contents
18
sealing materials
Hofland spiralwound
gaskets fig. G2004
Hofland spiralwound gaskets consist of a
V-shaped metal strip spirally wound in
combination with a soft, filler material. The
metal strip provides outstanding
recovery, while the flexible filler
guarantees excellent sealing. Due to this
combination of materials the Hofland
spiralwound gasket is suitable for sealing
under severely fluctuating temperature and
pressure conditions. Depending on the
application the spiralwound gasket can be
specified with outer and/or inner rings.
properties
Hofland spiralwound gaskets are suitable for use across a wide gasket
stress range.
Hofland spiralwound gaskets can be used to seal fluid pressures up to
250 bar and from cryogenic temperatures up to elevated temperatures
of 1000C.
Because of its sturdy design the Hofland spiralwound gasket is simple
to install without being damaged (although extra care should be taken
during transportation and installation of large diameter gaskets without
inner or outer guide rings).
The outer guide ring simplifies assembly and prevents blow-out of the
gasket.
By combining different winding materials and metals, the gasket can
be tailored to suit a wide variety of operating conditions.
Because of its non-adhesive properties the gasket is easy to remove
after service.
The gasket does not cause any damage to the flange faces.
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19
section 1 | metallic and semi-metallic gaskets spiralwound
technical data
gasket stress range:
The Hofland spiralwound gasket should preferably be mounted within
the following gasket stress range to ensure a leak-proof connection:
Filler
flange surface finish:
Single side confined
Both sides confined
Gasket stress (20C)
Gasket stress (20C)
Min.
[N/mm 2]
Opt.
[N/mm 2]
Max.
[N/mm 2]
Min.
[N/mm2]
Opt.
[N/mm2 ]
Max.
[N/mm2 ]
Graphite
PTFE
50
50
95
80
180
130
50
50
122
110
300
250
Non-asbestos
55
90
150
55
130
300
The recommended surface roughness of the flange faces, between
which a spiralwound gasket is to be mounted, is 3.2 - 6.3 m Ra (125 250 RMS), also referred to as smooth finish.
possible constructions
single side confined
Flange type: Raised Face
SPW type SG.
Flange type: Male/Female
SPW type RFI.
both sides confined
Flange type: Raised Face
SPW type SG IR.
Flange type: Male/Female
SPW type IR.
Flange type: Tongue/Groove
SPW type RF1.
contents
20
sealing materials
standard profiles
Econosto produces the following types of Hofland spiralwound gaskets.
RF1
IR
SG
SG-IR
SG-RTJ
HX-R
HX-RIR
This gasket consists of filler and V-shaped metal strip wound in combination. This profile is usually used in male/female and tongue/groove
flanges.
Identical to RF1, but fitted with an inner ring.
This standard spiralwound gasket type consists of a wound component
fitted with an outer centering ring.
Identical to the SG-type, but fitted with an inner ring.
A standard spiralwound gasket (SG-type) with dimensions tailored for use
with Ring-Type-Joint (RTJ) flanges.
This type of gasket consists of a wound component fitted with a narrow,
wound centering ring. Centering windings ensure correct centering in
flush flanges (e.g. in heat exchangers).
This gasket type is identical to HX-R, but also fitted with an inner ring,
rendering this gasket type suitable for mounting in male and female
flanges.
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section 1 | metallic and semi-metallic gaskets spiralwound
21
special profiles
profile with a GT-zone:
In the event of a graphite-filled spiralwound possibly causing an
undesirable reaction between graphite and the medium to be sealed, or
of possible medium contamination, the problem can be solved by using a
spiralwound gasket with a GT-zone.
The spiralwound element of a GT-zone gasket consists of outer windings
of non-asbestos or ceramic material with a central winding zone made of
graphite or PTFE (depending on the operating conditions) to improve
gastightness, see illustration.
This results in a spiralwound gasket with the following properties:
Does not pollute the sealed medium
Excellent gastightness
Combined with the other advantages of a spiralwound gasket, the
spiralwound with GT-zone may be used in a wide range of operating
conditions.
special shapes
type MH
type TC/HH
Spiralwound gaskets can be produced in
a wide variety of shapes, such as oval
and pear-shape, with pass-partition bars
and many other types. Generally, the
pass-partition bars on spiralwound
gaskets are metal-jacketed bars.
This spiralwound gasket is identical to
the RF1 profile but oval shaped to fit
manholes.
This type of gasket is for hand holes and
special flange assemblies (tube cap and
hand hole covers). They are available in
e.g. square, rectangular, oval diamond
and pear shapes.
A drawing specifying the correct dimensions is required to manufacture special
shapes.
For spiralwound gaskets with straight sides (e.g. for gate valve bonnets)
we recommend that an inner ring be used if the length/width ratio > 2.
contents
22
sealing materials
type WL
The gasket is identical to RF1, but fitted
with an outer winding. Centering is
achieved by positioning the winding over
two bolts opposite each other (see
illustration).
type HE
Fitted with pass-partition bars for use on
heat exchangers and vessels, this gasket
type is otherwise identical to the RF1
profile. Metal-jacketed bars generally have
a thinner design than that of spiralwound
gasket components.
