SYSTEM PRESSURIZATION AND
REGULATOR ADJUSTMENT
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.
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.
Document 560068
040924
DH Instruments, Inc.
Tel 602.431.9100
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.
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 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 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
a
djustment 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
4765 East Beautiful Lane
Phoenix AZ 85044-5318
USA
Fax 602.431.9559
www.dhinstruments.com
