Stress Analysis of a Cast Iron 125-lb. Valve Assembly

    Published: Jan 1950

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    During the war emergency, in view of the possibility that more strategic materials than cast iron might be conserved and procurement problems eased, some of the various standards associations, as well as consumers and suppliers, were advocating the use of cast-iron valves and fittings in place of steel. Unfortunately, there were few engineering data available and what were available-were too contradictory in nature, due to differences in test results caused by varying composition and cooling rates, to assure design and operating engineers that it was safe to rely on cast iron. Engineers had been trained for years not to use cast-iron valves, or fittings, in lines where a break might be costly in material or life or both. The A.S.M.E. code limitations on the use of cast-iron valves and fittings also hindered a wider use of the material. In order to determine accurately the feasibility of uprating various cast-iron valves, we started an experimental stress analysis program to determine the strength of cast-iron valves. As a 12-in. class 125 American Standard flanged-end valve represents a size and pressure class widely used in industry for all types of service, it was decided to carry out a series of tests on this type of valve. Figure 1 illustrates the valve and SR-4 strain gage locations. The investigative work was divided into 6 steps: 1. Location of governing stresses in the valve structure for various conditions simulating actual service. 2. Measurement of the hub flange stress (SH) in the valve flanges when made up with various types of gaskets. 3. Correlation of measured and calculated flange stresses. 4. Development of a method of calculating the hub stresses in a flanged joint made up with full face gaskets. 5. Comparison of the governing flange stresses in a valve and comparable pressure class fitting. 6. Fracture tests correlating tensile strength of the iron, as determined by 0.505-in. diameter tension test specimens cut from the casting, with the rupture stress of the casting.

    Author Information:

    Malcolm, V. T.
    Director of Research and Research Engineer, The Chapman Valve Manufacturing Co., Indian Orchard, Mass.

    Low, S.
    Director of Research and Research Engineer, The Chapman Valve Manufacturing Co., Indian Orchard, Mass.

    Committee/Subcommittee: A04.21

    DOI: 10.1520/STP48070S

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