Document V3RM6OqBy4LeVkVE68zQBeZLw

SECTION SEVEN ASKAREL TEST AND MAINTENANCE GUIDE COPYRIGHT, By Dobk Engineering Company DSW 357979 IF : STLCOPCB4086667 ASKAREL TEST AND MAINTENANCE GUIDE GENERAL This guide is intended to cover problems encountered with askarel-filled bushings, disconnect switches, and transformers and the askarel used therein, by operating and maintenance departments of utilities. No attempt has been made to cover other askarelfilled devices, e.g. , cables, capacitors, etc., since the askarel used in these devices is usually somewhat different chemically, electrically and/or physically, and they present different test and maintenance problems. The test and maintenance programs of askarel consumers vary from no tests or preventative maintenance, in the case of most small industrial plants having only one or two relatively inexpensive low-voltage, askarel-filled devices, to very complete accept ance and periodic tests and a comprehensive preventative maintenance program in the case of some large utilities. The majority of industrial plants and small utilities make only dielectric-strength tests on askarel samples. The extent of the askarel test and maintenance programs of any askarel consumer should be based on economics. A utility operating several askarel-filled bushings cannot justify the askarel test and maintenance i programs of a utility having thousands of gallons of askarel in service in disconnect switches and transformers. Consideration of these facts, variables resulting from local i conditions and the wide variation in the cost of various askarel-filled devices, illustrate the difficulty of attempting to recommend test and maintenance programs for askarel consumers. - To assist consumers in developing economical, practical askarel test and main tenance programs, the properties, application, and hazards of askarel are cited. Meth ods of handling, storing, sampling, and treating are described. The various askarel tests in general use are discussed and their significance, if known, is given. PROPERTIES The term "askarel" describes a broad class of non-flammable, synthetic, halogenated, hydrocarbon, insulating liquids processed by the Monsanto Chemical Company that have been used for over 30 years as an insulation and coolant in electrical apparatus and cables. This inert compound is chemical and heat-stable, fire-resistant, non-cor rosive, and has high dielectric strength under normal operating conditions in electrical apparatus and cables. Numerous manufacturers of electrical apparatus and cables have their own trade name for the askarels they supply, e.g. , Chlorextol, Dykanol, Inerteen, Noflamol, and Pyranol. In specifying a specific askarel, it is necessary to specif-- the designation and trade name, since some trade names cover a number of different types of askarel. The chemical, electrical, and physical properties of askarels vary widely as indicated by the following examples which are not all-inclusive: PROPERTY RANGE Dielectric Constant Electrical Resistivity Pour Point Physical Specific Gravity Viscosity 4.0 to 5.0 at 25C 10** ohms/CM^ minimum at 100C k 500 volts d-c -44C to + 10C Resin-like, non-crystalline composition to thin, mobile liquids 1.50 to 1.58 (15. 5/15. 5C) 43 to 100,000 seconds at 37.8C (SUS) RILG567 DSW 357980 7-1 STLCOPCB4086668 Other properties of askarel are given under the heading "SPECIFICATIONS. " At low temperatures, i. e. , well below zero degrees C. , the dielectric constant of askarel is approximately equal to the dielectric constant of insulating oil. At higher temperatures there is a region of anomalous dispersion in which the dielectric constant of askarel in creases. From room.temperature to the maximum practical operating temperature, the dielectric constant of askarel is approximately twice the dielectric constant of insulating oil. It is advantageous, in the design of some electric devices, that the dielectric con stants of askarel and cellulose insulation are approximately the same. Askarel is mixed with insulating oil to obtain a liquid insulation having the optimum dielectric constant for filling some types of bushings. Such mixtures are flammable. Fortunately, there are only two types of askarels used in transformers, Pyranol1470 and Inerteen-PPO. Askarels for transformers with other trade names will be iden tical with one of these askarels. The significant difference in these askarels are their pour points and the chloride "scavenger" compounds. However, these two types of askarels can be mixed in any proportion without any undesirable effects. The solubility of water in new askarel is approximately 125 ppm at 25C which is greater than in new insulating oil. As askarel ages, there is very little increase in the solubility of water in it; whereas the solubility of