Transient protection in pressure mains: which device is specifically provided to reduce water-hammer (surge) pressures?

Introduction / Context:
Water hammer is a transient pressure rise due to rapid changes in flow velocity. Protecting pipelines and appurtenances requires devices that absorb or quickly discharge the excess pressure to safe levels.

Given Data / Assumptions:

• Focus on common appurtenances: sluice valves, air valves, and relief valves.

Concept / Approach:
Pressure (surge) relief valves are designed to open rapidly when pressure exceeds a setpoint, venting water and capping peak surge. Air valves mainly admit/release air to prevent vacuum or air pockets; they are not primary surge-suppression devices. Sluice valves are isolation valves and do not abate transients.

Step-by-Step Solution:
Identify the device whose function is surge limitation: pressure relief valve. Exclude air valves (air management) and sluice valves (isolation only). Select “Pressure relief valves (surge relief)”.

Verification / Alternative check:
Transient analysis shows that properly set relief valves reduce maximum overpressure; additional measures include surge tanks, air chambers, and controlled valve/ pump operations.

Why Other Options Are Wrong:

• Sluice valves: Can actually create surges if operated rapidly.
• Air valves: Protect against vacuum and entrained air, not pressure spikes.
• None of these: Incorrect because a suitable device exists.

Common Pitfalls:

• Assuming air valves alone solve surge; they address a different failure mode.

Final Answer:
Pressure relief valves (surge relief).