given in table 21.
Table 21
Lubrication of crane gearboxes depending on the lifting capacity and operating modes of the crane
Oil change and gearbox flushing is done once every 4-6 months and is usually timed to coincide with scheduled repairs or crane inspection. For metallurgical cranes, the oil life is reduced to 2-3 months. Before opening the gearboxes, remove dust from their covers to prevent it from getting into the oil. The oil level in the gearbox must not be lower than the oil level indicator; in its absence, it is recommended to fill the oil no higher than a level reaching 3-5 cm to the bottom of the lower shaft, but not lower than a level that ensures the full height of the teeth of the lower gear is immersed in oil. Gearboxes must be free of oil leaks. Particularly unacceptable is it getting on trolleys, crane bridge deck and rails, as well as on brake pulleys, pads and belts. If leaks are found, they are immediately repaired.
Lubrication of bearings of crane gearboxes of old designs, where the bearings of the high-speed first shaft of the gearbox are ring-lubricated, when operating under normal temperature conditions, is carried out by filling them with industrial oil 20 once every 3 months, refilling is done once every 3-5 days. In conditions of high temperatures and dustiness, these bearings are poured monthly with industrial oil 50, topping up is carried out 2-3 times a week.
Plain bearings in gearboxes with cap grease fittings are lubricated at normal temperature with US-2 or USs-2 solid oil by turning the grease fitting cover 1-2 turns 1-2 times per shift. At elevated temperatures, they are lubricated with constantine UT-1 or UTs-1 by turning the lid of the oiler by 1-2 turns up to 2-3 times per shift.
In gearboxes of modern cranes, rolling bearings are usually installed, which at normal temperatures should be filled with US-2 solid oil once every 4-6 months, and for metallurgical cranes with 1-13 grease or UT-1 constantin at each repair. Grease is added on a monthly basis through cap or grease fittings supplied to these bearings. If gearboxes have rolling bearings with grease, pay particular attention to the serviceability of the seals and do not allow grease to leak out of the bearing housing or be flushed out by leaked oil from the gearbox bath.
On some cranes, gearboxes have a pump that supplies oil to the bearings. In this case, caring for them is reduced to monitoring the presence and quality of oil and the correct operation of the pump.
The mechanisms for moving the bridge of heavy-duty electric cranes, especially metallurgical ones, are currently produced with centralized lubrication systems from automatic or manual lubrication stations. In this case, lubrication is performed according to the operating instructions for these systems. The automatic centralized lubrication system ensures a reliable supply of lubricant to all lubrication points, including remote and hard-to-reach ones. This saves maintenance time, which is especially important for continuously operating cranes, and significantly reduces the consumption of lubricants.
In older cranes, lubrication of the travel wheel bushings of the transmission shaft slide bearings is usually carried out through cap nipples, grease nipples or from central lubrication units. Lubrication of cranes operating at normal temperatures, for example, in mechanical assembly shops, is performed with US-2 or USs-2 solid oil by turning the grease nipple caps by 1-2 turns or filling grease nipples with a syringe 1-2 times per shift. Lubrication of forging, foundry, trough-filling and other metallurgical cranes is carried out with contalin UT-1 or UTs-1 by turning the grease nipple caps by 2 turns or filling the grease nipples 2-3 times per shift. Extra care should be taken to lubricate remote points, wheel hubs and parts and assemblies that are directly exposed to high temperatures. The rolling bearings of the axle travel mechanisms are lubricated similarly to the rolling bearings of crane gearboxes.
Low-temperature greases CIATIM-201, NK-30, No. 21, GOI-54, etc. are used as greases for cranes operating outdoors in winter. The lubrication points of external cranes must be protected from snow water entering them.
In the bogie travel mechanism, gears and gearbox bearings, travel wheel bearings are lubricated in the same way as the corresponding components of the axle travel mechanism. Since the bogie constantly moves along the bridge, it is especially important here to prevent oil leaks from the gearboxes onto the deck and rails.
In the load lifting mechanism, gearboxes and bearings of the load drum are lubricated similarly to the same units of the bridge and bogie movement mechanism. Since the lifting mechanism works more intensely than other crane mechanisms, it is recommended to lubricate its components more often. Lubrication of rolling and sliding bearings, hook cage axles is carried out with solid oil US-2, at high temperatures with constantine by filling through grease fittings or plugs located at the ends of the block axes. For cranes operating at normal temperature, lubricant is supplied 2-3 times a week, and for metallurgical cranes - at least 1 time per shift. Cage hook ball bearings are filled at normal temperatures with US-2 solid oil once every 3-6 months, in metallurgical cranes - with constalin or grease 1-13 once a month.
