Steam Traps
Steam traps are an essential part of any steam system. They are
the link between good steam and condensate management, retaining
steam within the process for maximum utilization of heat, and the
release of condensate and incondensable gases at the right time.
With the help of Gestra, a leader in steam
trap technology, we not only supply steam traps, but industrial
valves, steam boiler equipment, controls and complete steam
systems for industrial plants; specializing in process equipment
for steam users. Consumers of steam all over the world have derived
considerable benefits from Gestra's "Zero Steam Loss" designs
for steam traps and steam equipment, allowing them to focus
more on energy conservation.
How Steam Traps Work
Steam is an invisible gas generated by adding heat energy to water
in a boiler. When enough energy is added to raise the temperature
of the water to the boiling point, additional energy (called the
heat of vapourization or latent heat) is added which changes that
water into steam. Steam is an extremely efficient and easily controlled
heat transfer medium. It is most often used for transporting energy
from a boiler to any number of locations in the plant where it is
used to heat air, water or process applications.
During this transportation of energy, condensate is generated in
the distribution system due to unavoidable radiation. It also forms
in heating and process equipment as a result of heat being transferred
from the steam to the substance heated. Once the steam has condensed
and lost its latent heat, the hot condensate must be removed immediately
or it will cause water hammer and other similar consequences. While
the available heat in a pound of condensate is negligible as compared
to a pound of steam, condensate is still valuable hot water and
should be returned to the boiler. This is where a steam trap comes
in.
Kinds of Steam Traps
Steam traps can be classified into three main groups:
Thermostatic - operate on the difference in temperature between
steam, the cooler condensate, and air. Includes MK
steam traps and BK bimetallic steam traps.
Mechanical - operate based on the difference in density between
steam and the condensate. These include the UNA
float and thermostatic steam traps.
Kinematic - operate based on the different flow characteristics
of steam and the condensate. This classification includes disc traps,
piston or impulse traps, and orifice traps.
What to look for in a Steam Trap
The steam trap is an automatic valve that purges or removes condensate
from a steam distribution system while preventing the loss of steam.
As an integral self actuated valve, its the job of the steam trap
to get condensate (as well as air, CO2 and other incondensable gases),
out the steam system as fast as it accumulates, allowing steam to
reach its destination in as dry a state/condition as possible. To
be efficient and economical, a steam trap has to:
1. Minimize the loss of steam.
2. Provide long lasting and dependable service by minimizing trap
testing, repair, cleaning, downtime and other associated losses.
3. Be corrosion resistance to prevent the damaging effects of acidic
or oxygen-laden condensate.
4. Ventilate air for efficient heat transfer and to prevent system
binding.
5. Remove CO2 to prevent the formation of carbonic acid. This means
that the steam trap must function at or near steam temperature since
CO2 dissolves in condensate that has cooled below steam temperature.
6. Operate against the actual back pressure buildup in the return
lines.
7. Be free of the dirt collected by the condensate as travels through
the distribution piping and on to the boiler. Even particles passing
through strainer screens are erosive and, therefore, the steam trap
must be able to function in the presence of dirt.
Steam traps delivering anything less than all these requirements
will impair the efficiency of your steam system and increase your
costs. When a steam trap does its job, your heat transfer equipment
will heat up faster, heat transfer rates should increase, fuel economy
should improve, there should be reduced labor costs per unit of
output and there should be little or no maintenance costs.
Selecting Steam Traps
Steam traps can operate anywhere from vacuum to well over a hundred
bar. To suit these varied conditions, there are many types of steam
traps, each having their own advantages and disadvantages. Experience
shows that steam traps work the best when their characteristics
are matched to that of the application. These may involve variations
in operating pressure, heat load or condensate pressure. Steam traps
may be subjected to extremes of temperature or even waterhammer.
They may need to be resistant to corrosion or dirt. Whatever the
conditions, selecting the right steam trap is essential to system
efficiency.
By definition, a steam trap must trap or hold back steam while
at the same time not restricting the passage of condensate, air,
and other incondensable gases. This means that plant performance
is a paramount consideration in steam trap selection. Plant performance
is typically lacking in the following ways:
Waterhammer: is a symptom of a problem in the steam system.
Dirt: when steam condenses to distilled water, it can contain
trace products of boiler feed treatment compound and natural minerals
found in water. In thermostatic traps this means that the balanced
pressure steam trap is preferable.
Strainers: often forgotten in an effort to reduce costs.
Steam Locking: can best be solved using a float ball steam
trap. Group Trapping: describes the use of one trap for more than
one application.
If any of these conditions persist in your plant performance, take
that into consideration when choosing steam traps.
Call us today. Tel: 905.940.0961
or by Email: info@valutechinc.com
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