water in insulating oil increases rapidly as the oil ages and deteriorates. The solubility of water in askarel, as in insulating oil, increases rapidly with temperature. Askarel demulsifies more than twice as fast as oil and since it is much heavier than water, water rapidly rises to its surface. Askarel has a greater affinity than insulating oil for moisture. It will transmit more moisture to cellulose insulation than insulating oil will under the same conditions. The insulation in an askarel-filled transformer is more difficult to dry than insulation in an oil-filled transformer. An outstanding advantage of askarel is that in addition to having excellent dielectric properties, it is non-flammable and will not evolve explosive gaseous mixtures when dis integrated either by extreme heat or by an electric arc. It is inherently stable, thus eliminating the oxidation and sludging experienced with insulating oil. Askarel is non corrosive and will not deteriorate cellulose insulation. Insulating oil and other petro leum products are completely miscible with askarel. Small quantities affect its non- flammable properties. Contamination of askarel with any petroleum product should be carefully avoided, particularly since it is practically impossible to separate askarel from petroleum products. In the case of mixtures of askarel and insulating oil, contam ination with any petroleum product may seriously alter the dielectric constant and result in an operating hazard. The addition of only two per cent insulating oil to askarel will decrease its fire resistance. When askarel is subjected either to temperatures in excess of 200C or to an elec tric arc it disintegrates and hydrogen-chloride gas is formed. Hydrogen-chloride gas dissolves in water and forms hydrochloric acid, the strength depending upon the ratio of hydrogen-chloride gas to water. Hydrochloric acid quickly attacks metallic parts and rapidly deteriorates cellulose insulation of electrical devices. This undesirable char acteristic can be mitigated by the addition of a fraction of one per cent of a hydrogenchloride "scavenger" which has no appreciable effect on the properties of askarel. If askarel is exposed to an electric arc in a closed vessel, high pressures are created because the volume of the products of disintegration are greater than the volume of the askarel. Where the arcing is severe, the vessel will rupture unless it has a suit able pressure-relief device. In case of violent arcing that results in extremelv ranid- pressure buildup, vessels with pressure-relief devices may rupture. DSW 357981 7-2 RILG567 ^ - - j STLCOPCB4086669  Askarel is an excellent solvent for many materials which perform satisfactorily in insulating oil, including paint, varnishes, gums, resins, some plastics, and many of the rubber and rubber-like materials. Such materials should neither be used in askarel-filled devices nor be allowed to contact askarel under any condition. Materials such as asphalts asphalt-base materials, moisture, and other foreign matter which contaminate insulating oil also contaminate askarel. It is, therefore, essential that askarel-filled devices be insulated with pure cellulose, untreated paper and cotton, porcelain, and other materials that neither affect nor are affected by askarel. Likewise, it is essential that cork gas kets or gaskets of other material that neither affect nor are affected by askarel be used in askarel-filled devices. HAZARDS It is not hazardous to handle askarel provided simple precautions are taken. Ac tually, it is handled practically the same as insulating oil. Unlike insulating oil, there is no fire hazard in handling askarel. Most people can handle askarel in the same manner as insulating oil without fear of toxic effects. Like insulating oil, some people are aller gic to askarel and continued exposure will result in local skin irritation. Avoiding un necessary contact with askarel and its vapor, particularly when it is hot, and cleanliness of workmen handling askarel, constitute adequate safeguards against such effects. Medic inal washes or detergents followed by an application of cold cream will eliminate any irri tation resulting from askarel coming into contact with an open cut or skin abrasion. A drop of castor oil will neutralize any irritation caused by contact of askarel with the eyes. There is no evidence that ordinary exposure to askarel vapors results in any ill effects. However, like other volatile materials, exposure to concentrated askarel-vapors should be avoided, particularly in closed, unventilated rooms. The odor of askarel vapor should give sufficient warning of a hazardous concentration of askarel vapor. As with many volatile liquids, the vaporization of askarel increases rapidly with temperature. There fore, ventilation, which is