In order to avoid rapid wear, open gear drives are lubricated: in light duty cranes with light duty and at normal temperature - with half-tar once every 5 days, with medium lifting capacity and medium duty at elevated temperatures - with graphite ointment every 5 days and heavy metallurgical cranes 2 times a week - graphite ointment, prepared by mixing 90% constalin and 10% graphite powder, when heated not higher than 110 °. Remove old grease before applying grease.
The lubrication of the electric motors is shown below. Drum controller bearings are lubricated with US-2 or US-3 solid oil, croutons, segments and ratchet wheels - with a thin layer of US-2 solid oil or technical vaseline. The hinged joints of the contactors are lubricated with industrial oil 30. The parts of the limit switches are systematically lubricated, at least once every 10 days, with the same oil or US-2 solid oil, depending on the design features of the unit. The fingers of the current collector rollers are lubricated with de-energized trolley wires once a week with solid oil US-2, and at high temperatures with constantine UT-1.
To avoid accidents, the cranes should be lubricated only in the de-energized state of all crane mechanisms on its landing site. The daily supply of lubricants in clean containers (separate for each grade) should be kept in a closed box on the crane bridge. In view of the danger to crane operators, as well as the presence of a large number of hard-to-reach lubrication points on cranes, it is especially insistent to transfer all units to centralized and automatic lubrication.
The parts of the drum unit to be calculated include: drum, drum axle, axle bearings, fastening the rope end to the drum.
The strength calculation of the drum is the calculation of its wall for compression. For the operating mode group, we take the drum material steel 35L with [comp] \u003d 137 MPa, the drum is cast
Cast drum wall thickness
0.01 Days + 0.003 \u003d 0.01 400 + 0.003 \u003d 0.007 m
Under the terms of the technology of manufacturing cast drums? 10 15 mm. Taking into account the wear of the drum wall, we take \u003d 15 mm \u003d 0.015 m
We check the selected drum wall for compression using the formula
We clarify the selected value of the drum wall thickness using the formula
where is the coefficient taking into account the effect of deformations of the drum wall and rope, is determined by
where Ek is the elastic modulus of the rope. For six-strand ropes with an organic core Ek \u003d 88260 MPa; Fк - cross-sectional area of \u200b\u200ball wires of the rope; Eb - the modulus of elasticity of the drum wall, for cast steel drums Eb \u003d 186300 MPa, according to the dependence of 0.0062 m with the ratio of the drum length to its diameter, the permissible stress in formula (46) should be reduced by c% when winding two ends of the rope onto the drum, and for the value c \u003d 5%. Then
[comp] \u003d 0.95 · 137 \u003d 130.15 MPa
1.07 · 0.86452 · \u003d 0.0058 m. Therefore, the accepted value \u003d 0.015 m satisfies the strength conditions.
At ratio \u003d 2.05< 3 4 расчет стенки барабана на изгиб и кручение не выполняется.
Ratio \u003d 2.05< = 6,5 , поэтому расчет цилиндрической стенки барабана на устойчивость также можно не выполнять.
The tension of the strip with semicircular grooves is used as the clamping device of the rope on the drum. According to the rules of Gosgortekhnadzor, the number of installed single-bolt strips must be at least two, which are set in increments of 60 0. The total tensile force of the bolts pressing the rope to the drum.
where f \u003d 0.1 0.12 is the coefficient of friction between the drum and the drum,
The angle of inclination of the side edge of the groove. \u003d 40 0;
The angle of the rope wrapping with inviolable turns, \u003d (1.5 2) 2P \u003d (3 4) P
Required number of bolts
where is k? 1.5 - safety factor of the rope attachment to the drum,
f 1 \u003d - reduced coefficient of friction between the ropes and the bar;
f 1 \u003d \u003d 0.155; l is the distance from the bottom of the rope on the drum to the upper plane of the clamping bar, constructively we take l \u003d 0.025 m
Steel ВСтЗсп steel with technical \u003d 230 MPa was adopted as the bolt material. Allowable tensile stress [р] \u003d \u003d \u003d 92 MPa; d 1 - the average diameter of the thread of the bolt, for a rope with a diameter d k \u003d 13 mm we take the bolt M12, d 1 \u003d 0.0105 m
We take z \u003d 8, four double-bolted bars.
The axis of the drum experiences bending stress from the action of the forces of two rope branches with a double chain hoist, the drum's own weight is neglected. The design diagram of the drum axis of the lifting mechanism is shown in Figure 8.
