scope:

PARTS ONE AND TWO. SOUNDNESS TESTING AND PURGING

Both parts of these Procedures cover pipework installations carrying 1st, 2nd or 3rd family gases, as defined by BS 1179. Cognizance should be taken of the particular characteristics of the gas concerned, including any adverse effects on operations.

For liquid LPG, reference should be made to the publication LPGITA, COP 17, issued by the LPGA.

These Procedures apply to all sizes of pipework, commencing downstream of the meter control valve through to the position of gas usage or to the termination of installation pipework. Where a meter is not fitted, the Procedures apply to all pipework downstream of the emergency control valve.

Further information on testing and purging pipework of diameter not exceeding 28 mm, in domestic premises, is provided in BS 6891.

These Procedures apply to industrial and commercial installations having a design pressure of not exceeding 7 bar.

Generally, LPG and LPG/air (3rd family gases) installations are restricted to a maximum pressure of 2 bar to prevent the possibility of reliquefaction, although operation at higher pressures is permitted provided trace heating of the pipework is installed to maintain flow in the vapour phase.

PART ONE. SOUNDNESS TESTING

For the purpose of these Procedures, soundness testing is defined as the testing of installation pipework for leakage. Strength tests and other aspects of pipework installations are not included.

Further information may be found in the Procedures IGE/UP/2* and the publication LPGITA, COP 22, issued by the LPGA.

If necessary, reference should also be made to BS 6400, which covers the soundness testing of gas meters.

The procedures prescribed are for use in the following circumstances:

- installation of new pipework and meters;

- alteration or replacement of existing pipework and meters;

- where there is a known or suspected gas leak, including existing pipework that has suffered a complete loss of pressure.

PART TWO. PURGING

For the purpose of these Procedures, purging is defined as:

(a) displacement of fuel gas by air or inert gas or,

(b) displacement of air or inert gas by fuel gas or,

(c) displacement of one fuel gas by another.

Operations (a) and (b) may embrace the two stage replacement of fuel gas by inert gas followed by air and the converse, i.e. the replacement of air by inert gas followed by fuel gas. Operations involving inert gas are sometimes referred to as "inert purges".

For the purpose of these Procedures, the inert gas referred to is assumed to be nitrogen.

The purging procedures prescribed are for use in the following circumstances:

- installation, exchange or removal of gas meters;

- installation, maintenance or removal of pipework and gas controls of all types, including secondary meters;

- loss of pressure within gas pipework due to valve closure. It should be appreciated that the closure of a valve, for example the main isolation valve to a factory, can result in loss of pressure which necessitates soundness testing and purging before the resumption of gas supply;

- where there has been an incorrect use of equipment using air or extraneous gas;

- where there is the possibility of air being present in pipework to be used for conveying fuel gas.

In certain situations, for example where the volume or diameter of pipework is considered by the responsible engineer to be sufficiently large as to warrant additional precautions, reference should be made to the Recommendations IGE/SR/22*. Although written for use in transmission, distribution and storage situations, those Recommendations readily may be applied for installation pipework. In such situations, safety procedures outlined in the Recommendations IGE/SR/23* * also may be applicable.

* Utilization Procedures IGE/UP/2 Installation Gas Pipework, Boosters and Compressors on Industrial and Commercial premises.

* Safety Recommendations IGE/SR/22 Purging Operations for Fuel Gases. Publication is anticipated in 1995.

* Safety Recommendations IGE/SR/23 Venting of Natural Gas. Publication is anticipated in 1995.