Operating instructions

TM 11574A-OI
3-31
(d) Emergency Repair Procedures. In the event that the SMV system has a failure and
replacement components are not readily available, the system can be bypassed by
removing the valve piston. To remove the piston, do the following:
1
Perform a low side pump down (refer to Pumping the unit down paragraph 3-
10b(2)(d)).
2
Remove SMV power head by loosening the 2-1/8 inch diameter nut (Figure 3-13) to
relieve any pressure and then sliding the power head out.
3
Remove the piston by loosening the Allen screw and removing the piston and screw.
4
Install the power head assembly (without the piston) and torque to 35 to 40 foot-lbs.
5
Open all valves.
6
Start the unit.
7
Adjust the suction service valve so that the approximate temperature OR current limit
is maintained. For perishable loads, it is recommended that the adjustment be made
so that the available capacity is slightly larger than the load. The unit will cycle OFF
and ON.
8
Once repair parts become available, repair as required.
(16) Discharge Pressure Regulator Valve
(a) Checking the discharge pressure regulating valve (DPRV). The DPRV is designed to
maintain a minimal level of pressure within the compressor. Refer to Table 1-1 for valve
setting. The following procedure can be used to perform a functional check:
1
Install a high pressure gauge at the discharge service valve.
2
Install another high pressure gauge at the liquid line service valve.
3
Run unit with 0 F (-17.8 C) set point.
4
After five minutes, read both gauges and subtract the liquid line pressure from the
discharge pressure. This is the actual differential pressure.
5
Using the ambient temperature and the chart below, determine the replacement
differential pressure.