Midland Rupture Disc Device Instruction Manual

Operation
Inspection
and
Maintenance
Rupture Disc Devices
Doc. No. A-424/A-460 Rev. 1.36/18
Supersedes: Rev. 1.2 9/11

Rupture Disc
Devices
Doc. No. A-424/A-460 2 Rev. 1.36/18
CAUTION: IMPORTANT SAFEGUARDS
Midland rupture disc devices are used in connection with a variety of products, many of which
are hazardous materials and could cause serious injury or damage.
Always use extreme caution and proper equipment when involved with hazardous materials.
This device should only be handled by qualified personnel.
Read all of these Instructions carefully before proceeding.
SAVE THESE INSTRUCTIONS!
ITEM No. PART NAME
1Top
2 Base
3 Disc
4 Retainer
5 Swing Pin
6 Nut
7 Stud
8 Hinge Pin
9 Eye Bolt Pin
10 Chain
11 Cotter Pin
12 Eye Bolt
13 Wire Seal

Rupture Disc
Devices
Doc. No. A-424/A-460 3 Rev. 1.36/18
Operation
A rupture disc device (RDD) is a non-reclosing
pressure relieving device. The pressure-
containing element is a rupture disc, which when
new is carefully tested in accordance with AAR
Appendix A, paragraph A5.03. It is actuated by
a pressure buildup inside the tank, due either to
substantial heat input into the tank, or pressure
spikes generated by surging liquid in the tank. It
is advisable for all personnel to stay away from
the device, unless inspection and maintenance
on it is to be performed.
Inspection and Maintenance
WARNING: Exercise extreme caution
when inspecting the RDD and/or its
disc if there is any pressure in the tank. Even
though there may be only a nominal amount of
pressure in the tank, the disc may be weakened
or cracked. If there is a hard-plastic disc in the
RDD, it may shatter explosively. Do not stand
directly over the RDD. Be prepared with the
proper protective equipment in the event there
is an unanticipated product emission through
the RDD.
1. To inspect the rupture disc, all Midland RDDs
have a patented inspection capability. Pull
out the swing pin (part number 5).
2. Open the top (part number 1). It is hinged
on the hinge pin (part number 8).
3. Inspect the disc for any evidence of
malfunctioning. Frequently, a crack in the
disc (part number 3) or the presence of
product residue in the center opening of the
retainer (part number 4) will indicate that the
disc must be replaced.
4. If you decide to change the disc, be prepared
for product to be released through the RDD.
Wear suitable protective clothing. Stand
upwind of the RDD. Another person should
be present to go for assistance if additional
help is unexpectedly required.
5. So that you won’t be taken by surprise,
crack open an air vent valve to check to see
if there is pressure in the tank. If pressure
escapes, you know there is pressure in the
tank. If no pressure escapes from the vent
valve, there still is no assurance that there
is no pressure in the tank as the air valve
may be plugged with product. Always be
prepared for the worst conditions and take
all necessary precautions.
6. Have available a replacement disc and disc
gasket.
7. The four 1/2" heavy hex nuts require a 7/8”
open-end crescent wrench. Also, have a wire
brush and a screwdriver available.
8. Back off all four 1/2" nuts up to the cotter pins.
The cotter pins are positioned to prevent the
nuts from being taken completely off the
studs, and possibly lost.
9. The eyebolt (part number 12) is hinged to
rotate outward. Swing it forward as far as it
will go.
10. Pick up the retainer. If it is stuck, use the
screwdriver to pry it up.
11. Take out the old disc. It may be necessary
to again use the screwdriver to dislodge it.
Be careful when using the screwdriver not to
gouge into the surface the disc sits on. This
could result in a leak path around the disc.
Discard the old disc.
12. Clean out the recess in the valve base (part
number 2) where the disc was located. Use
a wire brush to dislodge solidified product.
Use a clean cloth to wipe away the debris.
Inspect the surface to see that it is free of
defects that would cause a leak around the
disc to take place.
13. For composite discs (a sandwich of three
layers of materials) use a thin PTFE gasket
into the body recess. Softer metals, like
!

