Document 3Qr5JbMwqOkMvOm7V6O0yY3D0

ASKAREL Inspection and Maintenance Guide 0531672 1 TOWOLDMONOQ36103 TABLE OF CONTENTS SECTION A TRANSFORMER ASKAREL Page I. Introduction.......................................................................................................... 1 II. History of Trade Name Types........................................................................... Table I -- The Composition of Transformer Askarels 1 III. Table II -- Official Transformer Askarel Shipping Specifications................. A. General Electric Company's Transformer Pyranol A13B3B B. Westinghouse Transformer Inerteen PPO (7336-9) 2-3 IV. Interchangeability and Stability......................................................................... 4 V. Directions For Handling and Personal Precautions........................................ 4 VI. Expected Service Life............... ,,........................................................................ 5 VII. Dielectric Strength -- Moisture Relationship.................................................. A. Table III -- Dielectric Strength vs. Amount of Dissolved Water in Askarel and Mineral oil B. Table IV -- Approximate Solubility of Water in Askarel and Mineral Oil. 5 VIII. Table V --Typical Values Found in Askarel Fluid Under Various Con ditions of Use...................................................................................................... 6 IX. Check Points For Maintaining Askarel Insulation.......................................... A. General Considerations B. Modern Sealing Procedures C. The Older Sealing Arrangements 9 X. Periodic Fluid Inspection................................................................................... A. Visual Inspection B. Dielectric Strength 11 XI. Inspection Check List......................................................................................... 12 XII. Contamination in Transformers........................................................................ A. Table VI -- Effect of Common Insulation Materials on Power Factor and Dielectric Strength B. Table VII -- Effect of Common Insulation Materials on VolumeResistivity 12 XIII. Refining Askarel For Re-Use............................................................................ A. Filtering Through Dry Blotter Paper To Remove Moisture and Extraneous Particles. Table VIII -- Guide to Rate of Dissolved Water Removal By Filtration. B. Earth Treatment for Maximum Improvement of Power Factor and Volume-Resistivity 1. Procedure 2. Effect of Earth on Removal of Scavengers 3. Table IX -- Approximate Relationship Between Power Factor, Volume-Resistivity and Dielectric Strength of Transformer Askarel 14 XIV. Cleaning Arced Transformers............................................................................ 15 XV. Sampling ASKAREL......................................................................................... 17 0531673 TOWOLDMONOQ36104 SECTION B ASKAREL FILLED SWITCHES AND TERMINAL CHAMBERS Page I. Introduction........................................................................................................... 18 II. Sources of Contamination.................................................................................. 18 III. Sealing Switches and Terminal Chambers.......................................................... 19 IV. Askarel-filled Switches' Maintenance.................................................................. 19 SECTION C Monsanto Analytical Services on Transformer Askarel................................... 21 Appendix A. Askarel Stability and Composition of Arc Formed Gas.................................. 23 B. Solubility of Gas in Transformer Askarel.......................................................... 23 C. Approximate Vapor Pressure vs. Temperature For Transformer Askarel___ 24 D. Effect of Temperature on Dielectric Strength of Askarel................................. 24 E. Viscosity of Askarel and Mineral Oil................................................................. 24 F. Density of Transformer Askarels........................................................................ 25 G. Thermal Conductivity........................................................................................... 25 H. Heat Capacity........................................................................................................ 25 I. Coefficient of Expansion...................................................................................... 25 J. Fire-Resistance...................................................................................................... 25 K. Seals, Properties and Procurement...................................................................... 26 0531674 TOWOLDMONOQ36105 SECTION A TRANSFORMER ASKAREL I. INTRODUCTION: This manual describes the operating characteristics of transformer askarel liquid insulation and how it differs from mineral oil. The information given is based on facts gathered by Monsanto over 30 years as producer of askarel, plus knowledge gained from the experience of transformer manufacturers and users. This guide is provided to outline the very simple mainte nance required for askarel fluid in "modern" transformers and to offer suggestions for the sealing and maintaining of askarel in old units. By following this guide, users will obtain maximum service from askarel insulation with a reasonable minimum of maintenance. If questions arise relating to the designing and building of transformers -- these should be referred to regular transformer suppliers. Monsanto gratefully acknowledges the assistance, guidance, and the contributions of certain data by the following: Frank M. Clark............................................... General Electric Edward L. Raab.............................................. General Electric James G. Ford....................................... Westinghouse Electric George Shombert, Jr.........................................Allis Chalmers II. HISTORY OF TRADE NAME TYPES "Askarel" is the generic name for non-combustible (fire-resistant) liquid insulation. In this respect, the insulation is completely different from ordinary transformer mineral oils. Transformer askarel is marketed by Monsanto. Whatever the trade marked brand, the askarel contains Monsanto's Aroclor (chlorobiphenyl)... one of the best liquid insulations developed by science. This inert compound is chemically stable, fire-resistant, heat stable, non-corrosive, and has high dielectric strength under the operating conditions encountered in transformers. 0531675 TOWOLDMONOQ36106 Askarel liquid insulation is made by thinning Aroclor 1260 with trichlorobenzene or tri-, tetrachlorobenzene mix. The first transformer askarel was made in 1932, in accordance with General Electric Company's patents, and was trademarked Pyranol 1488. Westinghouse, too, offered this askarel insulation in 1936 under their trademark Inerteen. In the mid-1940's, as shown in the following table, tin tetraphenyl was added to General Electric's Pyranol to scavenge hydrogen chloride. Shortly thereafter, Westinghouse added phenoxy propene oxide to Inerteen for the same purpose. In 1963, General Electric replaced tin tetraphenyl with a diepoxide scavenger. This new formula, which replaces previous Pyranols, is called Transformer Pyranol A13B3B. Thus, today the two commercial types offormulations are General Electric's Transformer Pyranol A13B3B type and Westinghouse Inerteen PPO (7336-9) type. The composition changes made in transformer askarel formulations are shown in Table I. Table I THE COMPOSITION OF TRANSFORMER ASKARELS 1488 Year Introduced......................... 