Pressure Relief Valves
Instructions for
EXTERNAL-STYLE
Valves
A-1400
A-1600
A-1700
A-1900
A-15000
Installation
Operation
Inspection
Maintenance
Doc. No. A-1400/A-15000
Rev. 3.0, 02/16
Supersedes Rev. 2.7, 3/05
External- Style
Pressure Relief Valves
ITEM
3
4
5
6
7
1
2
10
11
8
9
12
13
14
15
16
17
18
19
20
21
22
26
27
28
29
23
24
25
QTY
1
1
1
1
1
1
1
1
1
1
1
1
4
4
1
1
1
1
1
1
1
1
1
1
1
4
1
1
1
PART NAME
TOP GUIDE
STEM
PLUG
BODY
OUTER SPRING
FOLLOWER
GUIDE
TOP NUT
TOP GASKET
SHAFT SEAL
ADJUSTING SCREW
SEAL RETAINER
INNER SPRING
CAP
SET SCREW
STUD
NUT
WIRE SEAL
RETAINER
SEAT "O" RING
PLUG "O" RING
FLUE "O" RING
RUPTURE DISC
FLUE (NOT SHOWN)
RUP. DISC FLG BOLTS
RUP. DISC FLANGE
1/8" VALVE
NAMEPLATE
UPPER FILLER
11
8
9
5
16
25
28
19
22
4
7
17
3
Doc. No. A-1400/A-15000
Figure 1 - External-Style Valve Components
2
Rev. 3.0, 02/16
2
1
13
10
12
21
20
27
23
29
26
14
18
15
6
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.
!
valves are spring loaded assemblies with a large with care to avoid damage to the valve stem, which could result in breakage and ejected piece parts.
!
the valve, DO NOT position oneself directly in front of the spring and stem. Instead, position oneself to the side away from the valve. Unexpected component failure – valve-stem or spring breakage may cause a sudden energy release that can discharge component parts a short distance in an uncontrolled manner.
Personal injury may be a result.
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.
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.
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.
1.2.3 Remove and discard all used gasket material.
!
CAUTION: Groove damage
Do not scratch the metal in the bottom of the groove when removing the old gasket.
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.
D o c .
N o .
A 1 4 0 0 / A 1 5 0 0 0
External-Style
Pressure Relief Valves
FLAT-FACE MOUNTING
FLAT-FACE FLANGE
SEALING SURFACE
TONGUE MOUNTING
3
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 fits tightly into the groove, any peening-over of the edges of the groove may make it difficult to properly fit the valve tongue into the groove. If the sides of the groove are peened over, make corrections to meet the AAR groove tolerances.
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.
!
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 retested
R e v .
2 .
7 3 / 0 5
1.0 Valve Installation (cont.)
valve by running your fingernail around its inner and outer edges to check for damage. The tongue dimensions have diameter tolerances of ±0.003", thus any excess material on these diameters will make it difficult to fit the tongue into the groove. If the tongue is peened oversize, remove excess material to meet AAR tongue tolerances.
!
CAUTION: Tongue Damage
Do not install a valve having damaged sealing surfaces.
1.2.8 Remove the rubber plug (inserted in step 1) from the cover plate.
1.2.9 Hold the valve by the top guide (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 groove.
!
CAUTION: Tongue not in groove
Verify that the valve tongue has fit into the
External- Style
Pressure Relief Valves coverplate groove. It must be so engaged before continuing with the next step or valve damage may result.
1.2.10 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
1
MIDLAND
SKOKIE, ILL
4
Figure 3 - Valve Top Guide
Doc. No. A-1400/A-15000
TOP GUIDE
3 2
Figure 4 - Mounting Nut Tightening Sequence the valve as this may tilt the valve and result in uneven gasket compression.
1.2.11 Inspect for leaks. Test all newly installed valves under pressure to confirm that no leaks are present.
!
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.