adequate for handling askarel at room temperatures, probably will not be adequate for handling askarel at elevated temperatures. The gases produced when askarel is disintegrated by very high temperatures or an electric arc contain a high percentage of hydrogen chloride, a small percentage of carbon dioxide, carbon monoxide and oxygen and, in some cases, a small amount of phosgene. Very small concentrations of this combination of gases are very unpleasant and irritating, thus giving ample warning of their presence and preventing dangerous exposure of per sons. The "all-purpose" gas-masks, available for use around oil-filled devices, offer ample protection from gases liberated from disintegrated askarel. APPLICATION Askarel-filled transformers should preferably be installed in well-ventilated en closures. Where necessary, a pipe may be run from the pressure-relief device to the outside of the building to safely dispose of the gases resulting from askarel disintegration. This pipe should not be smaller than the pressure-relief device and should contain the minimum practical number of elbows. Where such piping or adequately-ventilated en closures are impractical, gas absorbers may be used. Fireproof vaults are not re quired for askarel-filled transformers. The temperature of the top askarel in transformers should not exceed 90C. Askarel-filled transformers should be operated and loaded in accordance with the Amerlean Standards Association Designation C-57. RILG567 DSW 357982 7-3 STLCOPCB4086670 The effects of moisture on askarel-filled devices are even worse than on oil-filled devices. Water is more soluble in askarel than in insulating oil. The water solubility increases rapidly with temperature. In an askarel-filled device, water will float on the top of the askarel. In a transformer, water floats on top of the askarel where the ternperature is high during operation, thus saturating the top askarel with water at a rela tively high temperature. As askarel circulates in the transformer due to the tempera ture difference between the top and bottom of the radiator tubes, askarel saturated with water at high temperatures flows to cooler parts of the transformer tank where part of the water condenses out of the askarel. Some of the water will rise to the top of the aska rel and some will be attracted into the cellulose insulation of the transformer by the elec trostatic field. Since cellulose has a higher affinity for water than askarel, water can be removed from cellulose insulation in askarel only by very high winding temperatures. For these reasons, askarel-filled devices are generally sealed with a positive pressure of nitrogen maintained over the askarel. Sealing askarel-filled devices also insures against the loss of volatile fractions of askarel. Hydrogen chloride detectors are available for mounting in the top of askarelfilled transformers. They will operate when a small amount of hydrogen chloride is evolved from askarel due to a very small arc. These detectors may be applied either to sound an alarm or to de-energize the transformer. They are affected only by hydro- ' gen chloride. Pressure detectors are much slower than these detectors. The use of hydrogen-chloride detectors to de-energize askarel-filled transformers will insure the minimum deterioration of askarel due to an arc. CONTAMINATION Much greater care must be taken in applying, handling, storing, sampling, and testing askarel than is generally taken with insulating oil, since askarel is more sus ceptible to contamination and is more hygroscopic than insulating oil. Generally, aska rel-filled devices and storage containers are sealed to insure against the entrance of moisture. The maintenance of a slight positive nitrogen-pressure over askarel will insure against breathing. The contamination of askarel by many materials, i. e. , asphalts, asphalt-base materials, varnishes, gums, resins, dirt, and other foreign matter, some plastics, rub ber and some rubber-like materials, is usually apparent upon visual examination of a small sample. Such contamination, with the possible exception of dirt and some other foreign matter, can be readily detected with power-factor tests on small samples. As with insulating oil, the presence of suspended water and some foreign matter can be detected with dielectric-strength tests. Under some conditions, the Cloud-Point test is useful for detecting suspended and dissolved water in askarel. Contamination of askarel by insulating oil and other petroleum products is usu ally determined by Fire-Point (D-92) or preferably by Volume of Oil in Oil-Contaminated Askarels (D-1808) tests, the latter being the most sensitive test for slight contamination. It has been reported that accurate measurements of the Refractive Index (D-1807) of a sample of askarel that is not contaminated and an identical sample contaminated with a slight amount of insulating oil or other petroleum product may be different. Disconnect switches filled with askarel and transformer taps under askarel should not be operated while they are energized. Such operation will disintegrate the askarel; and if it does not contain a hydrogen-chloride "scavenger. " rapid deterioration -of insulation and severe corrosion of metallic parts will occur. If the askarel contains a hydrogen-chloride "scavenger,' such operation will use up the "scavenger" which may be badly needed later. 