Gas Transport in Underground Coal Mines

Mild steel pipes and casing (externally flush) were commonly used since 1940s. They suffer from many drawbacks. Some of them are listed below:

• 1.Very heavy in large sizes (above 5″ in diameter) and liable to hurt workers.

• 2.Must be on floor and prone to get damaged by both floor heaving and roof fall. The pipes, often, need wooden support to keep them in alignment.

• 3.In mines, using DC current for haulage, the steel pipes are corroded by ground current. They need cathodic protection in most cases.

• 4.They are also vulnerable to chemical corrosion inside the pipeline.

  
  

During 1970s, the author first replaced steel pipes by high-density polyethylene (HDPE) pipes that had many advantages as listed below:

• 1.It is lighter than steel and can be supplied in 20–200 ft length depending on the diameter. A crew of four can easily lay more than 1000 ft in a shift of 8 h compared with about 300 ft for heavy steel pipes.

• 2.It is noncorrosive. It does not need any cathodic protection.

• 3.It cannot be punctured by roof falls even if it is closed shut by the falling rocks.

• 4.It is nonconductive and immune to ground current.

• 5.It can be laid on floor or preferably hung from the roof.

  
  

Below table shows the specifications for some HDPE pipes. Early designs of plastic pipes, such as Aldyl-A by DuPont, were discarded in favor of new HDPE pipes.