Installation and Use of
1/2 in. Back Pressure Regulator Kit
P/N 402013
Instruction Sheet
This kit is used to upgrade a 1/2 in. single or dual
molstic-S platform that does not include the 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.
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 102923) inside the
female VCR swivel nut of the regulator’s outlet port (3).
Thread the included 8VCR male union (4) into the female
VCR swivel nut of the molstic-S.
Using a backup wrench hold the female swivel stationary,
and tighten the union 1/8 turn past finger-tight.
INSTALLATION OF REGULATOR
ONTO MOLSTIC-S
Place a new VCR gasket (P/N 102923) securely
against the sealing surface inside the female VCR
swivel nut at the molstic-S inlet (5).
Place the regulator with its bracket on top of the
molstic-S platform. Align the male VCR outlet fitting
with the mating female VCR swivel nut and thread the
nut onto the fitting.
Using a backup wrench hold the male VCR union
stationary and tighten the VCR swivel nut 1/8 turn
past finger-tight.
Place the flat side of the 60 mm nut plate under the
molstic-S platform (Fig. 2,1). Align it with the holes in
the platform and the regulator bracket. Hold it in place.
Figure 1. 1/2 in. molstic-S, with Back Pressure Regulator
PREPARING THE REGULATOR
FOR INSTALLATION
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 female VCR swivel
nut (5) as the molstic interface. Retain the adaptor for
use on the inlet of the regulator. The VCR gaskets
used in this connection are for one-time use and
should therefore be discarded.
Place a new VCR gasket (P/N 102923) securely against
the sealing surface inside the female VCR swivel nut of
the regulator’s inlet port (2).
Over-tightening VCR connections will damage the
sealing beads and possibly cause system
leakage. Do not re-use metallic VCR gaskets.
Install the adaptor retained from step into the inlet
port of the regulator. Using a backup wrench hold the
swivel nut stationary, and tighten the adaptor 1/8 turn
past finger-tight.
Figure 2. molstic-S Nut Plate
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.
®
gasket (P/N 102183) inside the
Install the included gauge into the port and hold in place
while tightening the VCR nut 1/8 turn part finger-tight.
SYSTEM PRESSURIZATION AND
REGULATOR ADJUSTMENT
Adjusting back pressure: Rotate the back pressure
regulator adjustment knob clockwise in order to raise the
pressure level upstream of the regulator. Rotate the back
pressure regulator adjustment knob counterclockwise in
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.
order to lower the pressure level upstream of the regulator.
Locking the Back Pressure Regulator
Adjustment (Optional)
Once the Back Pressure Regulator has been adjusted
to the desired level of upstream pressure, the
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
through. All that is necessary is a small flow to allow the
regulator to be adjusted.
molbloc, molbloc-S, molbox, molstic and molstic-s are trademarks, registered and otherwise, of DH Instruments, Inc.
Document 560069 040924
VCR is a registered trademark of the Swagelok Company.
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 103527
Regulator bracket 1 123657
Gasket, 8VCR 4 102923
Gasket, 4VCR 2 102183
Union, 8VCR male 1 103236
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
Adapter, 8VCR x 4VCRF 1 102920
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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