What is the maximum allowable pressure increase for the release valve and by-pass when passing the maximum rated capacity of the pump?

The maximum allowable pressure increase for the release valve and bypass when passing the maximum rated capacity of the pump is commonly set at 20%. This standard is established to ensure the safe operation of elevator systems. It accounts for the potential fluctuation in pressure that can occur during peak capacity operations while still maintaining system integrity and safety.

Operating an elevator pump near its maximum rated capacity can lead to pressure spikes, which, if unchecked, could result in equipment failure or hazards. The 20% threshold allows for a buffer that protects both the machinery and the users, allowing the system to handle unexpected variations without causing undue stress or failure.

In this context, the other choices represent limits that are either too low or unreasonably high when considering industrial norms and safety protocols. A limit of 10% would not adequately account for the common operational realities, while limits of 15% or 25% may either underestimate or overestimate the necessary safety margin for effective pump operation under high-load conditions. Thus, the 20% figure aligns with widely accepted practices and regulations in elevator safety.