inlet to the evaporator coil is negligible and pressure drop across the
evaporator is less than the pressure difference corresponding to 1 degrees
C (2 degrees F) 2 degrees F of saturated suction temperature at evaporator
conditions. Bulb charge shall be determined by the manufacturer for the
application and such that liquid will remain in the bulb at all operating
conditions. Gas limited liquid charged valves and other valve devices for
limiting evaporator pressure shall not be used without a distributor or
discharge tube or effective means to prevent loss of control when bulb
becomes warmer than valve body. Pilot-operated valves shall have a
characterized plug to provide required modulating control. A de-energized
solenoid valve may be used in the pilot line to close the main valve in
lieu of a solenoid valve in the main liquid line. An isolatable pressure
gauge shall be provided in the pilot line, at the main valve. Automatic
pressure reducing or constant pressure regulating expansion valves may be
used only where indicted or for constant evaporator loads.
2.5.5
Safety Relief Valves
Valve shall be the two-way type, unless indicated otherwise. Valve shall
bear the ASME code symbol. Valve capacity shall be certified by the
National Board of Boiler and Pressure Vessel Inspectors. Valve shall be of
an automatically reseating design after activation.
2.5.6
Evaporator Pressure Regulators, Direct-Acting
Valve shall include a diaphragm/spring assembly, external pressure
adjustment with seal cap, and pressure gauge port. Valve shall maintain a
constant inlet pressure by balancing inlet pressure on diaphragm against an
adjustable spring load. Pressure drop at system design load shall not
exceed the pressure difference corresponding to a 1 degrees C 2 degrees F
change in saturated refrigerant temperature at evaporator operating suction
temperature. Spring shall be selected for indicated maximum allowable
suction pressure range.
2.5.7
Refrigerant Access Valves
Refrigerant access valves and hose connections shall be in accordance with
ARI 720.
2.6
PIPING ACCESSORIES
2.6.1
Filter Driers
Driers shall conform to ARI 710. Sizes 15 mm (5/8 inch) 5/8 inch and
larger shall be the full flow, replaceable core type. Sizes 15 mm (1/2
inch) 1/2 inch and smaller shall be the sealed type. Cores shall be of
suitable desiccant that will not plug, cake, dust, channel, or break down,
and shall remove water, acid, and foreign material from the refrigerant.
Filter driers shall be constructed so that none of the desiccant will pass
into the refrigerant lines. Minimum bursting pressure shall be 10.3 MPa
(1.500 psi) 1,500 psi.
2.6.2
Sight Glass and Liquid Level Indicator
2.6.2.1
Assembly and Components
Assembly shall be pressure- and temperature-rated and constructed of
materials suitable for the service. Glass shall be borosilicate type.
Ferrous components subject to condensation shall be electro-galvanized.
SECTION 15182
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