Using combination ring gaskets and combination bolts
Certain nominal size API Spec 6A flanges with different working pressures have:
- The same diameter bolt circle (but different bolt hole sizes)
- The same pitch diameter ring groove (but different ring groove widths and depths)
- The same nominal bore.
Certain nominal size API Spec 6A flanges, with different working pressures have:
These corresponding flanges may join together in a crossover connection without using an adapter. The connection make-up requires a combination ring gasket and combination bolts. Such a connection has the rated working pressure of the lowest pressure flange.
To join 7-1/16″ 3000 to 7-1/16″ 5000 flanges utilize a R-45/R-46 combination ring gasket and 12, special 1-1/8″ x 1-3/8″ x 9-7/8″ long combination bolts with 1, 1-1/8″ and 1, 1-3/8″ nut each.
To join 9″ 3000 to 9″ 5000 flanges utilize a R-49/R-50 combination ring gasket and 12, special 1-3/8″ x 1-5/8″ x 11″ long combination bolts with 1, 1-3/8″ and 1, 1-5/8″ nut each.
When tightening combination flange bolts, do final tightening on the smaller nut and apply the amount of torque as normal for the smaller of the two flanges and that size stud and nut.
The illustration below shows the configuration of an installed combination ring gasket and special combination bolts necessary to join the above identified flanges.
| TYPICAL CONFIGURATION OF A MADE-UP CROSSOVER CONNECTION MADE WITHOUT AN ADAPTER: 7-1/16″ 3M to 7-1/16 5M, or 9″ 3M to 9″ 5M |
The illustration below shows the detail of a cross section of the combination ring gasket shape necessary to connect the above-identified flanges.
| THIS ENLARGED VIEW SHOWS A COMBINATION RING GASKET IN PLACE IN A MADE-UP CROSSOVER CONNECTION, EITHER R-45 / R-46 or R- 49 / R-50 |
| THIS SIDE OF THE COMBINATION GASKET CONFORMS TO THE NARROWER RING GROOVE (R-45 OR R-49) |
| THIS SIDE OF THE COMBINATION GASKET CONFORMS TO THE WIDER RING GROOVE (R-46 OR R-50) |
Using combination adapter ring gaskets
2-1/16″ 3000 R-24 and 2-1/16″ 5000 R-24 flanges have identical dimensions and connect without special provisions. Older 2-1/16″ 3000 or 2-1/16″ 5000 flanges with ring grooves to accommodate R-23 ring gaskets may connect to either 2-1/16″ 3000 R-24 or 2-1/16″ 5000 R-24 flanges with the use of R-23/R-24 special combination adapter ring gaskets and standard bolts.
2-9/16″ 3000 R-27 and 2-9/16″ 5000 R-27 flanges have identical dimensions and connect without special provision. Older 2-9/16″ 3000 or 2-9/16″ 5000 flanges with ring grooves to accommodate R-26 ring gaskets may connect to either 2-9/16″ 3000 R-27 or 2-9/16″ 5000 R-27 flanges with the use of R-26/R-27 special combination adapter ring gaskets and standard bolts.
The illustration below shows a cross section of the special combination adapter ring gasket shape necessary to connect the above-identified flanges.
SMALLER PITCH DIAMETER GASKET SURFACE
R-23 OR R-26
 |
R-24 OR R-27
LARGER PITCH DIAMETER GASKET SURFACE
No rule establishes guidelines for any derating of these joined 2-1/16″ or 2-9/16″ flanges.
Caution: Operators should take special care not to identify 3000 psi rated equipment with these R-23, R-24, R-26 and R-27 ring grooves as 5000 psi equipment based on flange measurement.