1932 Ingredients: Aroclor 1260 ................................ Trichlorobenzene........................ Tetrachlorobenzene................ Tin tetraphenyl....................... Phenoxy propene oxide......... Diepoxide................................. 60 40 Pyranol________________ 1467 1470 A13B3B 1944 1952 1963 Inerteen 1936 60 40 0.125 45 40 15 0.125 45 40 15 0.125 60 40 Inerteen PPO (7336-9) 1945 60 40 0.20 OTHER BRAND NAMES Various electrical equipment manufacturers use other trade-marked names for askarel liquid insulation, such as Chlorextol (Allis-Chalmers); Noflamol (Wagner Electric); Saf-T-Kuhl (Kuhlman Electric). These askarel insulating liquids are one . or the . other of the two standard formulations. Still other manufacturers, who designate their insulation only by its generic name, askarel, assign it a number or code. By this number, Monsanto knows whether to furnish Pyranol A13B3B or Inerteen PPO (7336-9) type formulation to the user. III. OFFICIAL TRANSFORMER ASKAREL SHIPPING SPECIFICATIONS The official shipping specifications for the two modern transformer askarel formulations are shown in Table II. ?0*3K,tb 2 TOWOLDMONOQ36107 Table n OFFICIAL TRANSFORMER ASKAREL SHIPPING SPECIFICATIONS General Electric Co. Westingbonse Typical Properties Transformer Pyraool A13B3B Transformer Inerteen PPO (7336-9) Color, APHA Condition Water content, ppm (ASTM D1533-60) Acidity, mg. KOH/g. (ASTM D974-55) 150 max. Clear 30 max. 0.014 max. 150 max. Clear 30 max. 0.014 max. Dielectric Strength, 2SC., 0.1 inch gap (ASTM D877-49) Dielectric Constant, 100C., 1 KC {ASTM D924-49) Volume Resistivity, 100C., 500 volts DC 0.1 inch gap, 10* ohm-cm. 35 KV, min. 3.8 to 4.3 100 35 KV, min. 3.7 to 4.0 100 Inorganic chlorides, ppm. (ASTM D1821 and G.E. Method E4C41B) Refractive index, 25C. (ASTM D901-56) Viscosity at 37.8"C. (ASTM D88-56) Saybolt Universal Seconds Pour point C. (ASTM D-97-57) Specific gravity 15.5/15.5C. (ASTM D287) 0.10 max. 1.6075 to 1.6085 41 to 45 --44 or lower 1.560 to 1.571 0.10 max. 1.6137 to 1.6147 54 2 --32 or lower 1.560 to 1.568 Burn point (ASTM D92) None to boiling None to boiling Distillation range (ASTM D20-56) corrected for stem and barometric pressure 1st drop 210C. min. 1st drop 200C. min. 35% 240 to 256 40% below 270C. 55% 290 to 330 90% 395 to 415C. 65% 385 to 400 95% 395 to 415 Fixed chlorine 60.5 * 5% 59.1% min. Corrosion test After heating with aluminum for 6 hrs. at 200 to 220C., the aluminum must not be corroded on either visual or weight in Color, APHA Acidity, mg. KOH/g. Inorganic chlorides ppm. Condition spection and the askarel should meet the following specifications: 200 max. 200 max. 0.014 max. 0.014 max. 2.0 (tent.) 2.0 max. Clear Clear Scavenger content 0.115 to 0.135% 0.18 to 0.22% Diepoxide phenoxy propene oxide Arc formed gases Less than 1.0% of total combustible gases including carbon monoxide, hydrogen and volatile hydrocarbons. Coefficient of Thermal Expansion (ASTM DI903), CC./CC./X. 0.0007 0.0007 The above two formulas are used in modern transformers. There are a number of units in service dating back to 1933 with askarels of somewhat different compositions. These will be compatible with the above modem formulations. 0531677 TOWOLDMONOQ36108 IV. INTERCHANGEABILITY AND STABILITY A. Interchangeability: The two general types of askarel insulation shown in Table II can be either mixed or interchanged and there will be no difference in the operation of the transformer. However, askarel insulation must never be mixed with mineral oil. Over 2% mineral oil in askarel begins to lower its fire resistance. Further, materials of construction in the transformer that are compatible with askarel may not be compatible with oil and vice-versa. For example: a significant amount of askarel in a transformer built for mineral oil will attack gaskets, adhesives, core bindings, impregnating varnishes, etc. B. Stability: Askarel liquid insulation is highly pure, fire-proof liquid made under close chemical control. It does not vary in composition like the commercial range of mineral oils. Askarel does not deteriorate when exposed to air, heat, hot metal; it does not break down over long use to form conducting or corrosive chemicals; it does not oxidize or sludge. Askarel will remain perfectly stable year after year unless broken down by exposure to severe arcing. The only real "enemy" of askarel is contamination by water. Keeping askarel water-free will insure long-time service. Askarel is heavier than water. If water gets into askarel insulation, only a tiny amount (125 ppm) dissolves -- the rest floats on top. V. DIRECTIONS FOR HANDLING A. Keep Dry: In handling, storing, sampling, inspecting askarel -- and in operating askarel transformers -- take every precaution to guard the askarel insulation from exposure to high humidity and moisture contamination. Keep 5, 30, or 55 gallon drums of askarel dry; lay stored drums on their sides with the bung at the highest point from floor to keep water off the drum head (which can be sucked into the askarel by the drum "breathing"). This precaution is not necessary when drums are stored indoors, which is the preferred way of storing. B. Use Ordinary Personal Precautions: Transformer askarel has been made, handled, and used for over 30 years without causing toxic or other ill effects. It can be handled with only minor precautions. If accidentally spilled on hands, no serious skin irritation will occur. However, liquid askarel has a solvent action (similar to paint thinner) on the fats and oils of the skin and prolonged contact may lead to drying and chapping of the skin. 4 0531678 TOWOLDMONOQ36109 In case of contact, wash off the skin with soap and water; remove and dry clean saturated clothing. Clean up spills with rags, sawdust or absorbent clay. Eye contact may result in painful irritation but no permanent damage to tissues. If askarel gets in the eyes, flush with large amounts of water. As with all eye first-aid, refer to a physician. To relieve irritation, physicians have used a 1% Pontocaine as well as opthalmic cortisone acetate solution, or castor oil. Infrequent exposure to askarel vapors will not cause ill effects. However, prolonged exposure to high vapor concentrations should be avoided. If hot askarel must be handled in a closed or confined area, provide the area with ordinary exhaust ventilation -- or -- wear an organic cartridge respirator approved by the U. S. Bureau of Mines. VI. EXPECTED SERVICE LIFE Properly designed and installed askarel transformers will give trouble-free service for a minimum of 30 years. Since their introduction in 1932, the manufacturers report finding the over-all failure rate to be less than 0.5% for all units under test and service conditions. The Edison Electric Institute's report (1956-1958) on their member utilities publishes the failure rate for askarel transformers as 0.13 per hundred banks per year. Even the rare reports of failure are invariably found to be due to improper sealing that