Fisher EH and EHA Control Valves - FISHER - #3

51.2:EH March 2009

EH and EHA Valves

end connections have Intermediate Standard Ratings. With nondestructive testing, these valves can conform to ASME Intermediate Special Ratings, which allow even higher pressure/temperature applications. See tables 7 and 8 for specific ratings.

• Long Trim Life—Hardened materials of construction for the cage, valve plug, cage guiding, and other trim parts are standard for all applications, providing excellent wear resistance. In all applications, rugged cage guiding provides increased valve plug stability. Increased stability results in reduced vibration and other mechanical stresses, which contributes to long trim life.

■ EHS (NPS 1-1/2 x 1 through 6), ■ EHD (NPS 2 through 20), and ■ EHT (NPS 2 through 14)

■ EHAS (NPS 3 through 8), ■ EHAD (NPS 3 through 8), and ■ EHAT (NPS 3 through 8)

These valves (figure 1) are specially designed for high-pressure applications. Fisher® EH valve configurations incorporate proven techniques in flow-stream contouring for higher capacities and in valve trim design for reliability in severe applications.

The temperature limits of EHT valves can be extended above 232°C (450°F) by using PEEK (PolyEtherEtherKetone) anti-extrusion rings in combination with a spring-loaded PTFE seal. The PEEK anti-extrusion rings expand to close off the clearance gap between the plug and the cage where the PTFE seal may extrude at high temperatures and pressures. The temperature limits are extended to 316°C (600° F) for non-oxidizing service and to 260°C (500° F) for oxidizing service.

Unless otherwise noted, all NACE references are to NACE MR0175-2002. Contact Emerson Process Management for information on NACE MR0175/ISO 15156 or NACE MR0103.

• Piping Economy—The availability of expanded end connections on EH valves may eliminate the need for line swages while accommodating oversized piping arrangements.

Micro-Form or Micro-Flute valve plugs (figure 6 or 7) provide superb rangeability in high-pressure, low-flow applications. A choice of several restricted port diameters helps match valve capacity to required flow, helps provide necessary control with full travel, and helps prevent throttling near the seat.

For EHA valves only, and in low-flow applications where cavitation damage may occur, the Micro-Flat style valve plug can be used. For soot-blower applications, where the valve must provide tight shut-off, a special trim design is available. Please contact your Emerson Process Management sales office for more information.

For low-flow applications where cavitation damage may occur and the minimum required C_v is equal to or greater than 0.05, Cavitrol® III with Micro-Flat trim can be used in both EH and EHA valves. Please contact your Emerson Process Management sales office for more information.

• Improved Cage Design—Drilled-hole cages, offering excellent strength and additional resistance to destructive vibration, are standard. Special materials of construction are readily available.

• Optional O-ring Seat Ring Gasket Construction—Use of O-ring construction provides excellent shut-off with minimal seat ring installation torques for temperatures up to 232°C (450°F). O-ring construction is standard on EHT valves.

Ratings—Steel EH and EHA valves with buttwelding

• High-Temperature, Class V Shutoff—Use of

C-seal trim (see figure 21) permits Class V shutoff up to 593° C (1100°F) for up to 4-3/8 inch port. Bore Seal trim will permit Class V shutoff up 593°C (1100° F) for 5-3/8 inch ports and larger.

• Excellent Sealing—HIGH-SEAL packing systems provide excellent sealing to conserve valuable or hazardous process fluid and to protect against the emission of hazardous or polluting fluids. This system (figure 2) features graphite packing material and heavy-duty live loading.