Class 2 (2nd Engineer) MEKG 📅 Oct 2022

Exam Question

With reference to feed regulation:

(a) Describe, with the aid of sketches, the operation of a boiler feed water regulator controlled by at least two other parameters besides water level in the drum

(b) Give reasons for the inclusion of the other elements besides water level in controlling feed flow

(c) Deduce the possible effects on the system when the drain valve in the constant leg in the level transmitter starts to leak

Reference Answer

### (a) Three-Element Boiler Feedwater Regulator Operation
A three-element feedwater regulator provides precise control over boiler drum water level, especially during fluctuating loads. It achieves this by monitoring and controlling three distinct parameters: **Drum Water Level**, **Steam Flow Rate**, and **Feedwater Flow Rate**.
**1. Elements and Principle:**
* **Drum Water Level (Primary Element):** This is the ultimate controlled variable. It is measured using a Differential Pressure (DP) transmitter. One tapping (the constant leg) provides a constant head of condensate, while the other (the variable leg) is connected to the drum at the desired water level. The differential pressure is inversely proportional to the drum level.

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