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Check Valves:Wafer, Wafer-Lug, andDouble Flanged Type

API STANDARD 594FIFTH EDITION, NOVEMBER 1997

COPYRIGHT 2002; American Petroleum Institute

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Check Valves:Wafer, Wafer-Lug, andDouble Flanged Type

Manufacturing, Distribution and Marketing Department

API STANDARD 594FIFTH EDITION, NOVEMBER 1997



SPECIAL NOTES

API publications necessarily address problems of a general nature. With respect to partic-ular circumstances, local, state, and federal laws and regulations should be reviewed.

API is not undertaking to meet the duties of employers, manufacturers, or suppliers towarn and properly train and equip their employees, and others exposed, concerning healthand safety risks and precautions, nor undertaking their obligations under local, state, or fed-eral laws.

Information concerning safety and health risks and proper precautions with respect to par-ticular materials and conditions should be obtained from the employer, the manufacturer orsupplier of that material, or the material safety data sheet.

Nothing contained in any API publication is to be construed as granting any right, byimplication or otherwise, for the manufacture, sale, or use of any method, apparatus, or prod-uct covered by letters patent. Neither should anything contained in the publication be con-strued as insuring anyone against liability for infringement of letters patent.

Generally, API standards are reviewed and revised, reaffirmed, or withdrawn at least everyfive years. Sometimes a one-time extension of up to two years will be added to this reviewcycle. This publication will no longer be in effect five years after its publication date as anoperative API standard or, where an extension has been granted, upon republication. Statusof the publication can be ascertained from the API Authoring Department [telephone (202)682-8000]. A catalog of API publications and materials is published annually and updatedquarterly by API, 1220 L Street, N.W., Washington, D.C. 20005.

This document was produced under API standardization procedures that ensure appropri-ate notification and participation in the developmental process and is designated as an APIstandard. Questions concerning the interpretation of the content of this standard or com-ments and questions concerning the procedures under which this standard was developedshould be directed in writing to the director of the Authoring Department (shown on the titlepage of this document), American Petroleum Institute, 1220 L Street, N.W., Washington,D.C. 20005. Requests for permission to reproduce or translate all or any part of the materialpublished herein should also be addressed to the director.

API standards are published to facilitate the broad availability of proven, sound engineer-ing and operating practices. These standards are not intended to obviate the need for apply-ing sound engineering judgment regarding when and where these standards should beutilized. The formulation and publication of API standards is not intended in any way toinhibit anyone from using any other practices.

Any manufacturer marking equipment or materials in conformance with the markingrequirements of an API standard is solely responsible for complying with all the applicablerequirements of that standard. API does not represent, warrant, or guarantee that such prod-ucts do in fact conform to the applicable API standard.

All rights reserved. No part of this work may be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise,

without prior written permission from the publisher. Contact the Publisher, API Publishing Services, 1220 L Street, N.W., Washington, D.C. 20005.

Copyright © 1997 American Petroleum Institute



FOREWORD

This standard is a purchase specification for wafer, wafer-lug and double flanged checkvalves designed for installation between Class 125 and 250 cast iron flanges as specified inASME B16.1, between Class 150 and 300 ductile iron flanges as specified in ASME B16.42,between Class 150-2500 steel flanges as specified in ASME B16.5, and between Class 150-600 steel pipeline flanges as specified in MSS SP-44 or carbon steel flanges as specified inASME B16.47.

This standard requires the purchaser to specify certain details and features. Although it isrecognized that the purchaser may desire to modify, delete, or amplify sections of this stan-dard, it is strongly recommended that such modifications, deletions, and amplifications bemade by supplementing this standard, rather than by rewriting or incorporating sectionsthereof into another complete standard.

API standards are published as an aid to procurement of standardized equipment andmaterials. These standards are not intended to inhibit purchasers or producers from purchas-ing or producing products made to specifications other than those of API.

API publications may be used by anyone desiring to do so. Every effort has been made bythe Institute to assure the accuracy and reliability of the data contained in them; however, theInstitute makes no representation, warranty, or guarantee in connection with this publicationand hereby expressly disclaims any liability or responsibility for loss or damage resultingfrom its use or for the violation of any federal, state, or municipal regulation with which thispublication may conflict.

Suggested revisions and requests for interpretations, are invited and should be submittedto the director of the Manufacturing, Distribution and Marketing Department, AmericanPetroleum Institute, 1220 L Street, N.W., Washington, D.C. 20005.

iii



IMPORTANT INFORMATION CONCERNING USE OFASBESTOS OR ALTERNATIVE MATERIALS

Asbestos is specified or referenced for certain components of the equipment describedin some API standards. It has been of extreme usefulness in minimizing fire hazards asso-ciated with petroleum processing. It has also been a universal sealing material, compatiblewith most refining fluid services.

