CALCULATING OPTIMUM NUMBER OF TEST INSTALLATIONS FOR INSTRUMENT-REPAIRAND

TESTING WORK

V. V. Belyakov and L. N. Zakashanskii

UDC 65.006.015.5:53.081

Metrological provisions constitute an indispensable element of production quality-control systems whose development and application is rapidly increasing in enterprises and scientific-production associations. In this connection many of them organize departmental testing and repairs for measuring equipment, and this constitutes an important tendency in metrological provisions for production. A necessary condition for establishing a measuring-equipment testing and repairs (or only testing) workshop at enterprises should consist of determining beforehand the amount of resources (nomenclature and quantity of testing equipment, the number of testers and repairers, the size of premises and location features) required for its normal operation and of evaluating the technicoeconomic effectiveness of the planned workshops. These indexes can be determined by means of [i], which includes the "Technique for computing the optimum number of test installations." In order to decide whether it is advisable to incorporate such a unit in the enterprise structure, it is first of all necessary to examine a number of factors whose study will serve as a prerequisite for adopting the correct decisions. It is then necessary to determine how many instruments out of the measuring-equipment stocks are subject according to [2] to compulsory state testing and to ascertain the annual payment for the measuring instruments testing and repairs by the USSR State Committee of Standards (Gosstandart) organizations. It is then also necessary to bear in mind even approximate expenses on the measuring-instruments delivery to the above organizations and back to the customers, as well as the expenses on reconditioning certain measuring instruments which became damaged in transportation. Following the analysis of the above-mentioned prerequisites and determination of the possibilities for organizing at the enterprise an instrument-repair or testing unit, it becomes necessary to determine the resources required for this purpose. Above all it is necessary to select the required testing equipment with respect to both nomenclature and quantity. Nomenclature is determined on the basis of [3]. According to this normative-reference document the measuring-equipment stocks at an enterprise can be divided into tested groups. An appropriate set of testing instruments (STI) is then selected for each of these groups. When the planned unit is intended to be used not only for testing, but also for repairing measuring equipment, it will be necessary, in determining the required number of STI and their elements, to bear in mind that according to [4] in this case additional reference measuring equipment is usually required. Since the units under consideration participate in compiling measuring-equipment delivery schedules for departmental testing and ensure their implementation, it should be assumed that testers will be loaded with adequate uniformity and large accumulations in laboratories of untested instruments will be eliminated. Under these conditions the amount of testing equipment will be determined only by the number of tested instrument groups if the relationship of annual productivity and the planned loading of each STI is taken into consideration, as well as the permissibility of using the same elements in the composition of different sets of testing instruments. If an enterprise measuring-equipment stocks include instruments for many different types of measurements, it is desirable that the unit should consist of laboratories each of which test measuring-equipment of a given or several related types of measurements depending on the volume of testing work. The number of testers required in a laboratory can be computed, on the basis of each one having been trained in all types of testing, and calculated from the formula Translated from Izmeritel'naya Tekhnika, No. i0, pp. 12-14, October,

0543-1972/77/2010-1407507.50

1977.

9 1978 Plenum Publishing Corporation

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m

~, Fi tt i=l

T where m is the number of instrument groups tested in the given laboratory; r i is the mean number of i-th group instruments tested annually in the laboratory; t i is the mean duration in working days of the i-th group instruments testing; T is the mean annual number of days worked by a tester. In computing the number of instrument repairers it is advisable to bear in mind the irregular delivery of measuring equipment for repairs and other related additional conditions examined in [5, 6]. Under these conditions it is recommended to use the computing algorithm which is based on the application of the mass-servicing theory method and is described in the "Techniques for Computing the Optimal Number of Testing Installations." In the case of limited initial data and for the purpose of facilitating their preparation, it is possible to use the simplifying assumption that instruments are submitted for departmental repairs singly and not in batches. For the same reason it is advisable in a general case to limit computations to only one of the efficiency criterions comprised in this technique, namely, to the criterion providing for a limited duration of the measuring instruments repairs and testing. From the departmental repairs and testing conditions of radiotechnical measuring equipment it follows that a fortnight of time, i.e., 10-12 working days should be considered as a maximum permissible time for repairs and testing of such instruments. Other values for this index are also provided (5-7 days according to [7]). Having determined the composition and quantity of measuring equipment and the number of testers and repairers, it is necessary to evaluate the size of the planned-unit premises which should include areas for the normal location of the working personnel, STI, and measuring equipment. The areas required f~r locating measuring equipment should be evaluated, bearing in mind the possible utilization of racks, on the basis of the instruments' probable accumulation in the testing unit to double the amount of their daily delivery norms, and in the repairs unit on the basis of the instruments' maximum simultaneous accumulation, which is determined in the course of estimating the optimum number of repairs. The technicoeconomic efficiency of such a departmental unit is determined from the relationship of the enterprises mean annual expenditure on their measuring-equipment testing and repairs in the USSR SLate Committee of Standards (Gosstandart) organizations (Eg) to the same expenditure in a given departmental unit (Ed) , bearing in mind the initial expenditure on the establishment of this unit (Eu). These computations amount to evaluating the mean annual saving S, the duration of the initial-expenses requitability Trq, and their efficiency coefficient Kef f represented by s following expressions: S =Eg --Ed; Eu Trg= S ; S

