Steam boiler use pressure gage to measure pressure at some places either for water fluid or steam fluid. Pressure gauge is useful for the operator or personnel who working in steam boiler area to see working pressure and try to control the pressure under MAWP (Maximum Allowable Working Pressure). The pressure gauge is place in area which easy to see or visible for the operator. The pressure gage is different with gage pressure. The pressure gage is the equipment to measure pressure while gage pressure is the unit of pressure (usually indicated as psi = pounds per square feet) above atmospheric pressure.
Pressure gage is commonly classified as three types as the following below:
1. Bourdon pressure gage
The bourdon pressure gage is type pressure gage which has bourdon tube, it s an oval cross section of hollow tube. The tube has two ends, open and close. Open end is connected to fluids either water or steam and close end is connected to mechanical linkage in gage pointer. When the pressure builds up, the bourdon tube will be straightened out.
2. Bellow pressure gage
This type is commonly applied for the pressure under 30 psi.
3. Spiral pressure gage
The spiral pressure gage is modification design from bourdon pressure gage type. It has spiral and long pressure sensing.