Certain serious adverse health effects are associated with asbestos, among them theserious and often fatal diseases of lung cancer, asbestosis, and mesothelioma (a cancer ofthe chest and abdominal linings). The degree of exposure to asbestos varies with the prod-uct and the work practices involved.

Consult the most recent edition of the Occupational Safety and Health Administration(OSHA), U.S. Department of Labor, Occupational Safety and Health Standard for Asbes-tos, Tremolite, Anthophyllite, and Actinolite, 29

Code of Federal Regulations

Section1910.1001; the U.S. Environmental Protection Agency, National Emission Standard forAsbestos, 40

Code of Federal Regulations

Sections 61.140 through 61.156; and the U.S.Environmental Protection Agency (EPA) rule on labeling requirements and phased ban-ning of asbestos products (Sections 763.160-179).

There are currently in use and under development a number of substitute materials toreplace asbestos in certain applications. Manufacturers and users are encouraged todevelop and use effective substitute materials that can meet the specifications for, andoperating requirements of, the equipment to which they would apply.

SAFETY AND HEALTH INFORMATION WITH RESPECT TO PARTICULARPRODUCTS OR MATERIALS CAN BE OBTAINED FROM THE EMPLOYER, THEMANUFACTURER OR SUPPLIER OF THAT PRODUCT OR MATERIAL, OR THEMATERIAL SAFETY DATA SHEET.

iv



CONTENTS

Page

1 GENERAL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3 Valve Nomenclature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

3 PRESSURE-TEMPERATURE RATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43.1 Valve Rating. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43.2 Body Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43.3 Seat Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

4 DESIGN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44.1 Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44.2 Plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44.3 Seating Surfaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44.4 External Bolts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54.5 Flow Indication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54.6 Gasket Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

5 MATERIAL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85.1 Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85.2 Plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85.3 Trim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85.4 Internal Wetted Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85.5 Body Seat Rings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85.6 Springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85.7 Pipe Plugs (Pin Retainers) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85.8 Nameplate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

6 INSPECTION, EXAMINATION, TESTING, AND REPAIR . . . . . . . . . . . . . . . . . . . 96.1 Inspection and Examination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96.2 Pressure Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96.3 Repair of Defects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

7 MARKING NAMEPLATES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97.1 API 594 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97.2 Resilient Seating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

8 SHIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98.1 Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98.2 Valve Openings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98.3 Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

9 RECOMMENDED SPARE PARTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figures1 Typical Single-Plate Wafer Check Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Typical Dual-Plate Wafer Check Valve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

v



Page

3 Typical Dual-Plate Wafer-Lug Check Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Typical Dual-Plate Double Flanged Check Valve . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Limitations for Flange Face Interruptions that Fall Within the Gasket

Seating Area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Tables1A Minimum Body-Wall Thickness (Exclusive of Removable Seat Ring)

by Class (Inches) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61B Minimum Body-Wall Thickness (Exclusive of Removable Seat Ring)

by Class (Millimeters). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62A Single- and Dual-Plate Valve Face-to-Face Dimensions by Class

(Inches) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72B Single- and Dual-Plate Valve Face-to-Face Dimensions by Class

(Millimeters) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Seating-Surface Nominal Trim Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

vii



NOTES TO PURCHASER

1.

If the purchaser needs a wafer, wafer-lug, or double flange check valve that deviates fromthis standard, the deviating requirements shall be stated in the purchase order.

2.

If no exceptions are to be taken to this standard, the purchase order need only make refer-ence to API Standard 594 and specify the items included in paragraph 2.1. Optional itemsincluded in paragraph 2.2 may also be specified.

2.1 Items Required on the Purchase Order

a. Valve size (see 1.2).b. Class (see 1.2).c. Wafer, wafer-lug, or double flange type body (see 4.1.3).d. Flange standard for NPS 26 and larger (see 4.1.4).e. Facing (see 4.1.5 and 4.1.6).f. Integral seating or removable seat ring (see 4.1.8).g. Single plate, dual plate, or manufacturer’s option (see 4.2 and Figures 1 and 2).h. Valve body material (see 5.1).i. Materials of construction, including those for trim (see 5.3.1) and those for internalwetted parts (see 5.4).j. Seating-surface material (see 5.3.2).k. Maximum service temperature above 300°F for proper spring selection (see 5.6)

2.2 Optional Items:

a. Drain connection (see 4.1.7).b. Tapped test openings (see 4.1.9).c. Lifting eyebolt (see 4.1.10).d. Flange bolt holes tapped through (see 4.1.11, Figures 3 and 4).e. Inspection (see 6.1).f. Color and coatings (see 8.1).g. Export packaging (see 8.3).h. Recommended spare parts list along with general assembly drawing that identifies theparts (see Section 9).

