As far as my knowledge about sealing goes TC Vs TC face combination has a very low PV ratio and hence is to be avoided as far as possible.secondly it is always preferable to have one hard and other comparatively softer face and hence Sic Vs TC is a much better option.I beg to differ with ACP, as...
take a thumb rule for single stage back suction cetrifugal pump as the suction pressure + 25 % of the differential between the suction and discharge pressures