INSTRUMENTATION Analytical process instrumentation

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by B. W. Thomas of the Instrument Society of America, it was well agreed that the success of process analytical equipment depends tual and formal, more general and ex- very heavily on the sample-handling pansive, and may even include a bit of facilities provided. One instrumentareminiscing and crystal gazing. NO tion engineer went so far as to place doubt the author has learned much 90% of the over-all responsibility for a more from the preparation and writing successful analyzer installation on the of these monthly columns than has proper functioning of the sampling sysbeen garnered from perusal by YOU tem. From contacts here and there readers. To the many followers of this across the country and from expericolumn who have requested reprints ences inour own Humbleoil and Refinor additional information on items dis- ing Company Plant at Baytown, Tex., cussed, my sincere appreciation for a more realistic distribution of imporyour interest and inquiries is hereby ex- tance associated with continuous anapressed. This is especially true for the lyzer programs would, in my opinion, gratifying letters of encouragement re- place about 40yGon sampling systems, ceived from: L. van Zeyl, Pretoria, 30% on instrument development, and South Africa; B. Stein, Jerusalem, 30% on overcoming operating difficulIsrael; Ren Ishikawa, SZio Paulo, ties caused by adverse atmosphere and Brazil; J. D. Vistulode Abreu, Portugal; weather conditions. Fouling of silverJean McPhail, Queensland, ilustralia ; plated electrical contacts in the presB.Berndtsson, Gothenburg, Sweden; ence of hydrogen sulfide is extremely Lars-G. Erwall, Stockholm, Sweden; troublesome for many present-day inCarl Freudenberg, Weinheim, Ger- strumentation tools when they are many; and W. F. Short, Nottingham, subjected to chemical and petroleum refining atmospheres. Some possible England. One is easily impressed with the aid in design of plant analyzer sampling tremendous interest in evidence today systems may be forthcoming within in the field of analytical process in- the next year or so from a recently apstrumentation. This impression be- pointed Recommended Practices Subcomes doubly felt, not only from a committee on this subject in the Inrapid survey of the newer and more strument Society of America. Too progressive scientific journals but also much should not be expected from a from attendance a t meetings of national committee on this subject, however, technical societies a t which vast arrays since only the more or less identical inof latest equipment development are struments on like applications can use on display. At times, I lean toward a similar facilities for controlling presfeeling that perhaps our new develop- sure, flow, and temperature plus proper ments in instrumentation come too withdrawal and adequate filtering for rapidly; that more time should be two analyzer installations. taken in proving the worth, dependability, and reproducibility of new Process analyzers of measuring devices before they are ad- major interest vertised or placed on the market for Continuous plant analytical tools sale. Also, I am often of the opinion that we do too much writing about and techniques that have received some small bit of progress and not widespread attention throughout the enough hard thinking about how to chemical and petroleum industries really make a better analyzer, a more during the past few years are the procappropriate application, or a foolproof ess mass spectrometer, the infrared sampling system. analyzer, the dielectric constant During a recent West Coast meeting meter, the viscosity recorder, and this is the last of a series of 33 S articles on instrumentation by your present author, it will be less facIXCE

Decembex 1955

more recently the vapor phase chromatographic column. The cycloidal focusing mass spectrometer, operating without a cold trap but with rather simple amplification circuitry, appears dependably engineered for long time performance on a flowing stream with minimum operator attention. Automatic recording facilities available a t present with the cycloidal mass analyzer, however, provide for analysis or monitoring of only six compounds or compound types. Also, the data provided are in raw spectral form and for most mixtures require the usual algebraic solutions for reduction of the instrument results to percentage compositional answers. Under certain circumstances, however, this instrument at present may be found extremely helpful in monitoring large and rapid changes in a few key components. This is especially true if the components of interest have at least one near unique mass. The addition of a detachable 8- t o 12-component computer and print out system to the cycloidal mass monitor would greatly improve and extend its utility as a flowing stream analyzer. Kevv infrared analyzer applications have favored the chemical rather than the petroleum plants in the last couple of years. The three-path nondispersion instrument known as the Tri-Non analyzer is reported to have performed satisfactorily in carbon monoxide, carbon dioxide, and acetylene analysis service. Both Perkin-Elmer and Beckman now make dispersion infrared equipment for operation on a flowing gas or liquid sample. With slight modifications it is possible to obtain infrared spectral data a t several preselected wave lengths with these instruments; this arrangement plus automatic computing of the infrared absorption data has been accomplished by Perkin-Elmer. Dielectric constant, because of the ease with which it can be measured electrically, continues to gain favor as

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‘“you can service an fl swivel joint without removal from line” NO EXPENSIVE RETURN TO FACTORY FOR REPAIR

lnstrumentation in analytical tool for monitoring the )peration of continuous processes in 3etroleum refining. If an extraction, ieparation, or chemical reaction proc:ss involves an increase or decrease in tromatic content, such a process can Jsually be monitored in terms of the :hange in dielectric constant. This is >speciallytrue if the mixture is narrow n boiling range and the principal :ompound types present are paraffins, iaphthenes, and aromatics. Extreme :aution should be exercised in use of the dielectric property, however, if water 3r other oxygenated compounds are ikely to be present. Fluctuations in dectrical conductivity within the test stream can completely destroy an itherwise useful correlation between dielectric constant and chemical conZentration of some highly dielectric material. Several successful instruments operzting in the 2-megacycle range are now available for measurement of interface, level, or composition in terms 3f dielectric constant. Sampling problems are markedly reduced in these instruments by use of Teflon-insulated, heavy-walled stainless steel capacitance elements and temperature compensation within the capacitance measuring circuits. Viscosity recording devices

