Page 16 - ExpansionJointsCatalog2010

LIMIT RODS & CONTROL RODS
Definition — A control unit assembly is a system of two or more control rod
units (limit rods, tie rods or compression sleeves) placed across an expansion
joint from flange to flange to minimize possible damage caused by excessive
motion of a pipeline. The failure of an anchor or some other piece of equipment
in a pipeline can cause excessive motion. The control unit assemblies can be
set at the maximum allowable expansion and/or contraction of the rubber ex-
pansion joint. When used in this manner, control units are an additional safety
factor and can minimize possible damage to adjacent equipment.
Use of Control Units with Rubber Expansion Joints
Rubber expansion joints must be installed between two fixed anchor points in a
piping system. The pipe system must be rigidly anchored on both sides of the
expansion joint to control expansion or contraction of the line. Piping anchors
must be capable of withstanding the line thrusts generated by internal pressure
or wide temperature fluctuations. When proper anchoring cannot be provided,
CONTROL UNITS ARE REQUIRED.
Listed below are three (3) control unit configurations supplied by PROCO and
are commonly used with rubber expansion joints in piping systems.
Figure 1 — Known as a “LIMIT ROD”, this control unit configuration will allow
an expansion joint to extend to a predetermined extension setting. Nuts shall be
field set to no more than the maximum allowable extension movement of a
rubber expansion joint. Refer to Tables 2, 3, or 4 in this manual. Consult the
systems engineer for proper nut settings prior to system operation.
Figure 2 — Known as a “CONTROL ROD”, this control unit configuration is
used to allow specified pipe expansion (expansion joint axial compression) and
pipe contraction (expansion joint axial extension) movements. Nuts shall be
field set to no more than the maximum allowable extension or compression of a
rubber expansion joint. Refer to Tables 2, 3 or 4 in this Manual.
Internal and external nuts can also be field set to allow for no movement in the
horizontal plane. This setting will allow the rubber to move laterally while keep-
ing expansion joint thrust forces low on adjacent equipment. Spherical washers
can also be furnished (upon request) to combat any potential “nut to plate”
binding during offset. Consult the systems engineer for proper nut settings
prior to system operation.
Figure 3 — Known as a “COMPRESSION SLEEVE”, this configuration is used
to allow for specified pipe expansion (expansion joint axial compression) and
pipe contraction (expansion joint extension) movements. Nuts shall be field set
to no more than the maximum allowable extension of a rubber expansion joint.
Refer to Tables 2, 3, or 4 in this manual. PROCO will manufacture each com-
pression sleeve to allow for no axial movement unless otherwise specified by
the purchaser. Compression sleeves shall be field trimmed to meet required
allowable axial movement as set forth by system requirements. Spherical washers
can also be furnished (upon request) to combat any potential “nut to plate”
binding during offset. Consult the systems engineer for proper sleeve lengths
prior to system operation.
Important Control Rod Considerations — The number of rods, control rod
diameters and control rod plate thicknesses are important considerations when
specifying control units for an application. As a minimum, specifying engineers
or purchasers shall follow the guidelines as set forth in Appendix C of the Fluid
Sealing Association’s Rubber Expansion Joint Division Technical Handbook (Sixth
Edition). PROCO engineers its control unit assemblies to system requirements.
Our designs incorporate an allowable stress of 65% of material yield for each
rod and plate (rod and plate material to be specified by purchaser). Therefore, it
is important to provide pressure and temperature ratings to PROCO when re-
questing control units for rubber expansion joints. It is also important to pro-
vide adjacent mating flange thickness or mating specifications to insure correct
rod lengths are provided.
Toll Free Phone . . . . . . . . . . . . . . . . . . . . . . . (800) 344-3246
International Calls . . . . . . . . . . . . . . . . . . . . . (209) 943-6088
Facsimile . . . . . . . . . . . . . . . . . . . . . . . . . . . (209) 943-0242
E-mail . . . . . . . . . . . . . . . . . . . . . . sales@procoproducts.com
Web Site . . . . . . . . . . . . . . . . . http://www.procoproducts.com
Series 230
Page 12 of 16
Figure 1: Limit Rod
Figure 2: Control Rod