Fisher EH and EHA Control Valves - FISHER - #4

51.2:EH March 2009

EH and EHA Valves

1. See the section titled Coefficients in this bulletin for additional sizing data.

• Long Thermal-Cycle Life—The seat ring design minimizes operational stresses, thereby reducing chances of distortion and resultant leakage caused by temperature cycling. The hung cage design allows thermal expansion of the cage without affecting the seat ring gasket loading.

• Operational Economy—Balanced trim constructions reduce forces acting on the valve plug, thus reducing actuator thrust requirements and permitting the use of smaller actuators. This, combined with capacities higher than comparably priced globe valves, makes the NPS 8 through 14 EH Series valves very economical for high-pressure, high-flow service. Actuator selection for NPS 20 valves can be made from electromechanical or electrohydraulic styles that use readily available power sources.

• Reliability—All aspects of the control valve (material selection, trim components, packing, and control accuracy) are designed, built, and tested to assure performance and reliability. Extensive metallurgical evaluation results in state-of-the-art cage and valve plug stem materials that help ensure trim life and dependable performance.

• Control Accuracy—The NPS 20 cage and valve plug deliver accurate control of high pressure and high capacity flow. Each cage has milled openings and is flow tested for the required flow characteristic. With precise, accurate cage openings, accurate installed characteristics result; valves in parallel have the same flow at the same plug position. The cone-shaped plug reduces fluid turbulence, helps ensure plug stability, and aids positioning accuracy.

• Easy Maintenance—The bonnet lifts off to allow trim access. The separate seat ring and cage allow parts removal and maintenance. The globe configuration reduces the uneven trim wear and resultant maintenance downtime normally associated with slant configurations. Installation with the stem vertical above the bonnet also makes trim removal and installation easy.

FOR EHT, CAVITROL TRIMS, AND SOUR SERVICE <E

CD PREFERRED FOR ALL OTHER BODY CONSTRUCTIONS WHERE TEMPERATURE ALLOWS.

• High Capacity—Careful consideration of

aerodynamic and hydrodynamic principles in the design of the flow stream passages results in 30 to 40 percent higher capacity than conventional valves with comparable port sizes and travels.