Midland A-23075 High-FlowX External-Style Pressure Relief Valve Installation Operating Manual
Below you will find brief information for Pressure Relief Valve A-23075 High-FlowX External-Style. The A-23075 Series External-Style Pressure Relief Valves are high-flow, corrosion-resistant devices designed for use with crude-oil and ethanol tank cars requiring high-flow pressure relief. The valves are tested and sealed at Midland and are easy to maintain with their replaceable seal design.
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Part Number: A-23075, Rev. 0
Issue Date: September 1, 2015
Supersedes: N/A
High-FlowX
™
External-Style Pressure
Relief Valve
A-23075 Series
7733 Gross Point Road • Skokie, IL 60077 • (847) 677-0333 • Fax (847) 677-0138 • www.midlandmfg.com
P/N: A-23075, Rev. 0
Page 2 of 45
Table of Contents
1.0
Introduction .......................................................................................................................... 3
1.1
Technical Specifications .................................................................................................. 3
1.2
Component Identification and Parts Listing ..................................................................... 7
1.3
Pre-Installation Regulations/Requirements ................................................................... 11
2.0
Valve Installation ............................................................................................................... 13
2.1
Preliminary Considerations ............................................................................................ 13
2.2
Procedure ...................................................................................................................... 13
2.3
Leak Inspection ............................................................................................................. 15
2.4
Valve Operation Notes and Precautions ....................................................................... 15
3.0
Valve Disassembly and Inspection .................................................................................... 16
3.1
Valve-Disassembly Procedure ...................................................................................... 16
3.2
Valve-Plug Disassembly ................................................................................................ 21
4.0
Detailed Valve Inspection .................................................................................................. 22
4.1
Inspection Procedure ..................................................................................................... 23
5.0
Detailed Valve Assembly ................................................................................................... 29
5.1
Valve-Plug Assembly (If Required) ................................................................................ 30
5.2
Valve-Assembly Procedure ........................................................................................... 31
6.0
Special Guidelines and Precautions on Pressure-Testing and Adjustment ...................... 35
7.0
Valve-Pressure Testing Procedure .................................................................................... 36
7.1
Initial Setup .................................................................................................................... 36
7.2
Testing ........................................................................................................................... 38
8.0
Valve-Adjustment Procedure ............................................................................................. 39
8.1
Valve-Setting Adjustment .............................................................................................. 39
8.2
Post-Test Procedure ...................................................................................................... 40
9.0
Maintenance ...................................................................................................................... 41
9.1
Prior to Maintenance Tasks Performed ......................................................................... 41
9.2
Leak Repair on a Mounted Valve .................................................................................. 41
10.0
Warranty .......................................................................................................................... 44
P/N: A-23075, Rev. 0
Page 3 of 45
1.0 Introduction
The A-23075 Series External-Style Pressure Relief Valves are high-flow, corrosion-resistant devices designed for use with crude-oil and ethanol tank cars requiring high-flow pressure relief.
•
High-quality steel construction
•
Triple seals on all potential leak paths to atmosphere
•
Easy-to-replace seal design for ease of maintenance
1.1
Technical Specifications
Valve Model Net Flow Area (in
2
)
20
Flow Rate (scfm)
29,550
Valve Pressure Setting
(psig)
75 A-23075
Table 1-1 Valve Specifications
Figure 1-1 A-23075 Valve Dimensions – Section B-B
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Figure 1-2 A-23075 Valve Dimensions – Side View
