Orifice Steam Traps - alert1090001

Facilities s Quailtiy Serrviice

Facilitie Qual ty Se v c e

Strategic Management Office

Department of Veterans Affairs

Office of Facilities Management

ORIFICE STEAM TRAPS

SEE DESIGN ALERT NO. 117 FOR UPDATED VERSION OF THIS ALERT

ISSUE:

These have been proposed to VA for use on energy-saving projects . They have been

installed on all the steam distribution systems at one (or more) VA Medical Centers as

part of an Energy Saving Performance Contract. It is recommended that this type of

steam trap not be used.

DISCUSSION:

This type of steam trap has no mechanisms to modulate and control the capacity of the

trap. The trap has only a small fixed orifice which is sized by the manufacturer, or his

representative, for a "normal" constant volume of condensate. The lack of any

mechanisms is a selling point for the trap design since, theoretically, maintenance will

be less than with other types of traps.

One problem is that there are almost no applications where there is a constant volume

of condensate. Even on a steam distribution system, the quantity will vary when the

system is warmed-up. In a warm-up situation, the amount of condensate will be much

greater than the amount of condensate from the normal radiation loss when the line is

in continuous service. Failure to promptly remove the condensate from the steam line

can result in dangerous water hammers.

A major problem with orifice traps is the potential plugging of the small orifice (or the

fine mesh strainer which precedes it) due to contaminants in the steam system. This

problem has been reported at a VAMC.

RECOMMENDATIONS:

Inverted bucket traps with thermal vent buckets should be used for steam line drip

service. Closed float-thermostatic traps should be used for heat exchangers which

have modulating steam control valves.

LINKS TO FM TECHNICAL INFORMATION LIBRARY (TIL)

See "HVAC Design Manual" at

http://www.va.gov/facmgt/standard/manuals_hvac.asp

See "Outside Steam Distribution Design Manual" at

http://www.va.gov/facmgt/standard/manuals_steam.asp

FOR ADDITIONAL INFORMATION:

Contact Jim Shoemaker at 202-565-5176 in the Consulting Support Service (183A).

4 DECEMBER 2001

FM-181A-DA-109

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