2.21.5
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NOTE: Three way valves should be used on ammonia
vessels and equipment.
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Valve shall be the [two-way] [three-way] type. Single type valves shall be
used only where indicated. 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.
2.21.6
Valve shall include a diaphragm/spring power 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 degree 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.
2.21.7
Refrigerant Access Valves
Refrigerant access valves and hose connections shall conform to ARI 720.
2.21.8
Service Gauge Fittings
Fittings shall be designed for connecting a pressure gauge with a hose
fitting. These fittings shall be provided in the suction pipe at each unit
cooler.
2.22
REFRIGERANT ACCESSORIES
2.22.1
Fans
Fan wheel shafts shall be supported by either maintenance-accessible
lubricated anti-friction block-type bearings, or permanently lubricated
ball bearings. Unit fans shall be selected to produce the cfm required at
the fan total pressure. Thermal overload protection shall be of the manual
or automatic-reset type. Fan wheels or propellers shall be constructed of
aluminum or galvanized steel. Centrifugal fan wheel housings shall be of
galvanized steel, and both centrifugal and propeller fan casings shall be
constructed of aluminum or galvanized steel. Steel elements of fans,
except fan shafts, shall be hot-dipped galvanized after fabrication or
fabricated of mill galvanized steel. Mill-galvanized steel surfaces and
edges damaged or cut during fabrication by forming, punching, drilling,
welding, or cutting shall be recoated with an approved zinc-rich compound.
Fan wheels or propellers shall be statically and dynamically balanced.
Forward curved fan wheels shall be limited to [_____] mm inches.
Direct-drive fan motors shall be of the multiple-speed variety.
Centrifugal scroll-type fans shall be provided with streamlined orifice
inlet and V-belt drive. Each drive shall be independent of any other
drive. Propeller fans shall be [direct-drive] [V-belt] drive type with
[adjustable] [fixed] pitch blades. V-belt driven fans shall be mounted on
a corrosion protected drive shaft supported by either
maintenance-accessible lubricated anti-friction block-type bearings, or
SECTION 15652A
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