TRAINING A SPECTROGRAPHIC TECHNICIAN GENERAL MOTORS SPECTROGRAPHIC COMMITTEE

Submitted by the Methods and Equipment Subcommittee, Roger D. Laib, Chairman (Copies available from Secretary of G. M. S. C., Research Staff,

Box 188, North End Station, Detroit 2, Michigan)

Foreword The value of the spectrograph was proven during World War II

and, m the years since the war, more and more analytical work has

been done on the emission spectrograph.

As the laboratomes expand and new men are brought an to take

over the routine analysis that has been set up, someone must show

these men how to do this.

Since this assignment is usually given to the experienced operator

who knows his 3ob but has no teaching experience, the committee

asked Mr E. G. Bowman of the General Motors Institute to speak at

the 1953 spring meeting of G.M.S.C. Mr. Bowman spoke on "Tra in -

mg to Meet Specific Needs " This paper gave a good background for

a training program.

The Methods and Eqmpment Subcommittee was given the project

of writ ing a training program for spectrographic techmc~ans. This re-

port has been reviewed and corrected by all the members of the sub-

committee thus ~t has been made general enough to be of value m all

types of laboratomes. Mr. Bowman has been consulted to make sure

the report adheres to the principles on which it ~s based.

This report is being made available to all spectrographic labora-

tories. We hope you w~ll find it useful. To those who are interested,

bound copies of this report are available which contain the Job Re-

qmrement and Job Breakdown sheets referred to m the report. Send

requests to the address above.

Training a Spectrographic Technician Any training program needs careful thought and plan-

ning to obtain the best results possible. This is especially true ff the trainer is not a professional instructor. Since this paper ~s designed for the present spectrographic per- sonnel to tram new men m spectrographic procedures, we will follow the ideas of E. G. Bowman, Program Develop- ment Department of General Motors Institute, m his pa- per "Training to Meet Specific Needs."

As a basis for this program, job requirement and job breakdown sheets outhne the skills and information the trainee must possess m order to become a skilled operator. These reqmrement sheets are arranged m the order in which the operations are usually performed and are included at the end of this report. The lob breakdown sheets take the individual operations mentioned in the job requirement sheets and expand therrl to a detailed hst of steps which take place in each operation.

Because the type of spectrographic equipment used by the Dlwslons is varied, the language of this paper will be in general terms unless a specific model requires special consideration.

The trainee is assumed to have some general knowledge of the analysis of materials, probably high school chemis- t ry and physics. This background need not include famil- iarization with quantitative analysis or theory and opera- tlon of a spectrograph, but only a basle knowledge to speed the asslmflat~on of new instruction.

I t ~s our purpose to provide a suggested standard me- thod of training the new techmc~an and this is intended as a grade to those unschooled in the art of teaching. The training program is designed as a help both to the trainer and trainee. Both can benefit by referring to the report. Especially helpful to the trainee will be the job breakdown sheets. These will help refresh his memory on some of the many details he must remember.

This program was planned for teaching the analysis of a specific material for specific elements. However, it has been made general enough so that it can be adapted to extend the training of the technician to all routine quantitative work.

Depending on the circumstances surrounding each sit- uatlon, it may be possible for the new technician to take some technical courses related to spectroscopy m night school. Suggest courses you think would be helpful to the man and encourage him in his studies. The more he knows and understands, the more help he will be to you.

Introduction Into Training When the trainee first comes into the spectrograph

room, he will feel strange among the unfamiliar eqmp- ment and operating personnel. He should be introduced to the people with whom he will work, then taken about the room to famflxarize him with the equipment. The ex- planation need only be a short statement as to the purpose of each component part. If the man is to perform only a portion of the total operation, e.g. sample preparation and plate processing, reform at this stage as to how this opera- tion xs interrelated with the other operations.

Af te r this general explanation, give him some time to browse around the lab. This will relax the new man and

gave h~m time to absorb what he has lust seen. When it is time to begin the training program, it will

be well to restate the purpose of spectrographic analysis and briefly run through the sequence of operations as outhned in the lob requirement sheet. Encourage him to ask questions. Watch for cues to see if your explanations are understood.

All people will differ in their amount of background as well as in their ability to learn. Keep watching for signs of disinterest or boredom. These can mean you are going too, fast and he is lost, or that you are prolonging the discussion on one point. I t will help speed the training program if you spend the time on those points which need thorough explanation while passing l ightly over those which he readily understands.

