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Q)
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What range of pressure regulators can TFC supply?
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A)
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Our main ranges of pressure regulators are Parker
Flocon and Parker
Refrigerating Specialties. Both ranges can operate on
HCFC and HFC refrigerants, whilst the Parker R.S. range is
also suitable for R.717 (NH3, ammonia) as well. All Parker
pressure regulators use a piston moving within the valve port
to modulate the flow of refrigerant through the valve. Versatile
Parker regulators are available for all types of refrigeration
and air conditioning applications.
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Q)
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What is the application of an Evaporator Pressure Regulator
(EPR)?
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A)
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If it is important to maintain a specific pressure (temperature)
in an evaporator, a modulating inlet pressure regulator
can be installed in the suction line. The set point pressure
that the valve is adjusted to is maintained by controlling
the flow of refrigerant through the valve port. If the evaporator
pressure rises above the set point the valve will open more
and when it falls below set point the valve will start to
close. The valve can be fitted with a solenoid which when
de-energized fully closes the valve. e.g. for defrost cycles.
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Q)
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What is the application of a Crankcase Pressure Regulator
(CPR)?
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A)
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To protect some designs of compressor from high suction pressures
causing the compressor motor to overload, an outlet
pressure regulator can be installed in the suction line before
the compressor. The set point of the valve is adjusted to
the maximum pressure that the compressor can safely operate
at. When the suction pressure rises above the set point the
valve will tend to close but when the pressure falls below
the set point the valve will open.
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Q)
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What is the application of a Liquid Backup valve?
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A)
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To maintain a constant condenser head pressure by flooding
the condenser an inlet pressure regulator can be installed
in the liquid drain line from the condenser to the receiver.
The set point is maintained by the valve closing and backing
up liquid in the condenser. When the set point is reached
the valve opens and modulates the flow to maintain the condensing
pressure.
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Q)
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What is the application of a Hot Gas By-Pass valve on
an evaporator?
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A)
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If the evaporator pressure (temperature) falls below 0 C
due to lack of duty, an ice bank could build up on the coil
reducing the duty and therefore creating even more ice. This
can be prevented by the introduction of discharge gas into
the pipe between the expansion valve and distributor. The
set point of the outlet pressure regulator would be
the lowest allowable pressure. When the pressure falls below
set point the valve opens and injects hot gas into the evaporator,
as the pressure rises the valve gradually closes. This valve
should be fitted with a solenoid for electric shut off when
used on pump down systems.
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Q)
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What is the application of a Hot Gas By-Pass on a liquid
receiver for head pressure control?
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A)
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If liquid back up is used, or the receiver is located in
a cold area, there may not be enough pressure in it to force
the liquid around the system. To maintain the receiver pressure
an outlet pressure regulator can be used. A by-pass
line is taken from the discharge to the liquid receiver and
a regulator fitted in this line. When the receiver pressure
falls below set point the valve opens and injects hot gas.
As the pressure rises the valve closes.
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Q)
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What is the application of a Liquid Line Differential
valve in hot gas defrost Systems?
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A)
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Some hot gas defrost systems, for example multiple evaporators,
require the liquid in the evaporator to be returned to the
liquid line. This requires a slightly lower pressure in the
liquid line to allow the flow to take place. A differential
regulator creates this pressure drop. The regulator is often
fitted with a solenoid valve which is energized when the system
is not in defrost, opening the regulator wide to remove the
pressure drop.
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Q)
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Why do Parker pressure regulating valves offer a choice
of port size for each connection size?
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A)
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It is important that valves are selected correctly, the connection
to match the pipe size, and the port (valve seat) size to
match the refrigerant duty and required pressure drop. The
refrigerant pipe size is dependent on the duty, length of
the line and pressure drop required. Port size is calculated
on duty and pressure drop through valve, therefore it is possible
to have a liquid control valve with 5/8" port and 1.1/8"
connections. Should you require valve selections, please contact
our Engineering
Dept.
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Q)
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How are Parker regulating valves affected by PED97/23/EC?
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A)
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The Pressure Equipment Directive affects Parker pressure
regulating valves in different ways. Final implimentation
of the Directive took place on 29th May 2002. Parker have
used TUV Germany to verify their compliance, and have been
given an ID No. 0035. Details can be downloaded
as an Acrobat Reader file (last update 29.5.02).
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Q)
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Do you have any training courses covering pressure regulators?
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A)
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Yes. For further information please download
details (13K Acrobat Reader file).
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