Pressure Relief Valves
Instructions for NGRTC
EXTERNAL-STYLE Valve
A-14378-ML
A-14308-ML
A-14228-ML
A-1403 series
A-1406 series
Installation
Operation
Doc. No. A-14378 Rev. 1, 02/16
Supersedes Rev. 0, 4/13
External-Style
Pressure Relief Valves
ITEM
QTY
PART NAME
1
1
TOP GUIDE
2
1
STEM
3
1
PLUG
4
1
BODY
5
1
OUTER SPRING
6
3
FOLLOWER
7
1
GUIDE
8
1
TOP NUT
9
1
TOP GASKET
10
1
SHAFT SEAL
11
1
ADJUSTING SCREW
12
1
SEAL RETAINER
13
1
INNER SPRING
14
1
CAP
15
1
SET SCREW
16
4
STUD
17
4
NUT
18
1
WIRE SEAL
19
1
RETAINER
20
1
SEAT “O” RING
21
1
PLUG “O” RING
22
1
FLUE “O” RING
23
1
RUPTURE DISC
24
1
FLUE
27
1
1/8” VALVE
28
1
NAMEPLATE
29
1
FLANGE GAP FILLER
31
1
PROTECTIVE CAP/CHAIN
32
1
RUPTURE DISC HOLDER – TOP
FLANGE
33
1
RUPTURE DISC HOLDER – BOTTOM
FLANGE
35
6
HEX SOCKET CAP SCREW –
MOUNTING
36
6
HEX SOCKET CAP SCREW – RUPTURE DISC HOLDER
25
26
30
34
Figure 1 - External-Style Valve Components
2
Rev. 1, 02/16
External-Style
Pressure Relief Valves
1.0 Valve Installation
CAUTION: Toxic Hazard
To avoid exposure to toxic or hazardous
materials, make sure the tank car is empty and
clean, and that the work area is free of hazardous
chemicals before removing or installing any valve.
!
WARNING: These external-style pressure relief
valves are spring loaded assemblies with a large
amount of stored potential energy in the spring. Handle with
care to avoid damage to the valve stem, which could result
in breakage and ejected piece.
! valve, DO NOT position oneself directly in front of
the spring and stem. Instead, position oneself to the side
WARNING: When assembling or disassembling the
TONGUE FLANGE SEALING SURFACE
Figure 2 - Gasket Sealing Surfaces
1.2.5 For tongue and groove mountings, examine
the sides of the groove. Because the valve tongue
away from the valve. Unexpected component failure –
valve-stem or spring breakage may cause a sudden energy the groove are peened over, make corrections to
release that can discharge component parts a short distance meet the AAR groove tolerances.
in an uncontrolled manner. Personal injury may be a result.
1.2.6 Install the new gasket. Ensure it is fully
seated. When a groove gasket is fully seated, 1/16”
of free space should remain above the gasket to
permit locating and entry of the valve tongue.
1.1 Preliminary Considerations
New valves are tested, adjusted and sealed at
Midland. If a new valve has been left in its original
packaging, is undamaged, and is not more than
six months old, it may be installed on a tank
car without retesting or recalibration. Prior to
installation, ensure that the valve remains clean
and that the gasket sealing surfaces (Fig. 2) are
not damaged.
CAUTION: Gasket Damage
Do not use a sharp tool to press the new
gasket into place or gasket damage may result.
1.2.7 Inspect the tongue of a reconditioned or
1.2 Procedure
1.2.1 Remove the old valve and then insert a soft
rubber plug into the tank opening to prevent debris
from entering the tank during cleaning of the
valve mounting groove and studs on the manway
coverplate.
its inner and outer edges to check for damage.
The tongue dimensions have diameter tolerances
of ±0.003”, thus any excess material on these
into the groove. If the tongue is peened oversize,
remove excess material to meet AAR tongue
tolerances.
1.2.2 Wire brush the threads of the mounting studs
to remove rust or scale. Nuts should run freely on
clean studs. Studs should not exhibit excessive
corrosion.
CAUTION: Tongue Damage
Do not install a valve having damaged
sealing surfaces.
1.2.3 Remove and discard all used gasket
material.
1.2.8 Remove the rubber plug (inserted in step 1)
from the cover plate.
