Both grade 12 and grade 22 materials are suitable for use up to 649 °C (1200 °F). Above approx. 510 °C the allowable stress for grade 22 material is higher than that for grade 12 material, so when designing a clamp for 546 °C the material section size will be heavier if it is designed using grade 12 material than if it is designed using grade 22 material.
In producing the PSL catalogue for alloy pipe clamps, we designed clamps which achieve the standard load group load capacities at four temperatures, 490, 530, 560 and 600 °C. We also calculated the actual load capacities for all of these clamps in the range 350 to 600 °C.
When selecting an alloy steel clamp, it is necessary to choose a clamp whose load capacity at pipe temperature exceeds the applied load at temperature. The part numbering merely indicates what design temperature was used to achieve the standard load group load capacity at this temperature. Clamps designated … – 490 can be used at 600 °C and clamps designated … – 600 can be used at 410 °C.
It is only necessary to ensure that the applied load at temperature is less than the load capacity at temperature. The last three digits of the part number do not imply a maximum allowable temperature for the component. Allowable load capacities for pipe clamps at temperature are clearly shown in the PSG catalogue. Our selections combine ‘fitness for purpose’ and ‘most economic choice’.