Load on the drum hubs (neglecting its weight)
where l n - the length of the threaded part of the drum, l n \u003d 303.22 mm; l ch - the length of the smooth middle part, l ch \u003d 150 mm (see figure)
The distance from the drum hubs to the axle supports is preliminarily assumed: l 1 \u003d 120 mm, l 2 \u003d 200 mm, the estimated length of the axis l \u003d L b + 150 200 mm \u003d 820 + 150 \u003d 970 mm.
Calculation of the drum axis is reduced to determining the diameters of the trunnions dw and the hub dc from the condition of the axis for bending in a symmetric cycle:
Where Mi is the bending moment in the design section,
W is the moment of resistance of the design section in bending,
[- 1] - allowable stress for a symmetric cycle, determined by the simplified formula:
Figure 8 - Design diagram of the drum axis of the load lifting mechanism.
where k 0 - coefficient taking into account the design of the part, for shafts and axles, pins k 0 \u003d 2 2.8; - 1 - endurance limit,
[n] - permissible safety factor for the 5M operating mode group [n] \u003d 1.7. Axle material - steel 45, tech \u003d 598 MPa, -1 \u003d 257 MPa
Load on the drum hubs according to the formula (50)
We find reactions in the supports of the drum axis:? M 2 \u003d 0
R1 l \u003d P1 (l - l1) + P2 l2
R 2 \u003d P 1 + P 2 - R 1 \u003d 14721.8 + 10050.93 - 14972.903 \u003d 9799.827 N
Bending moment under the left hub:
M 1 \u003d R 1 · l 1 \u003d 14972.903 · 0.12 \u003d 1796.75 N · m
Bending moment under the right hub:
M 2 \u003d R 2 l 2 \u003d 9799.827 0.2 \u003d 1959.965 N m
We find the diameter of the axis under the right hub, where the greatest bending moment M 2 acts:
We accept d C \u003d 0.07 m
We accept the remaining diameters of the drum axis sections according to Figure 9.
Figure 9 - Sketch of the drum axis.
Radial double-row ball bearings No. 1610 GOST5720 - 75 with an inner diameter of 50 mm, an outer diameter of 110 mm, and a width of 40 mm, dynamic load capacity c \u003d 63.7 kN, static load capacity c \u003d 23.6 kN were selected from the support bearings.
We check the selected bearings by. Required dynamic load rating
Стр \u003d F п · (53)
where F p is the dynamic conducted load, L is the nominal life, million cycles, 3 is the exponent of the Wehler fatigue curve for ball bearings.
The nominal life is determined by the formula
where n is the frequency of rotation of the bearing ring during steady motion, rpm;
T is the required bearing life, h. For the 5M operating mode group, the value is T \u003d 5000 h.
F p \u003d F eq · r b · r rate (55)
where F eq - equivalent load; k b - safety factor, k b \u003d 1.2; k temp - temperature coefficient, k temp \u003d 1.05 (for 125 0 s)
The equivalent load is determined taking into account the actual or average operating schedule of the mechanism (see figure), depending on the operating mode group:
where F 1, F 2…. F i - constant reduced load on the bearing at different mass of the transported load, acting over time
t 1, t 2,…. t i for the service life, subject to the rotation speed n 1, n 2 …… n i; T is the total estimated bearing life, h;
n is the frequency of rotation of the part at steady state for the movement that lasts the longest.
F p \u003d 11126 1.2 1.05 \u003d 14018.76 N
C tr \u003d 14018.76
therefore, the selected drum axle bearing is suitable.
We carry out an updated calculation of the drum axis in dangerous sections 1 - 1 and 2 - 2 (see figure), as well as in section 3 - 3.
Section 1 - 1. Bending moment Mi \u003d R 1 · (l 1 -), where l С is the length of the hub, l С \u003d (1 1.5) · d С \u003d 1.5 · 0.07 \u003d 0.105 m
Mi \u003d 14972.903 (0.12 -) \u003d 1010.603 Nm
The safety factor in the calculated cross-section for fatigue resistance is determined according to.
where [n] is the smallest permissible safety factor for the axis, [n] \u003d 1.7;
r \u003d 1.7 is the stress concentration factor in a given section of the axis; \u003d 1 - hardening factor,
E is the scale factor in bending, E \u003d 0.7; r y \u003d 0.67 - coefficient of durability, - bending stress in the calculated section.