CAUTION: Groove damage
Do not scratch the metal in the bottom of
the groove when removing the old gasket.
1.2.9 Rupture Disc Holder Installation: Install the
rupture disc holder onto the cover plate by lining-up
the holes for the 3/8” HSCS. Install and tighten 3/8”
HSCS in 1/3" torque increments in a diagonally
1.2.4 Using a lint-free cloth and appropriate
cleaning solvent, wipe clean the valve and
coverplate sealing surfaces and the mounting
stud threads.
Doc. No. A-14379
3
2/16
External-Style
Pressure Relief Valves
1.0 Valve Installation (cont.)
1.3.2 Inspect for leaks. Test all newly installed
valves under pressure to confirm that no leaks
are present.
alternating sequence to a torque specified by the
gasket specifier.
1.3 Hold the valve by the top guide/or flute (Fig.
3) and lower it gently into the mounting. Align the
body holes over the studs and lower the valve
while positioning the valve tongue in the coverplate
1
4
MIDLAND
SKOKIE, ILL
FLUE
TOP GUIDE
3
2
Figure 4 - Mounting Nut Tightening Sequence
WARNING: Valve Leakage
Improper valve tongue seating in the
flange groove, loose nuts and damaged
gaskets may result in leaks at the valve mounting
joint.
!
Figure 3 - Valve Top Guide/Flue
groove.
CAUTION: Tongue not in groove
Verify that the valve tongue has fit into the
coverplate groove. It must be so engaged before
continuing with the next step or valve damage
may result.
1.3.3 Valve Operation Notes and Precautions
1.3.1 Install the nuts and tighten them in 1/3 torque
increments in a diagonally alternating sequence
to a torque specified by the gasket specifier, as
shown in Figure 4.
CAUTION: Uneven gasket compression
Do not over tighten the nuts on one side
of the valve as this may tilt the valve and result in
uneven gasket compression.
•
Operation of the valve must conform with all
applicable TC, AAR, DOT specifications
(Parts 173.31, 174.67, etc.), Other
governmental bodies, and the operating
instructions of your company.
•
The pressure relief valves are spring loaded
and are actuated by overpressure in the railcar
tank. There are no provisions for manual
activation of the valve.
CAUTION: Needle Valve Closure
For valves equipped with rupture discs,
be sure that the needle valve is closed and the
plug is installed, if required.
4
Rev. 1, 02/16
External-Style
Pressure Relief Valves
1.0 Valve Installation (cont.)
2.1.5 Use a pipe wrench and unscrew the cap as
shown in Figure 7. Remove the cap.
CAUTION: Incorrect Setting
Never adjust the spring compression of a valve while
it is mounted on the vessel cover plate or incorrect
settings may result.
2.0 Valve Disassembly
(Disassembly is
required for inspection per para 3.0)
2.1 Procedure
CAUTION: Spring-Loaded Assembly
During valve-spring disassembly, the valve
contains springs under load. DO NOT attempt to
disassemble the valve without first reading these
instructions or injury may result. Spring pressure
must be adjusted to minimum and a bench clamp or
press used for disassembly.
Figure 6 - Valve Components
2.1.6 Remove the top gasket or bumper (item 9).
2.1.1 Remove the protective cap (Fig. 5) and cut
the seal wire (item 18) to release the cap chain.
Unscrew and remove the flue (tube) from around
the valve.
2.1.7 Loosen the top nut (item 8) one turn
counterclockwise. Loosen the adjusting screw
(item 11) until it can be easily rotated (is at
minimum adjustment limit).
2.1.2 If present, remove the plastic protector from
Figure 7 - Valve Cap Removal
Figure 5 - Flue and Protective Cap
2.1.8 With a locking bench clamp (Fig. 8), apply
pressure to the adjusting screw (item 11). While so
clamped, remove the four nuts (item 16) securing
the top guide (item 1) to the valve base.
the base or tongue of the valve.
2.1.3 If present, remove the flue o-ring (item 22).
CAUTION: Flange Damage
Handle the valve body carefully after
disassembly. Avoid allowing their
machined surfaces to contact the metal workbench
and hand tools or damage may result.
