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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.
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.
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.
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
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.
Hold the regulator stationary, and tighten the male VCR
union 1/8 turn past finger-tight.
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.
®
gasket (P/N 102183) into the outlet
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.
Thread the two M4 socket head cap screws and M4 flat
washers through the regulator bracket and tighten them
securely into the nut plate.
Place a new VCR
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.
®
gasket (P/N 101183) inside the
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SYSTEM PRESSURIZATION AND REGULATOR ADJUSTMENT
through. All that is necessary is a small flow to allow the
regulator to be adjusted.
Adjusting back pressure: Rotate the back pressure
regulator adjustment knob clockwise in order to raise the
During system operation, be extremely careful
not to apply pressure in excess of the maximum
operating pressure of the molbox: 600 kPaa
(87 psia) for molbox1-A700K, 250 kPaa (36 psia)
for molbox1-A350K.
pressure level upstream of the regulator. Rotate the
back pressure regulator adjustment knob
counterclockwise in order to lower the pressure level
upstream of the regulator.
Locking the Back Pressure Regulator Adjustment (Optional)
Once the test system with molbloc-S and molstic-S
has been completely interconnected, the following
procedure should be used for its safe pressurization
and operation.
The pressure directly upstream of a back pressure
regulator is controlled by adjusting the position of the
control knob. Rotating the knob in the clockwise
direction raises the upstream (control) pressure.
Counterclockwise rotation, coupled with venting of the
downstream side of the regulator plumbing, lowers the
upstream pressure. molstic-S regulators are NOT
self-venting therefore the upstream pressure will not
be adjusted with rotation of the control knob unless the
downstream gas is allowed to escape.
Make final adjustments of control pressure in the
direction of increasing pressure in order to obtain the
most accurate and stable set point.
System Pressurization
Begin with system pressure vented: Make sure that
the system pressure is vented.
Set the system pressure to minimum: Rotate the
system supply regulator’s adjustment knob
counterclockwise until the spring force has been
relieved.
Turn on gas supply: Apply the supply pressure to the
pressure control regulator.
Slowly raise system supply pressure: Using the
pressure reducing regulator upstream of the DUT,
slowly raise the system pressure (by rotating the knob
clockwise) to the desired operating pressure. Provide
additional margin only if the final pressure will be within the
safe operating range of the molbox. Do not exceed the
maximum operating pressure of the molbox.
Back Pressure Regulator Adjustment
Begin with pressure at minimum: Rotate the back
pressure regulator’s adjustment knob counterclockwise
until the spring force has been relieved.
Open molstic-S flow control/shut-off valve(s): Valves
must be open to allow test gas to flow through the
system.
Open the DUT’s flow control valve: If the test system
contains a DUT that has flow control capability, it must
be opened slightly in order to allow pressure to pass
Document 560068 040924
molbloc, molbloc-S, molbox, molstic and molstic-s are trademarks, registered and otherwise, of DH Instruments, Inc.
VCR is a registered trademark of the Swagelok Company.
Once the Back Pressure Regulator has been adjusted to the
desired level of upstream pressure, the adjustment knob can
be locked down in order to prevent future adjustment if
desired.
Remove regulator knob cover: Use a small flat
screwdriver to remove the plastic cap on the top of the
regulator adjustment knob.
Remove the top jam nut: Using the properly sized
socket wrench, loosen and remove the jam nut located
on top of the adjustment knob.
Retain for later
reinstallation.
Remove the adjustment knob: Rotate the regulator
adjustment knob counterclockwise to remove it from the
regulator. Retain it for future use.
Tighten bottom jam nut: Rotate the bottom jam nut
clockwise until it gently bottoms out against the
regulator body.
Tighten top jam nut: Using a properly sized wrench,
hold the bottom jam nut in position while using the
socket wrench to tighten the top jam nut.
Retest system pressure: Vent the system pressure.
Repeat system pressurization procedure to verify the
regulator back pressure setting. Readjust if necessary.
Back Pressure Regulator Operation
During operation the back pressure can be more finely
adjusted by rotating the back pressure regulator
adjustment knob to obtain the desired pressure.
The following parts are included in the shipment:
DESCRIPTION QTY PART NO.
Regulator, back pressure 1 103526
Regulator bracket 1 123657
Gasket, 4VCR 5 102183
Union, 4VCR male 1 103231
SHC screw, #10-32 x 3/8 2 103277-Z
Split lock washer, #10 2 103021-Z
Flat washer, #10 2 103278-Z
SHC screw, M4 x 12 2 101016-Z
Flat washer, M4 2 100918-Z
Nut plate, 60 mm 1 123621
Gauge, pressure 1 103528
DH Instruments, Inc.
4765 East Beautiful Lane
Phoenix AZ 85044-5318
USA
Tel 602.431.9100
Fax 602.431.9559
dhi@dhinstruments.com
www.dhinstruments.com
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