STEAM TRAPS

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STEAM TRAPS
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Trap Basics

• Whenever possible, steam traps should be located
  2 foot from, and below the discharge of the
  equipment.
• Strainers, whether built in or separate, are
  recommended with all steam traps.
• Install ball (or gate) valves before and after
  the steam trap to ease maintenance by isolating
  the trap from the rest of the system.

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Trap Basics

• Unions should be installed between the isolating
  valves and steam trap so that the trap can be
  easily removed and replaced as required.
• Blowdown valves are recommended at strainer
  outlet
• A test valve or a sight flow indicator are
  recommended to determine if system is operating
  and functioning properly

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Pipe Scale Dirt

• When new piping is installed, chunks of solder,
  fragments of metal parts, packing, and even nuts
  and bolts are often left inside.
• In older piping systems, there is a build-up of
  scale and dirt that can break free and travel
  through the steam system.
• Pipe scale and dirt can permanently damage steam
  equipment, especially steam traps. To overcome
  this
• Install a strainer prior to every steam trap
• Utilize a dirt pocket in front of the trap to
  accumulate dirt and scale.

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Steam Main Drip Leg

• Steam main drip pockets are recommended at every
  horizontal and vertical change of direction in
  piping, and in front of all equipment such as
  control valves, PRVs, or shut off valves because
  these are natural collection points.
• The distance between drain pockets should
  decrease as the steam main size increases because
  of the additional amount of energy (water hammer)
  larger mains have that could cause damage.
• A rule of thumb for spacing drip pockets is the
  higher the pressure or larger the main, the
  closer the spacing.

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Steam Main Drip Leg

• For steam main up to 6, a full size drip leg
  should be installed. Over 6, a collecting leg of
  ½ of the pipe size can be utilized, as long as it
  is not under 6
• The take off of the steam trap should be at a
  point 3 above the lower level of the drip leg,
  draining by gravity

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Back Pressure Effect

• The general rule of thumb for calculating the
  back pressure of condensate lift installations is
  1psig back pressure for each 2 foot of vertical
  lift. For low pressures, use 1psig per foot for
  lift.

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Bypass Loops

• Bypass loops are needed when the trap capacity
  can not meet the start-up requirements.
• CAUTION Bypass could be inadvertently left open,
  allowing large amounts of live steam to be lost
  when hot running load is achieved.
• Most steam trap manufactures discourage the use
  of bypass loops. By selecting a trap with high
  start-up capacity, the bypass is not needed.

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Traps in Parallel

• Parallel traps are used in critical process
  applications where the unit can not be shut down
  for servicing. One trap can be on while the other
  is serviced.
• Good alternate to the bypass loop installation
  because it eliminates the possibility of blowing
  live steam through an inadvertently open bypass
  valve.
• Negative More Expensive

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Space Heating Equipment

• In order to facilitate good drainage from the
  equipment, a vertical leg (at least 12 long)
  should be installed on the bottom of the
  equipment.
• If the unit heater has a modulating valve on the
  inlet, consideration must be given to the ?P
  across the trap so that there is always enough
  steam pressure to remove condensate.

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Space Heating Equipment

• The installation of a vacuum breaker is vital
  whenever steam is controlled to the unit heater
  with a modulating control valve.
• An air vent installed at the opposite corner from
  the inlet steam supply helps remove air from the
  remote areas of the equipment.

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Shell Tube Heat Exchangers

• Optional vacuum breaker installed to allow free
  drainage of condensate when system is off.
• The air vent is used to remove the air that may
  be introduced through the opening of the vacuum
  breaker or from the steam supply.

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Delta Element
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Delta Cycle-Start up

• At cold start up, stem is full open to allow high
  flow capacity
• Only one moving part for simple design

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Delta Cycle-Closing

• Stem starts to close as condensate temperature
  increases
• Flow will modulate as condensate is formed

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Delta Cycle-throttle

• Stem throttles shut when condensate reaches
  temperature of saturated steam
• Expansion chamber allows extra capacity before
  shut off

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Delta Cycle-Shut off

• Stem is tightly shut when steam is present
• Single, open blade design allows faster response
  to temperature changes

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The Delta Cycle
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Blowing Steam vs. Flash Steam