CAUTION: Tongue Damage
When clamping the valve, protect the
valve body to avoid damage.
2.1.9 Slowly release the clamp to relieve remaining
valve spring pressure and then lift the top guide
housing off the valve base.
2.1.4 Loosen the set screw (item 15) securing the
cap (item 14).
5
Rev. 1, 02/16
External-Style
Pressure Relief Valves
2.0 Valve Disassembly (cont.)
CAUTION: O-Ring Groove Damage
Remove the o-rings from the retainer using
only a non-scratching tool or scratching
and gouging of the o-ring grooves may result.
2.1.11 From the valve stem (item 2) remove the
follower (item 6), outer spring (item 5), inner spring
(item 13) and the guide (item 7).
2.1.16 Remove the two o-rings (items 20 & 21) from
the retainer using only a non-scratching tool.
2.1.10 Remove the adjusting screw (item11) and
top nut (item 8) from the top guide and from one
another.
2.1.17 Unscrew and remove the needle valve (item
2.1.12 Lift the stem (item 2) and seal retainer
(item 12) straight up and off the shaft off the plug
(item 3).
Figure 11 - Retainer, Valve Stem, O-rings and Plug
Figure 8 - Clamping for Top Guide Removal
27) from the valve base, if applicable.
2.2 Valve Reassembly
2.1.13 Remove the shaft seal (item 10) from the
seal retainer (item 12).
2.2.1 Reverse the disassembly instructions.
3.0 Valve Inspection
After disassembly per para 2.0, follow the guidelines
in this section for inspecting the condition of valve
components. In some instances a component
can be properly evaluated for damage or cracks
only with the use of specialized techniques, such
as dye penetration or magnetic particle testing,
according to a qualified procedure by certified
trained personnel. Such testing is indicated where
mandatory.
Figure 9 - Valve After Top Guide Removal
2.1.14 Lift or pry up the retainer (item 19). It will
likely lift off with the valve plug (item 3) as a single
unit.
2.1.15 Remove the plug from the retainer.
Additionally, specific inspections must be performed
during and after reassembly of the valve to ensure
proper and reliable operation.
3.1 Inspection Procedures
3.1.1 Top Guide
The top guide (Fig.12) is principally a structural
part. There should be no paint on any components
Figure 10 - Valve Stem and Seal Retainer
6
Rev. 1, 02/16
External-Style
Pressure Relief Valves
covered by the cap, or between adjacent surfaces
of the top guide and valve body. The vent area of
the valve body must be unobstructed by foreign
matter that would hinder free flow of discharging
fluid.
3.1.3 O-Ring Retainer Grooves
The grooves (Fig. 13) must be free of gouge
marks, corrosion, pits and rust. Since the O-rings
must seal against these surfaces, any irregularities
can cause the valve to leak. Clean the groove by
sanding it lightly with emery paper (400 grit). If this
does not effectively clean it, replace this part.
3.1.2 Adjusting Screw Threads
The threads of the adjusting screw (Fig. 12) should
be clean and lightly lubricated.
No paint allowed on
items inside cap
Cap
3.1.4 Valve Body and Plug:
Valve Body: The sealing surface is the crown
of the seat (Fig. 14). Clean the seat with emery
paper (400 grit) then wipe it clean with a cloth and
a suitable solvent. Run your fingernail around the
surface to detect any flaws. Repair work is limited
to cleaning and polishing (Paragraph A4.11.1 of
the Tank Car Specifications).
Adjusting
screw
Top Guide
BODY SEAT
(MUST BE FREE
OF NICKS, GOUGES
AND CORROSION.)
No paint
allowed
where
top guide
contacts
body
No paint
allowed
where seal
container
contacts
top guide
SEAT CROWN
(MUST BE FREE OF NICKS
AND CORROSION SINCE
O-RING IS IN CONTACT
WITH THIS SURFACE.)
No obstruction
Figure 14 - Valve Body Seat
Body
Valve Plug: The sealing surface is the plug seat
(Fig. 15). Clean the plug with emery paper (400
grit) then wipe it clean with a cloth and a suitable
solvent. Run your fingernail over the seat surface
to detect any flaws. Repair work is limited to
cleaning and polishing.