Section 2 - 2. Bending moment Mi \u003d R 2 · (l 2 -) \u003d 9799.827 (0.2 +) \u003d 2474.456 N · m
Section 3 - 3. Bending moment Mi \u003d R 2 · (l 2 -) \u003d 9799.827 (0.2 -) \u003d 1445.474 N · m
The axle strength in the calculated sections is ensured.
Let's calculate the bolts connecting the drum flange in the form of a toothed half-coupling with a shell. We install the bolts on the diameter of the circle D ocr \u003d (1.3 1.4) · D z, where D z \u003d 0.252 m is the outer diameter of the gear rim of the gearbox. D env \u003d 1.3 0.252 \u003d 0.3276 m.
The connection is carried out with bolts for holes from under the reamer in accordance with GOST 7817 - 80, the material of the bolts is steel 45, tech \u003d 353 MPa.
Circumferential shear force acting on all bolts
P env \u003d 2 S max \u003d 2 12386.364 \u003d 31079.426 H
The bolt diameter is determined by the formula
where m b \u003d 0.75 · m b is the estimated number of bolts, m b is the established number of bolts, we take m b \u003d 8, then m b \u003d 0.75 · 8 \u003d 6; - permissible shear stress, determined by the dependence
where t is the yield point of the bolt material;
r 1 - safety factor for mechanisms for lifting cargo, cranes working with a hook r1 \u003d 1, 3;
r 2 - load factor, r 2 \u003d 1, 2
Take the bolt diameter d \u003d 0.008 m
Blocks designed to maintain and change the direction of movement of a rope with a diameter dk... Blocks are subdivided into movable, the axis of which moves in space, and stationary. A type of fixed blocks is an equalizing block, which does not rotate when lifting and lowering a load, but serves to equalize the length of unevenly stretching rope branches in a double pulley block.
Rope blocks are made of steel by casting, welding or stamping. For cast blocks, steel with mechanical properties not worse than steel is used 45L-11, for stamped ones - no worse than steel 45 , and for welded - no worse than steel Art 3.
The profile of the block stream must ensure unhindered entry and exit of the rope and have the largest contact area with it (the largest surface area of \u200b\u200bthe stream). Based on this, it is recommended that the ratio of the main block sizes be taken as shown in Figure 3.10.
Blocks must have a device (bracket) that prevents the rope from leaving the block stream. The gap between the specified device and the block flange should be no more than 20% of the rope diameter.
Drums designed for winding a flexible traction element (rope or chain). They are made of cast iron (cast) or steel (cast or welded).
To reduce the specific pressure between the rope and the drum and prevent friction of the rope against an adjacent turn on the surface of the drum, helical grooves are made with a pitch 
mm. If one branch is wound on the drum (single chain hoist), it has grooves in only one direction. With two branches (double chain hoist), the grooves are in the right and left directions.
The design of the drums should provide for the placement of parts for fastening the rope to the drum, which can be carried out using overhead strips, clamping strips or a wedge (Figure 3.9).
Minimum drum diameters D, blocks D bl, and equalizing blocks D ur.bl.along the center line bent by steel ropes, is determined by the formulas:
With increasing ratio D / d k the durability of the rope increases as the contact and bending stresses decrease.
The drum diameter obtained by the formula (3.9) D should be rounded up to a value from the series: 160; 200; 250; 320; 400; 450; 500; 560; 630; 710; 800; 900 and 1000 mm.
Coefficient change is allowed h 1, but not more than two steps in the classification group up or down (Table 3.7) with appropriate compensation by changing the value Z p (Table 3.6) for that number of steps up or down. Drums for single-layer rope winding must have grooves cut along the helical line (Fig. 3.11). For grab cranes with single-layer winding of a rope onto a drum and for special cranes, during the operation of which jerks and loosening of the rope are possible, the drums should be equipped with a device (rope-laying device) that ensures the correct laying of the rope or control of the position of the rope on the drum.
Smooth drums are used in cases where, for structural reasons, a multilayer winding of a rope onto a drum is necessary, as well as when winding a chain on a drum (Fig. 3.12) Smooth drums and grooved drums intended for multilayer rope winding must have flanges on both sides of the drum. The ribs of the rope drums must rise above the top layer of the wound rope by at least two of its diameters, and for chains - at least by the width of the chain link.
The length of the drum, which determines its rope capacity, should be such that at the lowest location of the load-gripping body (hook, etc.), at least 1.5 turns of the rope or chain remain wound on the drum, not counting the turns under the clamping device. Taking into account flanges and turns for fastening the rope, the total length of the drum when winding:
· on one branch of the rope
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