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SMART STRAP
An Innovative Pipe Clamp and Support System
By Michael R. Istre, PE
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Smart Strap by AEPS is being developed to provide an alternative to rigid pipe support clamps. This document provides a summary of the evaluation of the design and observation of testing performed by the Author as Subject Matter Expert (SME).
The Smart Strap is a modification of a standard pipe support clamp utilizing a stainless steel mesh in place of the standard rolled steel plate for the hold down component. The design of the Smart Strap allows for retrofitting to existing supports by various other manufacturers. The connection of the strap to any anchoring system is made utilizing standard bolting through a fabricated plate integrated into the stainless mesh.
There are several advantages of using a mesh system in lieu of plate steel. Some of these are:
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Reduced weight. Regular inspection of the pipe requires removal of the clamping system. The reduced total weight of the clamp, especially on larger diameter pipe, facilitates the removal and reinstallation of the strap. In some cases, this could also eliminate the use of lifting equipment.
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Flexibility. Manufacturing tolerances of both pipe and rolled plate clamps can create hard points and stress concentrations. The use of a flexible mesh accommodates the imperfections in the pipe and can better distribute the load around the pipe to reduce stress concentrations and localized coating damage.
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Quality Control. The flexible mesh system is provided from a vendor with an established quality control system. The material is also load test certified. This provides for consistent and reliable performance.
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Corrosion Resistance. The use of stainless steel mesh eliminates the normal maintenance of the painting system used on common steel plate.
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Minimize Coating Damage. The reduced weight and flexibility of the Smart Strap minimizes the potential of coating damage to the pipe during installation, inspection and re-installation.
It can also be argued that the mesh system is superior to the U-bolt style clamps. The design can easily be modified to the same small footprint of the U-bolt system. The U-bolts suffer from inconsistent installation and tightening and are often found to be loose on the piping.
Regardless of any of the above advantages, the most important item is the performance of the component. The industry standard practice MSS SP-58 “Pipe Hangers and Supports – Materials, Design, Manufacture, Selection, Application, and Installation” provides some guidance on minimum design loads. For 30” OD pipe, Table 1 of MSS SP-58 specifies a minimum design load rating of 3500 lb. In this configuration, the mesh manufacturer has a certified rating of 17,000 lb. A full scale test using 16” OD pipe was performed at the AEPS facility to validate the prototype design and witnessed by the author. The initial test was suspended at 30,380 lb applied load. After disassembly, the strap showed no signs of permanent yielding or stretch.
A full test to failure was then performed. At an applied load of 95,810 lb, the test frame failed. After nearly a 6x design load, the measured stretch was approximately 1/8” or 0.25%. Full flexibility of the mesh was maintained.
Based on the prototype design and observed testing, it is the opinion of the author that the Smart Strap provides a superior performance standard to the rolled steel plate style clamp. The design appears to be compliant with MSS SP-58 and fully load rated in both hold down (pipe support) and hanger configurations.
About the Author:
Michael Istre is a registered professional engineer in multiple states and Canadian provinces. He has over 20 years of experience in piping design, installation and manufacturing. Mr. Istre holds degrees in mechanical engineering from the University of Louisiana-Lafayette and The University of Texas.