Page 325 - Advanced Mine Ventilation

302 Advanced Mine Ventilation

Depending on local conditions and the details of the mining situation, mining may
have to cease during this process. It is apparent, therefore, that in determining the
type of joining method to be used, reliability of the fitting is extremely important. If
it is properly and permanently made initially, later problems are proportionally
minimized.

18.2 Gas Leakage Detection and Safeguards

Early warning in case of small leaks or massive ruptures of the pipelines is essential for
the safe operation of an underground degasification system. A frequent inspection pro-
gram is necessary and will possibly detect pipeline problems soon enough to avoid
large problems later. However, massive ruptures of the pipeline must be detected
immediatelydwithin secondsdand the only practical method of doing so is by prop-
erly placed and installed methane detection instruments.
Instruments are available to monitor practically any in-mine environmental condi-
tion. The choice of instrument is dependent on reliability, maintenance requirements,
and the particulars of the hazard being guarded against. Basically, protection may be
required against the following:
1. Gas leakage into the mine from a rupture or leaking pipeline.
2. Oxygen leaking from the mine into the pipeline (especially when a compressor is used).
3. Gas leakage into the mine atmosphere through the coal rib when a well is shut in (it will be
discussed later in the chapter).

If leakage from a pipeline is from a massive rupture, a large influx of gas into the
airstream will be experienced, and easily measurable changes will occur in the pipeline
flow and in the methane level in the entries. This will not necessarily be the case for
small leaks. Pinhole leaks caused by corrosion pitting, slight pipe movements, or any
of a number of factors, although serious, will not be readily detected. The small leak
may go unnoticed until it has progressed to a large leak. Regular inspections of the
pipeline will be the best safeguard for such leaks. For this reason, it is important
that the pipeline be visible throughout its length. A daily fire bossetype inspection
of the pipeline and its components (water traps, valves, etc.) should provide early
warning of the development of leak-producing conditions. In this type of inspection,
the pipeline can be visually inspected for corrosion and to insure that all water traps
are functioning properlydnot dry or plugged; that all valves are properly aligned as
open or closed as applicable; that the detection equipment is operating; that no roof
falls have damaged the pipe; that no other leak-producing conditions are developing;
and that ventilation is being maintained in the entries.
A detailed inspection of the pipeline should be made weekly. This inspection
should insure that all detection instruments are properly charged and calibrated; that
automatic control equipment is functioning properly; and that all components of the
pipeline are operating properly and to test them if necessary.