3.

Items where agreement with the manufacturer is required.

a. Gasket surface interruption (see 4.6).b. Dimensional information for NPS 54 and 60 valves (see Tables 1 and 2).

4.

Refer to API 598 for additional items that may need to be specified, including supple-mentary examination, the extent of inspection by the purchaser, the inspector’s address, andthe alternative low pressure closure test.

vii





1

Check Valves: Wafer, Wafer-Lug, and Double Flanged Type

1 General

1.1 SCOPE

This standard covers design, material, face-to-face dimen-sions, pressure-temperature ratings, and examination, inspec-tion, and test requirements for gray iron, ductile iron, steel,and alloy single and dual plate check valves. Valve configura-tions include wafer, wafer-lug, and double flanged type withfacings that will permit installation between ASME and MSSflanges that conform to the standards and specifications listedin section 2.

1.2 SIZES

This standard covers the following nominal valve sizeranges:

a. Classes 125 and 250, NPS 2-48 (excluding NPS 31/2).b. Classes 150 and 300, NPS 2-60 (excluding NPS 31/2 and5).c. Classes 400 and 600, NPS 2-42 (excluding NPS 31/2 and5).d. Classes 900 and 1500, NPS 2-24 (excluding NPS 31/2 and5).e. Class 2500, NPS 2-12 (excluding NPS 31/2 and 5).

1.3 VALVE NOMENCLATURE

The standard nomenclature for valve parts is shown in Fig-ures 1, 2, 3, and 4. These figures illustrate some wafer, wafer-lug and double flanged type check valve designs. AlthoughFigures 1, 2, 3, and 4 show typical designs, they are not to beconstrued as precluding other available designs that complywith the requirements of this standard.

2 References

The latest edition or revision of the following standards orspecifications shall, to the extent specified, form a part of thisstandard. When specific parts (such as numbered paragraphsor tables) of other documents are referenced in this text, theedition current when this standard was issued shall apply.

APIStd 598

Valve Inspection and Testing

Std 600

Steel Gate Valves-Flanged and Butt-Weld-ing Ends

ASME

1

B1.1

Unified Inch Screw Threads (UN and UNRThread Form)

B16.1

Cast Iron Pipe Flanges and FlangedFittings

B16.5

Pipe Flanges and Flanged Fittings

B16.10

Face-to-Face and End-to-End Dimensionsof Valves

B16.11

Forged Steel Fittings, Socket-Welding andThreaded

B16.14

Ferrous Pipe Plugs, Bushings, and Lock-nuts with Pipe Threads

B16.20

Metallic Gaskets for Pipe Flanges-RingJoint, Spiral Wound, and Jacketed

B16.34

Valves-Flanged, Threaded and Welding End

B16.42

Ductile Iron Pipe Flanges and FlangedFittings, Classes 150 and 300

B16.47

Large Diameter Steel Flanges; NPS 26Through NPS 60

B18.15

Forged Eyebolts

ASTM

2

A 182

Forged or Rolled Alloy-Steel Pipe Flanges,Forged Fittings, and Valves and Parts forHigh-Temperature Service

A 217

Steel Castings, Martensitic Stainless andAlloy, for Pressure-Containing Parts Suit-able for High-Temperature Service

A 351

Castings, Austenitic, Austenitic-Ferritic(Duplex), for Pressure Containing Parts

A494

Castings, Nickel and Nickel Alloy

B 473

UNS N08020, UNS N08024, and UNSN08026 Nickel Alloy Bar and Wire

B 564

Nickel Alloy Forgings

AWS

3

A5.9

Corrosion-Resisting Chromium and Chro-mium-Nickel Steel Bare and CompositeMetal Cored and Stranded Welding Elec-trodes and Welding Rods

A5.13

Solid Surfacing Welding Rods andElectrodes

MSS

4

SP-6

Standard Finishes for Contact Faces ofPipe Flanges and Connecting-EndFlanges of Valves and Fittings

SP-25

Standard Marking System for Valves, Fit-tings, Flanges and Unions

SP-44

Steel Pipe Line Flanges

1

American Society of Mechanical Engineers, 345 East 47th Street, NewYork, New York 10017.