4
Rev. 3.0, 02/16
External-Style
Pressure Relief Valves
1.0 Valve Installation (cont.)
1.3 Valve Operation Notes and Precautions
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.
!
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.
2.1.1 Remove the protective cap (orange) and cut the seal wire (item 18) to release the cap chain.
Unscrew and remove the flue (tube) from around
the valve.
15
16
17
18
19
20
21
22
10
11
12
13
14
26
27
28
29
23
24
25
3
4
5
6
7
8
9
ITEM
1
2
QTY
1
4
1
1
4
1
1
1
1
1
1
1
1
1
1
1
4
1
1
1
1
1
1
1
1
1
1
1
1
PART NAME
TOP GUIDE
STEM
PLUG
BODY
OUTER SPRING
FOLLOWER
GUIDE
TOP NUT
TOP GASKET
SHAFT SEAL
ADJUSTING SCREW
SEAL RETAINER
INNER SPRING
CAP
SET SCREW
STUD
NUT
WIRE SEAL
RETAINER
SEAT "O" RING
PLUG "O" RING
FLUE "O" RING
RUPTURE DISC
FLUE (NOT SHOWN)
RUP. DISC FLG BOLTS
RUP. DISC FLANGE
1/8" VALVE
NAMEPLATE
UPPER FILLER
11
19
22
8
9
16
3
4
5
7
17
25
28
Figure 6 - Valve Components
23
29
26
2.1.2 If present, remove the plastic protector from the base or tongue of the valve.
2.1.3 If present, remove the flue o-ring (item 22).
2.1.4 Remove the four rupture disc flange bolts
(item 25) from the valve base. Separate the disc flange from the valve base and remove the rupture disc
(item 23) and upper filler gasket (item 29).
!
CAUTION: Flange Damage
Handle the valve body and rupture disc flange carefully after disassembly. Avoid allowing their machined surfaces to contact the metal workbench and hand tools or damage may result.
2.1.5 Loosen the set screw (item 15) securing the cap (item 14).
2.1.6 Use a pipe wrench and unscrew the cap as
14
18
15
6
2
1
13
10
12
21
20
27
Figure 5 - Flue and Protective Cap
Doc. No. A-1400/A-15000 5
Figure 7 - Valve Cap Removal
Rev. 3.0, 02/16
External- Style
Pressure Relief Valves
2.0 Valve Disassembly (cont.)
shown in Figure 7. Remove the cap.
2.1.7 Remove the top gasket or bumper (item 9).
2.1.8 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).
2.1.9 With a locking bench clamp (Fig. 8), apply pressure to the adjusting screw (item 11). While so clamped, remove the four nuts (item 17) securing the top guide (item 1) to the valve base.
Figure 10 - Valve Stem and Seal Retainer
(item 13) and the guide (item 7).
2.1.13 Lift the stem (item 2) and seal retainer (item
12) straight up and off the shaft off the plug (item 3).
2.1.14 Remove the shaft seal (item 10) from the seal retainer (item 12).
2.1.15 Lift or pry up the retainer (item 19). It will likely lift off with the valve plug (item 3) as a single unit.
Figure 8 - Clamping for Top Guide Removal
!
CAUTION: Rupture Disc Seat Damage
When clamping the valve, support the base only near the edges to prevent damage to the rupture disc seat on the underside of the valve.
2.1.10 Slowly release the clamp to relieve remaining valve spring pressure and then lift the top guide housing off the valve base.
Figure 11 - Retainer, Valve Stem, O-rings and Plug
2.1.16 Remove the plug from the retainer.
!
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.
2.1.17 Remove the two o-rings (items 20 & 21) from the retainer using only a non-scratching tool.
2.1.18 Unscrew and remove the needle valve (item
27) from the valve base, if applicable.
