Circulating pump for high pressure and high temperature applications
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that was used to throttle the flow and thence into a beaker where the liquid could be collected and weighed. A pressure transducer was fitted in advance of the valve to permit measurements of the pressure head generated by the pump.
The flow rate of toluene was measured as a function of the frequency f of reciprocation. During this test, the outlet needle valve was fully opened, and the liquid was collected over measured time intervals and weighed to obtain mass flow rates F with an uncertainty of about ±2%. The results are shown in Fig. 2 and, as expected, the flow rate was a linear function of f in the range investigated. At a frequency of 80 min−1, the mass flow rate obtained was about 280 g min−1, and this is equivalent to a volumetric flow rate of about 320 cm3 min−1. The slope of the line, equal to the mass discharged by the pump per cycle, turns out to be 3.9 g. This figure is equivalent to 4.5 cm3 or 75% of the theoretical discharge based on the cross section of the cylinder and the length of the stroke.
A second test was conducted at a fixed frequency of 60 min−1, but with the outflow throttled by means of the needle valve. During this test, the pressure head was measured as a function of the mass flow rate and the results are shown in Fig. 3. The greatest pressure head obtained in this way was 2.2 bars, and the corresponding flow rate was 18 g min−1. Further throttling resulted in the decoupling of the piston from the drive and the stalling of the pumping action. Once the outflow restriction was relaxed, the coupling was reestablished.
Circulating pump for high pressure and high temperature applications
IV. DISCUSSION
The pump described was designed to offer simplicity in construction and operation, robustness, flexibility, a wide operating window of temperature and pressure, as well as satisfactory performance.
Its fabrication is based mainly on commercially available parts, making it easy and simple to assemble. Only the end plates, carrier plate, ring magnet assembly, and piston are special parts. The maximum operating temperature is limited by the pneumatic actuation cylinder used for the pump drive. Otherwise, by selecting an appropriate grade for the SmCo ring magnet it could be extended to 350 °C. The maximum operating pressure is determined by the main body  nipple  rating and can be increased by sourcing nipples with higher ratings. Our application required pump mobility in a high-temperature environment, and therefore we opted for a pneumatical