2

American Society for Testing and Materials, 100 Bar Harbor Drive, WestConshohocken, Pennsylvania 19428-2959.

3

American Welding Society, 550 LeJeune Road, N.W., P.O. Box 351040,Miami, Florida 33135.

4

Manufacturers Standardization Society of the Valve and Fitting Industry,Inc., 127 Park Street, N.E., Vienna, Virginia 22180.



2 API S

TANDARD

594

Note: The optional configuration of a full flange or lug flange (similar to that shown in Figure 3) and of a double flanged type (similar to that of Figure 4) shall bethe manufacturer’s standard unless otherwise specified in the purchase order. All notes on Figures 3 and 4 apply.

Figure 1—Typical Single-Plate Wafer Check Valve

Figure 2—Typical Dual-Plate Wafer Check Valve

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Notes: 1. The optional configuration of a full flange or lug flange shall be the manufacturer’s standard unless otherwise specified by the purchaser.2. Unless otherwise specified in the purchase order, the bolt holes will be through-drilled.

Figure 3—Typical Dual-Plate Wafer-Lug Check Valve

Notes: 1. Insufficient space for nuts between flanges on some double flange valves may require other type valves be furnished.2. Unless otherwise specified in the purchase order, the bolt holes will be through-drilled (see 4.1.11).

Figure 4—Typical Dual-Plate Double Flanged Check Valve

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4 API S

TANDARD

594

3 Pressure-Temperature Ratings

3.1 VALVE RATING

The pressure-temperature rating of the valve will be thelesser of the body rating or the seat rating.

3.2 BODY RATING

The valve body rating for various body materials shall beas follows:

a. Gray iron: The pressure-temperature rating for the applica-ble flange class as specified in ASME B16.1.b. Ductile iron: The pressure-temperature rating for theapplicable flange class as specified in ASME B16.42.c. Steel, nickel alloy or special alloy: The pressure-tempera-ture rating for Standard Class valves made of identicalmaterial as listed in ASME B16.34.

3.3 SEAT RATING

The pressure-temperature rating of the valve seat for valvesfurnished with resilient seating materials shall be specified bythe manufacturer. Temperature limitations of the seat materialshall be marked on the nameplate, as required in 7.1.2.

4 Design

4.1 BODY

4.1.1

The minimum body-wall thickness shall conform tothose shown in Tables 1A and 1B.

4.1.2

The face-to-face dimensions of valves (includingvalves with ring-joint facings) shall conform to those shownin Tables 2A and 2B.

4.1.3

The valve shall have a wafer, wafer-lug, or doubleflanged body as specified in the purchase order. (Doubleflanged valves are available where nut space between flangesis adequate).

4.1.4

Valves larger than NPS 24 in Classes 150, 300, 400,and 600 shall have body-flange bolt patterns suitable for thewafer-lug or double flanged type, outside diameters suitablefor the wafer type, and gasket surface dimensions compatiblewith the flange standards specified in the purchase order.

4.1.5

Ring-joint grooves shall conform to the dimensionsshown in either ASME B16.5 or ASME B 16.47 as applica-ble.

4.1.6

Flange facings of gray iron and ductile iron valvesshall be finished as specified in MSS SP-6. The finish onflange facings of carbon steel, alloy steel, and nickel-alloyvalves shall comply with ASME B16.5.

4.1.7

Drain connections in the body shall be furnished onlywhen specified in the purchase order. The size, type, and loca-

tion of drain connections shall be the manufacturer’s stan-dard, unless other configurations are agreed to by themanufacturer and the purchaser and are so specified in thepurchase order. Minimum thread engagement and otherdimensions shall conform to the requirements for auxiliaryconnections in ASME B16.34.

4.1.8

The valve may have either an integral or a removableseat ring.

4.1.9

Tapped test openings are permitted only if specifiedin the purchase order. If a tap is made in the body for testingthe valve, the tap shall not be larger than NPS 1/2. After test-ing, the tapped hole shall be fitted with an ASME B16.11 orASME B16.14 threaded solid round or hex-head plug. Thetest tap may require a boss to provide the minimum threadengagement, as specified in ASME B16.34.

4.1.10

A tapped hole shall be provided in the body ofvalves which are either NPS 10 or larger, or which weighmore than 50 lbs (23 kg), for attachment of an eye bolt orequivalent lifting device. The hole shall be tapped with acoarse (UNC) Class 2B thread, conforming to ASME B1.1. Ifan eyebolt is specified in the purchase order, it shall conformto ASME B18.15.

