D.T.D Ministry of Defence Defence Procurement Agency, ADRP2 Abbey Wood Bristol BS34 8JH OBSOLESCENCE NOTICE

Transcription

1 Ministry of Defence Defence Procurement Agency, ADRP2 Abbey Wood Bristol BS34 8JH D.T.D. 629 OBSOLESCENCE NOTICE All DTD specifications were declared obsolescent from 1 st April All DTD 900 series approvals also lapsed at that time. The standards will no longer be updated but will be retained as obsolescent documents to provide for the servicing of existing equipment. Further Guidance The aim in declaring the specifications obsolescent is to recognise that the documents are not being updated and thus should be used with care by both purchaser and supplier. For example, a specification could contain valid technical information but may also contain type approval clauses that contradict procurement policy and/or use materials that do not comply with environmental legislation. The obsolescent specification can still be used as a basis for a purchase provided that the supplier and purchaser agree suitable changes to the specification within the purchase order/contract. For the DTD 900 system, each specification has provided an MoD approved material and process. For these items, the declaration of obsolescence will constitute the termination of both the extant MoD approval and the continuing MoD assessment that had underpinned those approvals. Again, the technical content of the document remains valid and can be used by both purchaser and supplier as a basis for a contract but an acceptable (to the parties) approval/assessment procedure would be required.

2 MINISTRY OF AVIATION D.T.D. 629 Crown Copyright Reserved March, 1946 Reprinted May, 1961 Aircraft Material Specification COOLANT TEST PAPERS NOTE This specification is one of a series issued by the Ministry of Aviation, either to meet a limited requirement not covered by any existing British Standard, or to serve as a basis for inspection of material the properties and uses of which are not sufficiently developed to warrant submission to the British Standard Institution for standardisation. 1. Description This specification covers the requirements of test papers, absorbent sheets and reference coolant standards supplied in the form of a kit for the purpose of testing aero engine coolants in the field. 2. Test Paper The Test paper shall consist of paper impregnated with Bromo Cresol Green and Ethyl Red. The method of impregnation and the materials employed shall comply with the requirements of Appendix I. When tested by the method described in Appendix II the finished papers shall also comply with the following requirements : (a) The paper shall show a purple colour with no evidence of green when applied to reference coolant standard having a ph value of 6.3. (b) The paper shall show a pale neutral colour with no evidence of purple when applied to reference coolant standard having a ph value of Absorbent sheets The absorbent sheets shall consist of best quality blotting paper. 4. Reference coolant standards The reference coolant standards prepared by the method described in Appendix III shall comply with the following requirements : (a) The standards shall possess ph values of 6.30 ± 0.02 and 6.50 ± 0.02 at 18 C. when measured potentiometrically using a glass electrode. (b) The standards shall contain not less than 29 per cent. and not more than 31 per cent. by volume at 18 C. of ethylene glycol conforming to the requirements of D.T.D. Specification 779. (c) The standards shall contain not less than 0.30 per cent. and not more than 0.50 per cent. by weight of phosphate expressed as ortho phosphoric acid (H 3 PO 4 ). 5. Package and nomenclature (a) Test papers. The test paper shall be cut into strips inch by 3 inch and shall be supplied in plastic containers, each holding 100 papers as depicted in Fig. 1, and shall be labelled with the following data:- (i) The title EC.64 Test Paper. (ii) The instructions given in Appendix IV for testing aero engine coolants. (iii) The name of the manufacturer. (b) Plastic Containers. The plastic containers shall conform generally to the dimensions shown in Fig. 2. The containers shall afford complete protection for the test papers within, from damage by moisture, heat or atmospheric conditions. When tested according to the method described in Appendix V, the test papers shall show no sign of deterioration. (c) Absorbent Sheets. The absorbent sheets, cut into 3-inch squares, shall be supplied in moisture-proof envelopes, each envelope shall contain 25 squares of paper and the envelopes shall bear the following data : (i) The title Absorbent Sheets. (ii) The name of the manufacturer.