Figure 12 - Valve Components (Inspection)
CHECK SURFACE OF
GROOVES FOR NICKS,
GOUGES AND CORROSION
Figure 13 - Retainer O-Ring Grooves
PLUG SEAT
(MUST BE FREE OF
NICKS AND GALLING.)
Figure 15 - Plug Seat
7
Rev. 1, 02/16
External-Style
Pressure Relief Valves
indicated in Table 1 (next page), replace the spring.
!
WARNING: Machining not allowed
Machining, grinding, welding or other
alterations to the valve seat or plug seat is not
allowed per AAR M1002, paragraph A4.11.1 of
the Tank Car Specifications.
!
WARNING: Deficient Valve Travel
Coil springs that have taken a “set,”
resulting in an undersize free height, will not allow
the valve to open fully.
Table 1
MINIMUM FREE HEIGHTS FOR SPRINGS
AFTER PRESSING SOLID FOR 2 MINUTES
3.1.5 Sealing Surface (Valve Mounting)
The underside of the valve body is the surface that
seals to the mounting plate on the railcar (Figs. 16).
Machining of this surface is permitted. (Refer to
paragraph A4.11.2 of the Tank Car Specifications.
Consult Appendix E for dimensions and applicable
tolerances.) A good seating surface is necessary
to ensure there are no leaks in this area.
Rupture disc assembly
mounting surface
Rupture disc
sealing surface
Valve body mounting
surface
SPRING PART
NUMBER
WIRE SIZE
(REF) (IN)
MINIMUM FREE
HEIGHT (IN)
14-13-SS
0.19
4.82
15-225-SS
0.28
4.80
15-375-SS
0.34
4.99
3.1.7 Spring Guide
This structural part has guides on its outer edges
(Fig. 17). Move it up and down the length of the
top guide as indicated below. If it binds, look for
dents or gouged surfaces inside the top guide.
Repair the damage to allow free movement of the
spring guide.
TONGUE FLANGE SEALING SURFACE
Figure 16 - Machinable Surfaces - Tongue Flange
3.1.6 Valve Spring
This part is highly stressed. The exterior surface
must be free of pitting, cracks, and corrosion.
If any corrosion is observed on the spring, use
magnetic particle or dye penetration inspection
(performed by certified trained personnel) to
evaluate the exterior surface and ensure that it is
free of cracks and corrosion pits.
POT
EDIUG
!
WARNING: Valve Spring Failure
Defects in coil springs, such as cracks and
corrosion pits, can act as stress concentrators.
Failure to detect these defects can result in coil
spring breakage and uncontrolled valve venting.
GNIRPS
EDIUG
Test the springs by pressing them to 80% of solid
height in a hydraulic press for 2 minutes. Remove
from the press and then measure the spring free
height. If free height is less than the minimum
GNIRPS EDILS
DNA PU EDIUG
ELIHW NWOD
OT GNITATOR
ROF KCEHC
NI GNIDNIB
.EDIUG POT
Figure 17 - Spring Guide
8
Rev. 1, 02/16
External-Style
Pressure Relief Valves
3.0 Valve Inspection (cont.)
!
and become harder or softer with age
and chemical exposure. An O-ring that
fits loosely in the cap, or can only be pushed into
the O-ring retainer with difficulty, is quite likely not
the correct size. Many of Midland’s O-rings are
made on special molds to nonstandard sizes and
are obtainable only from Midland.
WARNING: Valve Sticking
If the spring guide binds in the top guide
bore, the valve may stick in the open position or be
prevented from opening. Always ensure free travel
of the spring guide before reassembling the valve.
3.1.8 Rupture Disc
Examine the disc for nicks, damage or any signs
of stretching. Replace the disc if any defects are
observed.
CAUTION: Defective Parts
If any parts appear defective, it
is recommend they be replaced, or
consult with Midland for recommended
repair techniques when applicable.
3.1.9 Rupture Disc Holder:
Look very carefully at the section of the bottom
disc flange (Fig. 18) that is designed to hold the
disc. No scratches, radial tool marks, nicks, burrs,
or corrosion can be present in this area or the disc
will fail to maintain a pressure-tight seal. If dents,
pits or gouges are observed, do not attempt to
remove them by machining. Discard the flange
and obtain a new one.
