To provide a high level of technical maintenance for tracks there is a need for reliable and trouble-free operation of high-performance leveling and lining tamping machines whose main working member is a tamping unit. An overhauling shop was organized by the company of West-Ter for tamping units as well as production facilities for manufacturing complete sets of spare parts.
Currently, production facilities cover an area of 1000 sq.m. and include the following sections:
- Cleaning and washing
- Dismantling and condition checking
- Machining equipment
- Cladding (surfacing)
- Hydraulic cylinder repair
- Technical Supervision
- Test and quality control facility
- Warehouse for overhauled units
- Online monitoring of tamping unit operation.
Each section is equipped with modern facilities to ensure high quality manufacturing. The overhauling process fully corresponds to the technology that has been developed by the original unit manufacturer. The application of this technology makes it possible to prolong the service lifetime of a overhauled unit for a period that almost equals to the life of new tamping unit. After overhauling a guarantee of at least 500 thousand tamping cycles is given. In 2013, 15 sets of tamping units were repaired in the shop. Special attention is paid to the quality. The staff is professionally trained and regularly certified. Advanced quality control procedures and modern manufacturing equipment are used. The online operating parameters of overhauled tamping units are monitored to prevent failure and overload. As a result, the number of failures among operated units has been reduced to almost zero. But in a rare case of unexpected failures immediate service is provided. The time of troubleshooting is 1-3 days.
CLEANING AND WASHING
Tamping units are cleaned and washed at washing cabins with special detergents. The polished and sensitive parts are protected from damage before cleaning.
DISASSEMLING AND CONDITION CHECKING
Parts are checked for errors by visual inspection, assessed with the help of special tools and equipment in accordance with the overhaul manual. The control and measuring devices are calibrated in the metrological service and have a certificate or a stamp confirming that they have been tested. To detect hidden cracks in critical components methods of nondestructive examination are applied, such as: penetrant testing, magnetic particle inspection and eddy current testing. The magnetic particle and eddy current testing are conducted in accordance with the regulations for non-destructive testing of units and parts of locomotives and multiple units. After the magnetic particle inspection repairable parts are demagnetized. The indentation test is performed according to the guidelines for the penetrant testing.
The tested parts are divided into three groups:
- Mountable without repair
- Repairable and to be restored
- To be replaced.
The bearings are to be replaced. The frame is checked for pitting, buckling, deformation or other visible defects. Cracks detected in the frame are welded shut. Welding work is carried out according to the guidelines for welding and surfacing work on track-laying machines’ repairing.
The frame has to be replaced if:
- two or more cracks more than 50 mm long are detected
- cracks are found in the seating surfaces of the bearings, bushings, joints, threads and mounting holes.
Shafts and axles with unrecoverable defects (cracks of any size and location, deformations) are replaced. If defects of shafts and axles are detected such as worn surfaces of the seat counterparts, threaded surfaces, keyways, these parts are restored. Cracks or burrs on the shaft and axis that are associated with working surfaces of the sleeves and sealing rings are removed by grinding. Slots of the shafts, axles and sleeves are inspected for cracks, deformation, cuts and wear of the teeth by thickness and the slit grooves are checked by width. Upon detecting unrecoverable defects, the parts are replaced. Insignificant defects (cracks, burrs and impact marks on the slot surfaces) are reworked. The fasteners (bolts, screws, nuts and pins) with the improper threading defects (breaking, points of impact, crushing or avulsion of more than two threads), with damaged surfaces and bent attachment parts are replaced. The threaded surfaces with minor defects (small knocks, crushing or avulsion of not more than two threads stretched thread) are repaired with the help of the tap or thread rolling die. The threaded surfaces are checked with thread gauges. If there are thread defects in the form of knocks, crushing or avulsion of more than two threads, stretched thread or inacceptable thread wear, the threaded surfaces are repaired by tapping of the next standard size, bolts and pins are replaced appropriately or a screw-in is installed. The important thing is that the strength of the product is not reduced. Distance, spacing and intermediate sleeves and rings are checked visually. In case of irregular wear of the faces, presence of cracks, burrs or knocks the parts are replaced. When pins or the pin holes are worn, pins are replaced, where appropriate, holes are drilled to reach the next standard size.
In the mechanical processing section new parts for tamping blocks are produced to replace the parts that have been detected as defective and subject to replacement.
CLADDING (RECOVERY OF WORN SURFACES)
In the hard facing section the worn surfaces of levers, which have been declared as repairable in defect detection, are repaired. The worn surfaces are welded and heat treated.
After the cladding of the worn surfaces of levers, they are processed by a high precision four-coordinate metal processing machine.
The hydraulic cylinders are dismantled. The troubleshooting of the hydraulic cylinders shall be in accordance with the requirements of troubleshooting tab and tabs for repairing of parts and units.
At all stages of repairs technical monitoring with the use of modern measuring and control equipment is run.
The tamping unit is assembled according to the typical technological process for repairs of tamping units of relevant machines. After the assembly of the tamping unit, its external surfaces are covered by two layers of paint with an air gun.
Parameters of the overhauled unit are examined and reviewed by test services engineer. The test is performed by means of the special equipment according to the following procedures:
- The temperature of the vibration shaft bearing. The temperature of the bearing at the lubrication points cannot exceed the admissible values and have to be stabilized at the final stage
- The temperature of the axes of the hinge joints of the lever, frame and clamping hydraulic cylinder
- No leakage of the hydraulic fluid in the hose connections and seals the cylinder
- No oil leakage in the lubricating system of the central hinge joints
- Smoothness and quietness of operation during the test.
Total three tests are performed at different RPMs (see table below).
|No.||RPM, min-1||Time, min|