ABOUT FLANGES

 

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Revised: 07/17/2012

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Field Appraisal of Ring Grooves

(AND AN EXPLANATION OF

RING GASKET SEAL PERFORMANCE)

Any field judgment of ring groove condition depends on the assumption that the groove has the correct dimensions. Dimensional inspection of the groove requires special tools and instruments beyond the scope of field evaluation.   This Web Site Tool information should help you judge used ring grooves that originally had correctly machined dimensions and finish.

To judge a ring groove as suitable for use you must have a good understanding of the contact surface location against which the ring gasket seals. Ring gaskets seal over approximately 40% of the ring groove vertical surface.  For reliable sealing, flanges that utilize ring gaskets should have the middle 60% of their ring groove O. D. in good condition. If the middle 60% of the vertical O. D. of the groove has a good 1 uniform surface it will seal 1 with a new undamaged 1 ring gasket. 

The illustrations below show the approximate distribution of the seal contact area.

 

 

RING GROOVE IN 6 B FLANGES

R RING GASKETS COME IN OVAL AND OCTAGONAL CONFIGURATIONS.  R RING GASKETS HAVE THE SAME NOMINAL PITCH DIAMETER AS THE GROOVE INTO WHICH THEY FIT. WHEN PLACING A NEW R RING GASKET INTO A NEW OR LIKE NEW RING GROOVE THE GASKET SHOULD CONTACT OR NEARLY CONTACT ON BOTH O.D. AND I.D. COINING OCCURS ON BOTH O.D. AND I.D. DURING MAKE-UP.

 

"R" RING GROOVE WITH R OVAL GASKET

 

SEAL BEGINS 20% FROM TOP

COINED GASKET CONTACTS 40% OF GROOVE SURFACE ON BOTH SIDES 

 

                               

 

 

"R" RING GROOVE WITH R OCTAGONAL GASKET

 

SEAL BEGINS APPROXIMATELY 20% FROM TOP

COINED GASKET  CONTACTS APPROXIMATELY 40% OF GROOVE SURFACE ON BOTH SIDES

 

                              

 

 

 "R" RING GROOVE WITH RX GASKET

 

RX GASKETS HAVE A PITCH DIAMETER SLIGHTLY GREATER THAN THE PITCH DIAMETER OF THE RESPECTIVE GROOVE THEY FIT. NEW RX GASKETS PLACED IN CORRESPONDING NEW RING GROOVES WILL USUALLY CONTACT ON THE O.D. AND FIT LOOSELY ON THE I.D.  

RX GASKETS HAVE A DESIGN THAT PRODUCES COINING ONLY ON THE O.D.  THE GASKET HAS A LARGER BEARING SURFACE ON THE I.D. PRODUCING AN EXTREME LOAD ON THE O.D. OF THE GASKET TO ENHANCE COINING AND INTIMATE CONTACT  ON THE O.D. SURFACE. 

PULLING MATING RX FLANGES TOGETHER BY TIGHTENING THE BOLTS WILL COMPRESS THE GASKET, REDUCING ITS O.D. IN CONFORMANCE WITH THE GROOVE. THE GASKET FINALLY MEETING METAL TO METAL ON THE I.D., THE GASKET COMPRESSED BOTH VERTICALLY AND IN DIAMETER.

 

SEAL BEGINS APPROXIMATELY 20% FROM TOP

COINED GASKET  CONTACTS APPROXIMATELY 40% OF GROOVE SURFACE ON THE O.D. SIDE, SEALING ONLY ON THE O.D. SIDE.

 

 

 

RING GROOVE IN 6 BX FLANGES

BX GASKETS HAVE A PITCH DIAMETER GREATER THAN THE PITCH DIAMETER OF THE RESPECTIVE GROOVE THEY FIT. NEW BX GASKETS PLACED IN CORRESPONDING NEW RING GROOVES WILL ALWAYS CONTACT ON THE O.D. AND FIT LOOSELY ON THE I.D.  

PULLING MATING BX FLANGES TOGETHER BY TIGHTENING THE BOLTS WILL COMPRESS THE GASKET, REDUCING ITS O.D. IN CONFORMANCE WITH THE GROOVE. THE GASKET FINALLY MEETING METAL TO METAL ON THE I.D., THE GASKET COMPRESSED BOTH VERTICALLY AND IN DIAMETER.

WHEN FLANGES HAVE BEEN PULLED TOGETHER AND BOLTS TIGHTENED TO PROPER TORQUE, RING GASKETS EXPERIENCE "COINING." COINING FORMS THE GASKET TO THE EXACT FINISH AND FORM OF THE SEALING RING GROOVE SURFACES. INTIMATE CONTACT OF THE COINED RING GASKET WITH THE GROOVE SEALING SURFACE,  FORMS A SEAL TO CONTAIN THE FLUID OR GAS INSIDE THE CONNECTION.