allows moisture to enter. VII. DIELECTRIC STRENGTH -- MOISTURE RELATIONSHIP The dielectric strength of askarel is highly sensitive to excess moisture; not sensitive to ordinary dissolved contaminants. While the dielectric strength can also be lowered by severe arcing, askarel turns noticeably black or has particles of sooty carbon floating in it if arcing has occurred. Then the transformer should be repaired and the askarel replaced. New askarel has a minimum dielectric strength of 35 K.V at 25; a maximum mois ture content of 30 ppm. If the dielectric strength is checked periodically and decreases significantly -- this indicates moisture pick-up, arcing, or both. When the dielectric strength has dropped to 26 KV or less, an analysis for water is necessary. If water is found in excess of 100 ppm at 25 C., its source should be located and corrections made. When the moisture content approaches 125 ppm (saturation level), the dielectric strength of askarel drops below the value required for efficient insulating. The moisture content should not be allowed to rise over 70 ppm; it should be held as near as possible to 30 ppm. Maintaining a low moisture level will assure high dielectric strength and top operating efficiency. Table III shows the relationship of dielectric strength vs. moisture and Table IV indicates the approximate water solubility limits in askarel and mineral oil. TOWOLDMON0036110 Table HI RELATION OF "BREAKDOWN STRENGTH' TO AMOUNT OF DISSOLVED WATER IN ASKAREL AND MINERAL OIL Water Content (PPM) 0 20 40 60 80 110 Breakdown Voltage (ASTM) Askarel Mineral Oil 70 KV 55 47 40 38 10 50 KV 39 30 26 22 5 Table IV APPROXIMATE SOLUBILITY OF WATER IN TRANSFORMER ASKAREL AND MINERAL OIL Temperature C. F. Amount of Water (PPM) Dissolved Askarel Mineral Oil --30 --20 --10 0 10 20 30 40 --22 --4 14 32 50 68 86 104 8 16 28 41 65 94 128 170 8 10 13 20 33 58 85 130 TURBIDITY ... may be the visual sign of undissolved water, or may indicate contamination from core materials, dirt, or deteriorating construction materials. Cloudiness may also result from cold precipitation of tin tetraphenyl "scavenger" that was used in the earlier Pyranols. This scavenger begins to come out of solution around 15F. above zero. To redissolve it requires heating to 150 - 200F. and agitation. High dielectric strength will quickly indicate that any turbidity present is not moisture; that the insulating efficiency of the askarel is still excellent. However, if the dielectric strength is below 26 KV, moisture should be determined, using the Karl Fischer method (ASTM D1533-60). The dielectric strength test for askarel serves primarily as an indicator for moisture. It is by far the most important maintenance test for transformer askarel VIII. TYPICAL VALUES FOUND IN ASKAREL FLUID UNDER VARIOUS USE CONDITIONS Table V gives the entire spectrum of properties that are typical for freshly-made transformer askarel as it goes through the various normal and abnormal conditions of use. The data in Table V are in terms of only the askarelfluid and do not refer to insulation resistance or power factor measurements on the over-all transformer insulation. Several utilities studying the power factor values of the over-all transformer insulation system indicate that the unit power factor of a new askarel transformer should range from 1% to not over 5%. This would generally correspond with the askarel fluid properties as given under heading "B". 0531680 TOWOLDMONOQ36111 Table V TYPICAL VALUES FOUND IN ASKAREL FLUID UNDER VARIOUS CONDITIONS OF USE A New askarel Inspection Check Points Color Light straw Clarity Moisture 25C. Clear, free from particles 30 ppm B Askarel in prop erly built new or rebuilt units prior to use. cD After normal oper Non-arced but ation; a survey of slightly contami 50 units, most 2-5 nated askarel in yrs. old; some 10. improperly* built units, new or slightly used. E Same askarel as in Column D -- after refining. Light straw Light straw Clear, practically Clear, trace of free from particles particles 30 ppm 10-70 ppm all dissolved water Can have foreign Foreign shades shades, blue, green, remain showing red cast. extraction of oil soluble color. Clear, slight Clear, free from amount of particles particles 20-100 ppm all dissolved water 30 ppm Dielectric Strength 25C., 0.1' gap 35 KV minimum 35-48 KV Volume Resistivity 100 x 109 ohm-cm. lOTC, 500 Volts, DC., minimum 0.1' gap usually 500-1,500 40 x 10* ohm-cm. minimum usually at least 100 x |0 Power Factor: 100C. 60 cycles 25C. 60 cycles 2-5% 0.05-0.1% 10-25% 0.5-2% 35-45 KV 15-400 x 109 ohm-cm. 10 to near 80% 0.5 to near 10% 30-42 KV about 5 x 10* ohm-cm. 30 to 100% about 7 to over 15% 40-45 KV at least 1,500 x 109 ohm-cm. 2-5% 0.1-0.2% F Heavily arced askarel due to neglect and internal electrical malfunction. Black Contains carbon particles Near 125ppm saturation level -- plus possible undissolved water 5-15 KV about 3 x 10* ohm-cm. 100% at least 25% *A properly built transformer is defined as one in which the materials of construction are chemically and electrically compatible with askarel. 0531681 TOWOLDMON0036112 Starting ideally with situation "B'\ it is normal to expect the power factor of the fluid in a satisfactorily operating askarel transformer to increase as shown under heading "C". The "over-all" power factor of the transformer in normal service is expected to rise, but preferably not much beyond 5%. In this normal situation, the moisture level of the askarel fluid and its dielectric strength will be satisfactory, as shown in heading "C". Occasionally the power factor of a non-arced, satisfactorily-operating askarel transformer is found to be relatively high, i.e., 15%. In this caset the power factor of the askarelfluid will also be high, perhaps as high as 50% at 20C. and 60 cycles. It is not good practice merely to note that high power factor of the askarel fluid is to be expected. The important step is to check dielectric strength and note whether there has been a downward trend. A downward trend in dielectric strength very likely indicates moisture entrance and should be confirmed by a Karl Fischer test for water. The importance of any abnormalities in dielectric strength and moisture content of the askarel fluid cannot be overemphasized! Where abnormal values for the dielec tric strength or moisture content occur, the power factor of the transformer can be expected to be abnormally high; the expected high power factor of the askarel fluid will induce this. The indication that a high power factor on the transformer and on the fluid is due to contamination can be verified by earth refining the askarel fluid and noting whether after refining the test results correspond with heading Assuming no mechanical defect or arcing, if the power factor of a new askarel transformer is relatively high, the power factor of the fluid will also be high, giving the situation under heading This reflects contamination that should have been removed by the manufacturer of the transformer. In absence of mechanical defect, where there are no abnormal losses in dielectric strength, and no moisture pick-up in non-arced askarel -- the use history shows that a relatively high power factor for the askarel fluid (as compared with mineral oil) is to be expected. Normally, high power factor is due to contamination and not deterioration of the askarel operation. As shown by F. M. Clark in his book, "Insulating Materials For Design and Engineering Practice," John Wiley & Sons, N. Y., 1962 -- activated alumina can be used in the circulating system to bring the power factor down and keep it as low as possible. 