3 2 D.T.D. 629 (d) Reference Coolant Standards. The reference coolant standards shall be supplied in clear glass reagent bottles having a nominal capacity of 65 ml. and overall height of approximately 4 inches. The mouths of the bottles shall be narrow, but the smallest internal diameter shall be sufficiently great to allow free passage of an EC.64 test paper conforming to the dimensions given in Clause 5 (a). The bottles shall be fitted with ground-glass dust-proof stoppers and shall be labelled with the following data (i) The title Reference Coolant Standard. (ii) The ph value of the standard. (iii) The name of the manufacturer. (iv) On the 6.3 standard bottle only, with words. A colour reaction corresponding to that obtained with this solution indicates that the coolant is unsuitable for further use. (v) On the 6.5 standard bottle only, the words A colour reaction corresponding to that obtained with this solution indicates that the coolant is suitable for further use. (e) EC.64 Coolant Test Outfit. This shall comprise the following articles packed in a suitable cardboard container. (i) 6 plastic containers filled with EC.64 test papers. (ii) 6 envelopes of absorbent sheets. (iii) 1 bottle of reference coolant standard ph = 6.3. (iv) 1 bottle of reference coolant standard ph = 6.5. APPENDIX I Preparation of EC. 64 Test Paper The EC.64 test paper shall be prepared by impregnating paper with a solution of bromo-cresol green and ethyl red in alcohol. Materials required. Paper. No other than Whatman No. 541 quality filter paper shall be employed. Alcohol. The solvent shall consist of absolute ethyl alcohol or industrial methylated spirit, providing the latter be clear and colourless, and free from foreign matter. Bromo-cresol Green. Bromo-cresol green (also known as bromo-cresol blue) possessing a useful ph range of 3.6 to 5.2 shall be employed. Ethyl Red. Impregnating Solution. Ethyl red possessing a useful ph range of 4.5 to 6.5 shall be employed. Composition. The composition of the impregnating solution shall be:- Alcohol 1,000 ml. Ethyl red 0.41 ± 0.01 gram. Bromo-cresol green 0.34 ± 0.01 gram. Preparation. The following details for preparing 1 litre of impregnating solution will suffice to explain the method; other quantities may be prepared by keeping the same proportions between the constitutents and employing a standard flask of suitable capacity. Add the ethyl red to approximately 950 ml. of the alcohol and boil under reflux until the indicator is dissolved. Next add the bromo-cresol green, shake till dissolved, and filter the hot solution through a 15 cm. Whatman No. 541 paper, collecting the filtrate in a standard litre flask. Cool filtrate, wash the filter with cold alcohol, and collect the washings in the filtrate until the volume of the latter is exactly 1 litre. Shake well and transfer to a stoppered bottle. Impregnation of Paper. The method described herein is suitable for manually impregnating sheets measuring 7½ in. by 10½ in. The apparatus required is as follows : Tank. Any suitable vessel fabricated from glass, porcelain, monel metal or other non-corrosive material may be employed for holding the impregnating solution, providing the mouth of the vessel is sufficiently narrow to minimise evaporation losses, which have the effect of increasing the concentration of the solution. A vessel having convenient shape and dimenisons is depicted in Fig. 3.

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5 FIG. 2 PLASTIC CONTAINERS FOR EC.64 TEST PAPERS IMPREGNATION APPARATUS

