double disc gate valve

Babcock valve’s double disc gate valve detail

DOUBLE DISC GATE VALVES

Double disc gate valves are a special design of gate valves that improves considerably the performance of the unit.

DOUBLE DISC WEDGE ASSEMBLY ADVANTAGES

Main advantages of double disc gate valves vs gate valves are:

RELIABLE OPERATION

 Reliable operation The Double Disc Gate Valve has been desig ned to assure reliable operation under the most severe service conditions. Due to the special configuration and geometry of the upper wedge inclined face, any possibility of locking the disc in closed position is eliminated, even when closed quickly or subjected to severe thermal transients.
LOW PRESSURE SEALING
Low pressure sealing The wedge assembly is designed to impart sufficient thrust to each disc to maintain low pressure sealing. As the differential pressure across the disc increases, the seating load also increases, thus providing a tight seal throughout the entire range of operating differential pressures. Since the discs are independent of each other and the design is symmetrical, positive sealing can be maintained in either direction.
UNIFORM DISTRIBUTION OF SEALING PRESSURE
 Uniform distribution of sealing pressure The tight seal is guaranteed even when the valve seats have become out of parallel due to body distortion, due to the uniform distribution of the sealing pressures allowed by the exclusive wedge design.
EASY MAINTENANCE
 Easy maintenance The four piece double disc wedge assembly can neither be incorrectly assembled nor become disengaged while in service. No special fitting at site is required for maintenance. The repair of minor seat or disc damage is greatly simplified because the seats and discs can be lapped inde- pendently of each other. Disassembly and maintenance can be accomplished without special tools or elaborate rigging.
UNIFORM SEAT WEAR
Uniform seat wear The incorporation of a unique revolving disc feature assures maximum seat life. The two independent discs, during each closing stroke and immediately prior to the disc seating, rotate a few degrees in the plane of the seats. This rotating action forces the disc to seat in a different position on each stroke, equalizing wear on the seats and the discs. This movement of the discs creates a lapping effect whenever the valve is operated, removing particles from the sealing surfaces before they can become wedged between the seats and the disc and cause damage.
RAPID CLOSURE
Rapid closure BPE’s Double Disc Wedge system permits rapid closure without seat distortion. Internal moving parts decelerate independently of each other with the result that inertial forces are dissipated in a series of impacts over a period of time. The largest of these is transmitted directly to the bottom of the valve body on a non-sealing surface. Forces transmitted directly to the seats are a small percentage of the total inertial forces. This is a distinct advantage over valve designs in which the total inertial force is absorbed directly by the seating surface 
 
More info about double disc gate valves at:

BABCOCK GATE VALVES WEBSITE