~cff= Eu Owing to the present lack of acceptable means for finding initial data, the additional advantages obtained from departmental testing and repairs is not evaluated, thus resulting in an increased number of tested measuring instruments, and in a higher production quality and efficiency. The expenditure Eg is calculated from the formula Eg=Cg+~

q-Ct+ ~,

where Cg are the mean annual charges for state testing of the enterprises measuring equipment by the Gosstandart territorial agencies; C r are the mean annual charges for the enterprises measuring-equipment repairs and subsequent testing; C t are the mean annual charges for the measuring-equipment transportation to their testing and repair location, and for calling out testers to work at the enterprises; C s are the mean annual charges for maintaining measuring-equipment exchange stocks at the enterprises. When the departmental unit is established, the charges Cs are reduced according to [7] on an average by 75%.

i408

The expenditure E d can be evaluated by means of the following expression m

k

m

Ed = "t Cwt-k nr CwrAf",~ ~ (C,,A,-- Pii -- 11ii) "t Cp § Ca+ Cm-t-CI ~ Si, /=I 1=I

(3)

i=l

where n t is the number of testers in a unit; Cwt are the mean annual wages of a tester; n r is the number of repairers in a unit; Cwr are the mean annual wages of a repairer; m is the number of test-equipment sets in a unit; k is the number of elements in the i-th STI; Cij is the cost of the i-th STI j-th element; A i is the i-th STI depreciation norm; Rij is the mean annual cost of repairing the i-th STI j-th element, if the latter is subject to current repairs; Tij is the mean annual cost for testing the i-th STI j-th element, if the latter is subject to testing; Cp is the mean annual cost of electrical power spent in the unit for technological purposes; C a is the mean annual cost of auxiliary materials and reference substances used in the unit for testing purposes; Cm is the mean annual cost of spare parts and materials used for repairing measuring equipment; C 1 is the mean annual cost of maintaining a production and laboratory unit area; S i is the area assigned to the i-th STI location and operation. For determining the expenditure E u the following formula can be used m

EU=~

k

m

~ (C,I+ I ~i) + Cc(~Si--Sa)+CeSa+ Ci(nt +nr),

i=l/=l

(4)

i=I

where Iij is the cost of installing the i-th STI j-th element, if this installation requires additional expenditure; C c is the cost of the unit-area construction (according to [8] it is evaluated at 200 rubles per 1 m=); S a is the area of available premises allocated to measuring-equipment testing and repairs; C e is the total expenditure on acquiring the skill required to reconstruct or adapt an available unit area for the STI location and operation; C i are the initial expenses on training measuring-equipment repairs and testing experts. The evaluation of resources required for organizing the radio-measuring instruments departmental testing and repairs unit and evaluating the technicoeconomic advantages obtained as a result of its establishment were carried out according to the above technique at the Lenin Comsomol (Young Communist League) automobile plant (AZLK). The following current-year values were calculated for the summary indexes: S = 26,900 rubles, Trq = 3.6 years, and Kef f = 0.28. Therefore, each invested ruble will save in this case 28 kopeks, which exceeds the normalized value of Kef f = 0.15, which is the threshold above which the E u expenditure can be considered justifiable. It becomes often necessary to evaluate the above indexes from the future aspects. It is desirable to compile corresponding forecasts on the basis of the possible variations in the enterprises measuring-equipment stocks, as well as their testing and repairs means and methods. Such forecasting for the end of the five-year plan and further into the future can be carried out above all on the basis of normative and also extrapolation methods [9]. It was found in calculations for 1980 and the enterprise under consideration that S = 627,000 rubles, T r g = 1.75, and Kef f = 0 . 5 7 . It was found in approving this technique that it required certain additions and corrections. Thus, the following suggestions of a general nature were made, which it is advisable to bear in mind in preparing [i] for its next edition. The majority of metrological-service organizations improvement and supply problems have identical solutions for departmental testing units and Gosstandart territorial agencies and, therefore, it is desirable to extend the range of these methodic directives also to the state metrological service. Since many problems solved in organizing the departmental metrological-service instrument-repair units are similar to those in establishing testing units and often (as in the considered example) require to be solved simultaneously, it is advisable to include these problems in the methodic directives. It is necessary to supplement the directive with a section specifying the STI selection on the basis of [3]. Among the particular comments it is advisable to mention the following:

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It is desirable to have a more detailed method for computing economic effectiveness than the one provided in section 4 of the technique; it appears necessary to supplement and refine the meanings of certain parameters, and this has been taken into account in the formulas (i-4). It is also necessary to describe in greater detail the methodic directives which specify the requirements for the testing-unit premises; it is desirable to reflect the relationship of these requirements to the types of measurements and the place occupied by the STI in question in the all-union test scheme. LITERATURE CITED i.

.

. . .

6. 7. 8. 9.

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MI 15-74 Methodic directives on establishing and estimating the composition, equipment, and premises for departmental metrological-service testing units, Standartov, Moscow (1975). All-Union State Standard (GOST) 8.002-71 on "State system for ensuring uniform measurements (GSI). Organization and procedure for measuring-equipment testing, heavy inspection, and examination." Collection describing measuring-equipment aggregates. Comprehensive test-laboratories composition and characteristics [in Russian], Standartov, Moscow (1976). GOST 8.057-73 on "GSI. Procedure for approving, storing, and applying physical standards and reference measuring equipment." V. V. Belyakov and L. N. Zakashanskii, Izmer. Tekh., No. 7 (1976). L. N. Zakashanskii et al., Izmer. Tekh., No. 3 (1971). K. I. Abadzhi, Izmer. Tekh., No. 6 (1976). A. V. Lanskov and L. V. Babenko, Metrologiya, No. 7 (1973). L. N. Zakashanskii and K. V. Nekrasov, Metrol. Toch. Izmer., No. 8 (1976).