Figure 1-3 A-23075 Valve Dimensions – Bottom View
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Figure 1-4 A-23075-F Valve Dimensions – Section B-B
Figure 1-5 A-23075-F Valve Dimensions – Side View
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Figure 1-6 A-23075-F Valve Dimensions – Bottom View
1.2
Component Identification and Parts Listing
12
13
14
15
16A
8
9
10
11
5
6
3
4
7
Item
1
2
20
21
22
23
16B
17
18
19
24
25
2
2
2
1
1
2
2
2
2
4
1
4
1
1
2
1
1
1
1
1
1
1
1
4
Qty. Part Name
1
1
Housing Assembly
Valve-Plug Assembly
Retainer
Valve Body
Outer Spring
Follower
Tube
Screw Locknut
Nylon-Insert Locknut
O-Ring (2-431)
O-Ring (2-351)
Name Plate
Inner Spring
Adjustment Screw
Split Lockwasher
Threaded Rod with Hole
Threaded Rod
Nut
Eyebolt
Drive Screw
Wire-Seal Kit
Cap
Hex-Head Cap Screw
Hex-Head Cap Screw
Gasket
Locknut
Figure 1-7 A-23075 Component Callouts - Section B-B
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Figure 1-8 A-23075 Component Callouts – Side View
P/N: A-23075, Rev. 0
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Figure 1-9 A-23075 Component Callouts – Bottom View
22
23
24
25
17
18
19
20
21
11
12
13
14
15
16A
16B
7
8
9
10
4
5
6
Item
1
2
3
1
2
2
2
2
2
4
2
1
2
2
1
4
1
1
1
1
1
4
1
1
1
1
Qty. Part Name
1
1
1
Housing Assembly
Valve-Plug Assembly
Retainer
Valve Body
Outer Spring
Follower
Tube
Screw Locknut
Nylon-Insert Locknut
O-Ring (2-431)
O-Ring (2-351)
Name Plate
Inner Spring
Adjustment Screw
Split Lockwasher
Threaded Rod with Hole
Threaded Rod
Nut
Eyebolt
Drive Screw
Wire-Seal Kit
Cap
Hex-Head Cap Screw
Hex-Head Cap Screw
Gasket
Locknut
Figure 1-10 A-23075-F Component Callouts - Section B-B
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Figure 1-11 A-23075-F Component Callouts – Side View
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Figure 1-12 A-23075-F Component Callouts – Bottom View
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Page 11 of 45
1.3
Pre-Installation Regulations/Requirements
1.3.1 Regulations
Midland external-style 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. However, 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.
1.3.2 Safety Precautions
Midland valves are used in connection with a variety of products. Many are hazardous materials and could cause serious injury or damage if mishandled.
This valve should only be installed, operated and maintained by qualified personnel.
Read all of these instructions carefully before proceeding.
CAUTION
CAUTION: Toxic Hazard. Always use extreme caution and proper equipment when involved with hazardous materials. To avoid exposure to toxic or hazardous materials, make sure the tank car is empty and clean., The work area must also be free of hazardous chemicals before removing or installing any valve.
WARNING
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. Mishandling could result in breakage and ejected piece parts.
WARNING
WARNING: When assembling or disassembling 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 discharging component parts a short distance in an uncontrolled manner. Personal injury may be a result.
P/N: A-23075, Rev. 0
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1.3.3
Precautions for Mounted-Valve Repair
When performing maintenance on a pressure relief valve that is mounted on a railcar, observe the following precautions:
•
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
•
Work in a well-ventilated area
•
Work with a partner who can help you in the event of an emergency
•
Follow approved safety precautions for hazardous or toxic materials
•
Obtain MSDS sheets for all the commodities used with the associated valve
1.3.4 Required Tools
Before arriving at the installation site, obtain the required tools and supplies prior to performing the procedures indicated in this guide.
Recommended Wrenches
SAE
1-1/16"
Component
5/8 – 11 UNC-2B, Hex Nut
Torque (ft-lb)
130
Item #
17
1-7/16"
1-7/8"
3/4”
1 – 8 UNC-2B
1½ – 2 UNF-2B
Flats on Stem
7/16”
9/16”
1/4 – 2b UNC-2A, Cap Screws
3/8 – 1b UNC-2B, Locknut
Table 1-2 Required Tools with Torque Specifications
Other Tools and Supplies
Screwdrivers Lint-free Cloth
200
65
9
8
2
22, 23
25
Wire Brush
Silicone Grease (or equivalent lubrication)
Table 1-3 Additional Recommended Tools and Supplies
Emery Paper (400-grit, cut in 1" strips)
Torque Wrenches (0 – 300 ft-lb)
P/N: A-23075, Rev. 0
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2.0 Valve Installation
2.1
Preliminary Considerations
2.1.1 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 (6) months old, it may be installed on a tank car without retesting or recalibration.
2.1.2 Prior to installation, ensure that the valve remains clean and the gasket-sealing surfaces are not damaged.
Gasket-Sealing
Surfaces
Figure 2-1 Gasket-Sealing Surfaces
2.2
Procedure
2.2.1 Remove the old valve and insert a soft rubber plug into the tank opening. This will prevent debris from entering the tank during cleaning of the valve-mounting groove and studs on the manway cover plate.
