where steam pressures remain constant. It can handle superheat and
water-hammer but is not recommended
for process, since it has a tendency to
air-bind and does not handle pressure
fluctuations well.
A thermodynamic trap usually fails
open. There are other conditions that
may indicate steam wastage, such as
“motor boating,” in which the disc
begins to wear and fluctuates rapidly,
allowing steam to leak through.
No matter which types of steam
traps are in use, testing them is critical
because failed traps negatively impact
the entire steam system. They can
waste valuable energy, adversely affect
production, increase maintenance costs
and create safety issues.
Why Do Steam Traps Fail?
Three general conditions can adversely
affect traps, thus leading to premature
failure:
Dirt, the leading cause of failure,
results in leaking, blowing or
plugged traps.
Pressure surges due to sudden
steam-valve openings, improper
piping or trap misapplications, or
water-hammer can all damage
the internal components of a
steam trap.
Over-sizing can cause traps to
lose their prime, experience rapid
cycling or wire-drawing. Wire-drawing can occur when condensate is not successfully eliminated
from a steam system. Little beads
of water in a steam line can eventually cut any small orifices
through which the steam normally passes. Wire-drawing will
eventually cut enough of the
GOOD STEAM TRAP
MAINTENANCE
PRACTICE INCLUDES:
Blowing down upstream trap
strainers to keep the system clean.
Draining seasonally used equip-
ment of stagnant condensate to
prevent system corrosion.
Inspecting steam trap perform-
ance at least once a year.
metal in the valve seat of a
steam trap and prevents adequate closure of the steam trap,
producing leakage in the system.
Know Your System
At start-up any steam trap will be open
for a longer period of time depending
on the volume of condensate produced
COMING IN THE
SPRING 2009 ISSUE OF
VALVE MAGAZINE
• Our Nation's Crumbling Water Infrastructure
• The Offshore Oil & Gas Industry
• Valves in Coker Services
• U.S. & International Valve Standards
• Pulp & Paper Goes Green
And much more!
For advertising information, contact Sue Partyke, ad manager, at spartyke@vma.org or 540-374-9100.
To submit products and industry news, send releases to Chris Guy, assistant editor, at cguy@vma.org,
no later than March 1.
All other editorial queries, contact Judy Tibbs, editor, at jtibbs@vma.org.