The bars are usually fixed through
microplasm welding or silver soldering.
The welding method is chosen depending
on the gasket material.
type HE-SG
Fitted with an outer centering ring, the
HE-SG is otherwise identical to the HE
profile.
type HS/SG-IR
Fitted with an outer centering ring and an
inner ring, the HS/SG-IR is otherwise
identical to the HE profile.
type SP-N2
The SP-N2 is a highly specialized type
of gasket, consisting of a Hofland
camprofile gasket and a Hofland spiralwound gasket separated by a perforated
intermediate ring. The sealing layers on
the camprofile and the filler of the spiralwound gasket are made of identical
material. The perforated intermediate ring
is flushed with inert gas (such as
nitrogen).
This design enables the operator to
measure any leakage, making the gasket
suitable for use in critical applications
where a high degree of gastightness and
operational reliability is required.
In order to manufacture the above gaskets, we require a drawing
specifying the exact dimensions and position of the bars.
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section 1 | metallic and semi-metallic gaskets spiralwound
23
profile selection
advantages of the centering ring:
The spiralwound gasket centering ring offers the following advantages:
Optimum gasket positioning between the bolts.
Protection of the sealing element.
Additional security against gasket blow-out.
Acts as a compression limiter preventing overloading and
overcompression of the spiralwound element.
Prevents radial flow of soft fillers, such as PTFE.
For these reasons the use of spiralwound gaskets with outer
centering rings is generally recommended.
advantages of the inner ring:
Gaskets provided with an inner ring offer the following advantages:
Prevents radial flow of soft fillers, such as PTFE.
Reduces turbulence, minimizing flow resistance and crevice corrosion.
Acts as an additional heat shield when the spiralwound gasket is
subjected to high temperatures.
Inner and outer rings are particularly recommended for use on Hofland
spiralwound gaskets exceeding class 600 lbs, but specifically recommended for high temperatures and pressures to optimize reliable sealing
performance.
For special flanges (male-female, tongue and groove, etc.) the type of
spiralwound gasket selected will depend on the flange geometry,
operating conditions and bolt specifications. Econosto specialists will be
pleased to assist you where necessary.
The illustrations on the right
represent standard Hofland
spiralwound gasket shapes for
vessel and heat exchanger
flanges.
contents
24
sealing materials
ring and winding material selection
The material selected for the inner ring
and winding metal is usually SS316L for
both carbon steel and stainless steel
flanges. In other cases, it is normally the
same material as selected for the piping
system, in order to prevent corrosion
problems. In highly corrosive
applications PTFE may be
used for the inner rings.
The outer centering ring is generally
made of carbon steel with an anticorrosion coating; however, the ring
may also be manufactured in the same
metal as the pipe system to prevent
e.g. galvanic corrosion.
Hofland spiralwound gaskets
are available ex stock in
most standard materials.
The table below lists the
materials commonly used.
Material
(trade name)
DIN
Specification
DIN
Material No.
AISI
ASTM
B.S.
Hardness
HB / HV*
UNS
Soft Iron
(1)
Steel (LCS)
Stainless Steel 304
Stainless Steel 304 L
Stainless Steel 309
RSt. 37.2
X5 CrNi 1810
X2CrNi 1911
X15CrNiSi 2012
1.0038
1.4301
1.4306
1.4828
304
304 L
309
Temp.
[C]
Min.
304S15/16/31
304S11
309S24
90 - 100
100
130
130
130
130
180
190
190
Density
[gr/cm 3]
Max.
- 60
500
7.85
- 40
-250
-250
-100
500
550
550
1000
7.85
7.9
7.9
7.9
Stainless Steel 316 L (2)
X2CrNiMo 1713
1.4404
316L
316S11/13
130 - 190
-100
550
7.9
Stainless Steel 316 Ti
Stainless Steel 321
Stainless Steel 347
Aluminium
X6CrNiMoTi 1712
X6CrNiTi 1810
X6CrNiNb 1810
Al 99,5
1.4571
1.4541
1.4550
3.0255
316Ti
321
347
320S31
321S12/49/87
347S31
-
130
130
130
20
- 190
- 190
- 190
- 23
-100
-250
-250
-250
550
550
550
300
7.8
7.9
7.9
2.73
Silver
-250
750
10.5
Copper
Nickel 200
Monel 400
Inconel 600
Ni 99,2
NiCu 30 Fe
NiCr 15 Fe
2.0090
2.4066
2.4360
2.4816
N02200
N04400
N06600
3072-76 NA11
3072-76 NA13
3072-76 NA14
50
90
110
120
- 80
- 120
- 150
- 180
-250
-250
-125
-100
400
600
600
950
8.9
8.9
8.8
8.4
Incoloy 800
X10NiCrAITi 3220
1.4876
N08800
3072-76 NA15
140 - 220
-100
850
8.0
NiCr 21 Mo
NiMo 28
NiMo16Cr15W
Ti 99,8
2.4858
2.4617
2.4819
3.7025
N08825
N10665
N10276
-
3072-76 NA16
-
120
170
170
110
-100
-200
-200
-250
450
450
450
350
8.14
9.2
8.9
4.5
Incoloy 825
Hastelloy B2
Hastelloy C276
Titanium
(1)
Generally used for the centering ring
(2)
Generally used for metal gasket components that require non-corroding material
28*
180
230
230
140
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section 1 | metallic and semi-metallic gaskets spiralwound
25
filler selection
filler material:
The table below may be used to select the correct filler. It should be
pointed out that graphite will be the optimum filler in most cases. Only
where graphite could cause media pollution, or is not chemically resistant, should the use of another type of filler material be recommended. In
such cases, an alternative solution might be to use a gasket with GT-zone.