0531662 8 I TOWOLDMONOQ36113 IX. CHECK POINTS FOR MAINTAINING ASKAREL INSULATION A. General Considerations: Modern askarel transformers with welded construction or silicone gaskets for hand hole-cover, switch and terminal compartment covers, with properly constructed bushings require little or no maintenance. With properly con structed transformers, annual or semi-annual visual inspection and dielectric strength test of the askarel fluid should suffice for routine maintenance checking over many years of service. However, many askarel units were installed in the early 1930's -- before the development of some of the better modern gasketing materials and before improved designs were developed for sealing out moisture. Such early units should be, and can be, modernized. Leaky or deteriorated gaskets should be replaced. If the askarel has become contaminated, it should be reconditioned. At the same time, a general clean-up of the unit and possible reflnishing may be desirable. If it is not convenient to take an old transformer out of service for general repairs, leaky gaskets can be sealed temporarily by painting over the leaky area with epoxy cement. A survey of users indicates a good number of early-built askarel transformers (over 20 years old) are kept in continuous service in critical installations by the following steps (instead of modernization). The operating units are equipped with compound pressure gauges for reading pressure above and below atmospheric. Positive pressure is maintained on the shell by introducing nitrogen at 2 to 3 pounds above atomspheric. Regular workmen in the area daily record the temperature and pressure. If a sudend pressure drop is noted more nitrogen is introduced and the gaskets are checked for leaks with soap solution. Leaks are sealed by applying epoxy cement. B. Modern Sealing Procedures: Transformer purchasers should specify the following modern techniques for sealing: 1. Welding Construction: Covers, radiator connections, switch and terminal housings, instrument connections, etc. should be welded. 2. Bushing Connections: The most satisfactory bushings are the type with rolled-on flanges and two ring seals rolled into a depression in the porcelain -- sealed with silicone rubber rings held under compression. Metal-to-glass or metal-to-porcelain sealed bushings are also satisfactory. If for any reason the above type bushings cannot be used then use a por celain or glass bushing with a silicone or Viton gasket retained in a groove. The gasket can be either rectangular or circular cross section, usually V4 inch thick. 3. Small Size Connections: When not possible to weld, small size connection seals should be made with Flexitallic stainless steel rings. The surfaces must be machined and parallel. The filler between the steel laminations of the Flexitallic ring should be either silicone or Viton. 053X683 TOWOLDMONOQ36114 4. Gaskets For Hand-Hole Covers: Modern design specifies silicone gaskets. Such gaskets must be retained in a groove. The groove preferably is machined into the flange or cover. However, it can also be formed by welding concentric steel strips to the flange or the cover. Generally the gaskets should be s/16 to Vi inch thick for covers, depending on the depth of the groove. A rectangular section is usually used. The silicone material should be Dow-Coming No. 50 Silastic or equivalent. This is a low compression set material. For best sealing 20 to 25% compres sion is recommended, with ample clearance in the groove to allow for this compression. No cement is required. With reasonable care the gasket is removable without damage and is reusable. Silastic 50 is slightly swelled by askarel which contributes to the tightness of the seal. Jt is not deteriorated by askarel fluid or vapors. It resists weather ing and it is thermally stable and flexible at all operating temperatures. It is an excellent moisture barrier. Notes: a. Dow-Coming, Midland, Michigan will supply a list of Silastic 50 gasket fabricators to all transformer manufacturers or users. They will also furnish technical data. b. Any user of Pyranol transformers, made by General Electric Company at Rome, Ga., will receive prompt and generous help for converting to the modern silicone or Viton gaskets by contacting the General Electric Company's Service Engineering Department at Rome, Ga. See Appendix K: Seals, Properties and Procurements. C. The Older Sealing Arrangements: The older type gaskets consist of either cork or cork-nitrile rubber combinations or straight nitrile rubber. 1, Cork-Nitrile Combinations: Covers for the main tank, hand-holes, switch and terminal chambers, relief diaphrams etc. are held in place by studs welded to the flange or by bolts. The gaskets are cut with openings and placed over the bolts. Often Shellac (Westinghouse Style No. 1150419, or General Electric Company's Glyptal 1276) is used to cement the cork to the flanges. The following is recommended for sealing with the cork -- nitrile rubber combination: Use Armstrong NC-757 cork-nitrile material or equivalent. The gasket can be cut from a single sheet or by scarfing strips of the material. A convenient method for joining strips is to make a Keystone Type joint. For this, Westinghouse, Sharon, Pa., offers their gasket cutter Style No. 328 B614 G01, (about $15). The joints should be cemented and the gasket also cemented to the flange, using one of the above cements. Excess cement should not be allowed to reach the interior of the transformer. 0^3V`>a`' 10 ^ TOWOLDMONOQ36115 After installation and bolting, the outside edge of the gasket should be coated thoroughly with epoxy cement to increase weather resistance. This epoxy cement is a paste to which a curing catalyst is added immediately before use. Typical are: a. Epoxy Patch Kit Hl-C - Hysol Corporation, Olean, N. Y. b. Scotchcast Resin #4 Minnesota Mining and Manufacturing Co. St. Paul, Minnesota c. Adhesive A-l and Activator Type B Armstrong Products Company Argonne Rd., Warsaw, Ind. d. Adhesive 9860-1, Synthetics Organic Company, Cleveland, Ohio, used with activator diethylene triamine (Carbide and Carbon Chem. Co.) 2. Straight Nitrile Rubber: When straight nitrile rubber was originally used, invariably the gasket was recessed in a groove. This was to prevent gasket flow and to protect the material against excessive compression. Although this type seal was not cemented, the nitrile rubber gasket is not reuseable. Since grooves or stops have already been provided for the nitrile rubber seal, Silastic SO can be easily substituted and is recommended. This conforms with modern practice. X. PERIODIC FLUID INSPECTION AND WHAT CHECKPOINTS MEAN On a regular schedule -- at six, nine, or twelve month intervals -- make a simple visual inspection of your askarel insulation and run a dielectric strength check. A. Visual Inspection: Askarel is a clear, faint-yellow liquid. After long-term use this color may gradually intensify to light brown. The fluid should remain clear and free from turbidity or cloudiness. Any color