Pro­ce­dure

  • Place flow cup in a pre­cisely hor­i­zon­tal posi­tion using ring stand or tem­per­a­ture con­trol jacket
  • Close ori­fice
  • Pour in test liquid
  • Draw a clean glass plate over the rim of the cup, remov­ing super­flu­ous liquid into the over­flow reser­voir and clos­ing the cup
  • Open ori­fice
  • Remove glass plate hor­i­zon­tally and start stop watch
  • Stop the watch with the first break in the efflux stream
  • Repeat the mea­sure­ment three times, each with a new sam­ple of the same mate­rial

Vis­cos­ity Cups

A flow cup, some­times called an efflux cup or vis­cos­ity cup, is a sim­ple grav­ity device that mea­sures the timed flow of a known vol­ume of liquid pass­ing through an ori­fice located at the bot­tom of the shaped cup. Under ideal con­di­tions, this rate of flow would be pro­por­tio­nal to the kine­matic vis­cos­ity (expressed in stokes and cen­tis­tokes) that is depen­dent upon the spe­cific grav­ity of the liquid. For many appli­ca­tions it is not neces­sary to know the abso­lute vis­cos­ity. The efflux time, mea­sured in seconds, is often suf­fi­cient for a rel­a­tive clas­si­fi­ca­tion.

At least 50 types of flow cups have been devel­oped and used over the years, mainly for pro­duc­tion con­trol and field inspec­tion pur­poses. Most of these sim­ple cups are of two main types — mounted on a stand for filling and drain­ing, or dipped directly into the liquid con­tainer before drain­ing back into the same con­tainer. No mat­ter which type of cup is used there are sev­eral fun­da­men­tal prin­ci­ples that should be rec­og­nized:

  • Pre­cau­tions should be taken when­ever thix­otropic or other non-New­to­nian liquids are tested for vis­cos­ity, because there is no defi­nite rate of shear gen­er­ated in a flow cup.
  • The diam­e­ter of the ori­fice should be selected and main­tained so as to pro­vide flow times falling within pre­scribed min­i­mum and max­i­mum lim­its.
  • The tem­per­a­ture of the drain­ing liquid should be con­trolled and mea­sured only in the efflux stream, after it passes through the unda­m­aged bore.

Ford Cup Cal­i­bra­tion Curves

DIN and ISO Cups Cal­i­bra­tion Curves