Warning: Disabling That Alarm Can Be Costly

Executive summary

Warning devices are an important feature of any type of equipment or system. Correct procedures must be followed to ensure that alarms and back-up systems are operating properly and not disabled or circumvented when performing maintenance or repairs. A recent claim for damage to a wood finishing company’s boiler shows what can happen when those procedures are forgotten or ignored.

The full article

Warning: Disabling That Alarm Can Be Costly

Low Water Damage

An investigation by HSB revealed damage to the sole 750 hp, hand-fired boiler. The boiler had a low water condition, signified by the telltale melting of the fusible plug. Damages included 48 of 79, 3.5-inch tubes sagging and leaking at the tube ends of the rear tube sheet. Also, seven rivets for the diagonal stays in the rear shell to tube sheet reinforcement were leaking. Repairs included rolling, beading and seal welding of the 48 tubes, and seal welding of the seven rivets.

LWCOs Fully Operational

The boiler was equipped with two low water cut outs (LWCOs). The first unit actuated the feed pump; the second actuated the alarm. Both controls and the feedwater pump were fully operational. Due to a feedwater control problem, the boiler operator found the boiler and system flooded when he came to start up the unit on the morning of the incident. When he tried to drain the water through the bottom blow-down line, the line was stopped up.

Lessons Learned

What happened next illustrates how important it is that equipment operators and maintenance workers understand the critical role of alarms and other warning and backup devices — and the results of ignoring or disabling them.
The boiler operator shut off the bottom drain and released the water through the two LWCO drains. As he opened the drain valves, the feedwater pump ran and low water alarm sounded as intended. Ignoring procedures, he silenced the pump and alarm by securing them at their respective circuit breakers. He then continued to drain the boiler as he started the fire inside the firebox. The operator forgot to close the drain valves with the alarm and pump secured — ultimately dry firing the boiler.
Disclaimer statement:

All recommendations are general guidelines and are not intended to be exhaustive or complete, nor are they designed to replace information or instructions from the manufacturer of your equipment. Contact your equipment service representative or manufacturer with specific questions.

back to top