Ability to handle dirt


Comparative physical size


Ability to handle "flash steam"


Mechanical failure (open-closed)


Continuous Intermittent Continuous"

Good Poor Fair

Good Poor Fair

Good Excellent Good

Poor Excellent Poor

No No No

Excellent NRfc Good

Excellent Poor Excellent

Excellent Poor Excellent

Poor Good Good

Fair Excellent Good

Excellent Poor Excellent

Immediate Delayed Delayed

Poor Poor Fair

Large Small Small

Poor Poor Poor

Closed Opene Closed/

"Can be intermittent on low load.

^Not recommended for low-pressure operations.

cCast iron traps not recommended.

^In welded stainless steel construction—medium.

eCan fail closed due to dirt.

/Can fail open due to wear.

return system is pressurized), the pressure drop associated with flash steam and condensate flow through the return lines, and the head of water associated with risers if the trap is located at a point below the condensate receiver. Condensate return lines are usually sized for a given capacity to maintain a velocity no greater than 5000 ft/min of the flash steam. Table 6.11 shows the expected pressure drop per 100 ft of return line which can be expected under design conditions. Referring to the table, a 60-psig system, for example, returning condensate to an unpressurized receiver (0 psig) through a 2-in. line, would have a return-line pressure drop of just under 1/2 psi/100-ft run, and the condensate capacity of the line would be about 2600 lb/hr. The pressure head produced by a vertical column of water is about 1 psi/2 ft of rise. These components can be summed to estimate the back pressure on the system, and the appropriate pressure for sizing the trap is then the difference between the upstream pressure and the back pressure.

Table 6.10 Typical Factors of Safety for Steam Traps (Condensate Flow Basis)


Factor of


0 0

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