Similarly on the top disc flange (also in contact
with the rupture disc) must be completely
free of imperfections. Examine it carefully. No
remachining is permissible. Replace top flange if
defects are observed.
3.1.10 O-Rings
3/8" HSC
TOP RUPTURE DISC FLANGE
RUPTURE DISC
3.2 Special Inspection Considerations
3.2.1 Previous procedures may not cover all
conditions encountered in the field. Therefore, it
is the responsibility of the repair agency to obtain
approval from Midland for inspection, evaluation,
repair and maintenance procedures not covered
herein.
3.2.2 Facilities performing recommended dye
penetration and magnetic particle testing must carry
out such testing according to a qualified procedure
conducted by certified trained personnel.
1/4" HSCS
3.2.3 Evaluation of critical component metal
surfaces of the valves after cleaning, inspection
and specialized testing performed by agencies
other than the repair facility are the responsibility
of the repair facility.
3.2.4 Where numerical tolerances cannot be
provided, the disposition of the internal integrity and
surface quality of parts is under the jurisdiction of
the repair facility and dependent on its experience
and judgement.
BOTTOM RUPTURE
DISC FLANGE
Figure 18 - Rupture Disc and Disc Flange
These must be replaced at the time of the periodic
valve retest and when the valve is disassembled.
NOTE: It is essential to establish a periodic
retesting and preventive maintenance
program for pressure relief valves. The
DOT and AAR have set forth a retesting interval
CAUTION: O-Ring Degradation
O-rings develop micro cracks, can swell or shrink,
9
Rev. 1, 02/16
External-Style
Pressure Relief Valves
4.0 Maintenance
that should be considered the maximum length of
time between tests. If your company’s experience
indicates that a shorter interval is advisable, a
program with more frequent retesting should be
implemented.
NOTE: It is an AAR requirement (refer to
D4.04) that new O-rings be installed when
a valve is retested.
37 mm
mounting stud nuts
Flats on large valve
O-ring retainer, 3/4"
mounting stud nuts
mounting stud
5/16" Allen
3/8" HSCS (Rupture Disc
Holder)
3/16" Allen
1/4" HSCS (Rupture Disc
Holder)
Vise Grips
Lint-free cloth
Emery paper (400 grit, cut in 1" strips)
4.4 Special Guidelines and Precautions on
Pressure Testing and Adjustment CAUTION: Safety Protection
Wear appropriate safety glasses or face
shield and protective clothing when
conducting this procedure. Valve testing involves
high-velocity air and water flow that can cause
injury.
• Wear protective clothing and equipment
suitable for withstanding the materials
to which you may be exposed.
• Position yourself on the upwind side of the valve
when possible.
Determining Applicable Pressure Values
Refer to AAR publication “Regulations for Tank
Cars.” Appendix A applies specifically to valves.
This section prescribes the start-to-discharge
pressure (STD), the vapor tight pressure (VTP)
and their tolerances.
• Work with a partner who can help you in the
event of an emergency.
• Follow approved safety precautions for
hazardous or toxic materials.
4.3 Required Tools
NOTE: A “popping pressure” is not
specified. It is only necessary to ascertain
the STD pressure as pressure is increased, and
to establish the vapor-tight pressure as pressure
is being reduced. (STD is defined as a continuous
discharge in contrast to the start-to-leak pressure,
which is defined as the first bubble leak. Vapor-tight
is defined as being bubble-tight.)
Obtain the required tools and supplies before
attempting maintenance procedures.
Recommended Wrenches
1-7/16"
Screwdrivers
Wheel puller
Silicone grease
(or eqiv. lube.)
4.2 Precautions for Mounted-Valve Repair
When performing maintenance on a pressure
relief valve that is mounted on a railcar, observe
the following precautions.
METRIC
19 mm
23 mm
24 mm
27 mm
32 mm
Other Tools and Supplies
4.1 Retesting of Valves in Storage
Midland valves are factory set and sealed. If they
have been left in their original shipping containers,
are undamaged, and are not more than six months
old, they may be installed without being retested.
