Depending uponthe design of a specific modelof valve, it maynot be
suitablefor mechanicalcleaning.
∑ Pinchvalve: a pinchstylevalve consistsof a flexible rubberor polymerliner
withina metaltube.The flexiblelineris pinchedbetweenmetalcomponents
to restrictor stopthe product flow.
16.2.2 Valvesusedin fluidor dry productprocessingsystems
∑ Blenderdischargevalve: blender dischargevalves come in a variety of
shapesand sizesaccording to the manufacturer of the blender.In most cases,
the valvesare located on the bottomor one end of the blender.They consist
of eithersliding gate types or hinged lift gate types.A pneumatic or hydraulic
cylinder oftenpowersthe valve actuators.Thesedesignsrequiredisassembly
for cleaning.
∑ Butterflyvalve: this designutilizes a more-or-lessflat, rounddisk attached on
the edgesof the disk to an actuator and support shaft.The shafts pass through
a circular rubber or polymerseat that is clampedbetween two flanges. The
valvescan be set to regulateor blockthe flowthroughthe valve.While often
cleanedby mechanicalmeans, this designwill allowproduct to migrate along
the shaftsdue to the product pressuresin the system and should,therefore, be
disassembledfor manual cleaning.
Fig. 16.4 Ball-typecheckvalve.Fig. 16.5 Spring-loadedcheckvalve.Improvingthe hygienicdesignof valves 267