2.2.2 Using a wire brush, brush the threads of the mounting studs to remove rust or scale. Nuts should move freely on clean studs. Studs should not exhibit excessive corrosion.
2.2.3 Remove and discard all used gasket material.
CAUTION: Groove Damage. In order to avoid groove damage, do not scratch the metal in the bottom of the groove when removing the old gasket.
CAUTION
2.2.4 Using a lint-free cloth and appropriate cleaning solvent, wipe clean the valve and cover-plate sealing surfaces and the mounting-stud threads.
2.2.5 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’s groove tolerances.
2.2.6 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 the entry of the valve tongue.
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CAUTION: Do not use a sharp tool to press the new gasket into place or gasket damage may result.
CAUTION
2.2.7 For tongue-and-groove mountings, inspect the tongue of a reconditioned or retested valve by running your fingernail around its inner and outer edges to check for damage. The tongue dimensions have diameter tolerances of ±0.003". Any excess material on these diameters will make it difficult to fit the tongue into the groove. If the tongue is peened over, remove excess material to meet AAR tongue tolerances.
CAUTION: To prevent tongue damage, do not install a valve having damaged sealing surfaces.
CAUTION
2.2.8 Remove the rubber plug (which was inserted in Step 2.2.1) from the cover plate.
2.2.9 Position the valve gently into the mounting. Align the body holes over the studs and lower the valve while positioning the valve tongue in the cover-plate groove.
CAUTION: Tongue Not in Cover-Plate Groove. Verify that the valve tongue has fit into the cover-plate groove. It must be engaged before continuing with the next step or valve damage may result.
CAUTION
2.2.10 Install the nuts and tighten them in 1/3-torque increments in a diagonally alternating sequence to the torque specified by the gasket specified, as shown in in Figure 2-2 below. Consult gasket manufacturer for recommended torque requirements.
Figure 2-2 Tighten in Alternating Sequence
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CAUTION
CAUTION: Uneven Gasket Compression. Do not over-tighten the nuts on one side of the valve. Over-tightening may tilt the valve and result in uneven gasket compression.
2.3
Leak Inspection
2.3.1 Test all newly installed valves under pressure to confirm that no leaks are present.
WARNING
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.
2.4
Valve Operation Notes and Precautions
NOTICE: 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.
NOTICE
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
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.
P/N: A-23075, Rev. 0
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3.0 Valve Disassembly and Inspection
NOTICE
NOTICE: Valve disassembly should only be done by trained personnel with access to the proper machines, tools, procedures and personal-protective equipment
(PPE).
3.1
Valve-Disassembly Procedure
CAUTION
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.
3.1.1 With an appropriate lifting device, place the valve onto a suitable work surface fixture (i.e., bench clamp and press are required for disassembly).
Remove Wire
Seals (x2)
Remove Hex-Head
Cap Screws (x4)
Remove cap and gasket
Remove eye bolts (x2)
Figure 3-1 Component Disassembly for Steps 3.1.2 to 3.1.5
3.1.2 Remove eye bolts (item 18) from top of valve.
3.1.3 Remove the seal wire (item 20) from the threaded rods with hole (item 16A) and hex-head cap screws (item 23) with wire cutters.
3.1.4 Remove the four (4) hex-head cap screws (items 22 and 23) from the cap (item 21).
3.1.5 Remove cap (item 21) and gasket (item 24) from the housing assembly (item 1).
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Figure 3-2 Remove Gasket from Housing Assembly
3.1.6 Insert the valve into the disassembly tool fixture and place in a press, being careful to properly position the valve.
3.1.7 Lower the press onto the valve.
Figure 3-3 Lower Press on Valve
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3.1.8 Remove the four (4) nuts (item 17) and four (4) split lockwashers (item 15) from the threaded rods
(items 16A and 16B) in an alternating “star” pattern.
Figure 3-4 Remove Nuts and Lockwashers (x4)
3.1.9 Raise the press, allowing the outer and inner springs (items 5 and 13, respectively) to decompress.
Figure 3-5 Decompress Inner and Outer Springs
3.1.10 Remove the locating pins and slide the valve out from under the press.
3.1.11 Remove the housing assembly (item 1).
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Figure 3-6 Carefully Remove Housing Assembly and Follower
3.1.12 Remove the follower (item 6). Inspect the follower for any cracks. Clean and sandblast, if necessary, or replace if damage is significant.
