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Installation and Use of  

1/4 in. Back Pressure Regulator Kit 

P/N 402075 

Instruction Sheet

 

This kit is used to upgrade a 1/4 in. single or dual 
molstic-S platform that does not include an integrated 
back pressure regulator. This upgraded configuration 
is ideal for the situation where the device under test 
(DUT) will be tested while plumbed upstream of the 
molbloc-S, and where its outlet pressure must be set 
and controlled precisely, or its differential pressure 
must be limited. 

 

Using a pair of properly sized wrenches remove the 
VCR x tube adaptor (1) which is on the inlet end of the 
molstic-S.  This will leave a VCR coupler (3) as the 
molstic interface.  Retain the adaptor for use on the inlet 
port of the regulator.  The VCR gaskets are for one-time 
use and should therefore be discarded.

 

 

Place a new VCR

®

 gasket (P/N 102183) into the inlet 

port of the regulator.

 

 

Install the adaptor retained from step   into the inlet port 
of the regulator. Hold the regulator stationary, and tighten 
the VCR x tube adapter (1) 1/8 turn past finger-tight.

 

 

  High pressure gases are potentially hazardous.  

Energy stored in these gases can be released 
unexpectedly and with extreme force. High 
pressure systems should be assembled and 
operated only by personnel who have been 
instructed in proper safety practices.

 

INSTALLATION OF REGULATOR ONTO 

MOLSTIC-S 

 

Using a pair of properly sized wrenches remove the female 
VCR coupler and filter as an assembly (3 and 4) from the 
female VCR swivel nut (5).  Discard the VCR gasket.

 

 

Place a new VCR gasket securely against the sealing 
surface inside the female VCR coupler (3) of the 
molstic-S inlet fitting. 

 

Tighten the VCR coupler and filter subassembly to the 
regulator outlet fitting 1/8 turn past finger-tight. 

 

 

Place a new VCR gasket securely against the sealing 
surface inside the female VCR swivel nut (5).

 

 

Place the regulator with its bracket on top of the molstic-S 
platform.  Align the filter assembly’s male VCR outlet 
fitting with the mating female VCR swivel nut and thread 
the nut onto the fitting.

 

 

Hold the filter assembly stationary with a backup wrench. 
Tighten the female nut 1/8 turn past finger-tight. 

 

Figure 1.

  1/4 in. molstic-S, with Back Pressure Regulator 

PREPARING THE REGULATOR FOR 

INSTALLATION 

 

Place a new VCR

®

 gasket (P/N 102183) into the outlet 

port of the regulator.

 

 

Thread the included VCR male union (2) into the 
regulator outlet port and tighten finger-tight. 

 

 

Over-tightening VCR connections will damage the 
sealing beads and possibly cause system 
leakage.  Do not re-use metallic VCR gaskets. 

Figure 2.  

molstic-S Nut Plate 

 

Place the flat side of the 60 mm nut plate (Fig 2, 1) 
under the molstic-S platform.  Align it with the holes in 
the platform and the regulator bracket.  Hold it in place.

 

 

 

Hold the regulator stationary, and tighten the male VCR 
union 1/8 turn past finger-tight.

 

 

Thread the two M4 socket head cap screws and M4 flat 
washers through the regulator bracket and tighten them 
securely into the nut plate. 

 

Attach the regulator mounting bracket to the base of the 
regulator using the two included #10-32 socket head cap 
screws, #10 flat washers, and the #10 lock washers.  The 
long side of the bracket should be perpendicular to the 
direction of flow through the regulator. 

 

Place a new VCR

®

 gasket (P/N 101183) inside the 

gauge port of the regulator. This port is marked “IN” on 
the regulator body and is perpendicular to the axis of 
flow of the regulator. Install the included gauge and hold 
in place while tightening 1/8 turn past finger-tight.

 

 

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