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MDC supplies bellows capsules-only for variety of markets and applications. They include supplying expansion joint fabricators who weld-on their own fittings as they serve their geographical
areas quickly and efficiently.
Another example is supply of bellows made from exotic materials in critical applications for industrial customers who have the ability to reuse
expensive flanges or other types of attachments.
Bellows can be formed from most ductile materials that can be welded by the automatic T.I.G. welding process and result in a homogenous weld structure.
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It is imperative that companies specifying and purchasing bellows give thorough consideration to the selection of the bellows material. Due to the fact that media will vary from system to
system, and that most media specifications cannot accurately reflect what actually will occur during system operation, it is not appropriate for MDC to make specific recommendations
regarding bellows material.
If any doubt exists concerning proper material selection for the bellows, we recommend that a metallurgist with the appropriate basic material supplier be consulted. Available bellows
materials include:
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BELLOWS MATERIAL
T304 SS
T304L SS
T316 SS
T316L SS
T321 SS
Inconel 600
Inconel 625
Incoloy 800
Incoloy 825
Monel 400
Hastelloy C276
Titanium
Laminated(1)
Testable(2)
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(1) “Laminated” bellows are used in high pressure, high cycling (requiring flexible bellows element) and highly corrosive environment. Such bellows require a multi-ply construction.
In order to reduce cost, MDC will supply bellows with (ex.) Hastelloy C276 wetted ply and several middle and outer plies made of lesser grade materials such as stainless steels.
(2) Testable bellows provide the user with a guarantee against a catastrophic failure. They are quickly becoming a standard design in chemical and petrochemical industry, where “zero
spillage” regulations are mandatory.
Typical testable bellows consists of 2-ply bellows construction. Each bellows is designed individually to withstand system pressure and movement
requirements, making it essentially an “expansion joint within expansion joint”. As the sketch below illustrates, the tangent of the outer bellows has an opening with a welded-on coupling.
A monitoring device is attached to the coupling (such coupling can be monitored locally, on site or connected electronically to a central monitoring station). If the inner ply fails, the
cavity between plies becomes pressurized with system pressure and the information is relayed to the system operator/inspector.
Since the testable bellows provides the owner with,
essentially, another expansion joint, a replacement can wait until the next scheduled shutdown and more importantly avoid spillage, costly clean-up and fines.
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In order to properly design and fabricate bellows that will meet your need, please fill out the blank spaces on MDC DWG. 20739 and return to us as an attachment
with your Request for Quotation. Another area of MDC’s bellows supply are the various activities of the OEM market. The applications include:
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VACUUM AND HIGH VACUUM TECHNOLOGY
Flexible connectors for vacuum components.
Spindle sealing in vacuum valves.
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HIGH VOLTAGE SWITCHGEAR AND ELECTRICAL INDUSTRY
Vacuum and pressure-proof
shielding of conducting
elements against atmosphere.
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GENERAL ENGINEERING
Bellows assembly replaces
gland seal for maintenance-
free tightness of the spindle
in valves.
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MEASUREMENT AND CONTROL
In manometers and automatic
control instruments.
In thermostats.
In flow control instruments.
In high pressure valves.
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WEIGHT TECHNOLOGY
For the sealing and protection
of the electronic modules in
weighing scales.
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BELLOWS USED AS COUPLINGS
For torque transmission in
propulsion and positioning
units.
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SOLAR TECHNOLOGY
For stress-free couplings of
modules in solar panels and
solar energy plants.
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SHAFT SEALS
For the sealing of rotating
shafts and spindles (stirrers).
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VOLUME / PRESSURE
COMPENSATION
To accommodate volume /
pressure variations in
hermetically sealed vessels.
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