The following text may have been generated by Optical Character Recognition, with varying degrees of accuracy. Reader beware!

| is extremely desirable that all types of rotary pumps have a strainer placed in the suction line in order to keep out of the pump any large particles of foreign matter which otherwise would enter; for, owing to the construction of all types of rotary pumps this foreign matter would jam in the small clearance spaces and interrupt operation or break the pump. move the product through the line, since upon this latter fact depends largely the size of pump and lines. In pumping oil or other product from one location to another through pipes, the principles of suction and pressure are used—generally, a com- bination of the two. Pumps used in moving fuel oil and - lubricating oils are usually either of the piston or rotary types. In piston pumps a plunger moves the fluid and puts pressure behind it. Such pumps may be either steam or power-driven. There are two general classes of ro- tary pumps, namely, the gear or cy- cloidal pattern and the rotating-piston pattern. Centrifugal pumps are high- ly efficient for use in pumping light distillates, but in general because of inherent principles of design they are not suitable for handling heavy oils. Characteristics The piston pump is comparatively simple and sturdy piece of equipment. Usually, the steam piston is directly connected to the liquid plunger by means of a rod moving through stuff- gs m\\ iat), | = -M=BOLT CTR. mes SIDE would either EXTRA LARGE AREA SLOWS UP LIQUID ALLOWING FOREIGN MATTER _TOSETILE DICATES DIRECTS FLOW REDUCING FRICTION LOSSES 70 A MINIMUM SLOTS 70 SvIT SERVICE CONDITIONS -_—- on QCTION OF LIQUID DEPOSITS FOREIGN MATTER IN EXTRA LARGE SPACE Suitable Strainer for Fuel Oil Suction Line ing boxes. Piston pumps operate on steam at the boiler pressure and, con- sequently, with few exceptions, fail to utilize the expansive energy stored in the steam. -However, those types that do utilize this energy are fitted with fly-wheels, the energy stored in the moving fly-wheels permitting the variable steam pressure. Because of lost motion in the valves, piston pumps do not have so-called dead- centers; in other words it is impos- sible so to stop them that they will not start when the steam is again turned on. Air chambers are a necessary fea- ture of piston pumps because the movement of the pistons exerts a con- stantly changing pressure. Irregular pressure causes both acceleration and retardation to take place in the stream of liquid being pumped and a considerable amount of energy to be lost because of inertia and loss of mo- mentum. Air chambers placed in the discharge line tend to act as buffers and serve to equalize the pressure. Liquids are non-compressible and, therefore, transmit any pressure General outline of Belt-Driven Rotary Pump—S. F. See é& Co. Inc 38 MARINE REVIEW—September, 1930 placed upon them; air and other gases, on the other hand, are readily compressed and hence take up the shock that otherwise would result from sudden pressure changes. In action, the air in the air cham- ber is compressed as the pressure in- creases, and regains its normal vol- ume when the pressure again de- creases. In expanding, the air in the chamber exerts pressure on the liquid in the pipe, and thus keeps the veloc- ity of flow fairly uniform. The size of the air chamber for a particular pump system is chosen so that the pressure head in the system remains almost unchanged. In single pumps, the air chamber is about three times the volume of the liquid-piston dis- placement; in duplex pumps, it is about twice the piston displacement, this difference being due to the fact that the discharge from a duplex pump is much more steady than from a single pump. Single and Double Pumps Hither the single or the duplex types of steamdriven displacement pis- ton pumps are of low first cost, and, being simple in construction, trouble symptons are easily diagnosed and the necessary repairs are readily made. Single pumps are unequaled in their flexibility as to speed, capacity, and ability to handle either light or heavy oils against any discharge pressure up to the maximum for which their liquid ends are designed. They are especially satisfactory for handling small quantities of liquid against high pressure heads; and small quantities of liquid containing gases, or liquids that must be handled at temperatures at which they readily give off vapors at negative, or suction, heads. When the service so requires, steamdriven piston pumps may be automatically controlled by suitable speed and pres- sure governors. Such pumps may al- ways be protected by an excess pres- sure governor from any damage that would result from sudden closing of ‘the discharge valve. The first rotary gear pump was in- vented by Serviere, a Frenchman, born in 1593. In its simplest design it consists of two spur gears, meshed closely, and enclosed in a case that also fits closely to the sides and outer