Figure 9 - Valve After Top Guide Removal
2.1.11 Remove the adjusting screw (item11) and top nut (item 8) from the top guide and from one another.
2.1.12 From the valve stem (item 2) remove the follower (item 6), outer spring (item 5), inner spring
Doc. No. A-1400/A-15000 6
2.2 Valve Reassembly
2.2.1
Reverse the disassembly instructions.
Rev. 3.0, 02/16
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.
Additionally, specific inspections must be performed during and after reassembly of the valve to ensure
NO PAINT
ALLOWED
ON ITEMS
INSIDE CAP
CAP
ADJUSTING
SCREW
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.
3.1.2 Adjusting Screw Threads
The threads of the adjusting screw (Fig. 12) should be clean and lightly lubricated.
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.
TOP GUIDE
NO PAINT
ALLOWED
WHERE
TOP GUIDE
CONTACTS
BODY
BODY
NO PAINT
ALLOWED
WHERE SEAL
RETAINER
CONTACTS
TOP GUIDE
NO
OBSTRUCTIONS
CHECK SURFACE OF
GROOVES FOR NICKS,
GOUGES AND CORROSION
Figure 13 - Retainer O-Ring Grooves
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
BODY SEAT
(MUST BE FREE
OF NICKS, GOUGES
AND CORROSION.)
SEAT CROWN
(MUST BE FREE OF NICKS
AND CORROSION SINCE
O-RING IS IN CONTACT
WITH THIS SURFACE.)
Figure 12 - Valve Components (Inspection) 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
Doc. No. A-1400/A-15000 7
Figure 14 - Valve Body Seat
Rev. 3.0, 02/16
External- Style
Pressure Relief Valves
3.0 Valve Inspection (cont.)
and polishing (Paragraph A4.11.1 of the Tank Car
Specifications).
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.
TONGUE MOUNTING
PLUG SEAT
(MUST BE FREE OF
NICKS AND GALLING.)
Figure 15 - Plug Seat
!
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.
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 and 17). Machining of this surface is permitted. (Refer
FLAT-FACE MOUNTING
FLAT-FACE FLANGE SEALING SURFACE (MACHINABLE PER A4.11.2)
Figure 16 - Machinable Surfaces - Flat-face Flange
Doc. No. A-1400/A-15000 8
FLANGE SEALING SURFACE (MACHINABLE PER A4.11.2)
Figure 17 - Machinable Surfaces - Tongue Flange 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.
i NOTE: Some valves do not include a tongue flange. On valves with a flat-face mounting flange, refer to A4.11.2 of the Tank
Car Specification for machining specifications.
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.
!
WARNING: Valve Spring Failure
Defects in coil springs, such as cracks and corrosion pits, can act as stress concen-trators.
Failure to detect these defects can result in coil spring breakage and uncontrolled valve venting.
Test the springs by pressing them solid 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 indicated in Table 1 (next page), replace the spring.
Rev. 3.0, 02/16
External- Style
Pressure Relief Valves
3.0 Valve Inspection (cont.)
Table 1
MINIMUM FREE HEIGHTS FOR SPRINGS
AFTER PRESSING SOLID FOR 2 MINUTES
SPRING
PART
NUMBER
14-13-SS
15-75-MO
15-165-SS
15-0301-SS
15-150-MO
15-225-SS
15-300-SS
15-0376-SS
15-0451-SS
15-375-SS
15-0225-SS
15-450-SS
15-0300-SS
19-132-AS
16-13-SS
15-0375-SS
15-0450-SS
19-13-AS
36-5-AS
36-5-SS
19-255-AS
19-5-AS
WIRE SIZE
(REF)
(IN)
0.19
0.23
0.26
0.28
0.28
0.28
0.31
0.33
0.34
0.34
0.38
0.38
0.44
0.44
0.47
0.47
0.50
0.52
0.63
0.63
0.65
0.69
MINIMUM
FREE HEIGHT
(IN)
4.82
3.98
5.15
8.97
4.09
4.80
4.88
7.83
8.69
4.99
7.16
5.15
8.30
15.32
10.25
7.93
8.89
13.57
8.12
9.18
14.47
14.23
Doc. No. A-1400/A-15000
!
