VALVE MAGAZINE Winter 2024

GATE VALVES FOR WATERWORKS

Figure 2 Simulated corrosion of the valve castings

Figure 3 Beam load tests

Table 1: Corrected Valve and Wall Thickness Comparison.

After the introduction of the resilient-seated gate valve, the industry migration from gray cast iron to ductile cast iron continued in the development of the C515 standard. A comparison of these standards reveals only a few differ ences; they are virtually identical. Unlike C509, the newer C515 standard requires the use of ductile iron for the body and bonnet components. Because of the increased strength and elasticity of ductile iron, the allowable minimum wall thickness requirements are reduced, and the pressure rating has been increased. Different from the arbitrary wall thicknesses in C500 and C509, the wall thicknesses published in C515 were developed using finite element analysis (FEA), along with applied validation testing. Since being published, there has been a significant shift in demand toward ductile iron waterworks valves produced to the C515 standard. Another significant differ ence in the standard is an allowable 12.5% reduction in wall thickness accounting for casting deficiencies called out in the C500 and C509 standards. This reduction is not allowed in C515. A comparison of the allowable C500, C509 and C515 wall thicknesses appears in Table 1 and shows the differences to be very minimal. Table 1 thicknesses account for allowable tolerances. After the ANSI/AWWA C515 standard was published in 1999, there were occasional questions about the potential effects of corrosion related to reduced wall thickness. Of particular concern was how material loss, if any, might impact the strength of a valve while under pressure. Companies must address this during the validation of

Minimum Wall Thickness Adjusted for Allowable Minus Tolerances

AWWA C515 (inches)

AWWA C509* (inches)

AWWA C500 (inches)

Size

4 6 8

0.35 0.38 0.44 0.55 0.60 0.66 0.74 0.82 0.85 0.95 1.22 1.35 1.38 1.51 1.93 2.14 2.35 2.56

0.31 0.32 0.34 0.36 0.38 0.45 0.50 0.56 0.56 0.62 1.06 1.31 1.42 1.44 1.44 1.68 1.88 1.94

10 12 14 16 18 20 24 30 36 42 48 54 60 66 72

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VALVE MAGAZINE

WINTER 2024