Gate and knife gate valves can be used in many slurry services. With many gate valves, however, you must be willing to sacrifice tight shutoff in lime slurry service. Most gate valves force the gate into a wedge area to close the valve.

Knife gate valves have a sharpened edge to improve the ability to cut through solid particles. In lime service, the seating area will be a spot for material accumulation. The lime will accumulate in this area, cause difficulties in valve operation and could prevent sealing the valve completely against the line pressure.

The ideal knife gate valve for lime service features a hard-surfaced leading knife edge. For surfacing, stellite or some other material capable of protecting the softer steel blade is used. Actuator forces in knife gates also should be increased to give the valve the ability to cut through or close tightly against the lime buildup in the wedge.

The knife of the knife gate will be exposed to scaling. The scale buildup on the knife most likely will result in packing problems in knife gates. The scale will accumulate on the valve's knife. As the knife is opened, the scale buildup will be dragged through the packing, requiring increased forces to open the valve. The packing also will be affected severely when this material is dragged across it. With most knife gates, you will experience significant packing leaks.