ENC 92/532
Revised Paper No. ENC 92/532
EPG 92/96
ENC 92/415
BRITISH GAS PLC
IDENTIFICATION, OPERATION AND MAINTENANCE OF
ENGINEERING VALVES (<7 BAR)
1. INTRODUCTION
This report explains the company's policy on the
identification, operation and maintenance of Engineering
mains and service valves (<7 bar).
2. IDENTIFICATION
2.1 Mains Valves
These proposals are applicable to all valves with
the exception of valves for which there is no
further use. Such valves should be abandoned.
The valve record card should include the following
information:-
- unique valve number
- dimensioned sketch of the valve location
- OS map reference
- address of the site
- size and safe operating limit
- make and type of valve
- date fitted
- details of pressure and rider points fitted
- number of turns and direction of rotation
- function of valve
- maintenance history
An example of a valve record card is given in
Appendix 1.
A valve numbering system which specifies a unique
number for each engineering valve should be adopted
in each Region.
A procedure should be established for providing all
existing and new valves with this unique number and
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ENC 92/532
only when a valve has been fitted should the number
be finally allocated.
Responsibility for val ve numbering, keeping valve
records and issuing copies of valve details should
be controlled by a nominated officer in each
District to avoid duplication.
To standardise records and to avoid confusion about
valve data and position, the information concern ing
a valve should be held at a central location within
each District.
Each valve location should be recorded in such a way
that the valve can be located quickly in an
emergency.
For any valve abandoned or removed, the valve number
and record sheet shou ld be cancelled but the record
retained. The only exception should be where a valve
is replaced in the same position and which performs
the same function. In such a case the Original valve
number may be used but the original record sheet
should be disposed of and a new record sheet
substituted.
Valve locations and valve numbers should be recorded
on all mains records, plans, strip maps,
installation schematic diagrams. This information
should be recorded on the Digital Record System when
it is implemented.
Each valve should be identified by a disc or cap
secured to the valve spindle or non -interchangeable
surface box as appropriate.
As an aid to identification and location, a marker
plate or post should be installed at the site of
each external valve wher e necessary.
2.2. Service Valves
Service valves of 50mm dia. and above, service
valves operating at MP and IP and those supplying
multi-occupancy dwellings, places of public assembly
and premises where there are hazardous occupations
should be recorded on valve record cards with a
dimensioned sketch in a similar way to mains valves.
Any service valve on a service of 50mm dia. and
above which supplies mere than one floor of a
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ENC 92/532
building or supplies separate areas of a single
floor building is also subject to "The Gas Safety
(Installation and Use) Regulations 1984" - Section
23. This states that "a line diagram in permanent
form is to be attached to the building in a readily
accessible position as near as practicable to the
primary meter indicating the posi tion of all
installation pipes of internal diameter of 25mm or
more, meters, emergency controls, valves, etc.
i.e. this line diagram would include the position of
the service valve.
3. OPERATIONS
The following actions are primarily for the operation of
mains line valves but should also be applied to the
operation of isolation valves in association with
governor installations and to service valves where
appropriate (e.g. to monitor continuity of supply to a
process load)
No mains line valve is to be oper ated unless there is a
pressure gauge on the main either side of it. If pressure
points do not exist, they must be installed prior to
valve operations.
Pressure gauges are to be installed as close as possible
to the valve to ensure that there is no doubt that the
gauges are on the correct main and in the correct
position.
The gauges are to be closely monitored before, during,
and after the operation of a valve.
All such valve operations are to be subject to an
approved written procedure. All valve operat ions are to
be controlled by one person in accordance with the
procedure, and a record kept of each operation, whether
opened or closed, number of turns and direction of
rotation etc.
4. MAINTENANCE
4.1 General Information
Maintenance is to be ca rried out as detailed in
Regional Maintenance Procedures.
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ENC 92/532
4.2 Mains Valves
All strategic mains valves are to be maintained at a
maximum of 3 yearly intervals. All non -strategic
valves are to be maintained at a maximum of 5 yearly
intervals. A guide to the selection of strategic
valves is given in Appendix 2.
Valves on governor installations or gas holder
stations will normally be maintained at the same
time as their associated equipment.
An example valve maintenance specification is given
in Appendix 3.
Strategic valves should be partially operated where
possible during their routine maintenance as
detailed in Appendix 3.
4.3 Service Valves
4.3.1 Service valves on Intermediate Pressure
and Medium Pressure services are to be
maintained at 5 yearly intervals.
This maintenance should be carried out at
the same time as the maintenance of any
adjacent service governor installation.