7-4 DSW 357983 RILG567 PMPfOWM'r1 STLCOPCB4086671  STANDARD TEST METHODS The American Society for Testing and Materials (1916 Race Street, Philadelphia Pennsylvania - 19103), Committee D-27 on Electrical Insulating Liquids and Gases, has developed numerous methods of tests for askarels which have been published. These test methods cover all tests on askarel that are generally used today by askarel consumers. Many of their test methods have been approved as American Standard by the American Standards Association. All ASTM test methods are periodically reviewed and are re vised when advantageous. Additional test methods are developed as required. Since ASTM askarel test-methods are readily available at a nominal price, they will be fre quently referred to but not duplicated herein. Either separate copies of any ASTM test method or standard or various compilations of test methods and standards may be pur chased by anyone from the ASTM in any quantity. It is recommended that all askarel tests be made in exact accordance with the ap plicable ASTM test methods. If ASTM methods are carefully followed, accurate results will be obtained. The use of ASTM methods will permit correlation of results of two or more laboratories which is advantageous when determining limits of test values. This may be impractical for some field tests. However, field tests are, in general, screening tests used only to determine whether askarel samples should be sent to a laboratory for more complete and more accurate tests. It is essential that consumers use applicable ASTM test methods in making ac ceptance tests on askarel. These test methods are in general use in the industry and are invariably referred to in purchase specifications. The use of other test methods usually result either in a disagreement with the supplier or test results that are not in dicative of the true properties of the askarel. SPECIFICATIONS . The specifications shown on Table I are suitable for procuring either type of askarel for transformers. In specifying other types of askarel, it is probably the best practice to follow, the recommendations of the electrical apparatus manufacturer. TESTS UPON RECEIPT Upon receipt, bushings filled with askarel or a mixture of askarel and insulating oil should be inspected and tested in the same manner as similar oil-filled bushings. Samples of askarel are rarely taken from bushings for tests unless there is some def inite indication that such tests would be advantageous. Askarel-filled transformers and disconnect switches should be inspected and tested upon receipt in the same manner as similar oil-filled devices. In addition, any device designed for operation with nitrogen over the askarel should be carefully tested for gas leaks. The most sensitive method of detecting nitrogen leaks is to add a small percentage of helium to the nitrogen and check the outside of the device for helium with a Mass Spectrometer. A less expensive method with good sensitivity is to add a small percentage of halogen gas, such as sulfur hexafluoride, and check the outside of the de vice with a Halogen Detector. Large leaks can, of course, be located by applying nitro gen pressure and soaping the exterior surface of the device. However, this method is useless for small leaks. RILG567 DSW 357984 7-5 STLCOPCB4086672 o r- A A _ bo NgO >Gh m3 . o -I ^ ** 5 u G o <u A Is2m -- m -- or-oo^ovo cm "H rcm vO in in^ o m . ^ m *-Ucnocnm-- m i --h o in rM* oo o bo r- G m CO o W P M* IH G '-- o in m^ om o m o 4> o CO -H vD m m ^ o . in . . --i T* . o V c o h O ^ o fO^HHOO^ Tf i ^ Z H Q O ffi H W 2 0s m o o --* r- o 2 m -h m^r-^'OcMCM^4 mr-r-rM--'cooocMcooor-oorM E-i M ^ CO 0s ^ rM 0^ i--< flQ 0N (-H 0v 5 I Q I II I I II I I I III QQQQQQQQQQQQQ sGH fot Ou in flu>S 5 in U O' cm ^ m O, o TJ vgPs. vfeP oo Tf O' cH e o N m n Tji in -- ^ enW o 4o-* 4o-> 4o-> m in -- ^O' CO 0s N N N n fO & 0 TJ -SfrP' W Wop' wO <0 in m in m m in vO O' 4o-> >2C v Id TD O ?K ho u~ G 0) T3 U _ MH o G|G2 ^- o5 ua) O' B c 2 ^ m 2 h p 6 VM ft .5 3 G GI H 4-* H--OI 43 J3 O 00 V-I bO Gh in G a) 43 +1 m o nO s *5 L- 4- 0 <u 73 E 13 > G pG Ow 4) OH X o 4) G (M CM a4> o u Oa o --o o o G<y 0~0h >s x o G V o * ^ 43 CM O CM U O a CO G 0 pO u G o o h O 4>3s > >* G 4a3> a G u to G 4) CO J* id S| M 4< 60 4) s-s G hm G CM O 0) ^ O 1 cm m O 3 " J3 C 5O 7"r3t UX ^O id C ** E0 O' CM ^ -H h r- n r- (M CM O' 00 I I I -- Q QQQ Q X *e>4 x id 2id 2 2> E 2a .