Because of the routine nature of spectrographic analy- sis in a control laboratory, it is best to inform the man at

N U M B E R 1, 1 9 5 7 2 5

the beginning not to expect more of the job than it can provide. Although it is routine, impress on the trainee the need for accurate w o r k - - t h a t sloppy work can lead to errors.

Poor work resulting in inaccurate analysis of material can cost the company money not only in the assembly of defective units, but also in a loss of man hours spent in trouble shooting low quality products.

Processing of Films or Plates Start the trainee m actual work as soon as possible.

The processing of films or plates is usually chosen as the starting point because it ~s straightforward and requires no spectrographic knowledge. Af ter the procedure has been demonstrated several times and the trainee has gone through the motions himself with supervision, he can be put on his own.

Several points should be stressed on darkroom pro- cedure: 1. Protect film (or plate) from all possible hght leaks to

prevent fogging. 2. Check water bath temperature occasionally to assure

correct control by thermostat. 3. Follow foolproof routine to avoid over or under de-

velopment of film. 4. Avoid fingerprinting or marring of film. 5. Instruct in the method of mixing solutions for film

processing. 6. Change developing solutions when specified. 7. Point out where darkroom supplies are stored.

When the trainee has mastered the darkroom technique, he will be free to devote his time to the other phases of the work. To best acquaint him with these phases, have him watch as you perform the regular routine, explaining as you proceed.

From time to time, ask him questions to see if he un- derstands what you have told him.

Sample Preparation Sample preparation is not as glamorous as some of the

other operations, but it has a prime importance in assur- ing an accurate analysis. If the sample ~s improperly taken, has a varying surface or ~s contaminated, of what use are all the subsequent precautions for accuracy? The results can be only as good as the sample that is sparked. Impress the trainee with the importance of correctly preparing the sample. Some of the factors to watch to insure proper sampling and surfacing follow: 1. Cut off the section prescribed for spectrographic analy-

sis of the sample. 2. Select proper cloth or grinding wheel for the part icular

base metal. Avoid using an abrasive which will con- taminate the sample; for instance, avoid using alumi- num oxide abrasive on a sample which is analyzed for small amounts of aluminum, and silicon carbide on sample containing silicon. The harder the base metal, the less chance there is for contamination.

3. Assure a uniform and reproducible surface of soft metals such as tin, lead, magnesium, copper, and alum-

inum (which can smear on an abrasive surface unless special techmques are employed) by turning down on on a lathe.

4. Avoid fingerprinting the prepared surface. The spec- trogram will record everything it sees, whether it xs in the sample or a surface contamination.

Spectrograph and Source Unit Operation The trainee soon wants to spark samples himself. In

preparing him to operate the spectrograph, i t is best to m- corporate also the operation and adjustment of the source unit since the two are dependent upon one another.

Show the trainee how to select the proper source and settings from the procedure book or card file for each type of alloy. Explain the meaning of any abbreviations or symbols used, such as mr, m/z, ohms, etc. Set tip the source unit for an alloy, naming each switch or handle as i t is turned. If the oscilloscope is instrumental in the correct adjustment of the unit (the number of break- downs per half cycle) , go into detail on the adjustment of the oscilloscope, how it is operated and how to interpret the pattern. Stress the importance of making the settings in a routine way, covering the source unit panel from right to left, or left to right. The maintenance of the unit can be covered later.

Point out any safety precautions that are necessary. Af te r the source is readied, begin on the spectrograph

with the selection of the spectrograph settings. These would probably be listed on the same card or sheet as the source settings. Here again a routine will help ehminate possible oversights in making settings. I t is easiest to check by proceeding in the direction of light travel.

Mount the sample on the spark star/d, insert counter electrode with proper tip and adjust analytical gap dis- tance. Adjust position of the spark stand and lens if this is required. Next , check rotat ing sector or metallized quartz filters for correct amount of hght filtering. Set pre- spark timer for correct shutter opening. See that the pri- mary slit and grating doors are properly set. If it is a prism instrument, show how the prism adjustment ~s made and how to read its position.

The camera wdl be different with each make of spec- trograph and the settings for a part icular camera will be found in the procedure book. Details of camera adjust- ment will not be included here but wall be left to the trainer. I f the camera uses film, do not forget to show the trainee the movable filters m the camera.

Af te r you have set up the units repeatedly and when the trainee shows comprehension of it, he can be allowed to do it with supervision. Again, when he shows profici- ency, he may be allowed to spark the samples alone. De- pending on the procedure used for identifying types of samples in the laboratory, extra help in determining the alloy may be needed. In demonstrating the method of ig- nit ing the discharge, be sure to stress safety precautions.

