Section 25 • Cool Compression Control; Overview; Setup - Emerson Vilter Vission 20/20 Operation And Service Manual

Section 25 • Cool Compression Control

Overview

The cool compression compressor operation is similar
to the standard single screw compressor units, except
there is no external oil cooler to the unit. A blanket of
liquid ammonia lies on top of the oil in the oil separa-
tor. The liquid ammonia level is regulated by sensing
the liquid ammonia level with a level probe, and using
a positioning valve to vary the amount of liquid ammo-
nia being added to the separator. The cooling occurs
through the entire compression and separation process.
The Cool Compression compressor does not have an oil
pump. When the Cool Compression compressor unit is
commanded to start, the control panel fi rst insures that
the slide valves are at their minimum positions. The suc-
tion oil injection solenoid (SOI) is energized – allowing a
path for oil to fl ow into the compressor. The compressor
now starts. There is an initial pressure drop in the suc-
tion chamber of the compressor and a corresponding
increase in pressure on the discharge of the compres-
sor. This creates a pressure differential that forces the
oil and liquid ammonia mixture through the suction oil
Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 1.9
Figure 25-1. Cool Compression Control Screen
injection line into the suction chamber of the compres-
sor. This oil and liquid provides lubrication and cooling
until full pressure differential lubrication is attained. As
the differential pressure increases, the oil and liquid am-
monia is now injected into the screw during the com-
pression process and the oil injection valve is allowed to
close.

Setup

Confi guration Screen:
• To setup the Vission 20/20 panel for Cool Compression,
fi rst ensure that an analog output card is installed in
the panel, and it is selected from page 6 of the con-
fi guration screen, see Section 19. Navigate to confi g-
uration page 2, and select "R717-Cool Comp" from
the drop-down box that is labeled "Refrigerant",
see Figure 25-1. Cool Compression Control Screen.
Once selected "Cool Compression" option will ap-
pear in Oil Pump and Oil Cooling sections and "Cool
Compression" gets selected automatically. It will also
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