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.
3.1.7 Spring Guide
This structural part has guides on its outer edges
(Fig. 18). 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.
TOP
GUIDE
SPRING
GUIDE
SLIDE SPRING
GUIDE UP AND
DOWN WHILE
ROTATING TO
CHECK FOR
BINDING IN
TOP GUIDE.
Figure 18 - Spring Guide
!
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.
9
3.1.8 Rupture Disc
Rev. 3.0, 02/16
3.0 Valve Inspection (cont.)
Some external-style valves include a rupture disc
(Fig. 19) beneath the valve assembly. Examine the disc for nicks, damage or any signs of stretching.
Replace the disc if any defects are observed.
3.1.9 Rupture Disc Flange
External- Style
Pressure Relief Valves
These must be replaced at the time of the periodic valve retest and when the valve is disassembled.
!
CAUTION: O-Ring Degradation
O-rings develop micro cracks, can swell or shrink, 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.
!
CAUTION: Defective Parts
If any parts appear defective, it is recommend they be replaced, or consult with Midland for recommended repair techniques when applicable.
RUPTURE
DISC
RUPTURE
DISC FLANGE
Figure 19 - Rupture Disc and Disc Flange
Look very carefully at the section of the disc flange
(Fig. 19) that is contoured to hold the disc. No scratches, radial tool marks, nicks, burrs, or corrosion can be present in the groove 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 the tongue on the underside of the valve body flange (also in contact with the rupture disc) must be completely free of imperfections. Examine it carefully. No remachining is permissible. Replace the valve body if defects are observed.
3.1.10 O-Rings
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.
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 W here 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.
Doc. No. A-1400/A-15000 10 Rev. 3.0, 02/16
External- Style
Pressure Relief Valves
4.0 Maintenance
i
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 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.
i
NOTE: It is an AAR requirement (refer to
D4.04) that new O-rings be installed when a valve is retested.
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.
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.
z
Wear protective clothing and equipment suitable for withstanding the materials to which you may be exposed.
z
Position yourself on the upwind side of the valve when possible.
z
Work with a partner who can help you in the event of an emergency.
z
Follow approved safety precautions for hazardous or toxic materials.
Doc. No. A-1400/A-15000
4.3 Required Tools
Obtain the required tools and supplies before attempting maintenance procedures.
Recommended Wrenches
SAE
3/4"
7/8"
15/16"
1-1/16"
1-1/4"
1-7/16"
METRIC
19 mm
23 mm
24 mm
27 mm
32 mm
37 mm
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" mounting stud nuts
Flats on large valve
O-ring retainer, 3/4" mounting stud nuts
7/8" mounting stud
11
Other Tools and Supplies
Screwdrivers
Wheel puller
Silicone grease
(or eqiv. lube.)
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.
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.
i NOTE: A “popping pressure” is not specified. It is only necessary to ascertain the STD pressure as pressure is increased, and to
Rev. 3.0, 02/16
External- Style
Pressure Relief Valves
4.0 Maintenance (cont.)
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 the pressure at which no further fluid flow is detected. Midland recommends that no bubbles be observed for 2 minutes at vapor-tight.)
Test Stand and Gauge Requirements
The test stand must have a 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 Pressure Testing and Valve Adjustment
Procedures
If your company has an approved test procedure, follow it. If it does not, these procedures provide essential guidelines.
Form putty into elevated dam.
Figure 20 - Blocking Water Drainage With Putty slightly high and not indicative of the actual STD because the O-ring may have been partially stuck to the valve seat.
4.5.1.7 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.
4.5.1 Valve Testing Procedure
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.