Rupture Disc
Devices
Doc. No. A-424/A-460 4 Rev. 1.36/18
aluminum and lead, will serve as gaskets,
so no PTFE gasket is required.
14. Put the disc in the recess and reposition the
retainer (the 3-1/8" diameter surface faces
downward) and swing the eyebolt to the
vertical position.
15. If there is any pressure in the tank, it will try
to dislodge the disc as you tighten down on
the four nuts. Keep the disc centered in the
recess with a finger pressing lightly down
on it. Alternately tighten down on the nuts
–1 and 3, then 2 and 4 – to a torque of 30
ft-lb.
16. Since it may not be possible to get a
pressure test for leakage with the RDD
assembly mounted on the tank, close the
hinged cover and insert the swing pin.
17. If the RDD is being bench tested, and a
new disc has been installed into the vent,
it is possible to check around the disc for
leaks. In this case, bring the pressure in
the test chamber up slowly.Do not per-
mit the pressure to exceed 60% of the
disc’s rated rupture pressure, or the disc
may sustain damage by exceeding the yield
strength of the material.
18. Use soap suds around the retainer and in the
central cavity above the disc for evidence of
leakage.
19. If there is leakage between the disc and its
seat, disassemble the RDD (following steps
8 through 12) and reclean the recess in the
body. Anew disc or gasket may be required.
After reassembly, if the device still leaks,
do not send it out to have the seat refaced.
Consult Midland about the proper remedial
steps.
20. If no leaks are apparent, relieve the pressure
in the test chamber and unmount the RDD.
21. Drain whatever water may have accumulated
and wipe or blow away with an air hose any
soap suds and water remaining after the test.
22. Put an appropriate preservative or paint on
the exterior surfaces of the RDD. Store in a
dry place until ready to use.

Rupture Disc
Devices
Doc. No. A-424/A-460 5 Rev.1.3 6/18
NOTICES AND WARRANTY
Regulations
Midland Rupture Disc Devices are used in a variety of products,
many of which are hazardous materials. The acceptance and
transportation of the products are regulated by the DOT and AAR
in the U.S.A., and in Canada by the CTC and Transport Canada,
as well as other governmental bodies, particularly when used in
stationary applications. All personnel should be familiar with and
follow these regulations. Nothing in this pamphlet is intended to
conflict with or supersede these regulations.
The information in this document was gathered from
knowledgeable sources, but Midland Manufacturing Corporation
makes no representations or guarantees about its accuracy
or completeness and assumes no liability for this information.
Specifications are subject to change without notice.
Obtaining Product Drawings
Assembly drawings of Midland Rupture Disc Devices are
available at no charge, and will be mailed upon request. Address
any questions concerning valve maintenance or usage to the
Engineering Dept., Midland Manufacturing Corp.
Warranty
Midland warrants the products of its own manufacture to be free
of defects in material and workmanship, under normal use and
proper operation, for a period of one (1) year from the date of
invoice. Furnished materials and accessories purchased from
other manufacturers are warranted only by and to the extent of
those manufacturers’ warranties, if any.
MIDLAND MAKES NO WARRANTY OF ANY KIND WHATSOEVER,
EXPRESS OR IMPLIED, OTHER THAN AS SPECIFICALLY
STATED HERE MIDLAND MAKES NO WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR
PURPOSE OR USE. Midland’s obligation under this warranty is
strictly limited, at its option, to 1) repair or replacement at its factory
of a like quantity of product: 2) refunding to purchaser money paid
to Midland for its product: or 3) issuance of written authorization
for the Purchaser to repair or replace, at costs comparable to
Midland’s normal manufacturing costs those parts proven defective,
provided that Purchaser has given to Midland immediate notice upon
discovery of such defect Merchandise claimed to be defective shall
not be returned without first obtaining Midland’s written consent. The
undertaking of repair or replacement by the Purchaser, or its agents,
without Midland’s written consent, shall void Midland’s warranty
and relieve Midland of all responsibility. Under no circumstances
shall Midland be liable for any direct, incidental, consequential
or other damages of any kind in connection with the installation,
operation, maintenance, repair, inspection or other use of any
product purchased from it.
Mail to: P.O. Box 226, Skokie, IL 60076-0226
7733 Gross Point Road, Skokie, IL 60076-0226
Phone: [phone], Fax: [phone]