4.1.11

Unless otherwise specified in the purchase order,the lugs of wafer-lug type valves and flanges of doubleflanged type valves shall be provided with non-threaded(drilled) bolt clearance holes.

4.2 PLATES

Valves are classified as follows:

a. A single-plate valve has a plate that acts as a valve closurewhen forced against the valve-body seat by line back pressureor flow reversal. This closure may be aided by the use ofsprings or other devices.b. A dual-plate valve has plates that close the valve with theassistance of one or more springs, when flow reversal forcesthe plates against the valve-body seats.

4.3 SEATING SURFACES

4.3.1

The body and plate seating surfaces may be of depos-ited weld metal, integral metal, mechanically retained metal,or a resilient material.

4.3.2

Welding is not permitted on cast iron or ductile iron.

4.3.3

Brazing is permitted on cast iron and ductile irononly for attaching seating surfaces to the body or the plate andonly if agreed to by the purchaser and the manufacturer. Fur-nace brazing is the only type of brazing permitted and may beused only if the parts are heated under closely controlled con-ditions, in a uniform manner, and to a temperature no higher



C

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, W

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UG

,

AND

D

OUBLE

F

LANGED

T

YPE

5

than the lower critical temperature of the base material. Cool-ing shall be in the furnace or in still air.

4.4 EXTERNAL BOLTS

4.4.1

Bolts 1 inch or smaller shall have coarse (UNC)threads. Those larger than 1 inch shall be of the eight-thread series (8 UN). Bolt threads shall be Class 2A, andnut threads shall be Class 2B. Threads shall conform toASME B1.1.

4.4.2

For bolts 1 inch or smaller, threaded body-flange boltholes shall be drilled and tapped according to the require-ments for coarse thread series Class 2B in ASME B1.1. Forbolts larger than 1 inch, such holes shall be drilled and tappedaccording to the requirements for eight-thread series Class 2Bin ASME B1.1.

4.5 FLOW INDICATION

The valve body shall be furnished with a clearly visiblecast, forged, machined-in, or die-stamped arrow to indicatethe direction of flow through the valve.

4.6 GASKET SURFACE

Fasteners in the flange seating surface shall be recessed to orbelow the flange gasket level. Interruptions in the seating areaof a centered ASME B16.20 Spiral Wound Gasket for valvesizes NPS 6 and larger shall not exceed the limitations given inFigure 5. The permissible surface interruptions on smaller sizevalves shall be as agreed between purchaser and manufacturerbut shall not exceed 50% of the gasket seating width.

Note: The degree of interruption may affect the sealibility of a spiral-woundgasket.

Figure 5—Limitations for Flange Face Interruptions that Fall Within the Gasket Seating Area

A

D

E

C

B

B

Valve body OD

0.015 in. (0.38 mm)max. chamfer

Seat retainer

Valve centerline

D

E

Valve body OD

Seat retainer

Valve centerline

(A) PARTIAL FASTENER OVERLAP (B) COMPLETE FASTENER OVERLAP

594 Fig. 05Dimension Definition Range, inches Range, mm

A Protrusion of seat retainer plate above valve body face (after being compressed by mating flange). Negative value denotes insert below valve body face.

+0.010 to–0.010

+0.25 to–0.25

B Radial width of annular gap between valve body and seat retainer plate (exclusive of chamfer).

0.030 max. 0.76 max.

C Distance of screw head below face of seat retainer plate. 0 to 0.050 0 to 1.27

D Width of sealing area of spiral-wound gasket for valve’s size and rating.

- -

E Distance gasket sealing area overlaps fastener opening in face of seat retainer plate (may occur at the ID or OD of the gasket).

35 percent of D(max.)

35 percent of D(max.)



6 API S

TANDARD

594

Table 1A—Minimum Body-Wall Thickness (Exclusive ofRemovable Seat Ring) by Class (Inches)

Valve Size

(NPS)

Class

125 250 150 300 400 600 900 1500 2500

2 0.27 0.39 0.34 0.38 0.44 0.44 0.75 0.75 0.8821/2 0.27 0.43 0.38 0.44 0.47 0.47 0.88 0.88 1.00