4.5.1.8 Observe the STD pressure and then bleed off the pressure slowly to observe the VTP.
4.5.1.9 Repeat this procedure at least two more times. The STD and VTP should be consistent in all three occurrences.
4.5.1.2 Create a dam at the side port or plug drain holes of the valve body with putty (Fig. 20), or a similar material.
4.5.1.3 Fill the valve body to the top surface of the retainer with water to allow bubble detection at the valve seat.
4.5.1.10 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).
4.5.2 Valve Adjustment Procedure
4.5.1.4 Take a position allowing observation of the pressure gauge and bubbling of air in the valve body.
4.5.1.5 Increase the test air pressure slowly.
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).
4.5.1.6 Increase the air pressure until the valve STD is reached. The initial opening of the valve may be
Doc. No. A-1400/A-15000 12
4.5.2.2 Loosen the top nut to allow rotation of the
Rev. 3.0, 02/16
External- Style
Pressure Relief Valves
4.0 Maintenance (cont.)
spring adjustment screw.
4.5.2 Valve Adjustment Procedure (cont.)
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.
4.5.2.5 Retest the valve STD and determine how much pressure change occurred when the adjusting screw was loosened two turns. Based upon this
PROTECTIVE
CAP
ADJUSTMENT
SCREW calculation, re-compress the valve spring and alter the valve adjustment for the midpoint in the STD tolerance range.
4.5.2.6 Retest the valve.
4.5.2.7 If the test results are erratic, trouble-shooting is more complex. Consult your super-vising engineer or a Midland representative.
4.5.2.8 When the test results are acceptable, tighten the top nut to a torque of 45 ±3 ft-lbs.
4.5.2.9 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.
4.5.2.10 If the valve does not include a rupture disc, go to Post-test Procedures and perform them.
VALVE
CAP
TOP NUT
Doc. No. A-1400/A-15000
WIRE
SEAL
SETSCREW
DISCHARGE
FLUE
(UNSCREW
COUNTER-
CLOCKWISE)
NEEDLE
VALVE
(OPEN
COUNTER-
CLOCKWISE)
RUPTURE
DISC
RUPTURE
DISC FLANGE
Figure 21 - Valve Components
13
Combination Valve Rupture Disc Procedure
4.5.2.11 If the valve is a combination device (includes a rupture disc - Fig. 21), reinstall the rupture disc making sure that the disc and mounting flange are in serviceable condition as specified in 3.0 Valve
Inspection, subsection 3.1.8) Valve Disc and subsection 3.1.9) Rupture Disc Flange. Install the rupture disc flange bolts.
!
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.
4.5.2.12 Install the assembled combination valve on the test stand and bolt it in place. Screw the stud nuts down evenly.
!
WARNING: Flange Leakage
Cocking the flanges will cause the bodyto-disc-flange joint to leak.
Rev. 3.0, 02/16
External- Style
Pressure Relief Valves
4.0 Maintenance (cont.)
4.5.2 Valve Adjustment Procedure (cont.)
4.5.2.13 If there is a needle valve (Fig. 21), 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.
4.5.2.14 Slowly increase pressure in the test stand to 50% of the disc’s burst pressure.
!
WARNING: Disc Damage
Do not permit the pressure to exceed 60% 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
60 psi.
4.5.2.15 Put soap suds 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 soap bubble, slowly vent the pressure from the test stand and unmount the valve.
4.5.2.16 If the soap 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 flange.
4.5.2.17 Inspect the disc crown 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 and
Teflon liner, hold it up to a light to detect defects. Also look at the radial 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 flange and mating surface on the underside of the valve body
Doc. No. A-1400/A-15000 14 for any imperfection.
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.
4.5.2.19 Close the needle valve or reinstall the plug or indicator.
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 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.
!
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.
Rev. 3.0, 02/16
5.0 NOTICES AND WARRANTY
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
Doc. No. A-1400/A-15000 15
External- Style
Pressure Relief Valves
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: (847)677-0333, Fax: (847)677-0138
Rev. 3.0, 02/16
