Gaskets and RTJ Rings — Companion Article

What this tool does

The page shows gasket dimensions for a gasket type, a nominal size, and a class or, for type RX and type BX, an API pressure. This build stores spiral-wound gaskets for ASME B16.5 and for ASME B16.47 Series A and Series B, flat rings for those same flanges, type R rings, and type RX and type BX rings.

Opening /tools-training/gaskets/ with no query shows the spiral-wound gasket at NPS 2, Class 150.

The lookup runs in the browser. The stored unit is the millimetre. Inches are that millimetre divided by 25.4 and are labelled as a conversion.

When to use it

Use it when the flange class and NPS are already known and you want the matching interim gasket row: a spiral-wound gasket or a flat ring for a raised face, a type R ring for an ASME ring joint, or a type RX or type BX ring for an API 6B or 6BX flange.

Use the flange datasheet when you need the flange envelope and the studs for that same class and NPS. This page does not choose a gasket material, a filler, or a facing, and it does not rate the joint.

Inputs

1. Gasket. The label names the gasket. The list is flat rings, spiral-wound gaskets, type R, type RX, and type BX.
2. Nominal size. The ASME B16.5 spiral-wound list runs from NPS 1/2 through NPS 24, with no NPS 3-1/2. The page opens on NPS 2. ASME B16.47 tables start at NPS 26. Type RX and type BX use the API nominal sizes printed on their source pages.
3. Class, or Pressure, psi, on type RX and type BX. The ASME B16.5 spiral-wound list is Class 150, 300, 400, 600, 900, 1500, and 2500. The page opens on Class 150.
4. Ring number, on type R, type RX, and type BX. Choosing a ring number that has a published use sets the nominal size and pressure from the first use of that ring.
5. Units: millimetres, or inches converted from the millimetre table.

A flange datasheet can open a row directly: /tools-training/gaskets/?pdp=PDP-088&nps=2&class=150 for the spiral wound, or /tools-training/gaskets/?pdp=PDP-091&ring=R-20 for that type R ring. The page keeps those query values.

How it works

With no query, the page selects the spiral-wound gasket, NPS 2, Class 150, and reads that stored row. A query that names a catalogue id, an NPS, and a class uses that request when the id and the size are in the table.

The spiral-wound row returns four diameters. d1 is the inner-ring inside diameter. d2 is the sealing inside diameter. d3 is the sealing outside diameter. d4 is the centering-ring outside diameter. On the ASME B16.5 tables the centering-ring thickness is the stored range 2.97 to 3.33 mm and the sealing-element thickness is the stored 4.45 mm. The ASME B16.47 pages state the same ring-thickness range and do not state 4.45 mm, so that sealing thickness is not shown for Series A or Series B.

The flat-ring row returns inside diameter d1 and outside diameter d2. Thickness is specified by the customer and is not a stored number.

The type R row returns pitch diameter P, width A, oval height B, octagonal height H, octagonal flat C, and radius R1, plus the published use. Type RX returns outside diameter, width, flat width, bevel height, ring height, and radius. Type BX returns the millimetre nominal size printed on the dimension table, outside diameter, ring height, width, flat outside diameter, flat width, and hole size. Type R dimensions are not copied onto type RX or type BX.

Inches are the stored millimetres divided by 25.4, shown to three decimal places. They are not a second published column.

Understanding the result

The kicker is the NPS and class, or the ring number. The table under it is the stored row in the unit you chose.

The line above the selectors is the provenance note for that gasket. Every table on this page is currently interim data.

A blank cell on a source page is not stored. The message says this extract has no row for that request. It does not substitute a number from another class or another gasket type.

The source page address is printed under a row that has one.

Engineering considerations

A Class 300 raised-face flange uses the Class 300 row. It does not reuse the Class 150 row. NPS 4 Class 300 and NPS 4 Class 600 are different centering-ring outside diameters: 181.1 mm and 193.8 mm.

A ring-joint facing uses the type R ring for that NPS and class, not the spiral-wound row. NPS 2 Class 150 is in both tables: the spiral-wound row, and type R ring R-22. The flange datasheet sends a raised face to the spiral wound and a ring joint to the type R list.

Inner-ring, sealing, and centering-ring diameters are different diameters. d2 is the sealing inside diameter. d4 is the centering-ring outside diameter. The centering ring is not the flange outside diameter.

The page does not select a filler, a winding metal, or a ring material. It does not check whether the gasket suits the fluid or the temperature.

