Page 89 - Valve Selection Handbook

76 Valve Selection Handbook

chamber is, furthermore, filled with a grease that transmits the fluid pres-
sure to the top of the piston of the downstream reservoir. The closure
member consists of two discs, which are spread apart by springs. Both
the sealant and the body grease can be replenished from the outside while
the valve is in service. Each reservoir filling is sufficient for more than
100 valve operations. This mode of sealing achieves a high degree of
fluid tightness at high fluid pressures.
The conduit gate valve shown in Figure 3-32 is especially designed for
the hydraulic transport of coal and ore, and the transport of heavily dust-
laden gases. The gate, which consists of a heavy wear-resistant plate with
a porthole in the bottom, slides between two floating seats that are highly
pre-stressed against the disc by means of disc springs. To prevent any
possible entry of solids into the body cavity, the seats are provided with
skirts for the full travel of the disc. The faces of the disc and seats are
metallic and highly polished. The valve chamber is, furthermore, filled
with a lubricant that ensures lubrication of the seating faces.

Figure 3-32. Conduit Gate Valve with Metal Seatings and Oil-Filled Body Cavity for
Heavily Dust-Laden Gasses and the Hydraulic Transport of Coal and Ores. (Courtesy
of VAG-Armaturen GmbH.)