SAE
3/4"
7/8"
15/16"
1-1/16"
1-1/4"
Component
1/2" top guide nut
5/8" top lock nut
3/4" top lock nut
Flats on small valve
O-ring retainer, 5/8"
Test Stand and Gauge Requirements
It is recommended that the test stand have a
10
Rev. 1, 02/16
External-Style
Pressure Relief Valves
mounting equivalent to the AAR M1002 figures
E19.14 through E19.23 for the valve being tested.
The pressure gauge must meet the requirements
of D4.5 Test Gauge Standards and date tagged.
4.5.1.9 AAR Specifications state that the VTP
is 80% of the STD. Valves with good seats and
O-rings should exhibit a VTP above 80% of the
STD (usually up to 95% of the STD).
4.5 Pressure Testing and Valve Adjustment
Procedures
4.5.2 Valve Adjustment Procedure
4.5.2.1 Remove the wire seal from the valve cap
set screw. Loosen the set screw and remove the
valve cap to expose the top nut (spring adjustment
screw nut).
If your company has an approved test procedure,
follow it. If it does not, these procedures provide
essential guidelines.
4.5.1 Valve Testing Procedure
4.5.2.2 Loosen the top nut to allow rotation of the
spring adjustment screw.
4.5.1.1 Install the valve on the test fixture and
tighten down all the nuts alternately. Remove the
protective cap and discharge flue from the valve
body (Fig. 5), if required.
4.5.2.3 Loosen the spring adjustment screw two
turns (counterclockwise).
4.5.2.4 Tighten the top nut to lock the setting. Make
sure that the spring adjustment screw does not
rotate when tightening the top nut.
4.5.1.2 Fill the valve body to the top surface of
the retainer with water to allow bubble detection
at the valve seat.
4.5.2.5 Retest the valve STD and determine
how much pressure change occurred when the
adjusting screw was loosened two turns. Based
upon this calculation, re-compress the valve spring
and alter the valve adjustment for the midpoint in
the STD tolerance range.
4.5.1.3 Take a position allowing observation of the
pressure gauge and bubbling of air in the valve
body.
4.5.1.4 Increase the test air pressure slowly.
4.5.1.5 Increase the air pressure until the valve
STD is reached. The initial opening of the valve
may be slightly high and not indicative of the actual
STD because the O-ring may have been partially
stuck to the valve seat.
4.5.2.6 Retest the valve.
4.5.1.6 Reduce the air pressure until leakage
stops and then reduce pressure to less than one
half of the STD pressure. Then slowly increase
the pressure.
4.5.2.8 When the test results are acceptable,
tighten the top nut to a torque of 45 ±3 ft-lbs.
4.5.2.7 If the test results are erratic, troubleshooting is more complex. Consult your supervising engineer or a Midland representative.
4.5.1.7 Observe the STD pressure and then bleed
off the pressure slowly to observe the VTP.
4.5.2.9 Reinstall the valve cap, tighten the set
screw and install a new wire seal through the cap
setscrew hole. Reinstall the discharge flue and the
protective cap.
4.5.1.8 Repeat this procedure at least two more
times. The STD and VTP should be consistent in
all three occurrences.
4.5.2.10 If the valve does not include a rupture
disc, go to Post-test Procedures and perform
them.
11
Rev. 1, 02/16
External-Style
Pressure Relief Valves
4.0 Maintenance (cont.)
Rupture Disc Holder Procedure:
4.5.2.14 Slowly increase pressure in the test stand
to 50% of the disc’s burst pressure.
4.5.2.11 Install the rupture disc holder. Install and
tighten the 3/8" HSCS in 1/3 torque increments in
a diagonally alternating sequence to a torque a
torque specified by the gasket specifier.
!
WARNING: Disc Damage
Do not permit the pressure to exceed 50%
of the disc’s rating (or the disc may be damage or
distorted). For example, if the disc is rated at 100
psi, do not allow the pressure to exceed 50 psi.
4.5.2.12 Install the assembled combination valve
on top at the test stand and bolt it in place. Screw
the stud nuts down evenly.
4.5.2.15 Put leak solution over the bleed hole
opening or needle valve outlet and around the
circumference of the flange joint. A bubble may
form initially that is only the result of the disc
slightly deforming upward and displacing air in the
chamber above it. After two (2) minutes, if there
is no change in the size of the bubble, slowly vent
the pressure from the test stand and unmount the
valve.