Figure 3-7 Inspect the Follower
3.1.13 Remove the valve springs (items 3 and 5). Test the springs by compressing them to 80% of the maximum deflection in the press for two (2) minutes. Remove the press and measure the spring free-height. If the free-height is less than the minimum indicated in Table 4-1, replace the springs.
Remove Outer Spring
Remove Inner Spring
Figure 3-8 Remove Inner and Outer Springs
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3.1.14 Remove the valve plug (item 2) and retainer (item 3) assembly. See Section 3.2 for retainer assembly disassembly.
Figure 3-9 Remove Plug Assembly and Rod Tubes
3.1.15 Remove the four (4) tubes (item 7) from the four (4) threaded rods. Visually inspect the threads for damage. No nicks or gouges are allowed. Clean the threads and inspect with a 5/8” thread ring Go-Gage; the threads must accept the Go-Gage!
Inspect
Body
Rim
Figure 3-10 Remove Tubes and Inspect Valve Body Rim
3.1.16 Inspect the seat of the body (item 4) where the valve plug assembly sits.
NOTICE
NOTICE: Minor damage to the body can be remachined. If major damage is observed, the body must be replaced.
P/N: A-23075, Rev. 0
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3.2
Valve-Plug Disassembly
3.2.1 Place the valve plug assembly (item 2) in a vise, or a suitable tooling fixture.
WARNING
WARNING: Ensure that the vise is clamped to flat edge of the stem. If the vise is clamped to the rounded portion of the stem, damage can result and it will require replacement.
Nylon Insert
Locknut
Retainer
Figure 3-11 Valve-Plug Assembly
3.2.2 Unscrew nylon-insert locknut (item 9).
3.2.3 Remove retainer (item 3) from the stem.
3.2.4 Remove the large and small O-rings (items 10 and 11) from the retainer and inspect for damage or wear.
Figure 3-12 O-Rings
CAUTION
CAUTION: O-ring degradation. O-rings can develop micro-cracks, swell, shrink, harden or soften with age and chemical exposure. An O-ring that fits loosely in the retainer, or can only be inserted with difficultly, is not the correct size for the application and will need to be replaced. Midland’s O-rings are manufactured on special molds to non-standard sizes and can be obtained only from Midland.
Following the established processes and procedures set in this manual for valve component cleaning, inspection and, if necessary, replacement, reassemble the valve per Section 5.0 of this manual.
P/N: A-23075, Rev. 0
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4.0 Detailed Valve Inspection
Follow the guidelines in this section for inspecting the condition of valve components after disassembly. 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 within this document where mandatory.
Additionally, specific inspections must be performed during and after reassembly of the valve to ensure proper and reliable operation.
Cap
No Paint or Obstruction
Allowed Near Valve Stem
Follower
Inner Spring
Outer Spring
Retainer
Valve Body
Figure 4-1 Valve-Inspection Points
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4.1
Inspection Procedure
NOTICE
NOTICE: Repair work is limited to cleaning and polishing. See Paragraph A4.11.1 of the Tank-Car Specifications.
WARNING
WARNING: Machining Not Allowed. Machining, grinding, welding or other alterations to the valve seat or stem seat is not allowed per AAR M1002, Paragraph
A4.11 of the Tank-Car Specifications.
4.1.1 Follower
4.1.1.1 The follower (item 6) is a structural part. There should be no paint on the follower where the valve stem enters it, or between adjacent surfaces of the top guide and valve body. Also, inspect for cracks.
Figure 4-2 Follower
4.1.2 Valve-Plug Assembly
4.1.2.1 Remove scale, residual product and other foreign material from the stem. Use magneticparticle or dye-penetration inspection to detect cracks.
Figure 4-3 Valve-Plug Assembly
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CAUTION
CAUTION: Check for Cracks. Cracks are stress concentrators and can cause catastrophic failure of the stem and uncontrolled venting.
4.1.2.2 Also inspect for corrosion pitting. Any corrosion pitting is reason for rejection since it may indicate more severe corrosion at the threads. It can also be the starting point for difficult-todetect cracking.
Figure 4-4 Inspect Stem
4.1.2.3 All nickel-bearing stainless steels have a likelihood of galling. Wrenching the locknut may result in galled stem threads. Always check for galled threads and chase the threads with a thread die or replace stems that show significant thread damage.
4.1.2.4 Inspect sealing surfaces on stem, O-ring seal and outer edge of stem. They should be smooth and free of any damage.
