C .
R. W E B B
C . G. D A L L A S
W.
H. CAMPBELL
POSITIVE DISPLACEMENT PUMP developed for use with microscale reaction equipment
Miniaturization of research equipment is an euer increasing trend in manv petroleum and chemical laboratories. The advent of gas chromatography and its acceptance as a tool for rapid analysis of gases and light liquids have accelerated the trend. Bench-scale research abparatus can nore, be designed to process the minute quantities of materials required f o r chromatographic analyszs rather than for the relatively large quantities required f o r other methods.
ne of the major hurdles in the path of a miniaturization program is the procurement of hardware compatible with the goal of reducing size. Smallscale reaction apparatus must include provision for accurately introducing liquids or gases at controlled low rates. Equipment to perform these functions is not generally available and must be developed. Socony Mobil's Paulsboro, N. J., research laboratories have developed a liquid pump which will accurately feed liquids a t rates as low as 2 ml. per hour at pressures up to 1000 p.s.i. The pump, which operates on the well accepted positive displacement or high pressure syringe principle, is small in size and blends well with other components of a micro unit. The pump has been developed by our laboratory staff as a tool for use with microscale hydrocarbon rraction equipment. I t has features which are not available in any device manufactured commercially, and has proved to be an invaluable addition to our pilot plant equipment program.
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General Description
Pumping is achieved by introducing a plunger at a controlled steady rate into a liquid reservoir, displacing the liquid. The plunger is sized to give a 5-cc. displacement per inch of length and is driven by an accurately machined lead screw. The screw is rotated through a right angle drive by a multispeed quick-change gear box, which allows a choice of several rates-2, 4, 5 , 6, 8 , 10, 12, 15, 24, or 30 ml. per hour of liquid may be injected by positioning shift levers on the gear box cover. The amount displaced at any time is indicated by a counter mechanism which is coupled to the lead screw drive. The counter reads the number of revolutions of the shaft and indicates displacement to 0.1 cc. The mechanism is powered by a Superior Electric Co. Slo-Syn 72-r.p.m. syncronous motor, which gives constant feed rates regardless of the discharge pressure. 28
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vertical liquid End
One of the unique features of the Mobil pump is the vertical mounting of the liquid end which eliminates the troubles usually encountered in filling and draining the conventional pumps of larger but similar design. The discharge and vent connections are at the extreme upper end of the cylinder. The filling and drain connections are at the extreme lower end. Filling is accomplished by disengaging the drive assembly, withdrawing the plunger to its lowest position, and gravity feeding the charge liquid to the cylinder with the vent valve open. The air in the cylinder is displaced by the incoming liquid and vents out the top. When the liquid rises to the level of the vent valve outlet, the cylinder is completely filled. The exclusion of air is thereby accomplished without the necessity of evacuating the chamber. Draining and cleaning operations are also simplified by the vertical arrangement. Complete drainage of the cylinder is ensured by opening the vent and drain valves. The plunger is connected to a crosshead which is driven along two guide rods by the lead screw. As the screw is rotated, the plunger is forced vertically upward into the cylinder. Protection against overtravel of the crosshead is provided by a limit switch which will trip as the upper limit is reached. The stuffing box is packed with Teflon chevron rings. The rings seal on the hardened and ground K-Monel plunger. K-Monel is used because of its excellent corrosion resistance and ability to resist the abrasion which may be encountered in the stuffing box. The cylinder is jacketed so that constant temperature conditions can be maintained. Hot water or steam can be used if the material to be pumped is viscous at room temperatures. A limit of approximately 350" F. must be observed when using Teflon as the packing. Higher temperatures would necessitate the use of different packing materials. Acknowledgment
Assistance of William Spencer and Ernest Smith of the Paulsboro Laboratory Construction Group in the development of this pump is appreciated. AUTHOR C. R. Webb is the Senior Research Mechanical Engineer responsible for specialized test equipment at the Paulsboro Laboratory. C . G. Dallas is an Instrument Maker. W . H. Campbell as a Supervisang Engineer.
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DISCHARGE
f CHARGE
TNER FILLING CONNECTION
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VOL 54
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NO. 1
JANUARY 1962
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Gas pressure bonding produces solid-state bonds such as this Zircaloy-to-Zircaloy bond obtained w i t h belt-abraded material and pressure-bonded at 843" C. and 70,000 p.s.i. f o r 4 hours. The technique embodies two cost-reduction factors: in actual fabrication and in use of pieced components.
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