change -- such as to a green, red or blue cast -- indicates extraction of impurities from the solid insulation. If a distinct foreign color pick-up is noted, check the complete range of electrical characteristics and notify the transformer maker. The electrical characteristics may be found to be unim paired. Color change alone (except for black) is not a danger signal since the contamination is not likely to impair the dielectric strength. B. Dielectric Strength: If the dielectric strength has decreased significantly from the last inspection, or if it has gradually decreased below 26 KV range (at 25C.) -- RUN A CHECK FOR MOISTURE. Use ASTM D901, D877 (Karl Fischer Method). The dielectric strength of askarel is the major indicator to the operating efficiency of your liquid insulation and of the askarel transformer itself. Besides the "visual" inspection tests, dielectric strength is the only test necessary to run on a routine basis. Well-sealed askarel transformers have service records of 25 to 30 years on the original askarel. New askarel has a minimum dielectric strength of 35 KV at 35C., a maximum moisture content of 30 ppm. n 053, 685 TOWOLDMONOQ36116 XI. INSPECTION CHECK LIST 1. If askarel is clear, even though darkened to light brown; has no sediment or turbidity; has dielectric strength over 26 KV... give it the inspection "OK". 2. If askarel is clear; has foreign color of blue, green, red . .. it is "extracting color" from internal materials. This is not, of itself, an operating hazard when the dielectric strength stays over 26 KV and moisture remains low. However, this rare occur rence calls for checking into condition of the interior construction and consulting the transformer maker. 3. If askarel is clear; but dielectric strength drops to 22 or lower KV, and moisture rises over 80 ppm ... the askarel is ready for simple "refining". If the moisture is near the saturation level (about 125 ppm), a thorough inspection should be made for water droplets in the transformer tank, and even for "globules" or water floating on the askarel surface. If found, the transformer manufacturer should be consulted for reconditioning both the transformer and the fluid. 4. If askarel is dark brown to black; if black particles of carbon are seen; and dielectric strength is low... the askarel has been broken down by arcing. It cannot be refined and should be discarded. If any of these four simple inspection tests appear out of the ordinary, or the relationship between appearance and test values is abnormal -- contact your transformer supplier for a complete analysis. Whenever a sample is to be shipped to Monsanto, please follow the directions shown under: "SAMPLING ASKAREL". XH. CONTAMINATION IN TRANSFORMERS Unlike mineral oil which can oxidize, sludge and deteriorate -- askarel breaks down in transformer use only when strongly arced. Thus, while askarel does not decompose in normal use -- it can be contaminated more readily than the relatively non-polar mineral oil. For example the following Table VI shows how a small amount of synthetic rubber or a bit of varnished cloth markedly increases the power factor of the askarel. Please note, however, that such minor contamination has no adverse effect on the dielectric strength. As explained, moisture entrance through faulty seals seems the only contaminant in normal use that lowers the dielectric strength of transformer askarel. L12 053X6> TOWOLDMONOQ36117 Table VI EFFECT OF COMMON INSULATION MATERIALS ON POWER FACTOR AND DIELECTRIC STRENGTH (HEAT AGED 96 HOURS IN ASKAREL AT 100C.) Material Immersed None (control)........................................... ... Black varnished cloth............................... ... Copper......................................................... ... Pressboard.................................................. ... Manila paper.............................................. ... Phenol formaldehyde resins..................... ... Shellac......................................................... ... Iron.............................................................. ... Synthetic rubber........................................ ... Askarel After Exposure Power Factor, Dielectric Percent at 60 eye., 100C. Strength 25C. 1.0 85.0 35 KV 42 1.5 40 2.0 37 1.5 39 1.6 41 6.0 36 5.0 39 70.0 39 Similarly, trace contaminants from commonly used construction materials can lower the volume - resistivity of askarel, without affecting its dielectric strength. Table VII shows this. Table VII EFFECT OF COMMON INSULATION MATERIALS ON VOLUME RESISTIVITY OF ASKAREL Sample 1. New askarel before heat aging....................................... 2. New askarel after heat aging 96 hours at 100C......... 3. After heat aging with 1 sq. inch specimens of: a. Phenolic resin tap changer material......................... b. Paper............................................................................... c. Grade A press board (tan)......................................... d. Grade A press board (gray)....................................... e. Grade A press board, laminated strip..................... f. Cotton wrapping.......................................................... g. Glyptal 1276 cement, cured 48 hrs. at 110C.......... Volume Resistivity x 10s ohm-cm (at IO0C., 500 Volts DC., 0.1' gap) 2,000 1,900 1,200 750 500 500 400 300 100 While trace contamination easily lowers volume resistivity from high levels, it is important as previously noted in Table V Case F, that heavy contamination (as when arced) does not lower the resistivity below the order of 10* ohm-cm. at 100C. The different behavior of askarel vs. mineral oil in these respects can be summarized as follows: High power factor and low volume resistivity in transformer mineral oils are commonly regarded as "danger signals" that the oil has deteriorated and broken down chemically. This is NOT TRUE of askarel liquid insulation, unless the dielectric strength is low. TOWOLDMONOQ36118 XIU. REFINING ASKAREL FOR RE-USE A. Filtering Through Dry Blotter Paper to Remove Moisture and Extraneous Partciles: Most operators prefer portable refining apparatus, such as a plate press fitted with a dolly, (available from Sparkler, Mundelein, 111., Westinghouse Main tenance and Repair Dept., Chicago, or General Electric Co., Pittsfield, Mass.); or the earthen cartridge filter type, (available from Industrial Filter Corp., Lebanon, Ind.). Filter paper liners for the plate press are available from Carl Schleicher and Schuell Company, Keane, New Hampshire and manufacturers of filter presses listed above. The filter paper must be dried immediately before use. For best results, spread the paper for maximum surface exposure in a hot air circulating oven and heat it for 4 to 6 hours at 110C. If possible do not take the transformer out of service until ready to filter the fluid. This will keep the transformer coils relatively hot and dry. Processing the fluid should start immediately after de-energizing the unit. Circulate the askarel hot (but not over 55-60C.) through the filter fitted with the dry paper liners. After filtration the dielectric strength of the askarel should be 35 KV minimum. I. Precautions: Filtering should not be done when the relative humidity exceeds 75%. II. Any flexible hoses and gaskets on the refining equipment should be lined with or made