PK-753B-6 electro-pneumatic contactor

Project Description

Kazakhstan, North Kazakhstan region, Petropavlovsk, 2015, SKPTU № 3, Drawings on specialty: "Operation, repair and maintenance of railway rolling stock"

On the topic: "Electro-pneumatic contactor PK753B6." Performed by A.V. Kuznetsov

Archive Content:

In the graphic part there are 4 drawings of A1 format in Compass-V12 program:

1. Spring Stretch Tool

2. Electro-pneumatic contactor PK-753B-6

3. Arc extinguishing device

4. Diagram of accessory for valve tightness check

In Microsoft Word format:

Main components of pneumatic contactor pk753b6, their purpose and operation

Operating conditions of the unit on the locomotive, characteristic damages and causes of their occurrence

Technology of repair (replacement, restoration, way of restoration) and increase in reliability of PK-753B-6

REPAIR TECHNOLOGY (REPLACEMENT, RESTORATION, RECOVERY METHOD) AND IMPROVEMENT OF RELIABILITY

Contacts of contactors are PK‒753 made of solid-state copper. When heating copper contacts, it is necessary to grind them with a file with a small notch, removing protrusions and metal drops.

Copper contacts are replaced by electro-pneumatic contactors with wear by more than 25% of their thickness. Working surface of worn-out contacts is restored by copper surfacing with autogenous torch or soldering of plates made of copper, silver, metal-ceramic alloy based on silver by means of gas torch or contact welding using coal electrodes with further machining to established dimensions. Care for metal-ceramic silver contacts is reduced to checking their condition and cleaning in the event of contamination with a suede napkin or a woven napkin slightly wetted in gasoline, or a hard hair brush. If surfacings appear on the contact, they should be carefully removed with a small notch file.

The contacts installed on the machine should be checked for abutment. Movable and fixed contacts when the apparatus is in the ON position shall have at least 30% contact width in the line. When half the thickness of the fingers of the locking contacts or copper plates is worn, they must be replaced by new ones. When the fastener parts are loosened in the holes of the contact plate and the insulation block, a new thread must be cut to the next large size with the appropriate replacement of the bolt and screw.

Arc extinguishing chambers and coils at all types of maintenance and repair are cleaned from coke and soot with a filler or sandwich. Arc extinguishing chambers are replaced if there are cracks or breakaways in the partitions. It is necessary to monitor the attachment of nuts and the correct installation of the chambers. In arc-extinguishing coils, burned places are melted with copper, the connections of the coils with the brackets are switched, the damaged insulation is restored.

Multi-turn coils of relays, valves with damaged insulation due to inter-turn faults and breakdown are replaced. Coils are wound on hand-operated machines, a speed counter is used to count turns. When manufacturing coils, it is necessary to pay attention to the density of laying turns (the presence of dips leads to interturn faults and holes).

After winding, the coils are dried at a temperature of 100110 ° C for 2-3 hours, impregnated in varnish and dried again at the same temperature of 1012 hours. Instead of impregnation, the coils can be combined with a temporary band, which is then removed.

Compound or impregnated coils are insulated with three layers of lakotkany and one layer of glass tape at half-top, covered with bakelite varnish, cord band is applied and coated with BT99 varnish. The output clamps are rubbed with gasoline, then the coils are air dried for 2-3 hours. After that, coils are checked for interturning, tested for breakdown, ohmic resistance and dimensions.

On connecting tires, leads, damaged insulation is restored, contact surfaces are cleaned and sawn, bolts are tightened, washers are replaced, etc. Tips are replaced in case of wire fractures to the bottom of more than 10% at reduction of clamp surface due to fracture or melting of more than 20%, traces of overheating and wire burns. Tips for flexible connections woven from copper wires of the PSHh brand are often made from copper or brass tubes, and for flexible connections from copper foil (0.1 mm thick) - from a strip curved in the form of the letter P.

Soldering of tips of flexible joints, tires and contacts of surfaces is carried out on the contact welding apparatus, as well as by soldering iron using solder POS30.

Electro-pneumatic actuators at all types of repairs for accuracy of actuation at minimum pressure (375 kPa) and for air tightness at ON position and maximum pressure

(700 k Pa). Sluggish operation of the electro-pneumatic drive occurs in most cases due to the loss of elasticity of the leather cuffs due to drying. When checking new devices and during current repairs of TP1, the elasticity of leather cuffs can be restored by abundant lubrication with 1B lubricant with its subsequent rubbing.

