Boiler stops due to DRUM LEVEL HIGH alarm

If your boiler has a differential pressure transmitter, it is most probably connected to the Boiler Sequencer and has 2 functions:

1. Drum Water level indication
2. High/Low Water level alarm

Its signal used by Sequencer to determine when to start and stop Feed water pump.

Over the time sludge accumulates in pipes which connect transmitter to water and steam spaces (Low (left) and High (right) pressure sides of transmitter). This leads to erratic signal sent by the transmitter to the Sequencer. As a result, Feed pump may start and stop in the wrong time and overfill the drum.

From time to time it is advised to blow Low and High pressure pipes of transmitter.

1. Close High pressure (Steam, right) side stop valve of the transmitter.
2. Open transmitter Equalizing valve (middle)
3. Close Low pressure (Water, left) side stop valve.
4. Open drain valves of Water and Steam lines (valves with red handles). Keep draining until clean water/steam comes out of drain.
5. Close drain valves.
6. Fill sealing tank on the Steam line with water. Remember to close shutoff valve and carefully release the pressure before filling water.
7. After filling, close the vent valve of sealing tank, gradually open the shutoff valve thus introducing steam into the sealing tank.
8. Open Low pressure (left) stop valve of transmitter
9. Close the Equalizing valve
10. Open High pressure (right) stop valve

Wait for reading to stabilize. If transmitter blow down procedure is not helping, transmitter should be dismantled and diaphragm cleaned as per Maker's manual.