Sleeper changing is totally two concepts: working on open subgrade and working in tunnel.
Nothing on the subgrade. When the machinery is driven to the front, a clamp will be used to pull out the old sleeper and insert the new one. The tamping machine will walk after it. It can push out hundreds of meters at night. The process cannot be carried out when arriving at the tunnel. The space is so large that the machinery cannot rotate.
The old tunnels of trunk railway are generally narrow, with side walls on both sides and one line in the middle, leaving little allowance for operation. The metro tunnel looks wider and has an inner diameter of five or six meters, and the inner part has to be stuffed with auxiliary facilities such as conductor rail and cable trough, so there is less space for hands and feet. Medium-sized laying and changing vehicles and rail cranes commonly used for sleeper change are designed according to the outdoor conditions. Some of them get stuck at the tunnel portal and cannot get in at all. It is barely possible to get in, and there is still space for the boom to expand. The top and side walls of the tunnel limit its movement range to death.
Therefore, the main force for sleeper change in the tunnel is people and small machines and tools.
At this time, the weight of sleepers becomes the key. The wooden sleeper was 70kg each, and two people picked it up by one hand. The concrete sleeper is more than 200kg each, which is unrealistic to be lifted by people and must be loaded with machinery. For the place where the machinery cannot get in, if you want to change a concrete sleeper, you must first think about how to get the equipment in, and it will take a lot of time for the equipment to enter and leave the site.
The work in the tunnel is calculated according to the skylight point, and the time is too tight. A sunroof point is so long that it is necessary to check the machines and tools before entering, and recheck the line before removing it, with one button at both ends, so the time to be really capable is shorter. Metro windows are mostly at night, two or three hours a night, with safety redundancy. It takes so much time to save one process.
The process of changing wooden sleepers can be relatively short. Remove the ballast at one end of the old sleeper, remove the fasteners, and use a crowbar to transversely move the old sleeper into the cleared sleeper box and pull it out along the line direction. New sleepers shall be inserted from the bottom of sleeper box, crowbars and ropes shall be moved in place, rock ballast shall be backfilled and tamped by small machine groups. One sleeper shall be replaced. The complete set of motion revolves around a sleeper without first removing all the surrounding pieces.
The other layer is reshipment. The new sleepers shall be transported in by flat car or monorail trolley in one time. The sleepers shall be well stacked against the side wall and shall not intrude the gauge. The old sleepers were pulled out and transported out again. The heavier the load is, the more the round trip is, and the more the working hours are consumed. Wooden sleeper is light, and the account at this end is nice.
Working in tunnels is just as troublesome as the environment. Due to poor ventilation, lighting shall be temporarily erected. A layer of pulverized coal is accumulated on the tunnel wall of the special coal transportation line all the year round, so people may go into the tunnel with a poor face.
This environment is not very wood friendly. The moisture in the tunnel is heavy and air tight, which is what wooden sleepers are afraid of. The process of oil immersion is to repair this short plate. The oil immersion depth shall be 13mm. The oil shall penetrate into the surface of the wood and block the channel where the water can be drilled so that the wood can be carried in the damp place. Plain sleepers can be used for several years in dry areas. Their service life shall be obviously reduced when placed in tunnels that are wet all the year round.
In the same way, the advantages of wooden sleepers will be amplified where large equipment cannot be deployed. There is no ballast layer under the open deck of the bridge, and the bridge sleeper is directly seated on the steel beam. The track spacing of the old station is narrow, and the machinery cannot rotate. In the roadway of the mining area, the height and width are blocked. It is true that there are few means available for these places, and wooden sleepers can be finished by manpower and simple tools. What Qingdao Tiehan does is this kind of oil-filled sleeper.
There was a row of black wood in the tunnel, which was unnoticed at ordinary times. I really know it when I need to change it. It is lighter and can be disassembled and assembled one by one. It saves time.