Pneumatic actuators. Failure of pneumatic actuators

Air is passed between covers, cylinder flanges and through collars of piston or diaphragms (diaphragms). In the first case, air leakage is eliminated by tightening the fastening bolts or changing the sealing gaskets, in the second case - by adding a non-freezing lubricant in the amount of 1-6 cm3 through an opening in the cylinder wall with subsequent repeated actuation of the drive. If the addition of lubricant does not stop the passage of air, the drive is disassembled and the cuffs are burned. The passage diaphragm is replaced.

Electro-pneumatic diaphragm (membrane) drive does not require periodic disassembly as a piston drive, however, it is necessary to remove the cover and inspect the diaphragm when cold occurs. It should not have cracks, breaks, abrasions. Diaphragm is made of flat driven rubberized belt. Belt thickness 6 mm. In the absence of a drive belt with rubber liners, a rubberized belt with one or more rubber liners or, in extreme cases, a conveyor belt may be used. The required thickness of the membrane can be obtained with thicker materials by separating (delaminating) part of the layers. Membrane along contour of drive bodies is cut with knife or scissors. The necessary holes are made with the help of clearances.

Cracks, casting shells and other defects in the cylinder body are eliminated by welding with combined or brass electrodes.

Small supports can be eliminated by gluing with BF2 glue or bakelite varnish. Bearings of levers and brackets shall be replaced if clearances between rollers and bushings exceed 0.2 mm.

Skewing or shifting of movable contact relative to fixed contact is eliminated by installation of pressing gaskets between panel and bracket of fixed contact or between panel and cylinder cover. The valve is fastened to the housing by uniform tightening without special effort to avoid tearing of threads, studs and damage to the insulator. Worn breadcrumbs

and the drive levers of the speed regulator are replaced, square

breadcrumbs, which ensures constant rotation speed when turning the breadcrumb.

After repair the rods lifting is checked, which must be complete at pressure (5h5.5) 105 Pa.

In electro-pneumatic valves, air leakage is possible due to contamination of the valve pair or violation of its lapping. In this case, contaminated valves and bushings must be washed with gasoline or kerosene, and then dried. If flushing does not help, the valve is removed and the valve is lapped. I draw with GOI paste diluted with machine oil. After lapping, the valve and bushing are washed in kerosene and purged with air. The valve is tested for leakage by the density of the valve system on the bench. Air leakage when the valve is on means a malfunction of the upper valve, when the position is off - of the lower valve.

Air leakage through the atmospheric hole is considered permissible, and at compressed air pressure of 500700 kPa, the soap bubble holds at least 5 s. The air gap is measured with a special template. It is not uncommon to form cracks in covers made of zinc alloy.

Repair process steps include:

removal of the repair facility;

cleaning of the repair object before disassembly;

disassembly;

inspection of parts and establishment of scope of work;

restoring the main parts;

node-by-node assembly and required checks;

general assembly;

processing, testing, delivery of the repair object;

installation;

Final painting and testing.

Operating conditions of the unit on the locomotive, characteristic damages and causes of their occurrence

In the operation of electric rolling stock, electric devices, depending on the mode of running the train, are constantly in the following conditions:

shaking (vibration) in a wide range of frequencies, amplitudes and accelerations;

at temperature from ‒ 50 to + 70 ° С and relative humidity not more than 95% at temperature 25 ° С;

at significant voltage fluctuations in the power circuit and in the control circuit, as well as at pressure fluctuations in the compressed air line;

in case of pollution of ambient air with dust, moisture, oil and fuel vapors. These impurities are deposited on the apparatus and disturb their insulation, cause increased wear of moving and rubbing parts, and contaminate contact surfaces.

Therefore, frequent switching on and off, heating of the elements leads to increased wear of the hinged joints, parts of the pneumatic or electric drive, power ones and to burnout and rapid failure of the locking contacts.

Wear parts of contactors include power contacts, arc-extinguishing horns and coils, locking pins and blocks, flexible shunts, pneumatic control pistons, electro-pneumatic valves, arc-extinguishing chambers.

Increased fanning, and sometimes equalization of contacts is caused by :

skewed and inadequate contact proximity;

incorrect form of contacts;

insufficient pressing, wear of axles and bushings of drive levers ;

air leakage;

jamming of the piston ;

drying of leather cuffs of electro-pneumatic actuators of contactors;

lack of failure.

If the clearance between the axes and bushings is more than 0.3 mm, replace the axes. The piston jamming is eliminated by adding MVP or 1B lubricant to the cylinder with subsequent frequent switching on and off of the device.

The main causes of these types of defects include:

excessive or weak pressing of contact springs;

change of solution, occurrence of failure ;

developed profile of contact surfaces;

insufficient contact area;

jamming of parts in hinged joints;

compressed air leaks or mechanical failures of the pneumatic part;

ingress of foreign objects into devices.