Viscosity recording devices currently wailable for flowing streams leave considerable to be desired when one Within a few minutes you can inspect and service Emsco Ball considers accuracy, dependability, and Bearing Swivel Joints. Simply break the Emsco as you would a long term maintenance. The high frepipe union. Packing is then readily accessible and easily replaced quency vibrating probe viscometer is if necessary. This is vitally important to the field man and reExtremely simple to install. It is useful duces maintenance costs. With Emsco you can count on free &thigh temperature, on high pressure Bowing streams, and its temperature easy turning and years of economical service life. compensation unit is easy to adjust for Emsco Swivel Fittings are manufactured in popular sizes for a given oil a t a specified reference tempractically every type of service; from high vacuum to pressures perature. Because of the rather comof 15,000 psi, and from sub-zero temperatures to 750°F. Simply plex electronic circuitry and numerous tell us your application and type of end connections required. silver-plated friction contacts this inWhen you buy a swivel joint, specify Emsco. strument is likely to become unstable, however, after a few days’ operation in a refinery atmosphere. Improved electronic components and vaporEMSCO MANUFACTURING COMPANY proof housing for the computer cirBOX 2098, TERMINAL ANNEX cuitry may be all that is needed to 10s ANGELES 54, CALIF. change the vibrating probe instrument Houston, Texas into a dependable recording viscomeGarland, Texas ter. Major objection to the falling piston viscometer is the difficulty encountered in adjusting the mechanical temperature compensation unit and the sluggishness with which the comFor further information, circle number 7 O A o n Readers’ Service Card, page 111 A 70 A

INDUSTRIAL A N D ENGINEERING CHE: ISTRY

Vol. 41, No. 12

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Instrumentation pensator responds to a change in temperature of the flowing stream. Also, this apparatus requires that the test stream be entirely free of grit. sediment, or rust particles. Unless an electrical means for temperature compensation can be developed for the falling-piston viscometer, the best procedure may be precise temperature control of the stream without compensation in the measuring equipment. Although highly successful performance has been reported €orthe capillary tube instrument in which viscosity is measured in terms of pressure drop across a capillary tube, the requirement for precise control of both flow and temperature is undesirable. Absolute absence of dirt, sediment, or rust particles is also a must for continuous operation of this viscometer without excess maintenance. Vapor phase chromatography

O r d i n a r y v a l v e w o r r i e s of leaking packing, clogged b o n n e t s a n d corroded working parts are eliminated by the u n i q u e design of the Hills-McCanna Saunders P a t e n t d i a p h r a g m valve. A tough, resilient d i a p h r a g m completely isolates the b o n n e t and its w o r k i n g parts f r o m the v a l v e body. The cushion closure is d r i p tight. S u r f a c e irregularities or scale are n o c a u s e of leakage because the diaphragm accommodates itself t o them. . like a tire t o small stones. P a c k i n g w o r r i e s are easily forgotten, too-no packing is n e e d e d because n o fluid c a n enter the bonnet. Available with choice of 15 d i a p h r a g m materials, b o d y m a t e r i a l s of a n y m a c h i n a b l e alloy and a choice of linings, Hills-McCanna valves range in sizes f r o m t h r o u g h 14". May be used a t pressures t o 150 psi, t e m p e r a t u r e s t o 350" F. Choice of r e m o t e , h a n d w h e e l or lever operators. If y o u v a l v e corrosives, write for further information today! H I L L S - M c C A N N A CO. 2345 Nelson St., Chicago 18, Illinois.

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Vapor phase chromatography is especially attractive currently as a potential process analyzer because of the simplicity of equipment required to initiate exploratory operations. Each application of chromatography will require considerable laboratory effort to establish the optimum operating conditions for such variables as amount of test gas, type and temperature of adsorbent, diameter and length of column, type, pressure, and flow rate of Zarrier gas and type, speed of re3ponse, and sensitivity of detecting 3ystem. Once these variables are determined and the apparatus is selected tnd installed, relatively little attention md maintenance should be required 'or continuous performance in repeat malysis service. Prior to use of chronatographic results as a guide in proc:ss control, however, one must be iware of the erroneous recorder tracngs that could be caused by the presmce of extraneous components in the >estmixture. Several types of chronatographic separation columns and ,ecording equipment are on the market urrently and their purchase would robably result in greater returns than !auld be realized with equipment built n one's own laboratory. 2orrespondence concerning this column wiIl be orwarded if addressed t o the author, c/o Edior, INDUSTRIAL A N D ENGINEERING CHEMISTRY, 155-16th St., N.W., Washington, 6, D. C.

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