intervieW Questions
and ansWers
on pipeline
expansion
Joints
xpansion joints are flexible
connectors used to
reduce vibration, dampen
sound, and compensate
for movement in piping
systems handling pressurized fluids.
e
They are used in HVAC and power
generation systems, sewage and water
treatment plants, pulp and paper mills, and
in chemical processing, primary metals
production and petroleum refining plants.
Pipe movement (face-to-face, angular,
compression, lateral, elongation and
vibration) can be caused by a number
of factors, including system pressure
or vacuum, temperature gradients,
equipment vibration, system weight and
structural settlement.
Expansion joints are typically located at
the suction or discharge side of pumps,
and at directional changes and long runs
of piping.
They offer a number of advantages
compared with pipe loops and bends,
which are less expensive, but have hidden
costs in terms of space requirements,
installation labor and pipe supports.
22
PECM Issue 29
1.
H OW HAS EXPANSION JOINT
TECHNOLOGY EVOLVED OVER
THE PAST DECADE ? H OW IS THE
TECHNOLOGY OF TODAY MORE
EFFECTIVE / EFFICIENT THAN THAT
OF PREVIOUS GENERATIONS ?
Many of our customers are moving beyond
operational excellence to focus on safety
and sustainability as important business
objectives. Manufacturers of expansion
joints are working on developing next-
generation products and services to help
customers achieve these goals.
2.
W HAT ARE THE MAJOR
EXPANSION JOINT
TECHNOLOGIES AVAILABLE
TODAY ?
The two primary types of expansion
joints are elastomer and metal. Elastomer
expansion joints are usually fabricated
from natural or synthetic rubber and
reinforced with fabric. In some cases, metal
body rings are added for reinforcement.
Elastomer expansion joints accommodate
greater pipe movement than metal units,
offer a wider range of spring rates and
have higher abrasion resistance. They also
provide acoustical impedance and visible
signs of fatigue, alerting users to potential
failure.
Metal expansion joints are usually
constructed in a bellows-like configuration
from relatively thin-gauge material
designed to absorb mechanical and
thermal movements. They can withstand
temperatures of up to 1,800°F (982°C) and
pressures up to 1,000 psi, both of which
are beyond the capabilities of elastomer
joints.
3.
W HEN SELECTING EXPANSION
JOINTS , WHAT ARE SOME KEY
CONSIDERATIONS TO ENSURE
SUCCESS ?
It is important to understand how process
conditions will affect expansion joints. In
selecting the proper expansion joint for a
particular application, the following factors
should be taken into account:
t 1JQFTJ[F
t 'MVJENFEJVN
t .FEJVNUFNQFSBUVSF
t 4ZTUFNQSFTTVSFWBDVVN
t &YQBOTJPOKPJOUFOWJSPONFOU
t 'BDFUPGBDFEJNFOTJPOT
t 1JQFNJTBMJHONFOU
t %SJMMJOHQBUUFSO JFCPMUIPMFT
CPMU
hole diameters, etc.)
t 3FUBJOJOHSJOHT
t $POUSPMVOJUT