Spiral Wound Gaskets
The necessity for a gasket to have the ability to recover cannot be over emphasized. The effects of pressure and temperature fluctuations, the temperature differential across the flange face, together with bolt stress relaxation and creep, demand a gasket with adequate flexibility and recovery to maintain a seal even under these varying service conditions.
Sealing Technologies Spiral Wound Gasket is the perfect solution to such problems, meeting the most exacting conditions of both temperature and pressure in flanged joints and similar assemblies and against virtually every known corrosive and toxic media.
Spiral Wound gaskets can be fabricated of any metal which is available in thin strip and which can be welded; therefore they can be used against virtually any corrosive medium dependent upon the choice of the metal and filler. They can be used over the complete temperature range from cryogenic to about 1000 Deg C. This type gasket can be used in all pressures from vacuum to the standard 2500 psi flange ratings. They are more resilient than any other type of Metallic gasket with the exception of pressure sealing metal gaskets and due to that it can compensate for flange movement that may occur due to temperature gradients, variations of pressure and vibration.
Spiral Wound gaskets can also be manufactured with variable densities, i.e. relatively low density gaskets for vacuum service up to extremely high density gaskets having a seating stress of approximately 30,000 psi. The softer gaskets would require a seating stress in the range of 5,000 psi.
Properties and Applications :
Spiral wound gaskets are of great resilience, therefore they are very suitable for applications with heavy operating conditions. Spiral wound gaskets are manufactured by spirally winding a V-shaped metal strip and a strip of non-Metallic filler material. The metal strip holds the filler, providing the gasket with mechanical resistance and resilience. Spiral wound gaskets can be reinforced by an outer and/or inner retaining ring. The outer centering ring controls the compression and holds the gasket centrally within the bolt circle. The inner retaining ring increases the axial rigidity and resilience of the gasket.
Spiral wound gaskets should always be in contact with the flange and should not protrude into the pipe or project from the flange. Spiral wound gaskets can be used for sealing flange joints, manhole and handhold covers, tube covers, boilers, heat exchangers, pressure vessels, pumps, compressors and valves; in industries such as petrochemical, pharmaceutical, shipbuilding, and food processing, in power industries and nuclear power stations.
They are ideal for steam, oil, liquids, gases, acids, alkalis, various organic media and solvents.
Size and Construction
• Gaskets are made in a wide variety of sizes and shapes.
• Combinations of metal strip and filler are selected to suit the specific fluid media and operating conditions.
• Quick to install and remove.
• Operating temperatures from cryogenic up to about 1000°C.
• System pressures from high vacuum to over 2500 PSI.
• Support rings - inside and/or outside the spiral - make gaskets suitable for high pipeline pressures on flat or raised flange faces.
• Products are manufactured in accordance with all relevant gasket standards to suit flange designations: ASME B16.5, BS1560, ASME B16.47 Series A (MSS-SP44), ASME B16.47 Series B (API605), BS EN 1092 (BS4504); plus DIN, JIS and NF.
Maximum operating temperatures of facing materials :
Compressed non-asbestos fibre: 500°C.
Standard pure graphite : 500°C ( Oxidizing Media ) ; 600°C (inert/reducing media) ; 650°C (steam) .
High purity graphite : 500°C (oxidising media) ; 600°C (inert/reducing media) ; 650°C (steam).
Teflon / PTFE: 260°C.
High temperature filler: 1000°C.
Sealing Technologies “ Sealtight ST “ gaskets seal up to 2500 PSI , although higher pressures can be considered. Please consult our Technical Support Team when considering higher pressures.
Metal winding strips
• Standard materials: Stainless steels 304L, 316L.
• Alternative materials:
• Stainless steels 310, 320, 321.
• Monel 400, K500.
• Nickel 200.
• Inconel 600, 625, X750.
• Incoloy 800, 825.
• Hastelloy HB2, C276.
• Standard material: Carbon steel.
• Alternative materials:
• Stainless steels 304L, 316L, 320, 321.
• Monel 400, K500.
• Nickel 200.
• PTFE (inner rings only).
Nominal Thickness Compressed Thickness Minimum Diameter Maximum Diameter *
2.5 mm 1.9 / 2.1 mm 10 mm 300 mm
3.2 mm 2.4 / 2.6 mm 10 mm 760 mm
4.5 mm 3.4 / 3.45 mm 10 mm 1520 mm
7.3 mm 4.7 / 4.9 mm 60 mm 3550 mm
Largest non-standard gaskets manufactured to date are about 5000 mm in diameter.
