DH Instruments VACUUM PUMP DOWNSTREAM INTERCONNECT KIT FOR... User manual

Installation and Use of Vacuum Pump
Downstream Interconnect Kit
for molbloc-S®
P/N 401882
Installation Instructions
The use of a vacuum pump, connected downstream of
the molbloc-S®, increases the usable flow range of
each element. The purpose of this kit is to provide the
plumbing components required for the typical installation
of the molbloc-S system with the medium flow vacuum
pump, part number 401940 and 401883. This instruction
sheet is a guide to the recommended plumbing
interconnection between the molbloc-S test system
and the vacuum pump.
MOLBOX OVER-PRESSURE PROTECTION
Since the pressure in the test setup is directly connected
to the molbox, care must be taken to not exceed the
maximum operating pressure rating of the Reference
Pressure Transducers (RPTs) within the molbox.
The check valve included in this interconnection kit is
provided to prevent damage to the molbox and/or the
vacuum pump. In the event the pump looses power or
the user leaves the vacuum shut-off valve closed
during a calibration, this check valve will allow gas flow
to vent out of the system while keeping line pressure
below a damaging level.
The plumbing connected to the outlet of the check
valve is not included in this kit and is therefore the
responsibility of the installer. This plumbing should be
keep as short as possible and its diameter as large as
practical in order to minimize the restriction to the
venting gas flow. This will limit additional line pressure
build-up in the molbloc-S plumbing system.
molbloc-S Test Layout
Top View
1. Inlet Supply Regulator
2. Device Under Test
3. Check Valve
4. Medium-Flow Vacuum Pump
(Installed Outside of Lab Space)
5. Vacuum Shut-Off Valve
When performing a leak test of a plumbing system that contains the ISO-KF Style Vacuum Flanges, do not exceed the
maximum operating pressure of the molbox, 600 kPa (87 psia) for molbox A700K models, 200 kPa (30 psia) for molbox
A350K models.

molbloc-S and molbox are trademarks, registered and otherwise, of DH Instruments, Inc.
Viton is a registered trademarks of DuPont deNemours Company.
Document 560052 021119
DH Instruments, Inc.
4765 East Beautiful Lane
Phoenix AZ 85044-5318
USA
Tel [phone]
Fax [phone]
[e-mail]
www.dhinstruments.com
INSTALLATION OF MEDIUM VACUUM
PUMP DOWNSTREAM INTERCONNECT KIT
The above figure shows the basic interconnection
plumbing when using the Medium Flow Vacuum Pump
with the molbloc-S. This kit includes 2 conical reducers
with the ISO-KF Style Vacuum Flange ends. When
connecting a single molbloc-S to the vacuum pump,
use both the 40 mm x 25 mm, and the 25 mm x 16 mm
conical reducers. When utilizing the downstream tee
assembly (DHI P\N 401884) only the 40 mm x 25 mm
conical reducer is required.
For the sake of flexibility this interconnection kit
includes a coil of 1 1/2 in. wire reinforced PVC hose.
This hose can be cut to the precise length required in
each application. Hose barb fittings slip inside the
hose and are secured by worm drive clamps.
VACUUM SHUT-OFF VALVE
The vacuum shut-off valve is provided so that the
operator can continue to run the vacuum pump while
changing the Device Under Test (DUT) or the molbloc-S
between calibration runs. It is not recommended to
start and stop the pump more than a few times per day.
Therefore continue to run the pump with the gas ballast
valve open and the vacuum shut-off valve closed.
Power consumption is minimal when the pump is
running at its ultimate pressure.
CONNECTING, DISCONNECTING AND
MOUNTING MOLBLOC-S WITH ISO-KF
STYLE VACUUM FLANGES (MOLBLOC-S
OUTLET FITTING)
ISO-KF Style Vacuum Flange Fittings
The outlet connection system on the molbloc-S body is
the ISO-KF style vacuum flange. It utilizes an internal
centering ring, overpressure ring, and an external clamp.
The seal is effected by the uniform application of
pressure by the clamp on the 15° surface of the mating
stainless steel flanges. These mating flange surfaces
compress a Viton®O-ring that is held in place by the
centering ring. The overpressure ring keeps the O-ring
in place, and maintains a leak free connection when
the system is subjected to internal pressures above
vacuum level. This connection is reusable, rotatable,
and can operate leak free in vacuum applications up to
10-8 Torr. When an overpressure ring is used, KF25 or
smaller flange connections can operate leak free to
positive pressure beyond 600 kPa (87 psia)
Making and Breaking Procedure for ISO-KF
Style Vacuum Flange Connections
Place the centering ring (and overpressure ring if
applicable) into the groove of one of the ISO-KF
flanges to be mated.
Align the mating flange, and close the gap by hand.
Hold the flanges together while putting the clamp
around them.
Swing the clamp closed. If necessary loosen the
wing nut to allow the thrust washer and wing nut to
fall into position on top of the clamp. Fully tighten
the wing nut by hand.
To break the fitting, hold one of the plumbing
sections with your hand and loosen the wing nut
until the clamp can be separated. Remove the clamp,
centering ring, (and overpressure ring if applicable).