4.3.2 Service valves on Low Pressure services
will not normally be subject to
maintenance unless the property b eing
supplied is considered a special risk
(e.g. multi-occupancy dwellings,
hospitals, schools, places of public
assembly, and premises where there are
hazardous occupations).
This maintenance should be carried out at
5 yearly intervals.
Maintenance should also be carried out if
specifically requested by a consumer.
PWB/NA/505
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ENC 92/532
Appendix 1
o.
BRITISH GAS plc. VALVE N
VALVE DRAWING LINE REF.
AT: -
O.S. REF.
LOCATION PLAN. SCALE
DIMENSIONED LOCATION SKETCH OF VALVE & PRESSURE POINTS POSITION
MAKERS DESCRIPTION REMARKS
SAFE OPERATING LIMIT VALVE SIZE mm
VALVE OPENS CLOCKWISE/ANTI CLOCKWISE DATE FIXED
NUMBER OF TURNS TO FULLY OPERATE
LUBRICATION POINTS FITTED YES/NO EFFECT OF CLOSING/OPENING
NUMBER AND SIZE OF PRESSURE POINTS FITTED.
SIZE OF VALVE KEY REQUIRED … … … SQ MAINS PRESSURE
VALVE LEFT OPEN/SHUT BODY VENT FITTED YES/NO
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ENC 92/532
APPENDIX 2
A GUIDE TO THE SELECTION OF STRATEGICALLY IMPORTANT VALV ES
The following parameters should be considered in selecting
strategic valves.
1. Not more than one valve should be considered to be
strategic where there is more than one valve between off
takes on any section of main, unless the main is two -way
fed.
2. All off takes should have at least one valve that is
considered strategic.
3. Inlet and outlet governor valves should be considered as
strategic.
4. Valves inside holder stations should be excluded unless
they are identified as strategic under the Control of
Industrial Major Accident Hazard (CIMAH) Regulations.
5. Low pressure valves other than detailed above should be
excluded unless they have a significant effect on the
supply system.
PWB/NA/505
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ENC 92/532
APPENDIX 3
EXAMPLE VALVE MAINTENANCE SPECIFICATION
1. Operation of Valves
1.1 During the routine maintenance of strategic valves
the valve should be operated to ensure free
movement. The operation should be sufficient to move
the valve without severely restricting the flow of
gas.
1.2 An approved written procedure must be drawn up
whenever valves are operated. It is acceptable for
the operation of a number of valves to be covered by
one approved procedure where the valves form part of
a maintenance schedule and the locations are
separately listed.
1.3 No attempt should be made to partially operate a
valve if it is known or suspected to be a 1/4 turn
or Audco plug type valve.
2. Maintenance Specification
2.1 Issue Team Leader with copy of existing valve record
and sketch.
2.2 Locate valve-and carry out gascoseeker checks in
chamber.
2.3 Check dimensions, re -measure in metric (if
necessary), and amend valve record and sketch card
if appropriate.
2.4 Ensure that valve tag is fitted.
2.5 If marker post/plate is installed, ensure that
metric dimensions are displayed.
2.6 If marker post/plate is not present th en ensure,
wherever possible, one is installed. Refer back to
District office for remedial action if appropriate.
2.7 If valve and/or pressure point cover is not visible
then refer back to Distr ict office for remedial
action.
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ENC 92/532
2.8 Clean out valve/pres sure point chambers to ensure
access to pressure point valve/valve spindle etc.
Check that correct fitting is available on the valve
spindle for a standard valve key.
2.9 Confirm that pressure points are installed either
side of the valve and record size(s) i f not
previously recorded.
2.10 If no pressure points are installed then refer back
to District office for remedial action.
2.11 Fit gauges, confirm pressure point valves are
operable, and record standing pressure. (Grease
valves as necessary).
2.12 Ensure valve is in fully open position and, while
observing pressure gauges, partially close valve and
check direction of operation.
2.13 Fully open valve. Close pressure point valves. Vent
standpipe, then check for pressure build up to
ensure that pressure point valve is close d. Remove
gauges.
2.14 On I.P. valves, carry out greasing of all valve
bodies, as appropriate.
2.15 Clean out lifting "eyes" to surface covers.
2.16 Update all records and amend master sketch
records,necessary, with number of turns etc.
NB 1. This example specification is intended as a
guideline only. Regions may wish to provide a
greater level of detail for I.B.S, contract
purposes, etc.
2. Items 2.11, 2.12 and 2.13 should be omitted for non -
strategic valves.
PWB/NA/505
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