Style CG & CGI to suit AWWA C207 Class E Slip-On and Welded Neck Flanges

Dimensions for style WR/WRI to suit AWWA C207
Class E Slip-On and Welded Neck Flanges

Class 125
Nom. Pipe Size	Inner Ring I.D.	Winding	Centering Ring Outside Dia.
I.D.	O.D.
22	22	22.750	24.000	26.000
26	26	26.500	27.750	30.500
28	28	28.500	29.750	32.750
30	30	30.500	31.750	34.750
32	32	32.500	33.875	37.000
34	34	34.500	35.875	39.000
36	36	36.500	38.125	41.250
38	38	38.500	40.125	43.750
40	40	40.500	42.125	45.750
42	42	42.500	44.250	48.000
44	44	44.500	46.375	50.250
46	46	46.500	48.375	52.250
48	48	48.500	50.375	54.500
50	50	50.500	52.500	56.500
52	52	52.500	54.500	58.750
54	54	54.500	56.500	61.000
60	60	60.500	62.500	67.500

Class 175
Nom. Pipe Size	Inner Ring I.D.	Winding	Centering Ring Outside Dia.
I.D.	O.D.
26	26	26.500	27.750	29.125
28	28	28.500	29.750	31.125
30	30	30.500	31.750	33.375
32	32	32.500	33.750	35.375
34	34	34.500	35.875	37.500
36	36	36.500	37.875	39.500
38	38	38.500	39.875	41.500
40	40	40.500	42.000	43.500
42	42	42.500	44.000	45.875
44	44	44.500	46.000	47.875
46	46	46.500	48.000	49.875
48	48	48.500	50.125	51.875
50	50	50.500	52.250	53.875
52	52	52.500	54.375	56.125
54	54	54.500	56.375	58.125
60	60	60.500	62.500	64.125

DIMENSIONS IN INCHES.

Class 250
Nom. Pipe Size	Inner Ring I.D.	Winding	Centering Ring Outside Dia.
I.D.	O.D.
26	26	26.500	27.750	32.750
28	28	28.500	29.750	35.250
30	30	30.500	31.750	37.500
32	32	32.500	33.875	39.750
34	34	34.500	35.875	41.750
36	36	36.500	38.125	44.000
38	38	38.500	40.125	46.000
40	40	40.500	42.125	48.250
42	42	42.500	44.250	50.750
44	44	44.500	46.375	53.000
46	46	46.500	48.375	52.250
48	48	48.500	50.375	58.750

Class 350
Nom. Pipe Size	Inner Ring I.D.	Winding	Centering Ring Outside Dia.
I.D.	O.D.
26	26	26.500	27.750	29.625
28	28	28.500	29.750	31.625
30	30	30.500	31.750	33.875
32	32	32.500	33.875	35.875
34	34	34.500	35.875	37.875
36	36	36.500	38.125	40.375
38	38	38.500	40.125	42.375
40	40	40.500	42.125	44.375
42	42	42.500	44.250	46.625
44	44	44.500	46.375	49.000
46	46	46.500	48.375	51.000
48	48	48.500	50.375	53.000
52	52	52.500	54.250	57.375
54	54	54.500	56.500	59.375
60	60	60.500	62.500	65.375
66	66	66.500	68.500	72.500

DIMENSIONS IN INCHES.

 
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A Spiral Wound Gasket is the most widely used common metallic gasket used in industrial applications involving a range of pressure and temperatures. They are popular in the oil and gas, chemical, petrochemical, power, and food industries and prevents leak through flange joints. The concept of spiral wound gasket was first developed by Flexitallic in the year 1912 to serve US refinery operations involving severe temperature and pressure fluctuations.

Spiral wound gaskets are used for
High-Temperature service applications.
High-pressure applications.
Corrosive fluids.
Flammable Fluids.
Hydrogen, etc.

Construction of Spiral Wound Gaskets
A spiral wound gasket is a semi-metallic gasket. It consists of a spirally wound v-shaped metallic with a non-metallic filler material. There are three elements that constitute a spiral wound gasket. They are:
Outer ring: Also known as a guide ring or centering ring, the outer ring of a spiral wound gasket is usually made of carbon steel material. The main purpose of this element is to center the gasket while inserting it into a bolted flange joint.
Inner ring: The inner ring is one of the most important parts of a spiral wound gasket as it prevents windings from buckling inside the pipe. In the situations of buckling of a gasket, parts of it get sucked into the pipe and eventually flow through the piping system to get caught/wrapped on something. Inner rings prevent this phenomenon and help in avoiding the problem.
Sealing element: This is the element of the spiral wound gasket that creates a tight seal to prevent leaks. The sealing element encompasses both windings and filler material. In general, spiral wound gaskets use a flexible graphite filler material rated for high temperatures. The graphite as filler material also helps the gasket to avoid flange distortion and joint misalignment. Another common filler material is PTFE (Polytetrafluoroethylene). However, PTFE is not suitable for use in high-temperature applications. The most widely used winding materials are Stainless Steel and Monel.

Refer to Fig. 1, which clearly shows these three elements of a spiral wound gasket.

