Boiler Instrument and Control Part 1

INTRODUCTION

Instrumentation and controls in a boiler plant encompass an

enormous range of equipment from simple industrial plant to the complex

in the large utility station.

The boiler control system is the means by which the balance of

energy & mass into and out of the boiler are achieved. Inputs are fuel,

combustion air, atomizing air or steam &feed water. Of these, fuel is the

major energy input. Combustion air is the major mass input, outputs are

steam, flue gas, blowdown, radiation & soot blowing.

CONTROL LOOPS

Boiler control systems contain several variable with interaction

occurring among the control loops for fuel, combustion air, & feedwater .

The overall system generally can be treated as a series of basic control

loops connected together. for safety purposes, fuel addition should be

limited by the amount of combustion air and it may need minimum limiting

for flame stability.

Combustion controls

Amounts of fuel and air must be carefully regulated to keep excess

air within close tolerances-especially over the loads. This is critical to

efficient boiler operation no matter what the unit size, type of fuel fired or

control system used.

Feedwater control

Industrial boilers are subject to wide load variations and require

quick responding control to maintain constant drum level. Multiple element

feed water control can help faster and more accurate control response.