Commercial valves: identification and use

This is a general overview of the topic of commercial valves that appears in the May/June 2024 edition of Registered Gas Engineer. For further and detailed guidance, refer to IGEM/UP/2 Edition 3: Installation pipework on industrial and commercial premises.

It is essential to use the right valve for the right application. All valves should have a clear indication of the direction of operation to open and close, and make sure that they’re not susceptible to debris that would prevent closure.

Any maintenance carried out should be capable of being completed with the valve in situ. Additional emergency control valves (AECVs) should be readily accessible and valves should be selected for the maximum operating pressure (MOP) of the pipework, flow capacity, pressure drop, speed of operation and application – including the type of gas. The environment where the valve is located may also need to be considered in the context of corrosion resistance.

Identification
All AECVs and isolation valves should be clearly identified as gas control valves. An AECV should be labelled “Additional Gas Emergency Control” or similar. There should also be advice on what to do in an emergency, with the contact number of the emergency service provider (ESP) clearly shown. In addition to the label, on/off tape should be affixed, indicating the directions of the valve position.

Gas isolation valves should be readily identifiable. This is usually by means of a label indicating “gas isolation valve” attached to the pipework or nearby.

Gas installation pipework should be labelled to indicate that it contains gas. This is usually done by banding with gas marking tape or by being painted ochre yellow.

Types
The most common types of valve in a commercial environment are:
• Non-lubricated plug
• Lubricated plug
• Ball
• Wedge and parallel slide gate
• Butterfly
• Diaphragm.
For a full description of each type, refer to IGEM/UP/2.

Suitability
When choosing the valve type, you should consider its use: for example, some are suitable for isolating a section of pipework but not suitable for use as an AECV. The table below shows the correct type of valve for each intended application.

Automatic isolation valves (AIVs)
In normal circumstances, an AIV, operated from a gas or smoke detection system, is not automatically required for a gas installation. However, many buildings may require them for insurance purposes or following a fire-risk assessment, in which case it should be installed.

The type of AIV and its operating system should be considered carefully, especially with regard to re-establishing the gas supply in circumstances where appliances do not include automatic flame safeguards.

Where appliances are not fitted with automatic flame safeguards, an AIV system should be designed so that, if the gas valve closes, the gas supply cannot be restored until the downstream pipework has been examined for integrity and safety.

When the AIV has closed, it shall not be able to be reset automatically until all downstream pipework has been examined, ensuring that all appliance gas valves are closed or by fitting a low-pressure cut-off device.

Frequently asked questions
Q: Is a drop weight valve recommended for use on gas, held open either by a fusible link system or thermal sensors on an electrical solenoid latch?
A: No, this type of valve is not normally suitable for gas installation due to them being held open by interference. They are also prone to sticking in the on position.

Q: Can a butterfly be used as an ECV or AECV?
A: No, a butterfly valve is not acceptable.

Q: Can a lubricated plug valve be used when buried underground?
A: No, a lubricated plug valve cannot be used when buried underground.

Q: What is the maximum size of a non-lubricated plug valve when used as an ECV?
A: The maximum size cannot exceed 50mm NB.

Q: Should an AIV be fitted in a plant room?
A: If a manual isolation valve is not readily accessible where the pipework enters the plant room, then an AIV shall be fitted. A building may also require an AIV as part of additional insurance or for fire-risk assessment purposes.