4.1.3 Valve-Stem Concentricity
4.1.3.1 The valve stem must be straight within 0.010” (maximum). Rotate and center the stem on Vblocks equipped with a dial indicator. If the dial indicator readings are not within the allowable tolerance, replace the stem or return it to Midland for repair.
WARNING
WARNING: Valve-Stem Eccentricity. Excessive valve-stem eccentricity will cause binding that can result in high start-to-discharge pressure settings, reduced valve capacity and/or low vapor-tight pressures.
WARNING: Valve-Stem Failure. Cracks and corrosion of pressure relief valve stems can result in stem failure and uncontrolled venting.
WARNING: Valve-Stem Straightening. Straightening of the stem by bending it in a press may result in the buildup of uneven stresses in the stem, which may result in valve malfunction.
P/N: A-23075, Rev. 0
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4.1.4 O-ring Retainer Grooves
4.1.4.1 The grooves 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 the groove, replace this part.
Check Surfaces of Grooves for
Nicks, Corrosion and Gouges
Figure 4-5 Inspect Retainer Grooves
4.1.5 Valve Body
4.1.5.1 The sealing surface is the crown of the seat. 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.
Crown of the Seat
Figure 4-6 Inspect Valve Body
NOTICE
NOTICE: Repair work is limited to cleaning and polishing. See Paragraph A4.11.2 of the Tank-Car Specifications.
WARNING
WARNING: Machining Not Allowed. Machining, grinding, welding or other alterations to the valve seat or stem seat is not allowed per AAR M1002, Paragraph
A4.11 of the Tank-Car Specifications.
P/N: A-23075, Rev. 0
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4.1.6 Sealing Surface (Valve Mounting)
4.1.6.1 On the underside of the valve body (item 4) is the surface that seals the valve to the mounting plate on the railcar. Machining of this surface is permitted. A good seating surface is necessary to ensure there are no leaks in this area.
Sealing Surface
Figure 4-7 Valve-Body Seat Sealing Surface
NOTICE
NOTICE: Please refer to paragraph A4.11.2 of the Tank-Car Specifications and consult Appendix E for dimensions and applicable tolerances.
NOTICE: 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
4.1.7 Valve Springs
4.1.7.1 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 dyepenetration inspection (performed by certified trained personnel) to evaluate the exterior surface and ensure that it is free of cracks and corrosion pits.
Figure 4-8 Inspect Inner and Outer Valve Springs
WARNING
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.
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4.1.7.2 Test the springs by pressing them to 80% of maximum deflection in a hydraulic press for two
(2) minutes. Remove from the press and then measure the spring free-height. If free-height is less than the minimum indicated in Table 4-1, replace the spring.
WARNING
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. The spring should not be bowed more than 1/4" when in the assembled position. Bowing in excess of this amount can cause the spring to rub against the inside wall of the nozzle or guide tube. This will adversely affect the pressure settings. If any of the defects mentioned above are observed, the spring cannot be repaired and must be replaced.
Spring Part Number
23075-51-SS
Wire Size (REF) (Inches)
0.562
0.468
Height at 80% of Max.
Deflection (Inches)
5.5
5.3
Minimum Free-Height
(Inches)
14.7
12.8 23075-131-SS
Table 4-1 Minimum Free-Heights for Spring After Pressing 80% of the Maximum Deflection for Two (2) Minutes
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4.1.8 O-rings
4.1.8.1 O-rings must be replaced at the time of any periodic valve retest and when the valve is disassembled. There is no need to replace the gasket unless it is damaged.
Figure 4-9 O-Rings
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 non-standard sizes and are obtainable only from Midland.
CAUTION
CAUTION: Defective Parts. If any parts appear defective, it is recommended they be replaced. Consult with Midland for recommended repair techniques when applicable.
4.1.9 Stem Threads and Nuts
4.1.9.1 Stem threads and nuts are 1-8 UNC thread.
4.1.10 Special Inspection Considerations
4.1.10.1 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.
4.1.10.2 Facilities performing recommended dye-penetration and magnetic-particle testing must carry out such testing according to a qualified procedure conducted by certified trained personnel.
4.1.10.3 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
4.1.10.4 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 judgment.
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5.0 Detailed Valve Assembly
For recommended torque specifications for A-23075 Series valve reassembly, please refer to Table 1-2.