Example

NPS 2, Class 150, spiral-wound gasket for ASME B16.5. This is the row a direct visit shows. Stored cells:

• Inner-ring inside diameter, d1, 55.6 mm.
• Sealing inside diameter, d2, 69.9 mm.
• Sealing outside diameter, d3, 85.9 mm.
• Centering-ring outside diameter, d4, 104.9 mm.
• Centering-ring thickness, 2.97 to 3.33 mm.
• Sealing-element thickness, 4.45 mm.

The same NPS and class on the type R list is ring R-22. Stored cells: pitch diameter 82.55 mm, width 7.95 mm, oval height 14.2 mm, octagonal height 12.7 mm, octagonal flat 5.23 mm, radius 1.5 mm. The published use is NPS 2, Class 150.

The flange datasheet row that links here is Class 150, NPS 2, weld neck, raised face, id B16.5-CL150-NPS-2-WN. Its stored outside diameter is 6.00 in, minimum thickness 0.69 in, and length through hub 2.44 in. The link is /tools-training/gaskets/?pdp=PDP-088&nps=2&class=150.

NPS 4, Class 300, spiral-wound gasket for ASME B16.5. Stored cells: d1 106.4 mm, d2 127 mm, d3 149.4 mm, d4 181.1 mm. NPS 4, Class 600: d1 102.6 mm, d2 120.7 mm, d3 149.4 mm, d4 193.8 mm. Those two rows are the Wermac class pages. No second published millimetre table was found to cross-check them.

Type RX ring RX-20. Stored cells: outside diameter 76.2 mm, width 8.74 mm, flat width 4.62 mm, bevel height 3.18 mm, ring height 19.05 mm, radius 1.5 mm. Hole size is not published for this ring on the source page. Starflex America’s catalogue agrees on outside diameter 76.20 mm, height 19.05 mm, and width 8.74 mm.

Type BX ring BX-152. Stored cells: nominal size on the dimension table 52 mm, outside diameter 84.68 mm, height 10.24 mm, width 10.24 mm, flat outside diameter 83.24 mm, flat width 8.79 mm, hole 1.5 mm. The selector use is API 6BX, NPS 2-1/16, at 10000, 15000, and 20000 psi. Starflex and the MPAC Asia type BX sheet agree on outside diameter, height, and width. BX-168 ring height is stored as 65.86 mm from MetalsPiping. The MPAC Asia sheet prints 35.86 mm for that height. The other BX-168 dimensions agree. The page states that disagreement.

Standards/references (licensed vs interim)

The stored tables are interim.

The spiral-wound note on the page reads: Interim data from Wermac spiral-wound tables for ASME B16.5, dimensions in millimetres, not licensed ASME text. Verify against the current edition of ASME B16.20 before use.

The type R note on the page reads: Interim data from Wermac type R oval and octagonal table, dimensions in millimetres, not licensed ASME text. Verify against the current edition of ASME B16.20 before use.

Flat rings use the Wermac ASME B16.21 pages. Type RX and type BX use the MetalsPiping dimension pages. Each row stores the page address it was read from. These interim figures will be replaced by licensed ASME data when it is available.

Limitations/disclaimer

The disclaimer on the tool: this page is a design aid. It does not rate a joint and it does not replace the governing standard. Type R dimensions are not used for type RX or type BX.

• The ASME B16.5 spiral-wound tables have no NPS 3-1/2. Class 2500 stops at NPS 12. Wermac prints no class 2500 row above that.
• The ASME B16.5 flat-ring table has no Class 1500 or Class 2500 column. NPS 3-1/2 Class 900 is blank on the source page.
• The ASME B16.47 tables start at NPS 26. NPS 12 through NPS 24 are not copied from the B16.5 table. Series B Class 400 and Class 600 flat rings are blank from NPS 38.
• The type RX table lists 41 ring numbers. The type BX table lists BX-150 through BX-172 and BX-303. Other ring numbers are not stored.
• BX-168 ring height disagrees between MetalsPiping (65.86 mm) and the MPAC Asia sheet (35.86 mm). The stored height is the MetalsPiping figure.
• Inches on the page are a conversion of the millimetre table.

Use the tool

Calculate now: Gaskets and RTJ rings

Related tools

• Flange datasheet for the ASME B16.5 envelope and studs at the same class and NPS.
• NPS / DN / OD cross-reference for the nominal size.
• Unit converter for a factor between units. The gasket page already converts its own millimetres at 25.4 mm per inch and labels that conversion.

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