PNGRB T4S and Indian CGD valve upkeep

1. The verified duties stated by T4S

For Indian city gas distribution, PNGRB T4S sets sectionalising-valve spacing limits. High-pressure systems use spacing of 3 km or less, while low-pressure systems use 1 km or less.

T4S also sets annual tests for regulators, slam-shut valves and relief valves. These are the only T4S task facts used in this article.

Use the current regulation and regulator guidance for exact application and definitions. Do not treat this summary as a substitute for that text.

Our valve integrity management guide explains how stated duties and operator-set decisions can share one programme.

2. The mainline ball-valve interval gap

T4S is silent on one universal test interval for mainline ball valves. Its annual device tests should not be copied across by assumption.

A regulator, slam-shut valve or relief valve has a stated annual test in this verified summary. That fact does not create an annual rule for every mainline ball valve.

The gap also does not mean mainline valves can be ignored. Operators still need evidence that critical installed valves can perform their required duties.

The ASME B31.8 article explains the wider principle: procedures are required, while one universal interval is not prescribed.

3. Build the missing cadence from evidence

Operators typically set a defensible mainline interval through documented risk and condition review. The basis should reflect each valve's role and history.

1. Define the required isolation or operating function.
2. Assess consequence if the valve cannot move or seal.
3. Review service, access, movement history and earlier test results.
4. Apply current regulation, site procedures and OEM guidance.
5. Set triggers for earlier inspection or testing after changed condition.
6. Record the owner, basis, approval and next action.

Industry practice includes cycling valves at least twice yearly to reduce seizing risk. This is reported practice, not a stated PNGRB T4S interval.

4. Do not confuse spacing with condition

Spacing controls where sectionalising valves are provided within the stated system context. It does not prove that each installed valve closes or seals today.

A location plan can show coverage while individual valves remain untested. Asset identity, access, movement and isolation evidence must stay connected.

Pressure rise, continuing flow or noise can suggest a passing valve. These are screening observations, not confirmation of seat leakage or its cause.

Use a proper field test with a stated boundary and result. Our passing valves guide explains that confirmation step.

5. Turn the gap into a controlled programme

Start with a complete register of mainline and sectionalising valves. Assign each valve a duty, criticality, evidence status and next action.

Keep the annual tests for regulators, slam-shut valves and relief valves clearly labelled. Do not merge them with operator-set mainline ball-valve intervals.

Where maintenance is proposed, check suitability before treatment. Injection fittings must be sound, design and service must suit injection, OEM guidance applies, and operations must permit work.

The API 6D maintenance guide separates factory acceptance from installed condition. Our field services support surveys, controlled treatment and retesting for suitable valves.