Laboratory ump for Recycling Gases under Pressure R. A . BECK1,
A I . L. RAMBO, E. E. SENSEL, AND P. A. HARGHAVE The Texas Company, Beacon, N. Y.
A laboratory scale bellows-type pump for recycling gases at elevated pressures has been developed. The use of a fragile bellows has been made possible by maintaining a counterbalancing pressure on the outside of the bellows by means of a simple hydraulic system. The reciprocating motion for compression and extension of the bellows is transmitted from a piston through this oil medium. As the gases handled by the pump do not come in contact with any type of packing or gasket, the pump is leakproof in its operation. The design described is for a maximum system pressure of 500 pounds per square inch gage. Adjustment of flow rates from a difiplacernent of 5 cubic feet per hour to zero is possible.
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‘The obvious method of controlling the: displacement of the pump is by varying the length of the piston stroke. It has been found, however, that a very convenient way of adjusting thr bellows displacement is furnished by the regulation of valve G! With the gas lines disconnected, the stroke of the piston is firs2 set t o cause the maximum allowable bellows compression witk valve G closed, Valve G is then opened completely and thc pump installation completed. The desired bellows displace ment is obtained by partially closing valve G to decrease t o thr proper volume the flow of oil externally around the piston through line F. Subsequent control of the displacement by this methori can be accomplished very simply without interrupting tho opwa tion of the pump. RIaximum practical displacemenl for t h +
HE need for a laboratory pump capable of recycling small
quantities of gases under elevated pressures gave rise to the development of the pump described in this paper. A canvass of the usual equipment sources revealed that a pump with a displacement of the order of 5 cubic feet per hour and designed for operation to 500 pounds per squave inch gage was not available on the market. Two types of pumps, rotary and reciprocating, were COIIsidered. An adaptation of a pump of the first type was made that operated satisfactorily for short periods of time, but tended to develop leaks as the shaft packing wore. Of the reciprocating pumps the bellows type offered more promise of being made permanently leakproof than did the conventional piston pump. The operation of a bellows pump is dependent on the use of an expandable metal bellows with a suitable check valve system. In previously described installations ( 1 )the use of such a pump has been restricted in its application to operating pressures of the order of 0 to 50 pounds per square inch gage, the limiting factor having been the structural strength of the bellows material. The pump described in the present paper overcomes the pressure limitation by counterbalancing the elevated gas pressure within the bellows by the application of fluid pressure on the outside of the bellows using an oil system in communication with the gas to be recycled. CONSTRUCTIOh AND OPERATION
Figure 1 is a flow diagram of the bellows pump assembly. The brass bellows, in this case 36/8 inches in outside diameter X 246/64 inches in inside diameter X 3 inches in length, is surrounded by a n oil medium and is contained in the cylinder, the upper section of which is equipped with a 1839 Ford 60cylinder liner and is fitted with the corresponding Ford piston. The 6 / ~X 16 inch steel piston rod is brazed to the bearing ring. A standard wrist-pin is used for making the connection to the piston. The reciprocating motion for the particular installatiori described here is furnished by a commercial gear reductionpump assembly which converts the action of a l/S-hp., 1800r.p.m. motor t o 60 vertical strokes per minute. The movement of the piston is transmitted t o the bellows through the oil in cylinder I . Counterbalancing pressure t o prevent bellows fracture is supplied from the delivery side of the pump through line B which is in communication with the oil reservoir, C, from which emerge lines D E and D F leading to the cylinder.
DOUBLE BALL CHECK VALVE
1 present address, The Texas Company, P. 0. Box 300, Montebello, Calif.
Figure 1. Bellows Pump Assembly 144
INDUSTRIAL AND ENGINEERING CHEMISTRY
Januarv 1950
145
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1
Figure 2.