Figure 5-1 Valve Exploded View
5.1
Valve-Plug Assembly (If Required)
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Figure 5-2 Valve Plug Components
5.1.1 Place the small O-ring (item 11) onto the stem.
5.1.2 Place the large O-ring (item 10) onto the retainer (item 3).
5.1.3 Place the retainer on the stem.
5.1.4 Apply grease (DuPont
™
Krytox
®
, or similar) onto the threads of the stem.
5.1.5 Place the nylon-insert locknut (item 9) onto the threads of the stem.
5.1.6 Clamp the stem in a vise.
Figure 5-3 Clamp Stem and Tighten Locknut
WARNING
WARNING: Ensure that the vise is clamped to the flat edge of the stem. If the vise is clamped to the rounded section of the stem, damage can result and will require replacement. The recommended position is with the disc down. This helps with assembly and prevents the O-ring from being misplaced.
5.1.7 Tighten the nylon-insert locknut to 200 ft-lb.
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5.2
Valve-Assembly Procedure
5.2.1 Place the valve body (item 4) on the fixture.
WARNING: Seat Inspection. Inspect the seat for any corrosion, nicks, gouges or pitting. Clean and sandblast, if necessary, replace if damage is significant.
WARNING
5.2.2 Place the valve-plug assembly (item 2) on the body seat.
Figure 5-4 Place Valve-.Plug Assembly on Valve Body
5.2.3 Apply Loctite
®
242
®
(or similar) on threads of four (4) threaded rods (items 16A and 16B) and insert the threaded rods into the holes of the body. Tighten in a “star” pattern.
Figure 5-5 Install Threaded Rods
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CAUTION
CAUTION: The end of the threaded rods (item 16B) with the lesser amount of threads should be inserted into the body.
CAUTION: The threaded rods with holes (item 16A) must be adjacent to each other.
CAUTION
5.2.4 Place the four (4) tubes (item 7) on the threaded rods. Ensure that the two rods with holes are adjacent to one another; this is be required for the seal wire to be installed.
Rod w/Hole
Rod w/Hole
Figure 5-6 Install Tubes and Springs
5.2.5 Place outer and inner springs (items 5 and 13) on body.
5.2.6 Apply grease (DuPont
™
Krytox
®
, or similar) onto the end of the stem on the valve-plug assembly.
Figure 5-7 Grease Stem
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5.2.7 Apply grease (DuPont
™
Krytox
®
, or similar) onto the follower (item 6). Place the follower on top of the outer spring.
Figure 5-8 Grease and Install Follower
5.2.8 Apply grease (DuPont
™
Krytox
®
, or similar) onto the threads of the adjustment screw (item 14).
Figure 5-9 Grease Adjustment Screw and Install in Housing
5.2.9 Install adjustment screw into the hole on top of the housing assembly (item 1). Leave approximately two (2) inches of thread exposed.
5.2.10 Place housing assembly on top of the follower.
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Figure 5-10 Install Housing
5.2.11 Insert the valve assembly into the fixture, using locating pins to position the body onto the base of the fixture and housing assembly on top of the valve.
5.2.12 Compress the outer and inner springs to 65-70 ft-lb.
5.2.13 Place four (4) split lockwashers (item 14) on threaded rods.
Figure 5-11 Install Lockwashers (x4) and Nuts (x4)
5.2.14 Place four (4) nuts (item 17) on threaded rods and tighten in a “star” pattern to 130 ft-lb.
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6.0 Special Guidelines and Precautions on Pressure-Testing and Adjustment
CAUTION
CAUTION: Safety Protection. Wear appropriate safety glasses or face-shield and protective clothing when conducting this procedure. Valve testing involves highvelocity air and water flow that can cause injury.
6.1.1 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.
NOTICE
NOTICE: 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 the pressure at whch no further fluid is detected. Midland recommends that no bubbles be observed for two (2) minutes at vaport-tight.)
6.1.2 Test Stand and Gauge Requirements
It is recommended that the test-stand mounting be 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 must be date-tagged.
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7.0 Valve-Pressure Testing Procedure
If your company has an approved test procedure, follow it. If it does not, these procedures provide essential guidelines in regards to pressure testing.
