Stroke length

The following parameters are kept constant on the scale-up total throughput per unit area, plate spacing, and stroke length. The... 

Ap = cross-sectional net area of piston, in. If cylinder is head-end, Ap is total area of piston if cylinder is crank-end, Ap is net area of piston area minus rod cross-section area, s = stroke length, in. 

There are two first-stage cylinders, 16-in. dia. in parallel, one 14 Vs-in. second-stage cylinder and all on 9 Vs-in. stroke length. 

Reciprocating tray towers can have holes 9/16 in. dia, 50-60% open area, stroke length 0.75 in., 100-150 strokes/min, plate spacing normally 2 in. but in the range 1-6 in. In a 30 in. dia tower, NETS is 20-25 in. and throughput is 2000 gal/(hr)(sqft). Power requirements are much less than of pulsed towers. 

Traditional Apparatus. As indicated earlier, liquid delivery systems for controlled rate addition of monomers and initiators have tended to rely upon constant speed piston pumps (19) in which volumetric control is achieved by manual adjustment of stroke length, and monitoring is by discharge from measuring cylinders. 

The use of traditional rod and piston pumps continues at many LNAPL recovery locations, particularly at refineries and distribution terminals. These units are usually powered by single-speed electric motors and have adjustable stroke lengths to control the pumping rate. When installed with the intakes set at the optimum pumping depth, they function fairly well. The primary advantage of rod and piston pumps is that the smooth slow stroke rate can pump mixtures of product and water without creating a significant emulsion. 

With the pump running at a constant speed and stroke length, 350 gpm of water is pumped when the control valve is wide open and the pump discharge pressure is 200 psig. 

A Throttling characteristics of centrifugal (c) -and positive- displacement (e, reciprocating d, rotary) pumps. B Control characteristics of positive displacement pumps a,b, Systems characteristics (b, after speed control) VFluid flow Ap, Differential pressure n, Speed h, Stroke length A, B, B, Operating points. 

For a required volumetric suction rate Q (cfm), the required product of cross section As (sqft), stroke length Ls (ft), and speed N (rpm) is given by... 

The valves supplied with these pumps showed an erratic behavior at low flow rates, mainly due to a too large diameter of the valve balls and poor design of the valve seats and valve chambers. New pumpheads and valves were therefore developed, manufactured and mounted on the pumps. The heads and fittings were made from PVDF with valve seats and 3 mm diameter balls in acid resistant steel. On these pumps the stroke length has to be set mechanically and this set-screw was modified so that it could be turned by a simple manipulator, if necessary. The electronic frequency control was modified for remote operation. 

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