of materials that will not be softened by contact with askarel fluid. (Silicone or Teflon-lined, or flexible metal materials are suitable.) Table VIII GUIDE TO RATE OF DISSOLVED WATER REMOVAL BY FILTERING ASKAREL THROUGH A PAPER PRESS Passes Through Paper Press 0 2 3 4 5 6 Water in Askarel PPM ns 35 22 18 12 10 10 * 14 0531688 TOWOLDMONOQ36119 B. Earth Treatment for Maximum Improvement of Power Factor and VolumeResistivity: 1. Procedure: (The askarel liquid should be relatively dry prior to the following earth filtration.) Use finely divided Attapulgus clay or Fuller's earth (dried and activated by heating for 12 hours at 300-350F. immediately prior to use) as a coating on the filter paper surface. The amount of earth used should be 0.1 to 0.2 per cent by weight on the weight of the askarel to be treated. (Askarel weighs about 13 pounds per gallon). To deposit the earth evenly, stir one-third of the earth with a small portion of askarel in a clean container. Pump the mixture through the filter and follow with two more one-third portions. Then circulate askarel taken from near the top of the transformer, pass it hot (not over 55-60C.) through the earth coated filter and feed back through the bottom transformer outlet. Continue circulation until the fluid is clear and test shows that the electrical properties are fully restored. 2. Effect of Earth on Removal of Scavengers: Only slight and insignificant loss (by selective absorption) of tintetraphenyl and epoxides occurs when askarel is refined by treatment with 0.1 to 0.2 per cent by weight of earth. To remove significant amounts of the scavengers requires repetitious treatment with much larger amounts of earth. 3. Table IX -- Approximate Relationship Between Power Factor, Volume Resistivity and Dielectric Strength of Transformer Askarel: Power Factor (60 eye.) 100C. 2S?C. 2% 5% 15% 20-25% 40-50% 0.05% 0.1% 0.7% 2.0% -- Volume Resistivity x 10 ohm-cm. (at 100C., 500 Volts DC., 0.1' gap) 1S00 500 100 60-70 25 Dielectric Strength 25C., 0.1' gap 35 KV 35 35 35 35 If it is desired (although these factors are not generally considered important for askarel transformers), to keep the power factor as low as possible and the resistivity as high as possible, hang a container of anhydrous alumina or activated clay in the circulating system of the transformer. XIV. CLEANING ARCED TRANSFORMERS If a unit has arced so that the askarel is no longer fit for use, a thorough cleaning of the unit is necessary before refilling with new askarel insulation and returning it to service*. Follow this procedure: 0531b89 TOWOLDMONOQ36120 A. Drain out all dark, carbon-contaminated askarel. (Discard by dumping or burying where it will not contaminate a water supply.) B. Carefully brush carbon deposits from internal parts and insulation, using a soft bristle brush making sure that insulation is not damaged. C. Flush thoroughly using new askarel (not an oil, not a cleaning solvent). D. Flush a second time with fresh askarel; drain; then fill to the proper level with new askarel. E. Energize transformer to warm the fluid for 24 to 48 hours; then circulate the askarel through a filter, returning it to the unit filtered and ready for use. This assumes that the cause of arcing has been established and corrections made. When severe arcing occurs, major repairs are usually necessary and the unit rebuilt. This procedure can be applied for flushing out repaired units. 2 TOWOLDMONOQ36121 XV. SAMPLING ASKAREL Take a sample as close to the top of the liquid surface as possible. (Many large askarel transformers have a built-in sampling tube near the surface for convenient sampling). Then, to make sure that your SAMPLE truly represents your askarel insulation, take another sample from the bottom. If additional sampling tube connections are contrived on the valves for easier sampling, make the tubes of clean glass, stainless steel, aluminum or tin for rigid types; and silicone or Teflon tubing for flexible types. Use NEW containers for the askarel sample. A new and thoroughly pre-dried smallmouth quart glass bottle fitted with a Bakelite screw cap fitted with an aluminum or tin bottle cap liner is recommended for "quick on-the-site testing." (If complete analysis is to be made, a 5-pint size sample is required). Be sure that the new bottle does not stand open to collect dust or moisture. Rinse the sample bottle and cap lining two or three times with askarel from the transformer; then fill it. If the sample will be tested promptly, a clear glass bottle can be used. If sample is to be stored indefinitely, use an amber glass bottle or wrap clear glass with aluminum foil. A. Select a dry day. Do not sample insulation on a warm, moist day when humidity exceeds 75%, and ... B. Make sure that the askarel is at least as warm as the surrounding air. (Cold liquids can condense moisture from humid air.) C. When sampling askarel from transformers, it is best to take the sample when the unit is warm and operating at average or maximum load. Especially as a check on moisture (as reflected by a dielectric strength test), sampling the warm askarel more truly represents its condition during operation. Experience shows that water will migrate from a transformer's solid insulation to the askarel liquid and vice versa, depending on temperature. Therefore, when the transformer is hot, the moisture is most likely to be found in the liquid. This accounts largely for periodic variations in dielectric strength. For example: a relatively high dielectric strength may be found during winter months and a relatively low dielectric strength during the summer months on samples taken from the same unit. 0531691 17 TOWOLDMONOQ36122 SECTION B ASKAREL FILLED SWITCHES AND TERMINAL CHAMBERS I. INTRODUCTION: High voltage leads are usually connected to askarel or mineral oil-filled network transformers and power centers through terminal chambers and switches. In some cases terminal chambers are not used, and the high voltage leads are connected directly to the switch terminals. They may be filled with either askarel or mineral oil. Switches are usually rotary or drum type fitted with a revolving block and porcelain unit as the principal element arranged for three-phase service. (A cutaway view of a typical terminal chamber-switch combination is shown for reference.) Askarel transformers with attached switches have been in use for about 30 years. When they were first introduced, the availability of insulating and gasketing materials was rather limited and even the best materials at the time had no service history. As a result, inadequate gasketing materials such as cork, nitrile rubber, and nitrile rubber-and-cork particles were used. While satisfactory for a limited period of time, these materials cannot be depended on for the expected long life of the equipment. The terminal chamber is usually above or below the switch compartment and separated by a steel wall through which the bushings are inserted. When bushings are properly selected and correctly installed, there is no leakage from one compart ment to the other. With poor bushing seals, and the terminal chamber above the switch, potting compounds or cable oil can seep into the askarel. When the terminal chamber is below the switch, askarel can drain into the terminal chamber. II. SOURCES OF CONTAMINATION There are three possible sources of contamination for askarel in switches and terminal chambers; they rank in this order of frequency: (1) water entering through poor gaskets; (2) decomposition products from arcing when switch is used to break magnetizing current; (3) entrance of pothead or cable compounds through leaky bushing seals. Unlike an askarel transformer where the amount of contaminant is likely to be very small (probably only trace amounts) in relation to the volume of askarel fluid -- in switches or terminal chambers with faulty seals, the amount of contamination can be relatively large. 