Steam Trap Capacity: Use the Pressure Difference

Define the Thermal Model

Differential pressure is the inlet pressure minus the outlet backpressure on a compatible basis. Spirax Sarco’s drainage analysis connects trap capacity to this difference rather than supply pressure alone. The actual type and orifice curve remain necessary; pressure arithmetic cannot manufacture a capacity rating.

Compare a Hypothetical Case

Imagine an inlet operating at 3.0 barg. With 0.5 barg at the outlet, the difference is 2.5 bar. If the return condition rises to 2.5 barg, the difference becomes only 0.5 bar. Both cases have the same inlet value, yet a capacity check at 3 bar would represent neither of them.

Complete the Engineering Review

List inlet and return conditions over the duty envelope, including low-load pressure changes and any lift or return-line resistance. Read the selected trap’s published capacity at the resulting differential and stated condensate condition. Keep the required load and available capacity on separate lines so that a convenient line-size match does not substitute for drainage review.

For a processing-tank interface, obtain the actual utility schematic. The example does not specify a trap or operating pressure for HM equipment. If the system cannot provide the required positive driving pressure, discuss the complete drainage arrangement rather than assuming a larger nominal trap resolves it.

Does the stated capacity correspond to the inlet/outlet pressure conditions?

This blank worksheet is for your own project. It contains no H M machine trial result.

Customer Questions

Related Equipment References

Review the actual offered equipment and application separately from this educational example.

• processing-tank interface

Primary References

These references support the technical principles discussed in this guide. The worked examples and review questions are educational.

• Spirax Sarco’s drainage analysis
• processing-tank interface