Page 17 - Design Criteria.qxd

18 ® Welcome to the Next Generation of Sealing Technology
If leakage occurs across the pass
partition bar, the fluid will flow
along the length of the pass bar
arrangements, and then flow to the
outer diameter of the gasket being
retained only by the secondary seal.
The intermediate part of the gasket
does very little to effect the sealing
capabilities of the gasket.
With a welded pass bar arrange-
ment the fluid is retained by the
primary seal at the inner diameter
of the gasket. Thus the primary
seal maintains its function, provid-
ing a seal of higher integrity.
Due to the high bolt loads required
to seat metal jacketed gaskets,
designers often incorporate stress
raising nubbins on the flange seal-
ing face, the principle being that the
majority of the applied bolt load is
acting on a relatively small propor-
tion of the gasket surface area, thus
high surface stresses result. It is
essential that the gasket is installed
with the smooth side toward the
nubbin.
INTEGRAL CONSTRUCTION
‘A’
‘A’
FILLER
MATERIAL
METAL
JACKET
SECTION ‘AA’
WELDED CONSTRUCTION
‘A’
FILLER
MATERIAL
METAL
JACKET
SECTION ‘AA’
‘A’
PRIMARY
SEAL
SECONDARY
SEAL
NO PRIMARY
SEAL
PRIMARY
SEAL
DOUBLE JACKETED GASKET
SECONDARY
SEAL
GASKET OD GASKET ID
NUBBIN
Metal Jacketed Gaskets
Metal Jacketed Gaskets, as the name suggests, consist of a metallic outer shell with either a metallic or non-metallic asbestos-free filler.
The filler material gives the gasket resilience, while the metal jacket protects the filler and resists pressures, temperatures and corro-
sion.
A wide range of materials are available to suit specific temperature and corrosive conditions.
Metallic: Soft Iron Nickel Non-Metallic: Non-asbestos Millboard
Carbon Steel Aluminum PTFE
Stainless Steel Brass Flexicarb®
Inconel® Copper Ceramic
Monel® (Other materials on request)
Metal Jacketed Gaskets are available in a wide range of sizes and configurations. They are traditionally used for heat exchang-
er applications, pumps, and valves, however the resilience and recovery properties of these gaskets are limited. Metal Jacketed Gaskets
require smooth flange surface finishes, high bolt loads, and flange flatness in order to seal effectively.
When pass partition bars are required, it is sufficient to use a gasket with a welded pass bar construction, as opposed to an inte-
gral pass bar construction. Jacketed gaskets standard tolerances:
Jacketed Gaskets Standard Tolerances
Gasket Outer Diameter I.D. O.D.
Up to 6” +1/32” / -0 +0 / -1/32”
6” to 60” +1/16” / -0 +0 / -1/16”
Above 60” +3/32” / -0 +0 / -3/32”