4.5.2.13 If there is a needle valve (Fig. 19), pipe
plug, or indicator on the side of the valve, open the
needle valve or remove the plug or indicator. This
is necessary to equalize pressure in the chamber
above the disc.
4.5.2.16 If the bubble on the bleed hole or needle
valve continues to grow in size, a pressure leak
through the disc is indicated. Vent the pressure
from the test stand, unmount the valve and
unscrew the bolts securing the rupture disc holder
to the plate. Loosen the 1/4" HSCS holding the top
and bottom rupture disc flanges together.
CAUTION: Rupture Disc Damage
Rupture discs are made of very thin
metallic films (only .001 or .002 thick). Handle the
discs only by their edges and do not dent them.
4.5.2.17 Inspect the disc for a crack or pinhole leak
where the crown meets the flat part of the disc. If the
disc does not include a vacuum support, hold it up
to a light to detect defects. Also look at the seating
surface of the disc for creases, or small bumps
that could be leak paths. Since the disc is the most
fragile part of the assembly, imperfections in any
of the parts may be most easily seen in the disc.
Also inspect the disc flanges for any imperfection
as noted in section 3.0 valve inspection.
Figure 19 - Valve Components (Inspection)
12
Rev. 1, 02/16
External-Style
Pressure Relief Valves
4.0 Maintenance (cont.)
4.5.2.18 If there is any imperfection in the disc, it
cannot be used. Replace it. If there is no visible
cause for the leak, consult with your supervising
engineer or with a Midland representative to
determine other causes.
proper sealing on the tank-car mounting and result
in leakage of the tank contents.
4.5.2.23 Apply an appropriate preservative or paint
to the exterior of the valve. Be sure to mask the
nameplate so that it will be readable afterward.
4.5.2.19 Close the needle valve or reinstall the
plug or indicator. Place the disc on the bottom
flange and then place the top flange on top of the
rupture disc holder assembly. Tighten the 1/4"
HSCS in 1/3" torque increments in a diagonally
alternating sequence to a torque of 13ft-lbs for
the monel material bolts and for other materials
please consult Midland. After rupture disc holder
assembly is assembled together, install rupture
disc holder per 4.5.2.11.
3/8" HSC
TOP RUPTURE DISC FLANGE
RUPTURE DISC
CAUTION: Mounting Interference
DO NOT paint the sealing surfaces of the
valve that will contact the manway cover plate
surfaces or valve cocking may result.
4.5.2.24 Permanently attach a metal tag to the
valve body with repair/test date, repair facility
identification and technician I.D.
4.5.2.25 Store the valve in a clean, dry place until
ready to use.
1/4" HSCS
BOTTOM RUPTURE
DISC FLANGE
Figure 20 - Rupture Disc and Disc Flange
Post-test Procedures
4.5.2.20 After testing the valve, close the pressure
inlet valve to the test chamber, vent the pressure
in the test stand. Remove putty and drain water.
Then remove the valve from the test fixture.
4.5.2.21 Wipe or blow away any remaining soap
suds and water used in the testing.
4.5.2.22 Install a plastic protector over the valve
body tongue to prevent tongue damage.
!
WARNING: Tongue Damage
A damaged valve tongue may prevent
13
Rev. 1, 02/16
External-Style
Pressure Relief Valves
5.0 NOTICES AND WARRANTY
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.
5.1 Regulations
The Midland valves are used in contact with a
variety of products, many of which are hazardous
materials. The acceptance and transportation of
products are regulated by the DOT and AAR in
the U.S.A., and in Canada by CTC and Transport
Canada. Regulations of other governmental
bodies must be complied with for stationary and
mobile applications. All personnel should be
familiar with and follow these regulations. Nothing
in these instructions 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.
5.2 Obtaining Product Drawings
Assembly drawings of Midland pressure relief
valves 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.
5.3 Warranty
Midland warrants the products of its own
manufacture to be free of defects in material
and workmanship 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
Mail to: P.O. Box 226, Skokie, IL 60076-0226
7733 Gross Point Road, Skokie, IL 60076-0226
Phone: (847)677-0333, Fax: (847)677-0138
14
Rev. 1, 02/16
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