7.1
Initial Setup
7.1.1 Install the valve on the test fixture and alternately tighten down all of the nuts.
Figure 7-1 Affix Valve to Test Fixture
7.1.2 Seal drain holes of the valve body with putty, or a similar material.
Figure 7-2 Seal Drain Holes
7.1.3 Fill the valve body with water to allow bubble detection at the valve seat.
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Figure 7-3 Fill with Water
7.1.4 Take a position allowing observation of the pressure gauge and bubbling of air in the valve body.
Figure 7-4 Observe Pressure Gauge and Bubbling
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7.2
Testing
7.2.1 Increase the test air pressure slowly.
7.2.2 Increase the air pressure until the valve’s start-to-discharge (STD) pressure 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. See Table 7-1 for valve start-to-discharge (STD) and vapor-tight pressure (VTP) settings.
STD Settings
75 psig ± 3 psig
VTP Settings
60 psig minimum
Table 7-1 Start-To-Discharge (STD) and Vapor-Tight Pressure (VTP) Settings
7.2.3 Reduce the air pressure until leakage stops. Then reduce pressure to less than one-half of the
STD pressure. Then slowly increase the pressure.
7.2.4 Observe the STD pressure. Slowly bleed off the pressure to observe the VTP.
7.2.5 Repeat this procedure at least two (2) more times. The STD and VTP should be consistent in all three (3) occurrences.
7.2.6 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).
7.2.7 Retest the valve.
7.2.8 If the test results are erratic, troubleshooting is more complex. Consult your supervising engineer or a Midland representative.
7.2.9 Place screw locknut (item 8) on adjustment screw (item 14) and tighten to 65-70 ft-lb.
7.2.10 Attach safety wire from wire-seal kit (item 20) through the holes in the two (2) threaded rods with holes (item 16A) and tighten with pliers.
7.2.11 Place the gasket (item 24) on top of the housing assembly (item 1). Align the four (4) holes.
7.2.12 Place the cap (item 21) on top of the gasket. Align the four (4) holes.
7.2.13 Install four (4) hex-head cap screws (items 22 and 23) on the cap with the two (2) hex-head cap screws with holes (item 22) adjacent to each other. Tighten in a “star” pattern.
7.2.14 Attach the safety wire from the wire-seal kit to the hex-head cap screws with holes and tighten with pliers.
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8.0 Valve-Adjustment Procedure
If your company has an approved test procedure, follow it. If it does not, these procedures provide essential guidelines in regards to pressure testing.
8.1
Valve-Setting Adjustment
8.1.1 Remove the wire seal from the cap and remove the cap to access the spring-adjustment nut.
8.1.2 Lubricate the threads above the spring-adjustment screw.
8.1.3 Loosen the locknut a few turns to separate it from the spring-adjusting screw.
8.1.4 Tighten/untighten the spring-adjusting screw in one-turn increments in order to find the desired setting.
Figure 8-1 Compress Spring
CAUTION
CAUTION: Stem-Thread Damage. Since all nickel-bearing stainless steels have a likelihood of galling, wrenching the adjusting nut without relieving the spring’s load will frequently result in damaged stem threads.
8.1.5 Tighten the locknut against the spring-adjusting nut to 65-70 ft-lb to lock the setting.
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Figure 8-2 Tighten Locknut
8.1.6 Retest the valve STD and determine how much pressure change occurred when the springadjusting screw was rotated two (2) turns. Based upon this calculation, re-compress the valve spring and alter the valve adjustment for the midpoint in the STD tolerance range.
STD Settings
75 psig ± 3 psig
VTP Settings
60 psig minimum
Table 8-1 STD and VTP Settings
8.1.7 If the test results are erratic, troubleshooting is more complex. Consult your supervising engineer or a Midland representative.
8.1.8 When the test results are acceptable, tighten the spring-adjustment nut to the required torque in
Table 1-2.
8.2
Post-Test Procedure
8.2.1 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. Remove the valve from the test fixture.
8.2.2 Wipe or blow away any remaining soapsuds and water used in the testing.
8.2.3 Install seal wires (item 20).
CAUTION: Mounting Interference. DO NOT paint the sealing surfaces of the valve that will contact the manway’s cover-plate surfaces or valve cocking may result.
CAUTION
8.2.4 Permanently attach a metal tag to the valve body with repair/test date, repair-facility identification and technician I.D.
8.2.5 Store the valve in a clean, dry place until ready to use.
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9.0 Maintenance
NOTICE
NOTICE: 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.
NOTICE: It is an AAR requirement (refer to D4.04) that new O-rings be installed when a valve is retested.