0531692 TOWOLDMONOQ36123 Experience has shown that, based on the number of installed askarel-switch units, the percentage of failures is extremely small. When investigated, it has been found that most failures originate in the switch chamber. Water is the chief source of contamination. However, heavy contamination of askarel with petrolatum and asphalt material, due to leakage, have caused a few failures. Petrolatum is used frequently for filling terminal chambers. When either cable oil or petrolatum seeps into askarel, no great harm results. The fire resistance will be somewhat decreased and power factor of the askarel will increase with an accom panying drop in resistivity. While highly undesirable, it is doubtful that failure of the unit results. Where asphaltic compounds are used in place of petrolatum, the danger is increased somewhat because asphaltic contamination may cause exces sively high dielectric losses in the askarel. When the terminal chamber is below the switch chamber, the potting compound can be contaminated by askarel if the bushing seals are leaky. This is undesirable because the askarel will increase the power factor and conductivity of the potting compound or cable oil and develop heat from dielectric loss. If this mixture is drawn into the cable insulation, a cable failure is likely. This again emphasizes the impor tance of tight bushing assemblies. III. SEALING SWITCHES AND TERMINAL CHAMBERS Proper bushing construction, use of Silastic seals and welding wherever possible is highly desirable (as covered in Section A). Where an elastomeric seal is to be used in contact with both askarel and petroleum oil, DuPont's Viton is suggested. For new equipment the user should specify these modern sealing arrangements to keep out contaminants and minimize maintenance. IV. MAINTENANCE FOR ASKAREL FILLED SWITCHES A. Switches used for grounding after power source has been de-energized will not undergo arcing. B. Switches interrupting magnetizing current will be subject to arcing; the amount of decomposition will depend on power interrupted, time and frequency of oper ation. As a general rule, the liquid should be checked after 5 to 10 operations. 19 0*31693 TOWOLDMONOQ36124 1. On newly installed switches, check the askarel at 3,6 and 12 month intervals; if found satisfactory, check once annually thereafter. With proper attention to the gasketing of covers and bushings, experience will probably indicate that less frequent inspection is warranted. 2. Check askarel for: a. Dielectric strength (ASTM D877): It should be 26 KV minimum. If dielectric strength is low, confirm presence of water by Karl Fischer method ASTM D-I533. Filter to remove moisture. Dielectric strength should then be 30 KV minimum. b. Presence of carbon from arcing: Fluid should be relatively free of carbon. If badly arced and very black, replace fluid. If only minute amounts of carbon are present, filtration is recommended. Check power factor of liquid (should not be over 5% at 25C. and 60 cycles). Flush out switch chamber with several gallons of fresh askarel before refilling. 3. If there is discoloration, high power factor, detectable change in specific gravity or refractive index, or if fluid flashes below 250F., there is a possibility of seepage of potting compound into the switch compartment. In this case, correct any leaky bushing seals with proper replacements and fill with new askarel. 4. If terminal chamber is below switch, check potting compound for presence of askarel (can usually be detected by odor or by an increase in specific gravity). If askarel is present, correct any leaky bushing seals with proper replacements, and renew compounds. 5. Examine cover gaskets visually. Deterioration can be detected by swelling and cracking of the exposed edge. In cases of severe deterioration, liquid seepage is usually present. 6. Check for leakage at packing gland of switching shaft, (f leaking, repack with a Silastic ring type gasket. 0531694 -T TOWOLDMONOQ36125 SECTION C ANALYTICAL SERVICES ON TRANSFORMER ASKAREL AVAILABLE FROM MONSANTO Transformer users not wishing to make their own fluid analyses can obtain the service from Monsanto. Simply contact Monsanto and specify what analyses are wanted. You will be sent the proper-sized sample container filled with fresh askarel. When you receive this, empty it and carefully take your sample (following the procedure for sampling in this guide). Send the container to Monsanto's laboratory. Charges listed include sample container, shipping, handling and laboratory costs. Types of Analyses Available Analysis 1) ROUTINE MAINTENANCE CHECK Total Charge: $20.00 To determine the general condition of the fluid and find whether further analysis is neces sary. (one-quart sample required) Properties Tested Color and Condition Dielectric Strength Moisture You will be notified of the results of this test. If further testing is indicated, and you want a complete analysis, you will be sent a five-pint sample container. This sample will be used for the following series of tests: Analysis 2) COMPLETE ANALYSIS Total Charge: $50.00 (a) To determine the extent of fluid contamination, (b) earth refinement to determine what degree of restoration of electrical and insulating properties is possible, (c) check test to see how the fluid responded to earth treatment. a) Complete Analysis: to determine the extent of contamination Properties Tested Color and Condition Specific Gravity Refractive Index Water Free Chlorides Acidity Dielectric Strength Power Factor, Dielectric Constant, and Resistivity 21 0531695 TOWOLDMONOQ36126 b) Earth Refinement Response: Consists of treatment for 2.5 hours at 50-60C. with 0.1 to 0.2 percent by weight of properly conditioned Attapulgus clay and then filtration through dry filter paper. c) Analysis After Laboratory Earth Refinement: Properties Tested Refractive Index Water Free Chlorides Acidity Dielectric Strength Power Factor, Dielectric Constant, and Resistivity You will be notified of the results of this test series on your sample. Then aftei refining your entire transformer fluid fill you can check on the results by requesting the following analysis: Analysis 3) ANALYSIS AFTER EARTH REFINEMENT Total Charge: $30.00 (This charge will not apply when analyses 1 and 2 have already been made.) To determine whether the entire lot of the askarel fill responded to the same extent as the laboratory sample, (five-pint sample required) Properties Tested Color and Condition Refractive Index Water Free Chlorides Acidity Dielectric Strength Power Factor, Dielectric Constant, and Resistivity To arrange for the tests described above write to the following address: Paul G. Benignus Monsanto Chemical Company 800 North Lindbergh Blvd. ' St. Louis 66, Missouri Samples to be tested should be clearly marked for identification and sent directly to: Monsanto Chemical Company W. G. Krummrich Laboratory Monsanto, Illinois Attention: R. Kuster OS***96 1 22 TOWOLDMONOQ36127 APPENDIX APPENDIX A -- Askarel Stability and Composition of Arc Formed Gas: Askarei insulation is one of the most inert, chemically-stable heat resistant, non corrosive liquids known. It will not break down, oxidize or sludge when exposed to air and high temperatures, 150C. or even somewhat higher. Arcing, however, will break down the compound to liberate some hydrogen chloride and small amounts of carbon. APPROXIMATE COMPOSITION ARC FORMED GAS FROM TRANSFORMER ASKAREL Gas carbon monoxide........................ .. carbon dioxide............................... oxygen............................................. inert gases....................................... hydrogen chloride......................... (note the absence of phosgene) Amount 0.3 per cent 0.3 0.6 1.5 97.3 This arc-formed gas is non-flammable and non-combustible. These requirements must be met in accordance with the Underwriters' Laboratory for permission to use the term askarel. Mineral oil evolves combustible hydrogen and hydrocarbon gases. For all practical purposes, the amount of gas liberated from mineral oil or askarel under a given set of conditions is about 100 cubic centimeters per kilowatt-second. APPENDIX B Carbon dioxide............... Air..................................... Nitrogen........................... Hydrogen chloride1 .... 1) In absence of scavenger SOLUBILITY OF GAS IN TRANSFORMER ASKAREL Percent of Gas By Volume Corrected to: 2SC. 760 mm 0C. 760 mm 2SC. 100C 2SC 100oC. 71% 47% -- -- 5.7 4.9 5.8 5.0 6.0 4.8 5.5 4.4 37.8 50.9 -- -- 0*3^,T 23 TOWOLDMONOQ36128 APPENDIX C APPROXIMATE VAPOR PRESSURE vs. TEMPERATURE FOR TRANSFORMER ASKAREL Temperature C 40 60 80 100 120 140 Inerteen PPO, 7336-9 1 mm Hg. 5 9 30 60 90 Transformer Pyranol A13B3B 0.9 mm Hg. 3.5 8.3 18 32 53 APPENDIX D EFFECT OF TEMPERATURE ON DIELECTRIC STRENGTH OF ASKAREL Temperature C. --60 --40 --20 0 20 40 60 80 Dielectric Strength 67 KV 63 57 55 50 50 48 45 APPENDIX E COMPARISON QF THE APPROXIMATE VISCOSITY IN SAYBOLT UNIVERSAL SECONDS OF TRANSFORMER ASKARELS AND MINERAL OIL Temp. *C. --20 0 20 40 60 80 100 Transformer Pyranol A13B3B 1,000 (00 70 45 39 34 30 10-C Mineral Oil 1,000 150 85 49 40 34 30 Inerteen PPO, 7336*9 2,800 195 85 50 40 36 33 l24 0531698 TOWOLDMONOQ36129 APPENDIX F THE DENSITY OF INERTEEN PPO 7336-9 AND TRANSFORMER PYRANOL A13B3B Approx. Density gm /cc. Transformer -Temperature C. Inerteen PPO, 7336-9 Pyranol A13B3B 0 1.574 1.577 20 1.552 1.555 40 1.529 1.532 60 1.507 1.510 80 1.485 1.488 APPENDIX G The thermal conductivity values of transformer Pyranol A13B3B at 27C. and 58C. are 26.2 and 25.8 x 10'5 calories centimetersdegrees centrigradesecond'1, respectively. Or, approximately 0.06 BTU per (hr.) (sq. ft.) (F.) per foot. This same approximation applies to Inerteen PPO (7336-9). APPENDIX H Heat Capacity Over the temperature range of 25 to 125C. the specific heat of transformer askarel is close to 0.30 calories per gram per degree. APPENDIX I Coefficient of Expansion The average coefficient of expansion of transformer askarel over the temperature range 20 to 100C. is 0.007 cc /cc /C. One gallon would increase to 1.056 gallons on heating from 20 to 100C. APPENDIX J Fire-Resistance To use the generic name "askarel," the fluids must be approved by the Underwriters' Laboratories as possessing adequate fire-resistance and freedom from forming explosive gases when arced. These liquids do not have a burn point (ASTM D92-33) (Cleveland open cup method) up to about 205C., at which temperatures they begin to boil. The significance of this is that they do not burn or support combustion under conditions encountered in transformer operation. Thus the danger of secondary explosion (or fire) is eliminated. 0531699 25 TOWOLDMONOQ36130 APPENDIX K Seals, Properties and Procurement Dow Corning Corporation, Midland, Michigan with District's at Atlanta, Boston, Chicago, Cleveland, Dallas, Los Angeles, New York City, Washington, D. C. and Toronto has available Bulletin 09-019, August 1962 entitled "Silastic Design Data1*. This lists the gasket fabricators throughout the country from whom the "Silastic 50" gasketing can be purchased in sheet, extrusions or molded shapes. Generally Silastic 50 sheet goods are stocked by local die cutters, hence, could be generally purchased locally. Usually, small quantities of gaskets are die cut. If larger quantities are needed, tools are made of the same type used to cut other elastomersWhere the gasket is extruded for fitting into a machined groove or between gasket stops, Dow-Coming advises use of a scarved joint. This joint is then cemented using Dow Coming's Silastic 140 (clear) or their RTV 731 (white) materials, which air cure. Dow Corning points out that the local "rubber" fabricators purchase the Silastic 50 in billet form. This is worked on a roll mill in preparation for sheeting or extrusion. Then to obtain the desired physical properties the fabricator must oven cure the Silastic 50 for 24 hours at 480DF. SPECIFICATIONS* Color..............................................White Specific Gravity at 77F..............1.20 * 0.02 ASTM D676 -- Hardness, Shore A. Scale.......... 45 to 60 ASTM D412 -- Tensile Strength, psi. min........................... 800 ASTM D412 -- Elongation, percent, min.............................250 ASTM D395 -- Compression Set after 22 hours at 300F., percent, max............................... 30 * All physical properties measured on 0.075 inch thick samples molded 5 minutes at 240F., and oven cured 24 hours at 480F. General Electric Company, Redmond Circle, Rome, Ga., uses silicone or DuPont's Viton wherever it is not possible or desirable to weld. For some small seals, where good matching surfaces are provided, Flexitallic stainless steel rings are used. By contacting the Engineering Services Department of General Electric Company, Redmond Circle, Rome, Ga., users of Pyranol transformers made prior to develop ment of these modern seals will obtain prompt assistance for conversion. Users of askarel transformers made by other manufacturers should contact the original transformer manufacturer, or Monsanto for assistance in converting to these modem seals. 0531700 TOWOLDMONOQ36131 NOTES 53l/0i TOWOLDMONOQ36132 MONSANTO FUNCTIONAL FLUIDS DEPT. 800 N. LINDBERGH BLVD. ST. LOUIS, MISSOURI 63166 The information herein regarding obtaining optimum results from askarel fluids in your transformer has been accumulated by Monsanto for over 30 years from the experience of makers and users of askarel transformers and it is believed will be helpful. Nothing herein shall be construed as applying to other than askarel insulation. Data and maintenance suggestions herein do not apply to the other components of the transformer. All operating and maintenance suggestions recommended by the manufacturer of the transformer should also be carefully followed. Because these maintenance directions apply only to the askarel insulation, Monsanto disclaims any liability for damage to property or injury to persons arising from transformer operation. 8-5420-0567-44 033170* LIlho InU.S.A. TOWOLDMONOQ36133