* Maximum sizes are intended as a general guide. In certain cases they may be exceeded, however, as a gasket approaches (or exceeds) I.D. limits, it becomes increasingly unstable. The width of the winding and the materials specified for construction also affect the I.D. limits.
Flange Surface Finish
Spiral Wound gaskets offer the designer as well as the user a wider tolerance for flange surface finishes than other Metallic gaskets. Experience indicates that the appropriate flange surface finishes used with Spiral wound gaskets are as follows:
125 to 250 AARH Optimum
500 AARH Maximum
However, spiral wound gaskets can be used against most commercially available flange surface finishes.
Sealing Technologies “ SealTight “ Spiral Wound gaskets are available in a variety of styles to suit the particular flange facing being utilized on the flanges.
Style W is a Spiral Wound sealing component only which is normally used on tongue and groove joints, male and female facings and groove to flat flange facings. In this construction, inner and outer diameters are reinforced with several piles of metal without filler to give greater stability and better compression characteristics.
Style WIR is identical to style WR with the addition of an inner ring. The inner ring serves various functions.
Solid inner metal ring acts as a compression stop and fills the annular space between flange bore and the inside diameter. Designed to prevent accumulation of solids, reduce turbulent flow of process fluids and minimize erosion of flange faces. Suitable for male and female pipe flanges.
Its I.D. is normally sized slightly larger than the I.D. of the flange bore, minimizing turbulence in process flow. After the gasket is compressed, the flanges would normally be in contact with the inner ring and hence erosion and corrosion of the flange surface between the I.D. of the sealing component and the flange bore is minimized. The inner rings are normally supplied in the same material as the spiral wound component. For standard gasket dimensions to suit ASME B16.5 and ASME B16.47 flanges, please refer to the Spiral Wound dimensional tables.
Style WR gaskets consist of a Spiral Wound sealing component with a solid metal outer guide ring. A general purpose gasket suitable for use with flat face and raised face flanges.. The outer guide ring provides additional radial strength to prevent gasket blowout and acts as a compression stop. Normally the outer guide rings are furnished in mild steel, but can be supplied in other metal when required by operating conditions.
Suitable for use with flat face and raised face flanges and specified for high pressure/temperature service or where corrosive or toxic media are present. Note on use of inner rings: ASME B16.20 which covers spiral wound gaskets requires the use of solid metal inner rings in:
• Pressure Class 900, nominal pipe sizes 24” and larger
• Pressure Class 1500, nominal pipe sizes 12” and larger
• Pressure Class 2500, nominal pipe sizes 4” and larger
• All PTFE filled gaskets
ASME B16.20 recommends the use of inner rings if the user’s experience has shown inward buckling of the gasket. Flexitallic recommends the use of inner rings for the following applications:
• Vacuum service or suction side of rotary equipment such as pumps and compressors
• Aggressive media, high pressure or temperature
• Surface finishes smoother than 125 micro-inch
• If over compression of the gasket is a concern
The inner rings are normally supplied in the same material as the spiral wound component. For standard gasket dimensions to suit ASME B16.5 and ASME B16.47 flanges, please refer to the Spiral Wound dimensional tables.
Inward buckling of Spiral Wound gaskets is always a prime concern and research is on to find a permanent solution by improving the standard . Sometimes inner rings are not preferred due to cost. Until there is a permanent resolution.
For such clients, Sealing Technologies offers style WROE . This is based on the theory that by giving room for expansion between the outside of the spiral winding and the outer ring, the buckling along the inside can be controlled . This feature, combined with a reinforced inside circumference, help to further reduce the likelihood of inward buckling after installation.
Generally WROE sizing for NPS 2"-24" in pressure class 150, 300 and 600# is based on the use of Weld Neck flanges with Schedule 40 or thicker wall pipe. Consult our Technical Department to verify flange bore clearance for other sizes, of for specific application.
Style WR -RTJ
The style WR-RTJ gasket is identical to a Style WOR in construction features but is specially sized to be used as a replacement gasket for flanges machined to accept oval or octagonal ring joint gaskets. The sealing component is located between the I.D. of the groove machined in the flange and the flange bore.
