Provide crankcase oil heaters and controls. Piston speed for open-type
compressors shall not exceed manufacturer's recommendation or 5 m/s 1000 fpm,
whichever is less. Provide a hot-gas muffler.
2.3.2
Helical Rotary Compressors
Positive displacement, oil-injected and driven by an electric motor. Rotors
shall be solid steel, Society of Automotive Engineers Grade 1141 or 1144.
Shaft main bearings shall be either sleeve-design type with leaded bronze
or steel-backed babbit; or frictionless bearing design, ball or roller
type. Housing and covers shall be high-grade, cast-iron or aluminum
pressure castings. Lubrication system shall lubricate rotors, bearings,
shaft seal as well as rotor sealing and cooling. Provide an oil safety
cutout interlocked with the compressor starter to allow compressor to
operate only when the oil system is operational. Provide for lubrication
of bearings and shaft seals on shutdown with or without electrical power
supply.
2.3.3
Scroll Compressors
Three-dimensional, compliant, hermetically sealed design. Compressors
shall be mounted on vibration isolators. Rotating parts shall be factory
balanced. Main bearings shall be rolling-element type. Lubrication
systems shall be centrifugal pump type including oil level sight glass and
oil charging valve.
2.3.4
Controls
**************************************************************************
NOTE: Specify lowest percent of full capacity
required. Check for availability before inserting
number in blank.
**************************************************************************
**************************************************************************
NOTE: Specify required time delay for type and size
of unit after consulting current literature.
**************************************************************************
Provide a control panel fitted with a discharge pressure gage, suction
pressure gage, separate high pressure cutout with manual reset, separate
low pressure cutout, compressor operating control, and manual off-auto
switch. Provide oil pressure gage and low-oil-pressure cutout switch with
manual reset for compressors with positive displacement type oil pumps.
Provide signal lights or other visual "failed" indications for high
pressure, low pressure, and oil pressure protection devices.
Multicompressor units shall be provided with a lead/lag selector switch.
Provide a timer to prevent compressors from short cycling whenever stopped
by safety controls. Time delay shall be not less than [_____] minutes. A
pumpdown cycle of the nonrecycling start type shall be provided for
compressors 70 kW 20 tons or larger. Provide a minimum 100 mm 4 inch alarm
bell and alarm bell circuit to actuate bell in event of machine cutout on
protective devices, except when low-pressure cutout is used as an operating
control. Provide system capacity control to adjust output to a minimum of
[_____] percent of full load capacity without cycling operating compressor
and to automatically recycle system on power interruption.
SECTION 15601N
Page 26
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