Have the sparked sample and counter electrode put in their proper places. The sample should keep its ~dentity at least until there is no further need to rerun it.

26 APPLIED SPECTROSCOPY

Densitometry Identification of the analytical lines on the sample film

or plate is the most exacting detail of mlcrophotometer operation. In the laboratories which use plates, identifica- tion is by visual comparison with a standard spectrum which has been previously identified. The experienced op- erator will be able to differentiate the analytical lines with- out reference to the master. This identification will take a while to master, especially in laboratories which analyze a variety of metals. The more types of sample, the greater the confusion of the trainee.

Here, again, the best method of teaching is demonstra- tion. When picking out analytical lines on plates, use a pointed oblect, such as a sharp pencil, or mark the lines with ink dots. Be sure the observer can see the lines and have him look at the plate in the same direction as you do so that he will not have a reversed picture of the spec- trum.

When possible, relate the desired lines to other easdy identified hnes. These could be the 3100A iron triplet, the five magnesium lines m the 2780A region, or any other group that is easily recognized.

An aid to line recognition would be to have the trainee write on cards how best to locate the analytical lines or draw portions of the spectrum adjacent to the lines. This would help fix the spectrum in his mind.

In those laboratories using film, identification is some- what simpler since a master film is matched with the sample spectrum and the wavelength of each line can be quickly read. Film carriages on some of the densitometers permit shght film shppmg and it should be stressed that the films are to be aligned immediately before each wavelength iden- tification. In t~me, the new operator will be able to recog- nize the spectrum well enough to pick out the analytical lines without reference to the master film. This will usually take several weeks to master and a close watch should be kept on the trainee during the learning period to make sure he is reading the correct line.

Those actions which need be shown the trainee for mlcrophotometer operator follow:

1. How to mark analytical lines on plates. 2. How plates, sample film and master film are mounted

in microphotometer. 3. How the unit is turned on and operation of all switch-

es and knobs. 4. How master and sample film can best be aligned. 5. How to determine wavelength of a line. 6. How to identify analytical lines on the screen. 7. How to adjust galvanometer scale for 0 and 100 8. How to scan correct line. 9. Proper reading of galvanometer fluctuations.

10. Where to record readings.

Calculation of Results Converting densitometer readings into element con-

centration is not difficult in laboratories which have the revolving drum type calculators. In addition, all produc-

tion laboratories will have nomographs constructed for those elements which are run frequently. In some cases, a set of standards is included on each film and a curve is constructed each time the sample is run. In these instances, the choice of standards and graph construction should be explained at this time. When the nomographs are used, the explanation of curve construction can walt until the trainee is more familiar with the simpler operations.

Likewise, in those laboratories where each plate is cah- brated, the calibration procedure should be explained as part of the converting process. When only one calibration is made for each 100 foot roll or each film lot, wait until the trainee has mastered the daily routine before demon- strating it.

Interpretation of Results Most of the transmission readings of routine samples

are easily converted into per cent. The results of other samples must be scrutimzed and interpreted in view of known tendencies of certain factors which affect results. These special samples should be checked by experienced operators until the trainee becomes familiar with them.

An incomplete analysis can lead to an error in identi- fying a sample. I f an analysis calls for the determination of chromium in an austenitic stainless when the sample is really an 18-8 or t i tanium stabilized steel, other elements could easdy be overlooked. The same holds true for alumi- num alloys, low alloy steel, etc. Af te r the technician has become familiar with the spectrum, he can be told to check those other element lines which are supposed to be absent to make certain they are.

I f any peculiar effects or results are noted during the analysis, the trainee should be told to see his supervisor. The solving or Interpretation of these special cases will help stimulate interest in his new job.

Theory The trainer must decide on how much time to spend

on theory. Some people are content to perform their duties knowing only how to do their job. Others will not be sat- lsfied until they know the reason behind everything they do.

Af te r several weeks of working with the trainee, and after he appears to have a good understanding of the pro- cedure, he can be given a book to read that states the principles of spectroscopy in an easy to understand form. Several books are available: Harvey "Spectro-Chemical Analysis," Brode '~Chemieal Spectroscopy," Nachtr ieb "Spectrochemical Analysis," etc.

Pick out the chapters you consider to be the most use- ful at the time. Give him time to read the book at work and a place where he can concentrate. When he finishes each chapter, ask if there are any questions or any points not clear. Discuss the most important points. Chapters can be assigned at regular intervals until the whole book is covered. I t is best if the reading is done after the me- chanical operations are mastered.

Submitted July 3, 1956, accepted September 24, 1956,

NUMBER 1, 1957 27