Reciprocating single-piston

Figure 4.3. A schematic of a reciprocating single-piston pump.

Reciprocating pumps are those most commonly used in high performance Ic. The single-piston type usually has inlet and outlet check valves with some mechanism such as variable stroke frequency to minimize the effect of pump pulsations. Dual-piston pumps operate with the pistons 180° out of phase to minimize pulsations. For this system to work optimally, the piston units must be identical. 

The single piston reciprocating pump was the first of its type to be used in liquid chromatographs and is still very popular today. 

Figure 9.23. Schematic of a single piston reciprocating pump. Reprinted from Yost, Ettre, and Conlon, Practical Liquid Chromatography, 1980 by courtesy of Perkin-Elmer.

A single piston reciprocating pump has a 15-cm-diameter piston with a 15-cm length of stroke. If the pump makes 16 strokes per minute, what is the pumping rate in (a) L/min (b) gal/min ... 

Turn on the power to the chromatography module/SP via a switch located in the rear of the module. This will start the single-piston reciprocating pump on the Model 2000. 

The single piston reciprocating pump was the first of its type to be used in liquid chromatographs, it is the simplest, the least expensive, and is still very popular today. The single piston pump is shown at the top of Figure 2. The piston is made of synthetic sapphire in fact, most pistons of modern LC pumps are made of sapphire to reduce wear and extend the working life of the pump. The cylinder is usually made of stainless steel, which incorporates two nonreturn valves in line with the inlet and outlet connections to the pump. The piston is driven by a... 

Figure 3. Schematic diagram of a single piston, mechanical, constant volume, reciprocating HPLC pump.

FIGURE 2 A single-piston reciprocating pump, (a) schematic diagram (b) operation of a check valve. [From Yost, R. W., Ettre, L. S., and Conlon, R. D. (1980). Practical Liquid Chromatography, Perkin-Elmer Corporation, Norwalk, Connecticut, p. 146. Reprinted with permission.]... 

Fig. 13. Injection molding machine A, hydiaulic motoi foi turning the screw B, hydraulic cylinder and piston allowing the screw to reciprocate about three diameters C, hopper D, injection cylinder (a single-screw extmder) E, no22le F, fixed platen G, tie rods H, mold I, movable platen , hydraulic cylinder and piston used to move the movable platen and supply the force needed to keep the mold closed and K, machine base.

Several steps can be taken to maximize the run time for the reciprocating compressor. Since wear is a function of rubbing speed, the piston speed can be kept to a minimum. Chapter 3 made recommendations for piston speed. Reliability problems due to valves are reputed to account tor 40% of the maintenance cost of the compressor. Valves are the single largest cause for unplanned shutdowns. Basically, valve life can he increased by keeping the speed of the compressor as low as practical. At 360 rpm, the valves are operated six times a second. At 1,200 rpm, ihc valves operate 20 times a second or 1,728,000 times in a day. It is not difficult to understand why the valves are considered critical. To keep the reliability in mind, valve type, material selection and application considerations such as volume ratio, gas corrosiveness, and gas cleanliness need attention by the experts. One final note is that while lubrication is an asset to the rubbing parts, it is not necessarily good for valve reliability. 

Figure 3-71. Single-acting (trunk-type) reciprocating piston compressor [23].

A single-acting reciprocating pump has a cylinder diameter of 115 mm and a stroke of 230 mm. The suction line is 6 m long and 50 mm in diameter, and the level of the water in the suction tank is 3 m below the cylinder of the pump. What is the maximum speed at which the pump can run without an air vessel if separation is not to occur in the suction line The piston undergoes approximately simple harmonic motion. Atmospheric pressure is equivalent to a head of 10.4 m of water and separation occurs at a pressure corresponding to a head of 1,22 in of water. 

SINGLE - ACTING RECIPROCATING PISTON PUMP --[fixed speed - AD2U S ABL E S1LR0KE L E GT h]... 

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