Plugvalves are not generallyusedin dry productapplications.Thisdesign is
not suitable for mechanical cleaning techniques and requires complete
disassemblyfor manual cleaning.
∑ Leakprotectionvalve: a leak protectionvalvesis a specialized plug-type tank
outletvalvethat is usedon vat pasteurization equipment.The designincludes
specialfeatures that will preventleakagepast the valveby controllinghow
far the valvemaybe turnedand the inclusionof grooves to provideleak
detection.Thisdesignis not suitablefor mechanicalcleaningtechniques and
requires complete disassemblyfor manual cleaning.
∑ Compressionvalve(Fig.16.2):this designusesa valve seat located on the
end of a stem or rod thatliftsthe movableseatoff from a valveseat
incorporated into the bodyof the valve. Thesevalvesoperateefficiently when
locatedin a variety of positionsand havea large,unobstructed valvebody to
permitoptimum flow throughthe valve. Thisdesign is generally suitablefor
mechanical cleaningmethods.
∑ Mixproof valve: a mixproof valveis a specialized compression valvethat uses
doubleseats that can be operated independently,separated by a self-draining
openingto the atmospherebetween the valve seats.Theprimarydesign
advantageof thesevalvesis to accommodatethe separation of two different
product streamsor product fromcleaningfluidsduringmechanicalcleaning.
∑ Diaphragm valve(Fig. 16.3):this designusesa flexiblediaphragm to form
the seal. The valvesare usedto shut-offor regulate productflow.Theywork
wellwithsemi-solidand fluidproducts containingparticulates. Diaphragm
valvesare not commonly usedin dry productapplications.The valves can be
mechanicallycleanedprovidedtheyare equippedwitha power actuator and
are installedproperly to assuredrainageof the valve cavity.Manydesigns
includean orientationmarkon the housing to assistwithinstallation.
∑ Tankoutletvalve: outletvalves comein a varietyof configurationsdepending
on whether theyare mounted horizontallyor vertically.To eliminateor
reducethe amount of product that maybe retainedin the outletpassage,the
designprovides for the valveto be as closecoupledas possible to the product
vessel. They may be manually or mechanically operated and cleaned
depending upontheirdesignfeatures.
∑ Pressure reducing and regulating valve: thesevalves are designedto control
product outletpressureby responding to outletpressurechanges by meansof
a self-actingactuator.The self-acting actuator raisesor lowers the valve seat
withinthe valvebody by meansof fluidforceswithinthe valvebody.
∑ Checkvalve(Figs 16.4and 16.5):checkvalvespermit productflowin only
one direction.A reversal of product flowor pressure will result in the valve
sealing. The actuation of the valve is self-actingthroughthe use of internal
balls,valveflaps, or spring-loadedvalve seats.Because of theirbasicdesign,
spring-loadedcheckvalvesmustbe fully disassembledfor manual cleaning.
∑ Ballvalve: this design usesa ball connected to an actuationshaft.Product
flowis directedor stoppedthroughsingle or multiple passageswithinthe
ball.Thisdesignincorporates bodycavity fillersor encapsulatingsealsto
Improvingthe hygienicdesignof valves 265