3 0.33 0.49 0.41 0.47 0.50 0.50 0.75 0.94 1.194 0.43 0.54 0.44 0.50 0.50 0.62 0.84 1.12 1.415 0.43 0.60 — — — — — — —6 0.49 0.65 0.47 0.62 0.66 0.75 1.03 1.50 1.918 0.54 0.71 0.50 0.69 0.75 1.00 1.25 1.88 2.4410 0.65 0.82 0.56 0.75 0.84 1.12 1.44 2.25 2.6612 0.71 0.88 0.62 0.81 0.94 1.25 1.66 2.62 3.4114 0.77 0.98 0.66 0.88 1.06 1.38 1.81 2.75 —16 0.88 1.09 0.69 0.94 1.12 1.50 2.06 3.12 —18 0.93 1.21 0.72 1.00 1.19 1.62 2.25 3.50 —20 0.98 1.31 0.75 1.06 1.31 1.75 2.50 3.88 —24 1.09 1.42 0.81 1.19 1.44 2.00 2.88 4.50 —30 1.26 1.75 0.91 1.38 1.69 2.38 — — —36 1.42 2.08 1.00 1.57 1.95 2.77 — — —42 1.58 2.41 1.09 1.76 2.20 3.15 — — —48 1.75 2.73 1.19 1.95 — — — — —54 — — * * — — — — —60 — — * * — — — — —

Note: The wall thickness shown for Classes 125 and 250 conform to those in ASME B16.1,except for NPS 36, 42, and 48, Class 250, which have been extrapolated. The wall thicknessesshown for Classes 150-2500 for sizes through NPS 24 conform to those in API Standard 600.The wall thicknesses for NPS 30-48 are extrapolations of the values in API Standard 600.*Dimensional information to be agreed upon between purchaser and manufacturer.

Table 1B—Minimum Body-Wall Thickness (Exclusive ofRemovable Seat Ring) by Class (Millimeters)

Valve Size

(NPS)

Class

125 250 150 300 400 600 900 1500 2500

2 7 10 9 10 11 11 19 19 2221/2 7 11 10 11 12 12 22 22 25

3 9 12 10 12 13 13 19 24 304 11 14 11 13 13 16 21 29 365 11 15 — — — — — — —6 12 17 12 16 17 19 26 38 488 14 18 13 17 19 25 32 48 6210 17 21 14 19 21 29 37 57 6712 18 22 16 21 24 32 42 67 8714 19 25 17 22 27 35 46 70 —16 22 28 17 24 29 38 52 79 —18 24 31 18 25 30 41 57 89 —20 25 33 19 27 33 44 64 98 —24 28 36 21 30 36 51 73 114 —30 32 45 23 35 43 60 — — —36 36 53 25 40 50 70 — — —42 40 61 28 45 56 80 — — —48 45 69 30 50 — — — — —54 — — * * — — — — —60 — — * * — — — — —

Note: The wall thicknesses shown for Classes 125 and 250 conform to those in ASME B16.1,except for NPS 36, 42, and 48, Class 250, which have been extrapolated. The wall thicknessesshown for Classes 150-2500 for sizes through NPS 24 conform to those API Standard 600. Thewall thicknesses for NPS 30-48 are extrapolations of the values in API Standard 600.*Dimensional information to be agreed upon between purchaser and manufacturer.



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-LUG, AND DOUBLE FLANGED TYPE 7

Table 2A—Single- and Dual-Plate Valve Face-to-Face Dimensionsby Class (Inches)

Valve Size

(NPS)

Class

125 250 150 300 400 600 900 1500 2500

2 2.12 2.12 2.38 2.38 2.38 2.38 2.75 2.75 2.7521/2 2.38 2.38 2.62 2.62 2.62 2.62 3.25 3.25 3.25

3 2.62 2.62 2.88 2.88 2.88 2.88 3.25 3.25 3.384 2.62 2.62 2.88 2.88 3.12 3.12 4.00 4.00 4.125 3.25 3.25 — — — — — — —6 3.75 3.75 3.88 3.88 5.38 5.38 6.25 6.25 6.258 5.00 5.00 5.00 5.00 6.50 6.50 8.12 8.12 8.1210 5.50 5.50 5.75 5.75 8.38 8.38 9.50 9.75 10.0012 7.12 7.12 7.12 7.12 9.00 9.00 11.50 12.00 12.0014 7.25 8.75 7.25 8.75 10.75 10.75 14.00 14.00 —16 7.50 9.12 7.50 9.12 12.00 12.00 15.12 15.12 —18 8.00 10.38 8.00 10.38 14.25 14.25 17.75 18.44 —20 8.38 11.50 8.62 11.50 14.50 14.50 17.75 21.00 —24 8.75 12.50 8.75 12.50 15.50 17.25 19.50 22.00 —30 12.00 14.50 12.00 14.50 18.12 19.88 — — —36 14.50 19.00 14.50 19.00 25.00 25.00 — — —42 17.00 22.38 17.00 22.37 27.61 27.61 — — —48 20.62 24.75 20.62 24.75 — — — — —54 — — * * — — — — —60 — — * * — — — — —

Note: The face-to-face tolerance shall be as specified in ASME B16.10 for sizes through NPS 24and shall be ±0.125 inch (3 millimeters) for sizes larger than NPS 24.*Dimensional information to be agreed between purchaser and manufacturer.

