First: Cast-N-Place™ inserts do not suffer the cost disadvantages of bonded valves.
Second: molding the insert around serrations in the valve body locks the insert in place, without adding stresses to the insert.
Third: compressive stresses from shrinkage during curing increases abrasion and extrusion resistance for longer valve life.
Rather than bonding, Cast-N-Place™ Insert Valves utilizes machined serrations to replace the bond function. The urethane is poured directly around the serrations, mirroring the shape of the serrations. The urethane material is, thus, interlocked around the serrations, which anchors the insert without introducing stress to the insert. The serrations prevent any movement of the insert. Loss of the insert while pumping is extremely rare!
A major advantage of Cast-N-Place™ Insert Valves is improved service life due to induced compressive stresses in the polyurethane curing process. When inserts are manufactured, the inserts shrink by about 2% during the curing process. This shrinkage induces compressive stresses in the insert skin. Normally we think of compressive stresses as being beneficial in increasing fatigue life in steel parts, under cyclic fatigue loading. Similarly, compressive stresses have advantages for inserts by increasing insert abrasion and extrusion resistance. During abrasion or extrusion, the skin is stretched a very large amount, at a very localized area. In this finite small area the urethane material is stretched greater than the tensile strength of the material allows, which leads to tearing and failure of the insert. If compressive stresses in the urethane skin are present, the urethane must be stretched an even further distance, before the localized area of the skin exceeds the tensile strength of the insert material.
Valve and seat life is improved and made more reliable by the benefit of Cast-N-Place™ Inserts. |
KERR
