safety valves setting for boilers

Dear r-k-s.

Ask the boiler manufacturer! In the meantime do not attempt to operate the plant as your questions suggest a total lack of basic operational experience.

Have a safe 2010!

Massey.

i am not operating the boilers. i want to know just for my personal knowledge. if u know then tell about the same. otherwise dont give other type of suggessions. regads

I don't know the local regulations for how to set the various pressures, but here is the basic idea:

The boiler operating pressure control is typically a modulating device that gradually raises/lowers the fuel feed and air rates according to whether steam pressure is a little lower/higher than the desired setting, say 104 kg/cm². The boiler remains running, just faster/slower.

The boiler safety pressure control is typically an on/off pressure switch. It will be set somewhat higher, say 120 kg/cm². If the operating control malfunctions and pressure continues to rise, this switch will shut the boiler off.

The boiler safety valve will be set for a yet higher pressure, say 150 kg/cm², but not higher than the MAWP (maximum allowed working pressure), which for this example I am also assuming to be 150 kg/cm².

Local boiler safety codes may dictate what percentages these steps differ from each other, and maybe the safety valve setting must be less than rather than equal to the MAWP, which is stamped on the data tag for the boiler.

The safety valves is set at the factory (or, if being recertified, by a specialty shop), not normally on site.

It will be at whatever pressure the engineer/surveyor responsible for assessing the boiler for burst indemnity insurance by the operation's insurance company states on their periodic inspection report.