Page 190 - publication

technical data
www.anvilintl.com 190
movemenT-applicaTions
thermal movement Misalignment & Deflection
A suffcient amount of coupling joints must be provided to accommodate
the calculated movement (expansion or contraction) in a pipe run or
segment thereof .
The angular movement capability of the Gruvlok coupling permits the
assembly of pipe joints where the piping is not properly aligned. At least
two couplings are required to provide for lateral pipe misalignment.
Defection (longitudinal misalignment) may be accommodated within a
single coupling as long as the angle of defection does not exceed the
value shown in the coupling performance data for the particular size and
coupling type.
A pipe joint that utilizes the angular defection capability of the Gruvlok
coupling will react to pressure and thermal forces dependent upon the
manner in which it is restrained. An unrestrained joint will react to these
forces by straightening, thus reducing, if not eliminating, the defection at
the joint. If joint defection has been designed into the pipe layout and
must be maintained, then suffcient anchors must be provided to resist the
lateral forces and hold the joint in the defected condition.
eXample:
A 200 foot long straight run of 4" steel cut grooved pipe
between anchor points . Minimum Temperature: 40° F (4 .4° C) . (at time
of installation) .
Maximum Oper . Temperature: 160° F (71 .1° C) .
Thermal expansion tables show this system will expand a total of 1 .80"
due to the temperature change .
DesiGn QuesTion:
How many couplings are required to account for the thermal growth?
available linear movemenT per fleXible couplinG:
Using the table on page 171, we see that there is 0 .188" linear movement
per coupling (4" Flexible Coupling)
couplinGs reQuireD
As indicated above, the total movement is 1 .80". Thus, the number of
couplings is determined as follows:
No . of Couplings = Tot . Movement / Avail . Movement per Coupling
for our eXample:
No . of Couplings = (1 .80") / (0 .187") = 9 .6,
Therefore 10 couplings are needed
posiTion of couplinGs
In order for the couplings to provide for the movement indicated by the
above example, it would be necessary to install all couplings with the
maximum gap between pipe ends. Conversely, if the thermal movement
was contraction due to a reduction of system temperature, the coupling
joints would have be installed with the pipe ends butted, thus
accommodating the “shrink” of the pipe system.
In either case the pipe run in question would have to be anchored at the
proper locations to direct pipe system expansion or contraction into the
coupling joints.
As can be seen from the above example, the pipe end gap within the
coupling joint must be considered when designing a groovedend pipe
system to accommodate thermal movement. The couplings do not
automatically provide for expansion and contraction of piping.
The amount of defection from pipe run centerline can be calculated
utilizing the following equations:
Where:
M = Misalignment (inches)
G = Maximum Allowable Pipe End Movement (Inches) as shown under
“Performance Data” (Value to be reduced by Design Factor)
0 = Maximum Defection (Degrees) from centerline as shown under
“Performance Data” (Value to be reduced by Design Factor)
D = Pipe Outside Diameter (Inches)
L = Pipe Length (Inches)
200 FEET
G
M
L
G
M
L
GL-2.10