the 15 percent rubber content of the gasket makes it
unsatisfactory for modem high-temperature steam
When renewing a gasket in a flanged joint, use
equipment. Gaskets of corrugated copper or of asbestos
special precautions. When breaking the joint,
and copper are sometimes used on low- and
particularly in steam and hot water lines, or in saltwater
medium-pressure lines. The serrated-face metal gasket
lines that have a possibility of direct connection with
(view B) and the spiral-wound metallic gasket (view C)
the sea, be sure of the following conditions:
a r e used in present-day high-temperature,
1. There is no pressure on the line.
2. The line pressure valves, including the bypass
Plain Full-Faced Gaskets
valves, are firmly secured, wired closed, and
When cutting a plain full-faced gasket from
compressed gasket sheet, lay an appropriate size piece
3. The line is completely drained.
of the gasket sheet on the flange. Scribe in the bolt holes
4. At least two flange-securing bolts and nuts
and flange circle lines with light blows of a ball peen
diametrically opposite remain in place until the
hammer. Using a gasket punch, about l/16 inch larger
others are removed. These bolts are then
in diameter than the bolts, cut the bolt holes into the
slackened to allow breaking of the joint. They
gasket material Use a piece of hardwood as the
are removed after the line is clear.
supporting and backing surface for the material while
punching it to prevent damage to the lips of the punch.
5. Precautions are taken to prevent explosions or
After the holes have been punched, use shears or a sharp
fire when breaking joints of flammable liquid
knife to cut the center and outside circles to form the
6. Proper ventilation is ensured before joints are
broken in closed compartments.
Serrated-Face Metal Gasket
These precautions may prevent serious explosions,
Serrated-face metal gaskets (fig. 15-26, view B) are
severe scalding of personnel, or flooding of
made of steel, Monel, or soft iron. They have raised
compartments. Thoroughly clean all scaling and
serrations to make a better seal at the piping flange
bearing surfaces for the gasket replacement. Then
joints. These gaskets have resiliency; line pressure
check the gasket seats with a surface plate. Scrape as
tends to force the serrated faces tighter against the
necessary to ensure uniform contact. Replace all
adjoining flange. Two variations of serrated-face metal
damaged bolt studs and nuts. In flanged joints that have
gaskets are shown: the single-plate type and the
raised faces, the edges of gaskets may extend beyond
expanding type (double-plate).
the edge of the raised face.
Spiral-Wound Metallic Gaskets
Spiral-wound metallic gaskets (fig. 15-26, view C)
Observe the following general precautions with
are made of two parts. The first is interlocked piles of
regard to the use of packing:
preformed corrugated metal and paper strips, spirally
1. Do NOT use metallic or semimetallic packing
wound, called a filler. The second is a solid metal outer
on bronze or brass shafts, rods, plungers, or
or centering ring, sometimes called a retaining ring.
sleeves. If these materials are used, scoring may
The filler piece is replaceable. When renewing a
result. Use a braided packing that is lubricated
gasket, remove the filler piece from the retaining metal
throughout. Or, use a nonmetallic plastic
ring and replace it with a new refill. Do not discard the
packing in the center of the box with an end ring
solid metal retaining outer ring unless it is damaged.
of the braided packing at each end of the box.
Then place the gasket into a retainer or centering ring.
The solid steel centering also acts as reinforcement to
2. Do NOT use a packing frictioned with rubber or
prevent blowouts. The gaskets can be compressed to
synthetic rubber of any kind on rotary or
the thickness of the centering ring.
centrifugal shafts. Such packing will overheat.
3. Do NOT use braid-over-braid packing on rotary
or centrifugal shafts. The outer layer will wear