-Vo * E` .iXd oO 2 Oo Sin 2 o im "H . a to 4) Td X Id c V o M u ft A & u in D in O o cm id A in H mm 1-^-5 c ftffi " 2 g 2 S -S N - -o 00 co 4) t-3 in u *+o4 4) ti nd 44-) G to to u 4) 4) M a h O U uH u 4) fl5 a*io wH aPi w A s s EO Pi 2A -O g C 5h U q X Mm o 4 e o E .H .E "OnV"/ ^. 4i-nS h J .ti M -W o U O -g ^ iJ .2 o o - O .a .2 O O^ <Q Q uS _ il JS " lT 'O oC 6 > G 2 u u G 4-> u +j J; .#o4 ,[^xj >.4h- ^G pg4 oo o E rt n go A& H U 4> o S >4 2 o u a a os '*C4O > 02 4) h a wtn e iud Ou n rt o -0 s s f-<>d4 G tpo4 4) P G. 2 AO bo to x u--^ 4) 53 O ^5 o 2X G oeo ^o G M O & G *H G .tJ SP-3 4o- G O U o, u. 2 o u o <; 3 a V bo G 4) G O (A CO 4) CO G a T3 4) E ^4 o Ui o M < DSl/V 357955 7-6 RILG567 STLCOPCB4086673 When transformers are shipped without askarel, they are always filled with an in ert gas such as nitrogen. The transformer should be checked to determine if it contains a positive pressure of nitrogen. The dew point of the nitrogen should be tested to detect the entrance of moisture. Before anyone enters the transformer tank, the gas should be completely displaced with air to insure against suffocation. Under some temperature conditions askarel may condense on the surface of glass pressure-relief diaphragms and glass askarel-level gauges. Such condensation may ap pear to be water. Before condemning an askarel-filled device for being wet when such condensation is found, dielectric-strength and power-factor tests should be made on sam ples of askarel from the top of the device. If the results of these tests are satisfactory, the condensation is not water. An askarel sample should be taken from the top and bottom of each askarel-filled transformer, disconnect switch, and container upon receipt. The samples should be visually examined and subjected to a dielectric-strength test. If the samples are not a clear, light-straw color, careful checks should be made to determine the source of con tamination which should be quickly eliminated and the askarel should be treated in a man ner that will remove the contaminant. If the dielectric strength should be less than 30-kv, the cause should be determined and remedied and the askarel should be treated to remove the moisture or other contaminant. It is advantageous to make color and power-factor tests on new askarel. Powerfactor tests are invaluable for detecting slight contamination of askarel. In the past, several manufacturers have inadvertently used askarel-soluble materials in askarelfilled devices. Where these materials were not found and eliminated prior to placing the devices in service, the devices have failed. Where large quantities of askarel are purchased, it may be advantageous to sub ject several samples from the shipment to one or more of the following tests which are listed in the order of their apparent importance: ' TEST ASTM METHOD Combustible Arc-Formed Gases or Fire Point D-92 Hydrolyzable Chlorides D-1820 Inorganic Chlorides D-1821 Neutralization Number D-974 or D-664 Pour Point D-97 Scavenger Content D-1701 Under some conditions the Refractive Index (D-1807) and Viscosity (D-88 or D-445) may be of interest. It is suggested that all tests made periodically on askarel in service should also be made on each shipment of new askarel received whether required for the acceptance of new askarel or not. In making such tests, the same methods should be used that are used in making periodic tests. .If periodic and acceptance test methods are different, tests using both methods should be made. Such test data is invaluable in detecting changes in askarel during its life. 1 RILG567 DSW 357986 7-7 ------------------------------------- w STLCOPCB4086674 HANDLING AND STORAGE Absolute cleanliness is even more essential in the handling and storage of askarel than in handling insulating oil, because askarel is more susceptible to contamination and is more hygroscopic than insulating oil. Askarel may be handled and stored in a manner .similar to insulating oil, provided clean all-metal containers, piping, pumps, hose, fit tings, etc. , are used. During handling and storage it must not be allowed to contact nonmetallic material. It should preferably be handled in closed systems in a manner that will minimize aeration and the loss of volatile fractions of the askarel. Since askarel is very hygroscopic, it should not be exposed to humid air. It is recommended that com plete separate facilities be provided for askarel and insulating oil to insure against con tamination of askarel with insulating oil, as such contamination may result in a flamma ble, explosive mixture. It is possible, but rather impractical, to