RADIAL COMPRESSION ON THE OUTSIDE DIAMETER OF THE RING GASKET WILL MAINTAIN METAL TO METAL CONTACT ON THE O.D. SHOULD PRESSURE CAUSE SOME STRAIN (STRETCHING) ON THE CONNECTING BOLTS.

 

"BX" RING GROOVE WITH BX GASKET

 

 

SEAL BEGINS APPROXIMATELY 20% FROM TOP

SEAL CONTACTS APPROXIMATELY 40% OF GROOVE SURFACE ON BOTH SIDES  BUT RELIABLY SEALS ON O.D. ONLY

 

 

 

GROOVE CONDITION APPRAISAL

Keeping in mind that sealing usually occurs somewhere within the limits of the middle 60% of the O.D. of a ring groove. The middle 60% of the vertical surface of the O.D. of any ring groove must appraise as good 1 in order to judge the groove as satisfactory for service. The bottom of the ring groove does not contact the gasket or provide any contribution to sealing, therefore, its condition does not matter. The I.D. of the ring groove cannot reliably seal therefore it need only have a surface condition good enough 1 to allow the gasket to slide against it as the gasket moves down the groove into its seated coined position.

 

EXAMINE THE RING GROOVE

FIRST CLEAN IT:

  • REMOVE ALL GREASE AND DIRT, USE SOLVENTS, WIPING RAGS AND A WIRE BRUSH IF NECESSARY.

  • REMOVE ALL SURFACE RUST, USE A WIRE BRUSH AND EMERY CLOTH PAD BY HAND IF NECESSARY (50 GRIT TO START AND 100 GRIT TO FINISH).

  • REMOVE ALL NICKS 1 AND DINGS 1  ALONG THE TOP EDGES OF THE O.D. AND I.D. USE AN EMERY CLOTH PAD BY HAND FOR SMALL IRREGULARITIES AND A DIE GRINDER WITH A  SMALL FINE 1 MOUNTED POINT FOR ANY LARGER ONES. (NO DAMAGE CAUSED BY  HANDLING OR RUST SHOULD EXTEND MORE THAN 20% INTO/ONTO THE O.D. SEALING SURFACE OF THE GROOVE).

  • USE AN EMERY CLOTH PAD BY HAND (100 GRIT OR FINER) TO SMOOTH AND POLISH BOTH THE O.D. AND I.D. OF THE GROOVE.

 

SECOND, APPRAISE IT:

  • THE O.D. MUST HAVE A USABLE 1 SURFACE OR THE OTHER ASPECTS OF APPRAISAL DO NOT  MATTER.

  • THE O.D. MUST APPEAR SMOOTH WITHOUT ANY DEEP 1 RADIAL GROOVING AND NO VERTICAL GROOVING OF ANY KIND 1.

  • THE O.D. MUST NOT HAVE ANY LARGE RUST PITTING OR DENT 1 TYPE DAMAGE.

  • THE GROOVE MUST NOT HAVE CONTINUOUSLY CONNECTED 1 SMALL RUST PITS THAT CROSS 1  THE VERTICAL MIDDLE  60% OF THE O.D. SEALING SURFACE.

  • THE CRITICAL MIDDLE 60% OF THE O.D. SURFACE MUST HAVE A FINE 1 FINISH, BEST TESTED BY RUNNING A FINGERNAIL AROUND THE MIDDLE OF THE O.D. THE FINGERNAIL MUST NOT CATCH ON ANY VERTICAL IRREGULARITIES AND THE SURFACE MUST APPEAR UNIFORM.

  • THE I.D. MUST FEEL SMOOTH TO THE TOUCH,  BEST TESTED BY PASSING THE PAD OF A FINGER AROUND THE MIDDLE 60% OF THE I.D.

 
MIDDLE 60% SMOOTH WITH NO VERTICAL GROOVES  OR CONNECTED PITTING. MIDDLE 60% SMOOTH TO THE TOUCH.

 

IF A GROOVE MEETS THE ABOVE CRITERIA IT SHOULD TEST 1

EVERY RING TYPE JOINT SHOULD EXPERIENCE A HYDROTEST WITH A HOLD PERIOD AND NO LEAKS DETECTED BEFORE USE.
Click here for Test Rack Tips

Click here for Q & A 21 Ring Gasket Evaluation
 This question and its answer will guide you through its text, photographs, and links, to the most complete body of information about Ring Groove and Ring Gasket evaluation you will find on the web today.
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Words in bold italic indicate they have subjective meaning and persons using this information must use experience to improve the reliability of their judgment when the meaning of these words can have impact on performance.

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