spiral-wound gaskets

CONSTRUCTION
The spiral-wound sealing element of a LIMCT RW-type gasket consists of a thin metallic strip and a soft nonmetallic filler that are simultaneously wound on a rotating mandrel. The metal strip is pre-formed with a chevron, or V-shaped profile, which allows the winding to act as a spring between the flanges. Further, the metal strip provides the basic structural element for the gasket while the non-metallic filler material seals small imperfections on the flange surfaces.

The density of the gasket can be varied by changing the winding pressure and/or the filler thickness. As a general rule, thin fillers and higher winding pressures are used to produce higher-pressure gaskets.

In accordance with ASME B16.20-1993 several plies of metal with no filler are wound on the inner and outer diameters. Also, the specification requires a minimum of 3 welds on both the gasket I.D. and O.D.

LIMCT RW gaskets have a spiral-wound sealing element with a carbon steel outer ring. The sealing element is nominally .175” thick while the ring is nominally 1/8” thick.

The purpose of the outer ring is threefold:
1. Centers the gasket in the flange assembly,
2. Provides radial strength to prevent gasket blowout,
3. Acts as a compression stop, preventing flange overtightening.

INVENTORY
LIMCT offers a large inventory of standard mica/graphite gaskets with centering ring, from 1/2" through 18", in 150# and 300# ranges. We stock large quantities.

COLOR CODING
All our Spiral Wound gaskets are color coded on the outer edge to permit easy identification in inventory and when installed between flanges. These color codes have been adopted by API 601 and the Fluid Sealing Association (FSA) Metallic Gasket Division.

DIMENSIONS
By Pressure Class per ASME B16.20-1993 Flanges (Dimensions in inches). Nominal gasket thickness is .175". Nominal centering ring thickness is 1/8".

USE OF THE TABLES
To find true gasket dimensions, you must use all three tables below. The 'Gasket ID' table provides the actual inside diameter. The 'Winding OD' table provides the distance from the gasket ID to the outside diameter of the sealing element. And finally, 'Centering Ring (Gasket) OD' provides the outside gasket diameter. See drawing.

Nominal Pipe Size, Inches	Gasket I.D., Inches
Nominal Pipe Size, Inches	150	300	400	600	900	1500	2500
1/2	0.75	0.75	0.75	0.75	0.75	0.75	0.75
3/4	1.00	1.00	1.00	1.00	1.00	1.00	1.00
1	1.25	1.25	1.25	1.25	1.25	1.25	1.25
1 1/4	1.88	1.88	1.88	1.88	1.56	1.56	1.56
1 1/2	2.13	2.13	2.13	2.13	1.88	1.88	1.88
2	2.75	2.75	2.75	2.75	2.31	2.31	2.31
2 1/2	3.25	3.25	3.25	3.25	2.75	2.75	2.75
3	4.00	4.00	4.00	4.00	3.75	3.63	3.63
4	5.00	5.00	4.75	4.75	4.75	4.63	4.63
5	6.13	6.13	5.81	5.81	5.81	5.63	5.63
6	7.19	7.19	6.88	6.88	6.88	6.75	6.75
8	9.19	9.19	8.88	8.88	8.75	8.50	8.50
10	11.31	11.31	10.81	10.81	10.88	10.50	10.63
12	13.38	13.38	12.88	12.88	12.75	12.75	12.50
14	14.63	14.63	14.25	14.25	14.00	14.25	-
16	16.63	16.63	16.25	16.25	16.25	16.00	-
18	18.69	18.69	18.50	18.50	18.25	18.25	-
20	20.69	20.69	20.50	20.50	20.50	20.25	-
24	24.75	24.75	24.75	24.75	24.75	24.25	-

Nominal Pipe Size, Inches	Winding O.D., Inches
Nominal Pipe Size, Inches	150, 300 400, 600	900 1500, 2500
1/2	1.25	1.25
3/4	1.56	1.56
1	1.88	1.88
1 1/4	2.38	2.38
1 1/2	2.75	2.75
2	3.38	3.38
2 1/2	3.88	3.88
3	4.75	4.75
4	5.88	5.88
5	7.00	7.00
6	8.25	8.25
8	10.38	10.13
10	12.50	12.25
12	14.75	14.50
14	16.00	15.75
16	18.25	18.00
18	20.75	20.50
20	22.75	22.50
24	27	26.75

Nominal Pipe Size	Centering Ring (Gasket) O.D.
Nominal Pipe Size	150	300	400	600	900	1500	2500
1/2	1.88	2.13	2.13	2.13	2.50	2.50	2.75
3/4	2.25	2.63	2.63	2.63	2.75	2.75	3.00
1	2.63	2.88	2.88	2.88	3.13	3.13	3.38
1 1/4	3.00	3.25	3.25	3.25	3.50	3.50	4.13
1 1/2	3.38	3.75	3.75	3.75	3.88	3.88	4.63
2	4.13	4.38	4.38	4.38	5.63	5.63	5.75
2 1/2	4.88	5.13	5.13	5.13	6.50	6.50	6.63
3	5.38	5.88	5.88	5.88	6.63	6.88	7.75
4	6.88	7.13	7.00	7.63	8.13	8.25	9.25
5	7.75	8.50	8.38	9.50	9.75	10.00	11.00
6	8.75	9.88	9.75	10.50	11.38	11.13	12.50
8	11.00	12.13	12.00	12.63	14.13	13.88	15.25
10	13.38	14.25	14.13	15.75	17.13	17.13	18.75
12	16.13	16.63	16.50	18.00	19.63	20.50	21.63
14	17.75	19.13	19.00	19.38	20.50	22.75	-
16	20.25	21.25	21.13	22.25	22.63	25.25	-
18	21.63	23.50	23.38	24.13	25.13	27.75	-
20	23.88	25.75	25.50	26.88	27.50	29.75	-
24	28.25	30.50	30.25	31.13	33.00	35.50	-

Winding Material	Edge Color
304 Stainless	Yellow
316 Stainless	Green
347 Stainless	Blue

Filler Material	Edge Stripe
Asbestos (not available)	None
Mica Graphite	Pink
Flexible Graphite	Gray
PTFE	White