Page 335 - Advanced Mine Ventilation

312 Advanced Mine Ventilation

2. Pressure Testing: The entire length of pipeline between the bottom of the venthole and well
head will be tested to 1.25 times the shut-in pressure of the borehole or 90 psi, whichever is
greater.
3. Pipeline will be generally laid in the return and will not be buried. Whenever the pipeline
must cross a fresh air entry, it will be conducted through a steel line.
4. No hoses will be used in the system except while a hole is being drilled. Stress-relieving,
flexible tubing will be used at critical points such as the well head to pipeline connection.
This will be stainless steel tubing with a triple wire braid cover.
5. The steel pipeline will be firmly supported with no unsupported span greater than 2 ft.
6. A gas water separator will be installed at the bottom of the vertical venthole to remove
condensation that falls back down the casing. Other separators will be installed on the holes
or on the pipeline if water production from coal warrants. All separators will preferably be
commercially made. Water drains will be provided on the line wherever necessary.
7. Safety Devices: A potential survey will be made after the pipeline is installed, and cathodic
protection is provided where needed.
8. Automatic shut-in valves will be installed at each well head. These will be held open by
nitrogen or air under pressure contained in a fragile plastic pilot line running parallel to
and secured on top of the pipeline. Any roof fall or fires serious enough to damage the pipe-
line will damage the pilot line first and close the borehole immediately.
9. Inspection: The pipeline system will be firebossed daily by a competent person familiar with
system operation.
10. CH4 Monitors: If the quantity of air flowing over the pipeline is such that a complete rupture
of the pipeline and consequent discharge of methane in mine air will raise its concentration
above the limits specified by the law, a methane monitor will be used as shown in the
enclosed schematic. A commercially made flame arrestor will be installed within 10 ft of
the top of the vent stack. A check valve shall be used to guard against reversal of flow.
The check valve can be manually defeated if it is desired to purge the pipeline for repairs.
An orifice meter may be installed if so needed. All surface installation will be periodically
inspected to ensure satisfactory performance.
11. Surveying: All boreholes drilled for degasification will be accurately surveyed either during
drilling or after drilling is completed using commercially available borehole surveying
tools. These boreholes will be accurately plotted on mine maps to ensure the prevention
of any inadvertent mining through these boreholes.
12. All boreholes must be plugged prior to mining through them using Class A cement.
13. A compressor will be required at the surface if beneficial use is made of the gas at a future
date. Plans for the installation will be discussed with Mine Safety and Health Administra-
tion at the appropriate time.

References

[1] Thakur PC, Umphrey RW. Methane drainage and transport in CONSOL underground coal
mines. In: Annual meeting of Pittsburgh coal mining Institute of America; November 1979.
[2] Tisdale JE, et al. Piping methane in underground coal mines. MSHA, U.S. Department of
Labor; 1978. p. 34. Information Report, 1094.
[3] Lewicki TF. Corrosion protection. In: Proceedings of the 17th annual underground pipe
corrosion short course, Bulletin 106, West Virginia University; 1972. p. 34.