How to Select the Correct Boiler Trim Products for Your Application

Sep 25, 2023
2 min read

Updated: Aug 10

Check out our latest Reliance Reliable Solutions video, where Reliance Product Manager Nate Klein goes over selecting the proper boiler trim products for your specific application.

https://www.youtube.com/watch?v=fMF2XqSvCHQ

The Core Question: What Does Your Boiler Actually Require?

Selecting boiler trim products starts with understanding what ASME Code requires for your specific boiler's operating pressure, since the requirements genuinely differ depending on where your boiler falls:

At or below 400 PSI, at least one water gauge glass in continuous service is the baseline requirement.

Above 400 PSI, you need either two water gauge glasses, one gauge glass plus two independent level transmitters, or one gauge glass with camera, fiber optic, or mirror transmission to the control area combined with a separate level transmitter.

Getting this baseline right is the starting point for any trim product selection - everything else builds from here.

Direct Reading vs. Indirect Reading Components

Once you know your minimum requirements, the next decision is how to fulfill them:

Direct Reading Devices (gauge glasses) provide the code-required visual verification that ASME recognizes as the only true direct-reading level indication.

Indirect Reading Devices (magnetic level indicators, electronic transmitters, guided wave radar) provide supplemental or redundant indication, often with the added benefit of remote or automated signal transmission.

Most properly specified boilers use a combination of both - not because one technology is simply better, but because they serve genuinely different functions within a complete, code-compliant system.

Water Columns: Optional, But Regulated When Used

Whether to use a water column to house your gauge glass and alarm components, or connect instrumentation directly to the boiler, is a design choice - water columns aren't required by ASME Code. But if you do specify one, it must meet PG-11 Standard Pressure Part requirements just like any other pressure-retaining component.

Matching Trim Products to Your Specific Application

Beyond the baseline code requirements, application-specific factors shape the right selection:

Fluid characteristics: Surging, boiling, or low-boiling-point fluids may call for large-chamber gauges rather than standard-size components
Temperature extremes: Cryogenic or high-temperature service may require specialized window materials or non-frost accessories
Access and visibility: Wide-angle viewing systems address gauges that are hard to read from an operator's normal position
Environmental exposure: Marine, offshore, or highly corrosive environments may call for specific material certifications and grades
Space constraints: Skid-mounted or tightly packed installations may require inverted mounting or compact single-chamber designs

Why Working With an Applications Engineer Matters

Boiler trim selection involves genuine trade-offs between code compliance, application demands, budget, and physical constraints - which is exactly why working directly with an applications engineer, rather than selecting components off a catalog page in isolation, tends to produce a better-fitted result. A properly selected system accounts for how all the components work together, not just whether each one individually meets a minimum spec.