Steam Trap Selection and Installation Best Practices

Steam traps automatically discharge condensate and non-condensable gases while retaining live steam. Correct selection prevents energy waste, water hammer, and steam system inefficiency.

Steam Trap Operating Principles

Steam traps operate on density, temperature, or kinetic differences between steam and condensate. The three major types are mechanical, thermostatic, and thermodynamic traps.

• Float and thermostatic (F&T): Mechanical float opens for condensate; thermostatic vent purges air

• Inverted bucket: Buoyancy principle; bucket closes on steam, opens on condensate

• Bimetallic thermostatic: Opens when condensate temperature drops below saturation

• Thermodynamic disc: Opens on condensate, closes on flash steam velocity

Selection Criteria

Match the trap type to application pressure, differential, condensate load, and startup air venting requirements. No single trap type suits all applications.

• High condensate load: Float and thermostatic trap handles continuous high flow

• Superheated steam: Thermodynamic disc preferred; F&T not suitable

• Steam tracing: Thermostatic bimetallic or F&T for light condensate loads

• Freeze-prone locations: Avoid F&T; bimetallic thermostatic handles freeze-thaw cycles

Sizing Steam Traps

Size traps based on maximum condensate load with a safety factor. Oversized traps short-cycle and fail prematurely; undersized traps waterlog equipment.

• Safety factor: 2x to 3x design condensate load typical

• Differential pressure: Higher differential allows smaller trap orifice

• Pressure variation: Select trap that handles full operating pressure range

• Startup load: Often 5–10x normal operation; ensure trap can discharge rapidly

Installation Guidelines

Install steam traps at low points to collect condensate. Strainers protect trap internals from pipe debris. Bypass valves allow manual operation during trap maintenance.

• Trap location: Below and downstream of condensate collection point

• Strainer: Y-strainer with 20-mesh stainless screen upstream of every trap

• Bypass valve: Normally closed; globe valve for controlled bypass when required

• Isolation valves: Both sides of trap for safe removal without system shutdown