Table 2B—Single- and Dual-Plate Valve Face-to-Face Dimensionsby Class (Millimeters)

Valve Size

(NPS)

Class

125 250 150 300 400 600 900 1500 2500

2 54 54 60 60 60 60 70 70 7021/2 60 60 67 67 67 67 83 83 83

3 67 67 73 73 73 73 83 83 864 67 67 73 73 79 79 102 102 1055 83 83 — — — — — — —6 95 95 98 98 136 136 159 159 1598 127 127 127 127 165 165 206 206 20610 140 140 146 146 213 213 241 248 25412 181 181 181 181 229 229 292 305 30514 184 222 184 222 273 273 356 356 —16 191 232 191 232 305 305 384 384 —18 203 264 203 264 362 362 451 468 —20 213 292 219 292 368 368 451 533 —24 222 318 222 318 394 438 495 559 —30 305 368 305 368 460 505 — — —36 368 483 368 483 635 635 — — —42 432 568 432 568 701 701 — — —48 524 629 524 629 — — — — —54 — — * * — — — — —60 — — * * — — — — —

Note: The face-to-face tolerance shall be as specified in ASME B16.10 for sizes through NPS 24and shall be ±0.125 inch (3 millimeters) for sizes larger than NPS 24.*Dimensional information to be agreed between purchaser and manufacturer.



8 API STANDARD 594

5 Material5.1 BODY

The bodies of wafer, wafer-lug, and double flanged typecheck valves shall be made of a material conforming to a pur-chaser selected material specification listed in the applicableASME standard as referenced in 3.2.

5.2 PLATES

Plates shall be made of a material whose corrosion resis-tance is greater than or equal to that of the valve body.

5.3 TRIM

5.3.1 The trim includes the following:

a. Body seating surfaces.b. Plate seating surfaces.

5.3.2 Metallic seating surface material shall be manufac-turer’s standard which may be the same as the body material.Where specific trim is requested, it shall be as shown in Table3. The typical specifications in Table 3 represent some accept-able grades. The resilient seal material, when required shallbe specified by the purchaser and if located in the body thereshall not be an overlay in the seat area unless specified in thepurchase order.

5.4 INTERNAL WETTED PARTS

Internal wetted parts shall be suitable for the specified ser-vice conditions and their material will be manufacturers’

standard unless otherwise specified in the purchase order. Theterm “wetted parts” shall include, but not be limited to,hinges, pins, bolts, bearings, and any other part in contactwith the fluid medium other than the body, plates, trim,springs and pipe plugs.

5.5 BODY SEAT RINGS

If the body seat ring material is different from the seating-surface material, its corrosion resistance shall be greater thanor equal to that of the valve-body material.

5.6 SPRINGS

Depending on the service, the material requirements forthe spring may differ from those of the seat and other trimmaterial and will be the manufacturer’s standard unless other-wise specified in the purchase order.

5.7 PIPE PLUGS (PIN RETAINERS)

Any pipe plugs used shall be solid and shall have the samenominal chemical composition and material properties asdoes the valve body.

5.8 NAMEPLATE

The nameplate shall be 18Cr-8Ni steel or nickel alloyand shall be attached to the valve body by pins or welding.The pin material used for attachment shall be similar to thenameplate.

Table 3—Seating-Surface Nominal Trim Material

Typical Specification (Grade)

Trim No. Nominal Trim Material Typea Cast Forged Welded

1 Type 410 11-13Cr ASTM A 217 (CA15)

ASTM A 182(F6)

AWS A5.9 (ER410)

2 Type 304 18Cr-8Ni ASTM A 351 (CF8)

ASTM A 182 (F304)

AWS A5.9 (ER308)

5 Hard-faced Co-Cr-Ab Manufacturer’s standard

Manufacturer’s standard

AWS A5.13 (E Co-Cr-A orR Co-Cr-A)

5A Hard-faced Ni-Crc Manufacturer’s standard



9 Monel Ni-Cu alloy ASTM A 494(M-35-1)

ASTM B 564 (UNS N04400)


10 Type 316 18Cr-8Ni-Mo ASTM A 351 (CF8M)

ASTM A 182(F316)

AWS A5.9 (ER316)

13 Alloy 20 19Cr-29Ni ASTM A 351 (CN7M)

ASTM B 473 AWS A5.9 (ER320)

15 Bronze Bronze Manufacturer’s standard


—

aResilient seating materials shall be specified by the purchaser.bThis classification includes but is not limited to, such trademarked materials as Stellite 6™, Stoody 6™, andWallex 6™.cThese materials shall have manufacturer’s standard hard facing with a maximum iron content of 25 percent.



