ROTARY GEAR PUMPS
Technical Bulletin: Gear Pump Material Compatibility, Viscosity Conversion

The materials listed for use in the construction of pumps for different liquids are for general application only. In the selection of materials consideration should be given to general practice and the experience of the user in handling the liquids. In handling food, medicinal and similar products consideration must be given, also to laws and regulations in force at the locality where the pump is to be used.

Clark Gear Pumps:

All Iron pumps are constructed with steel gears, iron casings, and iron bearings. All Bronze pumps are constructed of bronze casings with bronze gears and shafts. For some applications the shafts of these pumps may be stainless steel. Standard Fitted pumps are similar to All Iron pumps. If necessary, bronze or carbon bearings may be used instead of iron bearings. Stainless Steel pumps are constructed of 316 stainless steel casings with 17-4 stainless steel gears and shafts.

Useful Pump Terminology

A foothead of water represents 0.4331 lbs. per sq. in. at 60ºF. In common practice 1/2 lb. per sq. in. is used.
Mean atmospheric pressure at sea level is 14.7 lbs. per sq. in. and is equivalentto a column of mercury 29.92 inches high or a column of water 33.97 ft. high.
Doubling the diameter of a pipe increases its capacity per unit length 4 times. Friction of low viscosity liquids such as water varies approximately as the square of the velocity. Friction of viscous liquids such as oil varies under normal conditions directly as the velocity.
Static Suction Head is the vertical distance from liquid level to center line of pump in feet when level is higher than pump.
Static Suction Lift is the vertical distance from liquid level to center line of pump in feet when level is lower than pump. Friction Head is the resistance to flow caused by contact between liquid and pipe and, in addition, other frictional losses within the liquid itself as it moves in the pipe.
Discharge Head is the vertical distance between center line of pump and point of discharge.
Velocity Head is the pressure required to produce the velocity of the liquid and is equal to V2/64.4 when V equals feet per second velocity.
Total Head is the sum of total of the suction, friction, discharge and velocity head.

Power required for pumping may be computed by use of the following formula:

H.P. = WxH/33,000xE or 0.000584 QP/E, where W is the weight of the liquid pumped per min. in pounds, H is the total head in feet (including frictional losses) and E is the efficiency of the pump. Q=gals per min.;P=lbs. per sq. in.

Viscosity is that property of a liquid which resists any force tending to produce
flow. The greater the resistance to flow, the higher the viscosity. Thus, molasses has a higher viscosity than water. Viscosity is usually expressed in Saybolt Universal Seconds (S.S.U.) although there are various other systems.
Specific gravity is the ratio of the weight of a known volume of a material to the
weight of an equal volume of water at 40ºF. Thus at 40ºF, the specific gravity of
water is 1.0. Material having a specific gravity of 0.90 has a weight per unit
volume of 90% that of water. When handling heavy liquids or liquid of a high viscosity, it is recommended that the pump speed be reduced and pipe sizes increased.