Flange type

RAISED FACE (RF) FLANGE

RF flanges seal with a flat gasket, formerly made of asbestos but now made of more environmentally friendly material, designed for installation between the raised faces of two mating flanges (both with raised faces). The raised faces have a prescribed texture to increase their gripping and retaining force on this flat gasket. Some users of raised face flanges specify the use of spiral wound gaskets. These gaskets may often have an inner ring on their I.D. and an outer disc around their O.D. This feature will hold the gasket concentric with the bolt circle and bore to make precise assembly easier with the gasket centered on the flange sealing surfaces. See an explanation of Spiral Wound Gaskets below

SPIRAL WOUND (SPWD) GASKET

SPWD identifies a flat gasket used between two RF flanges (without ring grooves). SPWD gaskets contain a "spiral wound" metallic filler forreinforcement.

RING TYPE JOINT (RTJ) FLANGE

RTJ flanges have grooves cut into their faces which accept steel Ring Gaskets. RTJ flanges seal when tightened bolts compress the gasket between the flanges into the grooves, deforming (or "Coining") the gasket to make Intimate Contact inside the grooves, creating a metal to metal seal.

An RTJ flange may have a raised face with a ring groove machined into it. This raised face does not serve as any part of the sealing means. For RTJ flanges that seal with BX ring gaskets, the raised faces of the connected and tightened flanges may contact each other. In this case the already coined gasket will not bear additional load beyond the bolt tension, vibration and movement cannot further crush the gasket and lessen the connecting tension.

Specification for CRA Clad or Lined Steel Pipe

8 Special Tests

8.1 Ferrite/Austenite Ratio for Duplex Stainless Steel

When the CRA layer is composed of duplex stainless steel the ferrite/austenite ratio shall be measured. The requirements of API 5LC, Section 8.1 shall apply for test methods, test frequency and acceptance requirements. If this test has been performed on CRA tubes used for liner pipe as part of the specification for that material and the results are documented, there is no need to repeat the test for conformance to this standard. 

8.2 Corrosion Testing

A corrosion sensitivity test shall be performed as a manufacturing procedure qualification test (MPQT) on the CRA layers of austenitic steel and Ni-base alloy as described below. The purpose of this test is to assure proper manufacturing procedures for austenitic steeland Ni-base alloys. It is not a test to determine susceptibility for use with a particular environment.

a)Summary of test procedure. 

The testing procedure shall conform to the requirements of the latest editions of ASTM A262, Practice E or Practice B,or ASTM G28, Method A or ASTM G48, Method A (Section 8), whichever is

suitable for the cladding or liner material and as agreed between the purchaser and manufacturer. The method that is used shall be agreed to between the purchaser and the manufacturer. Other practices may be agreed upon.

b)Specimen sampling. One specimen shall be taken from the CRA layer of as manufactured pipe in the same condition as pipes to be delivered.For welded clad pipe and welded liner pipe of lined pipe an additional specimen shall be taken from across the longitudinal weld (i.e. original CRA cladding + weld seam). The specimen axis shall be transverse to the pipe axis. One test for each heat oreach heat-treatment lot shall be performed as described in the footnote to API 5LC, Table 7. 

As part of the MPQT a parallel specimen shall be tested with a sample of the same CRA which has been

deliberately sensitized in order to demonstrate that the chosen test method is capable of detection of a

microstructure which is sensitive to intergranular corrosion. The sensitizing heat treatment shall be agreed upon between the purchaser and the manufacturer.

c)Specimen preparation. The specimen shall be made of CRA layer and be approximately 76.2 mm (3 in.) long and 25.4 mm (1 in.) wide. Detailed sampling condition may be specified in the agreement between the purchaser and the manufacturer. Sawing is preferred to shearing; but if sheared, the sheared edge of the specimen shall be machined or ground-off. The specimen shall be tested in the as-received condition except that it may be flattened, if desired. Any scale on the specimen shall be removed mechanically with 120 grit iron-free aluminum oxide abrasive. Alternatively, chemical removal of scale is permissible. Each specimen shall be degreased using acetone, alcohol, or a vapor degreaser prior to testing.

d)Test condition. The test solution and testing conditions shall be as stated in ASTM A262, ASTM G28 or ASTM G48 for the specific practice being conducted. 

