Instruction Manual

330 Diaphragm Seal Installation
and Maintenence Manual
© 2022 Ashcroft Inc. 250 East Main Street 06614, Tel: [phone] • Fax: [phone], All specifications are subject to change without notice.
All sales subject to standard terms and conditions. www.ashcroft.com All rights reserved. 330_seal_I&M_008-10266_RevB_04-21-22
1. Introduction
A diaphragm seal is a device
that attaches to the process
side of a pressure-measuring
instrument to separate the
instrument from the process
fluid while transmitting
pressure across a flexible
membrane. The volume
enclosed by the diaphragm,
the top housing, and the
measuring element is completely
filled with a pressure transfer fluid.
A change in pressure at the process connection causes
a displacement of the filling fluid due to deflection of
the diaphragm, transferring the change in pressure to
the sensing element of the pressure instrument.
2. Safety Information
WARNING: Serious injury or equipment damage can result from
failure to properly install, maintain, or operate these compo-
nents. To assure safe operation and maintenance procedures,
read carefully and follow the instructions in this manual.
• Follow all instructions in this document to avoid exposure to
pressurized fluid
• Use proper tools and safety equipment in installing or main-
taining components
• Assure that process pressure and temperatures are prop-
erly monitored and maintained, and the process fluid is
appropriate and compatible with the wetted materials of the
diaphragm seal
• Follow all of your company’s safety procedures in the event
of a leak or diaphragm seal failure
3. Diaphragm Seal Components
Though the exact components will vary between specific
models, most diaphragm seals will share the same essential
parts.
3.1 Top Housing
The top housing of the diaphragm seal is used to connect
to the pressure measurement instrument. The fill port allows
for assemblies to be vacuum filled, then sealed with a ball
bearing in a conical seat and secured with a set screw.
3.2 Diaphragm
The diaphragm serves to separate the process fluid from
the filling fluid, and as such is a component wetted to the
process. Diaphragms can be welded or threaded into the
top housing, which in turn can be welded or clamped to a
lower housing. Changes in pressure cause the diaphragm to
deflect, displacing fill fluid and transmitting pressure to the
pressure-measuring instrument. It is important to ensure that a
diaphragm has sufficient displacement to operate a pressure-
measuring instrument across its entire span. For detailed
diaphragm seal and instrument compatibility, see Ashcroft
Product Information Page DS-PI-82, “Minimum and Maximum
Pressures for Diaphragm Seals,” found at Ashcroft.com
3.3 Fill Fluid
A filling fluid (sometimes referred to as “system fill,” “pressure
sensing fluid,” or, “hydraulic fluid”) is required to transmit
pressure from the diaphragm membrane to the pressure
sensing device. Diaphragm seal assemblies are filled via a
vacuum filling process that ensures the system contains no
air gaps. Fill fluids are normally selected based on operating
conditions; primarily temperature. Though normally not in
contact with the process media, a diaphragm failure may bring
process media in contact with the fill fluid, so compatibility
with the process media should be a consideration.
4. Specifications
4.1 330 Flush Seals
4.2 Temperature Information
4.2.1 Thermal Dissipation
Seals will dissipate thermal energy, though ambient and
process conditions will greatly affect the amount of heat
that can be lost through the seal. Accessories designed for
dissipating heat, such as siphons or capillaries, should be
used whenever dealing with elevated process temperatures.
Top Housing
Fill Port
Diaphragm
Connections: 330 flush threaded process
Process Connection Sizes: 1 NPT male
Instrument Connection Sizes: ¼ NPT female
Pressure Ratings: 330: 3000 psi
Added Instrument Tolerance: 330: ± 1% typical
Wetted Components: 330: diaphragm and threads
Non-Wetted Components: Top housing