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technical data
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L 2
D 2
D1
C R 2 R 1
L 3
L1
L1
L2
COUPLING FLEXIBILITY:
The grooved coupling’s capability to allow angular and rotational
movement within the coupling joint must be considered when
deciding hanger and support locations. Spring hangers and
supports providing for movement in more than one plane are
often used to allow the pipe system to move without introducing
additional stress into the pipe system.
EXAMPLE 1
This example demonstrates the need
for each pipe length in a grooved
system to be supported. The sag due
to the fexibility of the Gruvlok joint
could be eliminated with the proper
positioning of hangers on both pipe
segments “L1” and “L2”.
EXAMPLE 2
This illustrates the effect of pump
oscillation on a piping system.
A spring hanger should be used
to support the pipe section and
also respond to the induced
vibrations. The couplings in the
horizontal run above the riser,
should accommodate the defection
without transmitting bending
stresses through the pipe system.
PRESSURE THRUSTS:
Gruvlok couplings react to the application of system pressure and
restrain the pipe ends from separation due to the pressure force.
However, the coupling joint may not be in the self-restraining
confguration prior to the application of system pressure. The
Gruvlok coupling does not restrain adjacent pipe sections from
separation due to pressure forces until the coupling key sections
engage the groove walls.
Random fexible coupling joint installation will produce installed
coupling conditions ranging from pipe ends full butted to fully
separated to the maximum available gap. Thus, only after system
pressurization will the self-restraining function of the coupling be in
effect.
The designer must account for the movement to be encountered
when the system is pressurized and the joints are fully separated.
Anchor and guide positions must be defned to direct the pipe joint
movement that it is not detrimental to the pipe system.
Examples of the effect of pressure thrust are shown in the
following illustrations.
EXAMPLE 1
The coupling joints have been installed butted or partially open. When
pressurized the pipe ends in the coupling joints will separate to the
maximum amount permitted by the coupling design.
EXAMPLE 2
In the system shown here, the pipe will move and defect at the elbow
joint due to pressure thrust.
The pipe designer must assure himself that the system has the capability
of defecting suffciently to absorb this movement without introducing
additional stresses into the pipe system. In the defected condition
shown, temperature increases would produce further expansion of the
pipe system thus increasing the defection.
EXAMPLE 3
To restrain this system provide a pressure thrust anchor at “R1” to resist the
pressure thrust acting through the tee “D1” at the cap “C”. Provide a hanger
at Point “R2”, or a base support at Point “D2” to support the vertical
column. If the offsets L1, L2, and L3 are of adequate length to handle
expected pipe movements,
no additional anchoring is required.
Thermal movement of the pipe
system should also
be considered, and
intermediate anchors located as
required, to direct the pipe movement
so as to prevent introducing bending
stresses into the system.
System With No Pressure
System Pressurized
SUFFICIENT
LENGTH TO
OFFSET
PRESSURE
THRUST
The coupling key
sections will make
contact with the
groove walls and
restrain the pipe from
further separation.
The movement at each
coupling joint will add
with all other joints
and produce ∆ L.
GL-2.10