See page 21.
Material
graphite:
Ceramica :
Gastightness
Application
-200
-200
550
250
250
100
Good
Good
Agressive media
Agressive media
Non-asbestos
Ceramica
-100
-200
250
1100
100
100
Good
Poor
Liquids & Gases
Very high temperatures
Graphite is a universally applicable, high-quality, non-asbestos material
with the following properties:
Very good chemical resistance
Resistant to high (fluctuating) temperatures and pressures
Resistant to ageing
Excellent gastightness
PTFE (Teflon) is a high quality synthetic material with the following
properties:
non-asbestos:
Max. Operating
Pressure [Bar]
Graphite
PTFE
PTFE:
Temperature [C]
Min.
Max.
Excellent
Resistant
Resistant
Excellent
chemical resistance
to temperatures up to 250C
to ageing
gastightness
Non-asbestos is a non-asbestos sealing material consisting of synthetic
fibre, with nitrile rubberbinder and mineral fillers.
Ceramica is an aluminium silicate suitable for applications at high
operating temperatures. The material is characterized by poor
gastightness and is therefore frequently used in combination with
graphite.
See spiralwound gasket with GT-zone.
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26
sealing materials
gasket thickness
gasket thickness before
and after fitting
Depending on the
diameter, the spiralwound gasket is
available in a variety
of thicknesses. The
table below specifies
the thicknesses and
the recommended
optimum thickness
after fitting.
t1
[mm]
bm ax
[mm]
t2
[mm]
thickness after assembling
[mm]
7.2
100
3600
33
5.3
5.6
6.4
200
1601
1600
3000
30
28
4.7
4.9
3.2(1)
3.2
3.4
2.3
2.5
1.5
1.8
2.0
4.5
(1)
d
[mm]
16
630
35
631
1601
1600
3000
30
25
3.2
16
631
630
1500
25
20
2.5
10
200
Standard spiralwound gasket. In case materials other than carbon steel are used:
thickness 3 mm.
selection of gasket thickness:
The spiralwound gasket is usually produced with a thickness of 4.5 mm.
However, in some cases a different thickness may be selected to obtain
effective sealing.
The table below specifies gasket thickness for certain applications.
Gasket thichness
[mm]
Flange size
[mm]
6.4
Nominal pipe sizes from 1001 - 3000
Machine flanges from 801 - 3000
4.5
Nominal pipe sizes up to 1000
Machine flanges up to 800
3.2
Valve bonnets
2.5
Nominal pipe sizes up to 100
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section 1 | metallic and semi-metallic gaskets spiralwound
27
production tolerances
The table below
specifies the
production tolerances
for Hofland spiralwound gaskets.
production tolerances
SPW1
ASME B16.20
DIN
ASME/ANSI B16.5
d1
15 - 80
100 - 600
650 - 1500
/2 " - 3"
4" - 24"
-
d2
15 - 200
250 - 600
650 - 850
15 - 200
250 - 600
-
ASME B16.47 series B
BS 1560
[mm]
26" - 60"
26" - 60"
1
/2 " - 3"
4" - 24"
-
+
+
0.8
1.5
0.8
1.5
3.0
/2" - 8"
10" - 24"
-
26" - 34"
26" - 34"
1
/2" - 8"
10" - 24"
-
+
+
0.4
0.8
0.4
1.5
0.8
36" - 60"
36" - 60"
1.3
/2" - 8"
10" - 24"
-
1
/2" - 8"
10" - 24"
0.8
+ 1.5 - 0.8
- 0.8
- 1.5
26" - 60"
26" - 60"
1.5
/2" - 24"
-
0.8
0.8
650 - 1500
d4
15 - 600
650 - 1500
Tolerance
ASME B16.47 series A
900 - 1500
d3
BS 3381
/2" - 24"
-
26" - 60"
26" - 60"