CHECK VALVES: WAFER, WAFER-LUG, AND DOUBLE FLANGED TYPE 9

6 Inspection, Examination, Testing, and Repair

6.1 INSPECTION AND EXAMINATION

6.1.1 Each valve shall be visually examined by the manu-facturer in accordance with API 598.

6.1.2 When inspection by the purchaser is specified by thepurchase order, it shall be in accordance with API 598.

6.2 PRESSURE TESTS

Each valve shall be pressure tested in accordance with APIStandard 598.

6.3 REPAIR OF DEFECTS

6.3.1 Defects in the body of a cast or forged, carbon oralloy steel valve may be repaired as permitted by the mostnearly applicable ASTM cast or forged material specificationlisted in ASME B16.34.

6.3.2 The repair of defects in cast iron or ductile iron cast-ings, by methods such as welding, brazing, plugging, orimpregnation, is not permitted.

7 Marking Nameplates7.1 API 594

Nameplates (see 5.8) of valves made in compliance withthis standard shall be marked “API 594” and shall be addi-tionally marked as follows:

a. For a valve made of steel, nickel alloy or special alloy,marking shall be in accordance with the requirements ofASME B16.34.b. For a valve made of other materials, marking shall be inaccordance with MSS-SP-25.

7.2 RESILIENT SEATING

Nameplates of valves furnished with resilient seating mate-rials shall be marked to establish the temperature limitationsof the seating material.

8 Shipment

8.1 COATINGS

8.1.1 The machined surfaces of materials that are not rustresistant shall be coated with an easily removable rust preven-tive.

8.1.2 Coatings shall not contain lead. Nonferrous and aus-tenitic stainless steel valves shall not be coated. Unless other-wise specified in the purchase order, the external surfaces ofvalve bodies shall be painted with the following colors:

a. Carbon and low-alloy steel—aluminum.b. Ductile iron—green.c. Cast iron—black.

8.2 VALVE OPENINGS

8.2.1 Except for the ends of small, individually packagedvalves, valve ends shall be covered to protect the gasket sur-faces and valve internals during shipment and storage. Theprotective covers shall be wood, wood fiber, plastic, or metaland securely attached to the valve ends by bolts, steel straps,or suitable friction locking devices. The covers shall be nosmaller than the outside diameter of the valve ends anddesigned so that the valves cannot be installed without com-plete removal of the covers.

8.2.2 All threaded connections in the valve body shall befitted with solid, fully tightened plugs conforming to ASMEB16.11, or ASME B16.14. Gray iron or malleable iron plugsshall only be used on gray iron or ductile iron valves respec-tively.

8.3 PACKAGING

8.3.1 When export packaging is not specified in the pur-chase order, valves may be shipped loose, palletized, orpacked in a box or crate. Valves shall be packaged to preventdamage during shipment.

8.3.2 When the purchase order specifies export packaging,valves shall be shipped in wooden boxes or crates, individu-ally or collectively, and packed to prevent their shifting withinthe package. (The shipping agent representing the purchaserwill normally provide detailed instructions.)

9 Recommended Spare PartsWhen specified on the purchase order, the vendor shall

submit a complete list of spare parts. The list shall includecross-sectional or assembly-type drawings for identificationwith part numbers.





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Std 589, Fire Test for Evaluation of Valve Stem Packing

RP 591, User Acceptance of Refinery Valves

Std 598, Valve Inspection and Testing

Std 599, Metal Plug Valves—Flanged and Welding Ends

Std 600, Steel Gate Valves—Flanged and Butt-Welding Ends

Std 602, Compact Steel Gate Valves

Std 603, Class 150, Cast, Corrosion-Resistant, Flanged-End Gate

Std 607, Fire Test for Soft-Seated Quarter-Turn Valves

Std 608, Metal Ball Valves—Flanged and Butt-Welding Ends

Std 609, Lug- and Wafer-Type Butterfly Valves

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