Effectively Using Drum ­Level Instrumentation

Our own Reliance Boiler Trim Product Manager, Jim Kolbus, published an article on this exact topic in the April edition of Today's Boiler, the American Boiler Manufacturers Association's publication. The subject deserves the attention: using and maintaining the water-level instrumentation on your boiler is of vital importance for the safety of your plant personnel and the longevity of your equipment.

Why Drum Level Instrumentation Deserves Ongoing Attention

The ASME Boiler and Pressure Vessel Code has several sections that define the requirements for water-level instrumentation applied to boilers constructed to this code (see our companion article on Subsection PG-60 for the specific requirements around direct and indirect level indicators). But meeting the letter of the code at installation is only the starting point. Effectively using drum level instrumentation day-to-day is a separate discipline from simply having it installed.

What "Effective Use" Actually Means

Cross-Checking Multiple Instruments

A boiler drum typically has more than one level-indicating device — a gage glass plus one or more remote/electronic indicators. Effective use means operators actively compare these readings against each other, not just glancing at whichever instrument is most convenient. A discrepancy between a gage glass and a transmitter is a signal worth investigating, not something to dismiss in favor of the easier-to-read instrument.

Understanding Instrument Limitations

Every level indication technology has known failure modes: gage glass can fog or erode, magnetic indicators can have crushed floats from improper commissioning, DP transmitters can drift out of calibration, and water columns can accumulate sediment that restricts flow. Operators who understand these failure modes are better equipped to recognize when a reading might be unreliable rather than simply trusting the display.

Following Correct Startup Sequences

Level instrumentation is particularly vulnerable during commissioning and startup, when pressure differentials are introduced rapidly if procedures aren't followed carefully. Proper sequencing — equalizing pressure gradually rather than opening valves quickly — protects sensitive components like magnetic level indicator floats from damage.

Maintaining a Regular Blowdown Schedule

Sediment and scale accumulation degrade the accuracy and responsiveness of level instrumentation over time. A consistent blowdown schedule, adjusted for water quality, keeps instrumentation reading accurately between major maintenance intervals.

Inspecting for Hidden Degradation

Some failure modes are invisible from the outside. Glass erosion inside an armored gage, for example, often can't be detected without disassembly. Effective use includes periodic inspection practices that catch these hidden issues before they become failures.

Why This Matters Beyond Compliance

Meeting ASME code requirements ensures a boiler is legally and safely constructed with adequate instrumentation. But code compliance doesn't automatically translate into effective day-to-day operation. Plants that treat level instrumentation as "install and forget" are more exposed to the failure modes that proper operating discipline is designed to catch.

This is the distinction Jim Kolbus's article addresses: the gap between having compliant instrumentation and actually using it effectively to protect personnel and equipment.

Learn More

Clark-Reliance's boiler trim specialists, including Jim Kolbus, are available to discuss drum level instrumentation strategy, maintenance practices, and code compliance for your specific boiler application.

📧 sales@clark-reliance.com📞 +1 (440) 572-1500