1) ASTM A262, Practice E, bend test.

For acceptance, the tested specimen shall be bent through 180°over a diameter equal to twice the thickness of the specimen. Bending axis shall be perpendicular to the direction of the test specimen. Unless otherwise specified, the bend test system shall be a root bend (i.e. the inside surface of the pipe shall be strained in tension). The wall thickness need not be greater than 9.53 mm (0.375 in.).

In case of material having low ductility, the maximum angle of bend without causing cracks in the material shall be determined by bending an untested specimen of the same configuration as the specimen to be tested. For welded specimens, the fusion line shall be located approximately at the centerline of the bend.

2)Minimum acceptance criteria. The bent test specimen shall first be examined at low magnification. If the evaluation is questionable,the specimen shall then be examined at a magnification of ×100. No cracking is permitted. An investigation to determine cause of failure is required and agreement by the purchaser is required prior to any retest procedure.

e) ASTM G28 or ASTM G48, Practice A. 

Minimum acceptance criteria. The acceptance criteria shall be agreed upon between the purchaser and the

manufacturer. See ASTM G28, 8.2 and 8.3 or ASTM G48, 8.0 for guidance. 

8.3 Tests for CRA Cladding Bond Strength and CRA Liner Tightness

Tests for CRA cladding, bond strength and CRA liner tightness are as follows.

a)Clad steel pipe. Special bond shear strength tests shall be performed. Typical tests for bond shear strength include those found in ASTM A264 and ASTM A265.Selection of the test method shall be by agreement. The test shall be carried out on one per 50 pipes during the manufacturing process. The minimum acceptable bond shear strength shall be 137.8 MPa (20000 psi). 

As an alternate to the bond shear strength and by agreement between the purchaser and the manufacturer, a flattening test may be conducted. Acceptance limit of clad separation orcrack length shall be specified by agreement between the purchaser and manufacturer.

b)Lined steel pipe. The gripping force (σy) to determine the tightness between the lining and the backing steel shall be measured. The method of measurement shall be byagreement between purchaser and manufacturer. The gripping force (σy) shall be measured on one pipe during the MPQT, and on one per 50 pipes during production. 

8.4 Residual Magnetism

The residual magnetism shall be recorded at both ends of each finished pipe and shall not exceed 15 Gauss. Magnetism levels higher than this value shall require the pipe end to be demagnetized until the level is reduced below 15 Gauss.

SPECIAL NOTES, API

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

Neither API nor any API's employees, subcontractors, consultants, committees, or other assignees make any warranty or representation, either express or implied, with respect to the accuracy, completeness, or usefulness of the information contained herein, or assume any liability or responsibility for any use, or the results of such use, of any information or process disclosed in this publication.

Neither API nor any of API's employees, subcontractors, consultants, or other assignees represent that use of this publication would not infringe upon privately owned rights.

API publications may be used by anyone desiring to do so. Every effort has been made by the Institute to assure the accuracy and reliability of the data contained in them; however, the Institute makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any authorities having jurisdiction with which this publication may conflict.

API publications are published to facilitate the broad availability of proven, sound engineering and operating practices. These publications are not intended to obviate the need for applying sound engineering judgment regarding when and where these publications should be utilized. The formulation and publication of API publications is not intended in any way to inhibit anyone from using any other practices. Any manufacturer marking equipment or materials in conformance with the marking requirements of an API standard is solely responsible for complying with all the applicable requirements of that standard. API does not represent, warrant, or guarantee that such products do in fact conform to the applicable API standard.