Flat Face Flange Surface Finish Has No Serration

This depends on several issues. If any of the contract documents or specifications call for raised-face and/or serrated flanges in the given location, then these flanges will be unacceptable.

If the documents are silent, you should at least consider any safety implications. If the fluid is toxic, corrosive, or expensive, it would be a good idea to disallow these flanges.

However, if the fluid is water, say at 100 psi, there should be no problem if the mating flanges are well aligned.

Quick answer- NO PROBLEM!

As long as your gasket is compatable with the material in the piping and your bolts are tightened to the recommended, there will be no problems. Seal is dependent upon the alignment of the flange faces and the compression of the gasket which is dependent upon the tightness of the bolts.

Unless you have some exotic system with unique factors there will be no problem.

Good Luck

It would depend on 2 things ..... (unless the service is not critical and you do not have issues with leakage from the assembly)

1). the type of gasket you are to use in the assembly

2). the mating flange surface finish

Answer to point 1 ..... generally the use of class 150 lb flanged system is for low pressure, less agressive service/media for which a cut gasket from sheet sheet materials such as non-asbestos, Graphite, PTFE or rubber is usually the first choice .... the materials need the surface finish to 'bite' into the material to avoid 'blow-out' under service conditions. The result of using of a spiral wound gasket on smooth surface finish flanges is the collapse of the inner windings (can be stopped by the use of an inner guide ring) this can result in the braking of the weld around the bore of the gasket leading it to 'unwind and be pushed along the pipework by the pressure/media in the system. All will result in the bolt loading and lead to leakage.

Answer to point 2 .... both mating flange must be the same surface finish or the gasket will slide on the smooth surface and not seat on either flange leading to gasket collapse and leakage.

GRAHAM LOVEDAY

SPIRA POWER SEALING TECHNOLOGY, SHARJAH, UAE www.spirapower.com

Thanks a lot for respond guys, those flanges for chlorinated seawater service with design pressure 10 barg.

We have decided to rejected flanges due to reason above, one thing PO call for serrated spirall finish.

have a nice day

gui

apparently everyone has missed the boat on this, the reason they are flat faced is an important issue.

When bolting up to a cast valve that is flanged you could crack the flange on the valve if the mating flange is raised face.

anyone that has basic knowledge of piping should know this, I question why you are involved with this with very little knowledge on the standards in the industry?

If you use ASME codes & standards, there must be a serration for flange facing as clearly indicated at Para. 6.4.5 of ASME B16.5:

6.4.5 Flange Facing Finish.

Flange facing finishes shall be in accordance with paras. 6.4.5.1 through 6.4.5.3, except that other finishes may be furnished by agreement between the user and the manufacturer. The finish of the gasket contact faces shall be judged by visual comparison with Ra standards (see ASME B46.1) and not by instruments having stylus tracers and electronic amplification.

6.4.5.1 Tongue and Groove and Small Male and Female. The gasket contact surface finish shall not exceed 3.2 µm (125 µin.) roughness.

6.4.5.2 Ring Joint. The side wall surface finish of the gasket groove shall not exceed 1.6
µm (63 µin.) roughness.

6.4.5.3 Other Flange Facings. Either a serrated concentric or serrated spiral finish having a resultant surface finish from 3.2 µm to 6.3 µm (125 µin. to 250 µin.) average roughness shall be furnished. The cutting tool employed should have an approximate 1.5 mm (0.06 in.) or larger radius, and there should be from 1.8 grooves/mm through 2.2 grooves/mm (45 grooves/in. through 55 grooves/in.).

6.4.6 Flange Facing Finish Imperfections.

Imperfections in the flange facing finish shall not exceed the dimensions shown in Table 3 (Table II-3 of Mandatory Appendix II). A distance of at least four times the maximum radial projection shall separate adjacent imperfections.

A radial projection shall be measured by the difference between an outer radius and inner radius encompassing the imperfection where the radii are struck from the centerline of the bore. Imperfections less than half the depth of the serrations shall not be considered cause for rejection. Protrusions above the serrations are not permitted.