9.1
Prior to Maintenance Tasks Performed
9.1.1
Retesting of Valves in Storage
9.1.1.1 Midland valves are factory set and sealed. If they have been left in their original shipping containers, are undamaged and are no more than six (6) months old, they may be installed without being retested
9.1.2 Required Tools
9.1.2.1 Obtain the required tools and supplies before attempting maintenance procedures. Table 1-
3 outlines some suggested tools that will be needed.
9.2
Leak Repair on a Mounted Valve
9.2.1 Repair the retainer O-rings. Exception: When performing that procedure, there should be no pressure in the test chamber and the retainer O-rings should be loose, not epoxied into the O-ring retainer as specified in that procedure.
9.2.2 It is possible to replace only the retainer O-rings on an external-style valve mounted on a pressurized tank car. This procedure may be conducted to stop minor leakage when valve rebuilding or replacement must be delayed.
CAUTION
CAUTION: The repair procedure for a mounted valve is intended only as a temporary repair. Once the product is unloaded and pressure is relieved, the valve should be removed for further repairs and full requalification.
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NOTICE
NOTICE: Conducting this procedure may be hazardous (depending on the material in the tank car). Maintenance personnel should be carefully trained before being permitted to perform the procedure below on a pressure relief valve mounted on a pressurized tank.
9.2.3 Remove the seal wires (item 16).
9.2.4 Remove the four (4) top-guide bolts (items 11 and 12). Ensure they won’t be dropped or lost.
9.2.5 Mark the housing assembly (item 1) and body (item 4) with a vertical line to allow the top guide to be reinstalled in the same orientation.
9.2.6 Lift up and remove the housing assembly (item 1).
9.2.7 Put a wrench on the flats of the O-ring retainer (item 3) and another wrench on the top locknut
(item 7). See Table 1-2 for recommended wrenches. Hold the retainer in place to prevent it from rotating while backing off and removing the top locknut.
CAUTION
CAUTION: Valve Discharge. When the O-ring retainer cap is raised up, there will be a significant amount of product discharging. Have the emery paper, cleaning cloth, replacement O-ring retainer cap (with epoxied O-rings) and silicone grease close at hand. Use a wheel puller, or two screwdrivers 180° apart, to quickly dislodge the O-ring retainer.
9.2.8 Remove the O-ring retainer (item 3). Remove the two (2) O-rings (items 8 and 9) from the retainer and inspect the O-ring grooves.
9.2.9 Look carefully for nicks, rust, scale, solidified product and other foreign material on the valve seat.
The O-ring makes its seal on the top of the crown of the valve seat and on a small area (on the outboard side) past the top of the seat. Use emery paper (400-grit) to clean this surface then wipe away any loose residue. Visually inspect this surface to detect any irregularities that may still be there.
9.2.10 After cleaning and confirming that the valve seat area is clean and free of defects, apply a small amount of lubricant to the exposed thread of the valve stem.
9.2.11 Install the new O-ring retainer (item 3) and secure it with the top locknut (item 7). Take care to prevent rotation of the retainer by using two wrenches. Refer to Table 1-2 for tools and torque requirements.
9.2.12 Install the top guide (item 1) and gasket (item 15), then secure with the four (4) top-guide bolts.
Refer to Table 1-2 for tools and torque requirements.
CAUTION
CAUTION: Replace Retainer. After the tank-car pressure is relieved, replace the retainer having epoxied O-rings with another one containing non-epoxied O-rings. If valve leakage exceeds the sealing capability of the O-ring, replace or rebuild the valve.
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Page 43 of 45
9.2.13 For special guidelines and precautions on pressure-testing and adjustment, and for 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.
NOTICE
NOTICE: A “popping pressure” is not specified. It is only necessary to determine the
STD pressure as pressure is increased and to determine 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, with no bubbles for two (2) minutes.]
9.2.14 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.
9.2.15 Valve-Testing Procedure. If your company has an approved test procedure, follow it. If it does not, this procedure provides essential guidelines.
P/N: A-23075, Rev. 0
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10.0 Warranty
Midland Manufacturing Corp. 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 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.
© Copyright 2014, OPW. Printed in USA.
© 2014 Delaware Capital Formation, Inc. All Rights Reserved.
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Key Features
- High flow
- Corrosion-resistant
- Replaceable seal design
- Triple seals
- High-quality steel construction