6 5 D.T.D. 629 Paper Holders.-A number of rods, to each of which are fixed two spring-clips in the manner depicted in Fig. 3. The rods and clips shall be non-corrosive. Drying Oven. An electrically heated hot air oven, the interior of which is fitted with two horizontal rods parallel to the sides for supporting the paper holders. The sequence of operations employed in the method of impregnation is as follows: 1. Fill the tank to within approximately inch from the top with impregnating solution. 2. Attach a sheet of the paper to a paper holder in the manner depicted in Fig Lower the paper vertically into the impregnating solution as far as possible without wetting the paper holder clips. 4. Remove the paper from the solution after 2 or 3 seconds immersion and immediatley transfer it to the drying oven, the temperature of which should be maintained between 90 and 100 C. The paper holder is supported on the horizontal rods in the oven so that the paper hangs vertically. Fluid draining to the bottom of the paper is removed by running a Whatman No. 41 paper along the lower edge of the paper while suspended in the oven. 5. Remove the paper from the oven when drying is complete, a process usually taking about 30 seconds. 6. Cut away and discard a strip from the lower edge of the paper where any difference in colour intensity due to local concentration brought about by drainage is evident. 7. Cut the remainder of the paper into strips of requisite size. It is important that strict attention be given to the following precautions :- (i) The atmosphere shall be free from alkaline or acidic fumes. (ii) When the paper is removed from the impregnating solution it shall not be allowed to remain in the wet condition for more than 10 seconds before it is transferred to the oven. (iii) The paper shall not be touched while it is wet, nor shall it be allowed to come into contact with other papers or the walls of the oven. (iv) The strength of the impregnating solution shall be maintained within the limits specified above. It will be found, on using the apparatus and method described above, that no correction is necessary for evaporation losses when the process is in continuous operation. If, however, the process be carried out intermittently, and the impregnating solution be allowed to remain in the tank, evaporation losses may bring the strength of the solution outside the limits specified, when it will be necessary to adjust the strength of the solution by the addition of alcohol. The strength of the solution may be verified by colorimetric comparison between two standard solutions, one containing the maximum, and the other the minimum, concentration of indicators specified. For the purpose of colorimetric comparison, it is best to dilute the solution with two-thirds its volume of alcohol. Mechanical methods of impregnation may be employed providing the finished test paper satisfies the requirements specified in Clause 2. APPENDIX II Method for the Determination of the Colour Change of the Test Papers Take a strip of EC.64 test paper (fingers must be clean and dry) and immerse it in the reference coolant standard for a period of not less than 10 seconds. Remove the surplus fluid by drawing the paper lightly across a clean piece of absorbent sheet. Immediately after removing the surplus fluid, observe the colour of the paper in natural or artificial daylight. The colour change is stable over a period of two minutes from the time of removing the paper from the coolant standard, but no significance should be attached to colours shown by the paper after longer periods of standing. APPENDIX III Preparation of Reference Coolant Standards Solution Required. A. 30/70 Treated Glycol/Water Mixture. Mix together at room temperature 70 volumes of distilled water and 30 volumes of ethylene glycol conforming to the requirements of D.T.D. Specification 779.

7 6 D.T.D. 629 Should the ph value of the distilled water be low due to dissolved carbon dioxide, it is unnecessary to expel the latter by boiling, as the resultant glycol/water solution is sufficiently buffered to prevent any effect of carbon dioxide on ph value. B. 30/70 Treated Glycol/Water Phosphoric Acid Mixture. Dissolve approximately 1 per cent. of solid ortho phosphoric acid in a portion of mixture A. Preparation of the Standards Titrate mixture A with mixture B potentiometrically until the solution possesses the the requisite ph value at 18 C. 100 ml. of mixture A requires approximately 12 ml. and 15 ml. of mixture B for ph values of 6.5 and 6.3 respectively. APPENDIX IV Instructions for Testing Aero Engine Coolants Instructions for Testing Unused and Used 30/70 Glycol/ Water Coolant 1. Take a strip of paper (fingers must be clean and dry). 2. Immerse in coolant for 10 seconds. 3. Remove surplus liquid by lightly drawing the paper across piece of clean absorbent paper. 4. Immediately after removing surplus liquid: observe colour of paper in natural or artificial daylight. 5. (a) A green colour, or a pale neutral shade similar to that obtained from the ph 6.5 standard, indicates. the coolant is suitable for use. (b) A red or purple colour similar to that obtained from the ph 6.3 standard indicates that coolant is unsuitable for use. Instructions for Testing Unused Concentrated Glycol 1. Take a piece of paper (fingers must be clean and dry). 2. Immerse in the glycol for 10 seconds. 3. Remove surplus liquid by lightly drawing the paper across piece of absorbent paper. 4. After a period not less than 30 seconds observe colour of paper in natural or artificial daylight. 5. (a) A green colour indicates the glycol is satisfactory for use. (b) A red, purple, or neutral colour indicates the glycol is unsatisfactory for use. APPENDIX V Instructions for Testing Plastic Containers A plastic container filled with EC.64 test papers, complete with washer and cap, screwed hand-tight, shall be exposed in a suitable vessel to steam at 100 C. for 48 hours. At the end of this period, after cooling, visual inspection of the papers shall be made. Approved for Issue N. J. L. MEGSON Director of Materials Research and Development (Air) Printed in England by M. Harland & Son Ltd. and published by HER MAJESTY S STATIONERY OFFICE Price 1s. Od. net (4880) Wt K2 6/61 M.H.&S. Ltd