Steam Boiler: Auxiliaries of Steam Boiler

Differential pressure transmitter is one of pneumatic transmitter types. Pneumatic transmitter uses high-pressure air as the medium. The air pressure is generated by compressor. The air is supplied to the transmitter with pressure approximately 20 Psi. The next step, transmitter issue standard signal with pressure 3-15 Psi.

Pneumatic transmitter types are often used for measurement is Differential Pressure Transmitter as show in Figure 1 below.

Figure 1: Differential Pressure Transmitter

In differential pressure transmitter, the pressure of fluid that will be measured is connected on two sides of transmitter; high pressure side and low pressure side, where both sides are mounted in area between diaphragm capsules. The side that has low pressure will flow on the right side of diaphragm capsule. At high pressure side, fluid flows greater than fluid at low pressure side, so the push force of diaphragm from left side to right side of diaphragm will be greater.

The change force of diaphragm is then channeled through flexible bar to move the force bar, where the bar rotates counter-clockwise. Seal diaphragm acts as a fulcrum and as a result, cavity between nozzle and flapper becomes smaller. So air will normally come out from nozzle cavity. Nozzle gap must be limited so that the pressure generated by nozzle transmitter will increase and the output will get reinforcement from pneumatic amplifier.

Part of the output is used as feed back bellows which is modified in the form of reinforcement. The reinforcement of differential pressure transmitter is used by range bar and use range wheel as a fulcrum. By making changes to the flapper position will reduce pressure transmitter. The end result is difference pressure between before diaphragm and after diaphragm will occur. Gap between flapper and nozzle transmitter that has been reduced will increase the output and stabilize it, by this way both pressure will be balanced.

Auxiliaries of steam boiler are devices that be installed to the steam boiler, and can make it operates efficiently. These devices should be maintained and controlled, so steam boiler can run in good condition. Some of auxiliaries which are installed in steam boiler are:

· Air heater

Air heater is device of heat exchanger to increase temperature of air before supplied to steam boiler usually located between the boiler and stack. Primary air and secondary air are heated by air heater before enter the combustion process, so the combustion process will be more efficient.

· Gas system

Gas system is a group of devices that consist of control valve, solenoid valve, gas regulator, and mechanism control to arrange mixture ratio between air and gas in the furnace of steam boiler, so combustion can take place completely.

· Oil system

Oil system is a group of devices that consist of oil pre heater, storage tank, piping, fuel strainer, and relief valve to control mixture between oil and air can be combusted perfectly.

· Economizer

Economizer is device of heat exchanger to increase temperature of feedwater before to be supplied in steam boiler, efficiency of steam boiler is expected higher than without using economizer.

· Feedwater regulator

Feedwater regulator is device to control feedwater that be supplied and maintain water level in the steam boiler at normal condition, so reduce excess of fuel consumption and thermal shock.

· Feedwater heater

Feedwater is device of heat exchanger to increase temperature of feedwater before entering boiler feed pump.