Knowledge Of Seamless And Electrified Track Lines

1. What is seamless line?

Answer: The jointless track is a long rail line with a length of not less than 300m welded from many rails of standard length.

2. What are the types of jointless track?

Answer: It can be divided into two types: temperature stress type and release temperature stress type.

3. What are the components of the temperature stress type jointless track?

Answer: It is composed of fixed zone, buffer zone and expansion zone.

4. What is the length of fixed zone, buffer zone and expansion zone?

A: Fixed area: its length is determined according to the line and construction conditions, and the shortest length shall not be less than 50m.

Expansion zone: the length of expansion zone is determined by calculation, generally 50-100m.

Buffer zone: when common insulated joint is used, it is 4 standard rails. When bonded insulated joint is used, the bonded insulated rail can be inserted between 2 or 4 standard rails.

5. What is temperature stress?

Answer: If the rails are all fixed and cannot expand freely with the change of rail temperature, the stress will be generated inside the rail. The stress generated inside the rail with the change of rail temperature is called temperature stress.

6. What is locking rail temperature?

Answer: The locked rail temperature is the actual locked rail temperature during the long rail laying construction. At this time, there is no temperature stress in the rail. Generally, the average rail temperature measured after the rail is closed, the rail falls into the groove and when the joint bolts are tightened is taken as the locking rail temperature.

7. The rail temperature of every line must be accurate and uniform. In what cases, it must be dispersed or adjusted?

Answer: (1) The actual locked rail temperature is not within the range of the designed locked rail temperature, or the difference between the actual locked rail temperature of the left and right long rails exceeds 5 ℃.

(2) The locking rail temperature is unclear or inaccurate.

(3) The locking temperature difference between the two adjacent unit rails of the inter-regional and inter-regional non-contact lines exceeds 5 ℃, and the difference between the minimum and maximum locking rail temperatures of the unit rails in the same section is 10 ℃.

(4) Improper laying or maintenance methods will cause abnormal expansion and contraction of long rails.

(5) There is serious uneven displacement in the fixed area and seamless turnout.

(6) In summer, the track direction of the line is seriously poor and there are many broken bends.

(7) Through the test, it is found that the temperature force distribution is seriously uneven.

(8) The original locked rail temperature has been changed due to handling line fault or construction.

(9) When laying long rails at low temperature, the stretching is not in place or uneven.

8. What are the methods for stress release of CWR? What are the requirements?

Answer: The stress release of jointless track can be carried out by using the roller combined with rail collision method and the roller combined with tension combined with rail collision method. When releasing, the following requirements shall be met: the total amount of release shall be enough, the release shall be uniform along the full length of the rail, and the final locking rail temperature shall be accurate. At the same time, it is required to control the line creep in combination with the release of stress.

9. What are the precautions for stress release of jointless track?

Answer: (1) The change value of the locked rail temperature caused by line creep shall be considered for the release.

(2) Those that have not been taken out of the broken cracks during welding after the broken rail in the past years shall be added to the total amount of release.

(3) The rail temperature can be appropriately increased by 5 ℃~10 ℃ by controlling the release by length to overcome the resistance of fasteners. If the temperature is low, the construction plan can be changed.

(4) The release work should be combined with the root treatment of diseases, such as the treatment of long rail joint dislocation and other diseases.

(5) During the construction of slow operation, the fasteners shall not be loosened too much to prevent track expansion.

(6) For the stress relief work, the work area shall investigate and put forward the plan, the work section shall approve and organize the construction, and the technical personnel shall assist and guide.

(7) After the stress release meets the design requirements, the relevant technical data and displacement observation marks shall be modified according to the actual locked rail temperature.

10. What are the technical requirements for the weld?

Answer: The weld position in the long rail and turnout should be kept straight, and the concave-convex should be welded and polished. Measure with a 1m ruler, and the sagittal of the working edge and the concave and convex sagittal of the top surface shall be greater than 0.5mm.

11. How are the creeping observation piles of jointless track arranged?

Answer: 5~7 pairs of displacement observation piles shall be set for each section of jointless track. When the fixed area is long, the number of pairs can be appropriately increased. When the length of the unit rail is greater than 1200m, 7 pairs of displacement observation piles shall be set (the starting and ending points of the unit rail, 100m and 400m away from the starting and ending points of the unit rail and 1 pair at the middle point of the unit rail); When the unit rail is no more than 1200m, 6 pairs of displacement observation piles shall be set (1 pair of displacement observation piles shall be set at 100m and 400m from the starting and ending points of the unit rail).

12. What are the rail temperature conditions for the maintenance of concrete sleeper jointless track?

Answer: Note: The operating rail temperature range is calculated according to the actual locked rail temperature