Markings on Spiral Wound Gasket
Spiral wound gaskets are identified using different markings on the gasket. Each marking provides brief information about the spiral wound gasket specification important during the gasket selection process.
Some of the necessary information that the markings on the spiral wound gasket provide are:
Design Standard or Code: The code based on which the spiral wound gasket is designed and manufactured is clearly marked. In Fig. 1, you can easily find the standard ASME B16.20.
Name of the Spiral Wound Gasket Manufacturer: One can easily understand the manufacturer of the gasket by looking at the manufacturer name mentioned on the gasket.
Winding and Filler Material: Both the winding and filler materials are clearly specified on the spiral wound gasket. Specific gasket colors also provide a lot of information regarding the materials.
Diameter and Pressure class: The size of the gasket and the load the spiral wound gasket can handle, are specified by the Diameter and Pressure Class marking on the gasket. The usual pressure classes for spiral wound gaskets are 150, 300, 400, 600, 900, 1500, and 2500. With an increase in pressure class, the ability of the spiral wound gasket to withstand pressure increases.
Inner and Outer ring material

Materials for Spiral Wound Gaskets
The usual materials that are used in a spiral wound gasket are provided in table-1 below:

Metal Winding Strip Material	Filler Material	Guide Ring Material
Stainless Steel Grade 304	Graphite	Stainless Steel Grade 304
Stainless Steel Grade 304L	PTFE	Stainless Steel Grade 316L
Stainless Steel Grade 316L	Ceramic	Stainless Steel Grade 316Ti
Stainless Steel Grade 316Ti	Non-sintered PTFE	Stainless Steel Grade 321
Stainless Steel Grade 310	Non-Asbestos Fiber	Stainless Steel Grade 347
Stainless Steel Grade 321	Aluminum	Stainless Steel Grade 410
Stainless Steel Grade 347	Treated Asbestos Fiber	Monel 400
Stainless Steel Grade 430		Nickel 200
Stainless Steel Grade 317L		Alloy 20
Alloy 20		Titanium
Monel 400		Hastelloy B2
Titanium		Hastelloy C276
Nickel 200		Incoloy 800
Inconel 600		Incoloy 825
Inconel 625		Inconel 600
Inconel X-750		Carbon Steel
Hastelloy B2
Hastelloy C276
Incoloy 800
Incoloy 825
Duplex Stainless Steel
Tantalum
Zirconium

Table 1: Spiral Wound Gasket Materials

ASME B16.47 Series A (MSS SP-44) Flanges Notes – ASME B16.47 Series A flanges (> NPS 26) are MMS SP-44 flanges. MSS SP-44 also covers NPS 12 to NPS 24 flanges which are equivalent to ASME B16.5.

Both spiral-wound as well as kammprofile (derived from the German word ”Kamm”=comb) or grooved gaskets are used in various applications such as refineries, petrochemical plants, powert plants etc. Over the past few years, the use of kammprofile gaskets have seemed to gain momentum over the conventional spiral-wound gaskets, since they tend to provide tighter sealing and increased service life.

Spiral-wound gaskets
They basically consist of alternating plies of compressible filler material and a metallic strip (winding) wrapped in a way similar to the grooves of a phonograph record. The most common method for centering this type of gasket is through the use of a metal outer ring. Besides serving the role of centering the gasket, this metal outer ring also limits the gasket’s compression. Once the gasket is installed, the filler material is pushed between the plies, thus creating a seal between the flange mating surfaces, also covering any imperfections.

Initially, a common filler material used in gaskets was asbestos. However, due to health-related issues, use of asbestos is no longer allowed and other materials like rubber, PTFE, graphite etc have replaced use of asbestos nowadays.

Spiral-wound gasket dimensions and sizes for ASME B16.5 (flanges up to 24 inches nominal size) and ASME B16.47 flanges (flanges with a nominal size equal or bigger than 26 inches) are stipulated in ASME B16.20 standard (”Metallic gaskets for Pipe Flanges”).

Spiral-wound gaskets present some disadvantages:

• They are very susceptibe to damage and prone to ”springing” when dropped, bumped or not properly handled.
• Large size gaskets tend to be very dificult to handle, since their windings have a tendency of coming out.
• Quite often, it may be necessary to equip them with inner rings as well. If inner rings are not supplied, then the windings run the risk of buckling, thus considerably reducing the load that can be safely imposed and maintained on them. Adding an inner ring gives an additional compression limiting stop and provides a heat and corrosion barrier protecting gasket windings and preventing flange erosion. It is usual to select inner ring material to be the same as the metal winding.

Kammprofile gaskets
Kammprofile gaskets were first developed in Germany and following DIN 2697 standard approximately 40 years ago. They consist of a solid metal core with concentric serrations and faced with a non-metallic material like graphite, various types of PTFE etc.

Once the gasket is installed, the soft non-metallic material is forced into the metal core serrated grooves. As a result, as the compressive stress increases, multiple concentric high-pressure seals are created along the gasket face surface.

Brief comparison

Unlike a spiral-wound gasket, all of the compressive force is exerted on the kammprofile graphite facing, thuse resulting in a very tight seal. Since the kammprofile is basically solid metal, as opposed to alternating plies of metal and filler applied at spiral-wound gaskets, it is extremely resilient and easy to handle even in large diameters.
Kammprofile gaskets compress significantly less than spiral-wound gaskets, approximately in the order of 0.022 inches in comparison to average 0.050 inches for spiral-wound gaskets. As a result, kammprofile gaskets load more quickly with reduced risk of non-parallel flanges.

Price-wise, kammprofile gaskets are significantly more expensive. However, their increased upfront costs can be compensated by avoiding costly, unscheduled outages and loss of production.

Spiral-wound gaskets may have a small advantage in case the mating flanges are too close and if the gasket is expected to be susceptible to mechanical damage or abuse during installation, since the graphite facing is more vulnerable to mechanical damage. Likewise, in some occasions, spiral-wound gaskets may be more resistant to oxidation, since the windings keep the graphite in place and protect it.

On the other hand, kammprofile gaskets are more tolerant to sealing surface defects and seal more effectively in fugitive emissions services.

Summing up, although there appears to be a shift towards the use of kammprofile years in the last years, the choice is not always clear and could finally come down to personal preference.
In any case, when properly manufactured and installed, both gasket types provide reliable seal arrangements.