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Piimp Assembly
Figure 3. Bellows Pump Complete with Reciprocator and Motor
Figure 4. Exploded View of Piston, Cylinder, and Bellows
installation described is 5 cubic feet per hour at 60 strokes per minute. This corresponds t o a delivery rate of 175 standard cubic feet per hour when the system is operated a t 500 pounds per square inch gage. Figure 2 is a more detailed sketch of the pump assembly proper J represents a slotted cylindrical guide for the belIows while K is a Waukesha No. 43350 valve spring. Figure 3 is a photograph of a n actual bellows pump complete with reciprocator and motor while Figure 4 is an exploded view of the piston, cylinder, and bellows. It can be seen from the photographs that, in event of a bellows failure, a replacement unit can be slipped in place in a matter of minutes by merely unbolting the bellows unit from below. A span of operation for t h e bellows of the order of thousands of hours has been experienced with some of the pumps now in continuous service. Both single and double-ply bellows of several different metals are available commercially in a variety of sizes. System pressures are limited only by the construction and design of the cylinder and its auxiliary equipment. The pump described has been designed for use at pressures t o 500 pounds per square inch gage. Pressure differentials on the opposing sides of the bellows are limited t o 25 t o 30 pounds per square inch gage, but it can be seen from Figure 1 that only a sudden failure in one side of the pressure compensating system could cause a significant unbalance to occur. One of the chief advantages of the pump described is t h a t the only part t h a t may develop leakage with use is the packing H, Figure 1, around the piston rod. Only the hydraulic oil will leak and no gas will be lost from the system until the oil reservoir C is empty. When runs of the order of weeks in length are planned, provision is made for injecting make-up oil to the reservoir t o prevent such a contingency. The reservoir consists of a Jerguson sight glass so t h a t a check on oil level can easily be made. A trap is installed in the back pressuring line B to
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INDUSTRIAL AND ENGINEERING CHEMISTRY
prevent flooding of the check valve with the hydraulic oil. However, when pumping perfectly dry gases it has been found that a drop of oil in the check valve helps its operation. What might in some cases be construed as a drawback iri pulsating the use Of such a pump lies in the fact that a gas flow is obtained. One method to decrease this tendency is kt use surge drums and line constrictions. Another suggestion by Gibson e' a'. ( 1 )is to use a pair of bellows pumps out of phase with each other-i.e., one is at compression while the other is a t
Vol. 42, No. 1
extension. Only the former method has been used by the authors. LITERATURE CITE11
(I) Gibson, J., Heron, J., and Nicholson, G. A , J. Sci. Instruments, 24, 273 (1947). RECEIVEDApril 25, 1949. Presented before the Division of Petroleum Chemistry a t the 116th Meeting of the ~ m m o A Nc H ~ \ ~ I C A LSOCIETY, San Franoisco, Calif
Reactions of Resins with Drying Oils P. 0.POWERS, Battelle Memorial I n s t i t u t e , Columbus, Ohio
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Drying oils react with resins either by acid, alcohol, o r ATURAL and synever, alkyd resins will not be ester interchange or by addition reactions at the double considered in any great dctail thetic resins are often incorporated in the production bond. The occurrence of the ester reactions is well esin this discussion, but the emphasis will be placed on of varnishes and other preptablished and is often the basis of the formation of alkyd the resins which are usually arations for protective coatresins. Ester-type resins combine with the drying oils by ester interchange, and while quantitative measure of added in the varnish kettle. ings. I n some cases, as with the alkyd resins, the chemithe extent of this reaction cannot readily be obtained, I n the drying oils, there are cal reaction is well underdefinite indications of the reaction have been obtained two positions in the molecule which are readily susceptible by marked changes in the solubility of the resin on heating stood and is carefully controlled in the manufacture with the drying oil and by changes i n the viscosity. These t o chemical reaction. The effects are most pronounced with resins of high viscosity of the preparations. With ester group can readily enter many other resins, the extent into acid interchange, alcohol and low solubility. Reactive phenolic resins are known interchange, and ester interof the reaction with the oil to combine with the drying oils, particularly the conjuchange. This type of reacis not known and could be gated type, but this reaction must be regarded as seconddetermined only with diffition occurs frequently and is ary to the polymerization reaction, and the unreactive exceedingly important, parphenolic resins usually used with drying oils give little culty. I n some cases, it has ticularly with the acid- and evidence of any appreciable chemical reaction with the not been clearly shown ester-type resins. The fatty whether a chemical reaction oil. Hydrocarbon resins, in general, do not combine acid in the glyceride structure occurs or, when there is with drying oils. can readily be replaced by evidence of combination, what rosin acids. natural resin type of reaction takes place. Chemical combination between the resin and the drying oil is acids, and a wide variety of synthetic acids, The glycerol in the recognized as a desirable occurrence. Resins which are soluble ester structure also can be replaced by other polyhydric alcohols &nd by synthetic resins containing hydroxyl groups. Esters of in drying oils without chemical reaction are limited in number, resin acids readily interchange with the drying oils, forming mixed and they often do not possess the most desirable properties. fat-rcsin glycerides. In many cases, resins of the same series of higher molecular The unsaturated groups are not so readily combined with weight have much better properties but cannot be used because resinous materials. This type of addition is often postulated of their insolubility in the drying oil. A resin which does not even when there is no definite proof of such combination. Rereact with a drying oil can act only by dilution of the properties cently, there has been considerable study of the formation of of the drying oil. Thus, many of the qualities of both the resin addition products of hydrocarbon monomers with the drying and the oil may be apparent. With extensive combination oils effected by polymerization in the presence of the drying oil. between the resin and the oil, a new structure is formed which In this case, it is apparent that more desirable results are obtained may be superior to that of either component. when some degree of combination of the hydrocarbon resin and TYPES OF REACTIONS the drying oil is achieved. Proof of Combination of the drying oil and resin is not always While the idea that a reaction does occur is widely accepted, readily obtained, and it will be shown later that certain types of the type of the reaction is not always fully understood. In behavior which have been taken as evidence of chemical commost cases, the extent of this reaction has not been measured in bination are not necessarily proof of such combination. quantitative terms because such measurement, frequently, can
be made only with great difficulty. I n many cases, no serious attempt has even been made to measure the extent of the combination of the resin with oil. The alkyd resins, however, do not fall in this classification, because, in this case, the type of reaction is well understood and the extent of the combination of the polyester structure with the drying oils is, in most cases, rather accurately controlled. How-
REACTIONS WITH T H E ESTER GROUP
It has been long known that rosin, when added to tung oil, retards gelation of the oil. If enough rosin is used, gelation is prevented. This effect is not due t o dilution of the oil alone, since neutral diluents do not prolong the gelation in such a manner but the effect of the rosin results from combination with the
