NFPA T3.6.37 Revision R1, September 7, 2010
Hydraulic fluid power - Cylinders - Method for determining the buckling load
Includes all amendments and changes through Reaffirmation Notice , 2015
Additional Comments: SECOND EDITION
Published By:National Fluid Power Association ((NFPA))
Scope and field of application
This standard establishes a method to calculate the theoretical critical column buckling load of a loaded fluid power cylinder. Having the knowledge of the point at which, under ideal theoretical conditions, a hydraulic fluid power cylinder would fail, the designer can then apply an appropriate factor of safety for a safe design.
This standard applies only to pin-mounted (clevis mounts) fluid power cylinders and does not apply to trunnion mounted cylinders.
The method specified in this standard has been compared favorably in several buckling tests of fluid power cylinders in the range of three- to six-inch bores with one- to two-inch piston rods. Accordingly, the application of the method specified in this standard to larger- or smaller-sized cylinder designs should be approached with caution, and traditional methods should be used and compared in order to assure a safe design.
All cylinder installations have some added loads imposed beyond the calculated system pressure. These extra loads are often due to misalignment, friction and weight. As a result, such factors shall be taken into account. In addition, the Hoblit method (see Annex A) provides a theoretical result and as such produces a critical buckling load higher than attainable in controlled laboratory tests. Accordingly, adequate factors of safety shall be applied to ensure that the actual working load is well below the critical buckling load.