This style to be used on standard ring joint flanges. The outer ring is
designed to cover the ring joint grooves and to prevent the spiral wound portion from entering the groove. This type of gasket is intended to be used only as a replacement part or maintenance repair item.
In new construction, where Spiral Wound gaskets are intended to be used, raised face flanges should be utilized. When a guide ring is required that is too narrow for practical fabrication of solid metal guide rings, We offer Spiral Wound gaskets with a guide made entirely of spiral metal winding. These spiral metal winding serve the same basic purpose as the solid metal ring, that is as a compression limited and a centering device. The spirally wound ring is normally supplied in the same metal as the metal in the gasket. This type of wound guide ring is usually limited to a 1/4" radial width or less.
Style HT gaskets are used for boiler handhold and tubecap assemblies. They are available in round, square, rectangular. diamond, obround, oval and pear shapes. These are also available in special sizes and shapes.
Style HT gaskets rely on internal pressure in the boiler to properly seat the gasket. This means, when a hydrostatic test is performed on the gasket, the pressure exerted against the plate will further compress the gasket-and it is necessary to tighten each nut to compensate for the additional compression of the gasket under load.
To order special gaskets, dimensional drawings or sample cover plates should be provided in order to assure proper fit.
Style MH , MHC and MHCS
These gaskets are available in round, obround, and oval shapes and are designed for boiler manhole cover assemblies. They are usually round, obround or oval shape, depending of course on the manhole plate configuration. Style MC gaskets have pre-formed inner and/or outer rings made of spiral winding. This centering guide permits the gasket to assume its correct position and to compensate for inequalities in plate contours and fillets in cold-pressed plates as well as to prevent shouldering and pinching caused by radial misplacement. Style MCS gaskets are manufactured with a solid metal inner and/or outer ring which also prevents over compression of the gasket in high pressure systems.
special gaskets lso be manufactured against submission of complete information, including a sketch or blueprint or a sample cover on which the gasket is to be fitted.
When Spiral Wound handhold and manhole gaskets with a straight side are required it is necessary that some curvature be given to the fact that Spiral Wound gaskets are wrapped under tension and therefore tend to buckle inward when the gaskets are removed from the winding mandrel. As a rule of thumb, the ration of the long ID to the short ID should not exceed 3 to 1.
Style HE , HE- WIOR and HE- IR
These gaskets are similar to Style W and Style WOR with the addition of pass partitions for use with shell and tube heat exchangers. Partitions are normally supplied with a double-jacketed construction of the same material as the spiral wound component. The partition strips can be soft soldered, tack welded or silver soldered to the spiral wound component. The double-jacketed partition strips are normally slightly thinner than the spiral wound component in order to minimize the bolt loading required to properly seat the gasket.
Note-Style HE and Style HE- IR gaskets have a primary seal of spiral wound construction with its inherent resiliency and excellent sealing quality. It is necessary that dimensional drawings locating the pass ribs and the configurations be submitted for these style gaskets. In conjunction with an inner ring, the standard spiral wound construction also supports an outer wound steel nose, designed for the purpose of accurate gasket location. It is also available with solid metal outer ring.
The spiral wound Style WL gaskets are similar to those of Style W but additionally they are provided with a wire loop welded to the outer periphery of the gasket, sized so as to fit over diametrically opposite bolts, for proper centering of the spiral wound gasket on the seating surface. Where possible, it is highly recommended that a Style WOR gasket be used in place of a Style WL gasket because of the obvious advantages of the outer solid metal centering ring. The Style WL is of higher cost than the style WR because they are Practically more difficult to produce .
Spiral Wound Gaskets - Dimensions and Tolerances – Go to the link for
the dimensions :
Styles WIR , WOR and WIOR Dimensions ; 1/4" to 24" Flanges :
ASME B16.20 Gaskets for ASME B16.5 Flanges
Styles WIR , WIOR Dimensions 22" to 60" Series A Flanges :
ASME B16.20 Gaskets for ASME B16.47 Series A Flanges (MSS SP-44)
Styles WIR , WIOR Dimensions 26" to 60" Series B Flanges
ASME B16.20 Gaskets for ASME B16.47 Series B Flanges (API-605)
Style WIR Dimensions Other Large Diameter Flanges, 26" to 96"