High Performance Butterfly Valves
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Product General • High performance |
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AM771 SERIES BUTTERFLY VALVES Face to Face according to API 609 T2 AM772 SERIES BUTTERFLY VALVES Face to Face according to API 609 T2 |
 Doubel Eccentric Structure |
AM770 High Performance Double Eccentric Butterfly Valve
The HLV AM770 Series High Performance Double Eccentric Butterfly Valve is a heavy duty automatic throttling control valve that incorporates the two basic features of the AM770 types. These features differentiate the AM770 from the conventional swing through butterfly valve in regards to sealing method and operational characteristics. Specifically, the two basic features are: (1) A PTFE, RTFE, or metal seal ring instead of a liner, and (2) The employment of double offset (eccentric operation). Each of these features contributes to the improved performance of AM770’s compared to conventional butterfly valves. The use of a seal ring (PTFE, RTFE, or metal) eliminates the inherent problems of high sealing forces, due to interference fit, and the resultant high wear rates due to scraping and scuffing of liners. Also, due to the design of the seal itself, which is a dynamic pressure-assisted member, ANSI Class VI shutoff rates are available throughout the full range of ANSI Class 150 and 300 ratings (soft-sealed constructions only). The double offset (eccentric) operating principles of both seal offset (the seal ring centerline is offset from the shaft centerline - see Figure 1) and shaft offset (the shaft centerline is offset from the valve centerline – see Figure 1) allows the disc to get off the seal quickly due to the camming rotation with respect to the valve/seal centerlines. This results in minimal sliding (friction producing) contact between the disc and the seal ring with complete separation after only a few degrees of rotation.
The overall characteristics of the AM770 Series are listed below:
• Long seal life – Offset (eccentric) operation gets the disc off the seal quickly, minimizing sliding contact and friction,resulting in reduced seal wear and lower breakaway and seating torque requirements.
• Fast/dynamic operation – Offset (eccentric) operation eliminates disc-to-seal friction throughout the operating range resulting in fast response to input signals. Also, the disc tends to move in the direction of flow, assisting the valve and actuator to maximize the allowable operating pressures.
• Excellent flow characteristics - the offset (eccentric) disc design provides an approximate equal percentage flow characteristic through its full travel of 90° rotation yielding a Cv ratio of 100:1.
• Extra heavy shafts with keyed ends for actuator mounting - precise and accurate positioning without lost motion or backlash. PTFE-lined low-friction bearing – Reduces operating torque and promotes fast response to valve and actuator action. The triple bearing support of the shaft prevents deflection of the shaft due to side-loading and incorporates a grounding circuit.
Field replaceable components – Unlike most competitive valves, shaft and disc need not be purchased as a set. The AM770 Series uses tapered pins to attach the shaft and disc positively, yet provide component interchangeability.
