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Drain Valve
1/4” FNPT

Model Number RL12S

 

Bootstrap Compressor • Installation and Operating Instructions

Midwest Pressure Systems, Inc.

RAV

Rev. 0

MPS

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MPS

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MPS Logos

12/5/91

1/2" Square

3/4" Square

1" Square

1-1/4" Square

1-1/2" Square

2" Square

MPS

M ID WE ST

PR ESSURE
SYS T E MS

Mount the Model RL12S Bootstrap Compressor on a horizontal 
surface. Other mounting orientations are not recommended.   
The booster system vibrates while operating, so use the four 1/2” 
mounting holes, shown in the diagram to the right, to bolt it to a 
solid surface.

1

Connect your shop air line to the 1/4” FNPT air inlet filter on the 
front of the booster.  A shutoff valve can be installed upstream of 
the filter for convenient removal of the system for maintenance. 
The booster has a built-in discharge pressure regulator. Do not 
install a supply pressure regulator. Lowering the supply pressure 
reduces the efficiency of the system. The unit is permanently 
lubricated.  

Use of an inlet lubricator will void the 

warranty. The maximum inlet pressure is 150 psig.

2

Attach discharge line to the 1/2” FNPT port on the left side of 
the receiver tank.  

If the application requires a 

lubricator, make sure the lubricator is installed 
downstream of the booster.

 A filter should be installed to 

protect downstream components from seal/booster wear 
particles. 

3

The discharge pressure regulator is set by the black, snap-
lock knob mounted on the top of the unit. Pull up on the knob 
to unlock it. Adjust the knob by turning it clockwise for a 
higher discharge pressure (up to a maximum of 230 psig), or 
counterclockwise for a lower discharge pressure. Inlet 
pressure is read on the gauge closest to the inlet connection. 
The second gauge indicates discharge pressure. Supply shop 
air to the booster and it will start to operate. Set the regulator 
to attain the desired discharge pressure, and push down on 
the regulator knob until it “clicks” to lock the regulator on 
that setting. The regulator is self-relieving. When the 
discharge pressure setting on the regulator is reduced, the 
higher pressure stored in the system will vent through the 
regulator until pressure equilibrium is reached. 

If the inlet 

pressure is higher than 115 psig, it is possible to 
set the regulator so the booster exceeds the 
maximum discharge pressure of 230 psig. Do not 
operate the booster under these conditions. It is 
designed to operate continuously at a maximum 
discharge pressure of 230 psig.

5

The Bootstrap Compressor will operate as long as there is 
demand for high pressure air. When there is no demand, the 
booster will “stall” at the pressure set by the discharge regulator. 
The stalled condition consumes no energy and does not damage 
the booster. The booster will start up automatically when the 
pressure falls slightly as a result of demand for high pressure air.

7

Mounting Bolt Pattern:

 16.5” 

 10” 

Inlet port
1/4” FNPT

Discharge port
1/2” FNPT

The accumulator tank has a 1/4” ball valve to drain condensate. A 
drain line or automatic drain valve can be attached to this valve 
when needed. Close the valve before starting booster.

4

The accumulator is rated for 235 psig and includes a relief valve 
set for 235 psig. 

This relief valve was selected to prevent 

operation of the booster above its maximum 
allowable discharge pressure of 230 psig. 

8

For more precise booster control, set the discharge regulator for 
a higher pressure than required, and install a filter and secondary 
regulator on the discharge line of the accumulator. This allows 
for greater accumulator storage capacity, and minimizes pressure 
fluctuations in the system. For maximum high pressure air 
storage, Bootstrap Compressors are set to charge the 
accumulator to 230 psig, and the secondary regulator in the 
discharge line of the accumulator is set at the desired, lower 
pressure. Make sure that any downstream components are rated 
for the accumulator pressure, or are protected by a relief valve in 
case the secondary regulator fails.

6

235 psig
Pressure
Relief Valve

Midwest Pressure Systems, Inc.

850 Transport Drive, Valparaiso, IN 46383

Phone 219-462-0070

www.midwestpressuresystems.com

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