What is the safety valve capacity requirement for an existing boiler?

The safety valve capacity requirement for an existing boiler dictates that the safety relief valve must be set to ensure the system can handle potential overpressure scenarios safely. The correct approach is to set the safety valve capacity to at least 6% above the highest pressure to which any valve is set, while also ensuring that it does not exceed 6% above the Maximum Allowable Working Pressure (MAWP). This requirement is designed to maintain safety by providing sufficient capacity to relieve pressure without risking the boiler's integrity during operation.

The rationale behind this requirement is grounded in maintaining proper performance under pressure fluctuations. If the safety valve capacity were set too close to the MAWP or to the exact highest pressure setting, the system could become vulnerable to dangerous overpressure conditions, jeopardizing both equipment and personnel safety. Additionally, by setting a margin of 6% above critical pressure levels, the safety mechanism can function effectively as a buffer against unexpected pressure spikes that might occur during operation or due to system malfunctions.