VALVE MAGAZINE Winter 2024

GATE VALVES FOR WATERWORKS

GATE VALVES Which Gate Valve is Best for Today’s Waterworks Systems?

A historical perspective may provide the answer.

Figure 1 Finite element analysis (FEA) Photo Credit: American Flow Control

BY: DEREK B. SCOTT Marketing And Technical Manager JOHN R. HELF Product Engineer COMPANY: AMERICAN FLOW CONTROL

The gate valve is the most common valve used in a waterworks utility system. Gray cast iron metal-seated gate valves have been produced since the 1800s. They are governed by the ANSI/AWWA C500 standard tilted Metal Seated Gate Valves for Water Supply Service. The standard was developed in 1913 but did not receive the C500 desig nation until 1953. In 1980, as rubber molding and coating technologies advanced, the waterworks industry intro duced the ANSI/AWWA C509 Resilient-Seated Gate Valves for Water Supply Service standard. The C509 standard, unlike C500, has no allowance for leakage. It also requires more corrosion-resistant coatings. Responding to trends that saw the industry’s migration from cast iron to ductile iron pipe and fittings, field trials were conducted on a reduced wall, ductile iron gate valve beginning in 1985. This advancement resulted in a new standard for resilient-seated gate valves being published in 1999. The standard was designated ANSI/AWWA C515 Reduced Wall, Resilient-Seated Gate Valves for Water Supply Service. The standard leveraged the strength and durability of ductile iron by reducing the wall thickness of the valve. Today, most utilities specify C515 gate valves. Occasionally, however, specifications are published requiring C500 or C509 compliance even when the utility is using C515 compliant valves. These outdated specifications, or erro

neous references to older standards, result in confusion regarding which gate valves should be used. More problem atic are specifications that require contradictory criteria from multiple standards, which can require a valve that may not exist. These problematic situations result in unin tended interpretations of the requirements. To understand the source of the confusion, one must first look at how the standards have evolved and why. The minimum wall thicknesses required in the C500 standard were largely based on industry experience, valve application and the standard gray iron casting methods used at the time. These limitations resulted in the published wall thicknesses being somewhat arbitrary. Also common to these valves is an allowable leakage that worsens with time, as well as higher operating torques that result from significant friction across the metal seats. The resilient-seated gate valve addresses these primary issues with a one-piece rubber-encapsulated wedge that is leak-tight and that allows for lower operating torques. Originating in Europe, the resilient-seated design was received with widespread acceptance and in 1980 resulted in the development of the C509 standard. The wall thick nesses published in the standard were carried over from the C500 standard, making the C509 wall thicknesses arbi trary as well.

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VALVE MAGAZINE

WINTER 2024