JCM Large Diameter Repair Clamps Selection and Application
In the repair applications to large diameter pipe, there are several factors to be considered to maintain pipe integrity and return to 100% service capacity. These factors, which are critical to the application, include: size and type of pipe, severity of damage, working pressure or service requirements, location of repair and time factor. Line pressure forces encountered in repair applications will determine the success or failure of a repair fitting. The forces of large pipe reduce the working capability and safety factor of large repair clamps. Performance of these fittings is determined by the relationship of bolting power to gasket area, fastener attachment, bolt efficiency and thickness of metal. Therefore, a repair clamp may not be the proper fitting for certain applications. JCM offers various repair fittings which are suitable for repairs to large pipe operating at higher working pressures. To understand the forces involved in the application, see the comparison values listed below relating size of pipe to the internal forces involved.
Nominal Pipe Size (In.)
Stress/Force on Clamp at 100 PSI
Area of 1/4” Break
12 16 20 24 30
13.20 17.40 21.60 25.80 32.00
10.37 sq. in. 13.67 sq. in. 16.96 sq. in. 20.26 sq. in. 25.13 sq. in.
1,037 lbs. PSI 1,367 lbs. PSI 1,696 lbs. PSI 2,026 lbs. PSI 2,513 lbs. PSI
On a repair clamp the mechanical seal is made by tightening bolts to create a greater force on the gasket (PSI) than is in the pipeline. Safety factor is that amount of sealing capability the clamp has above the operating pressure of the pipeline. Clamps are limited in performance by the relationship of bolting power to gasket area. Also entering into the picture are the fastener attachment, bolt efficiency and the thickness of the metal. JCM clamps have been designed to limit traditional clamp weaknesses, thereby giving a higher working capability and safety factor. Even so, they do have a limited capability. Other types of repair fittings should be taken into consideration. Fabricated repair sleeves are designed to overcome the forces involved with large diameter pipe and its characteristics.
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