clean facilities nor mally used for handling and storing insulating oil sufficiently to insure against contam ination of the askarel. If the facilities are used for storing and handling both insulating liquids, sooner or later someone will forget the essential cleaning job. Where it is essential to clean handling and/or storage facilities used for insulating oil so that they can be used for handling and/or storing askarel, all oil should be care fully removed with a volatile solvent such as white gasoline, benzine, etc. Thorough cleaning will, no doubt, require several applications of the solvent. The solvent should be completely evaporated before using the facility for askarel to insure against contam ination. Askarel-filled devices and askarel containers should not be opened unless the temperature of the askarel-filled device and container is higher than the ambient air tem perature. When necessary to store askarel-filled devices, they should be stored with aska rel up to the normal operating level. They should be sealed and, if possible, there should be slight positive pressure of nitrogen over the askarel. It is essential to store askarel in sealed containers, preferably under dry nitrogen at a slight positive pressure. This insures against contamination by moisture, dirt and other foreign matter. It also prevents the loss of the volatile fractions of the askarel. In order to minimize the aeration of askarel, containers and electrical devices should be filled from the bottom. It is preferable to flush air out of the device or con tainer with dry nitrogen before filling with askarel, and maintain nitrogen over the askarel during the filling operation. ROUTINE MAINTENANCE The usual test, inspection and maintenance program for oil-filled bushings, dis connect switches and transformers should be followed for similar askarel-filled devices. The pressure of nitrogen over askarel should be checked each time an askarel-filled de vice is inspected or samples of askarel are taken from the device. Askarel should be sampled and tested upon receipt of askarel-filled disconnect switches and transformers immediately before placing the device in service, after the device has been in service a week, and then semi-annually thereafter under normal op erating conditions. Under abnormal conditions, more frequent sampling and testing may be advantageous. DSW 357987 7-8 RILG567 STLCOPCB4086675 During routine inspections of askarel-filled devices, a careful check should be made for askarel on the outside of the device due either to spilling or leaking. In order to protect paint and insure against corrosion, askarel should be promptly removed from the exterior of askarel-filled devices with a suitable solvent, i.e., white gasoline, ben zine, etc. When it is necessary to replace gaskets on askarel-filled devices, care should be taken to insure against the use of gaskets or gasket-compounds that are affected by, or that may contaminate askarel. If it is not definitely known that the gasket or gasketcompounds are compatible with askarel, a test of compatibility should be made. Askarel-filled transformers usually have pressure-relief devices. These devices should be included in the transformer inspection program. It is advisable to add a hydrogen-chloride "scavenger" to askarel in disconnect switches and transformers that do not contain one, to reduce the danger of serious de terioration of insulation and rapid corrosion of metallic parts in case of an arc-over in the askarel. The power factor of askarel may be increased slightly by the addition of a "scavenger." The disadvantage of the increase in power factor is more than offset by the advantage of the "scavenger." A suitable "scavenger" can be obtained in sealed con tainers from suppliers of askarel-filled devices. The supplier's instructions for adding the "scavenger" to askarel should be carefully followed. It is desirable to notify the manufacturer when a hydrogen-chloride "scavenger" is added to askarel in an electrical device. The name-plate of the device should be marked to indicate this change. Under some low temperature conditions, some "scavengers" will precipitate out of askarel. This is not harmful and will not change the electrical properties of the aska rel. The "scavenger" will redissolve when the temperature rises. SAMPLING The sampling of askarel is similar to the sampling of insulating oil. It is rec ommended that the ASTM Method for Sampling Askarels (D-1809) be used for all sampling. Accurate sampling is extremely important from the standpoint of evaluating the quality of askarel. Particular care must be taken to prevent askarel touching any material which may contaminate it during sampling, handling or storage of the samples. Aeration of askarel during sampling should be held to the practical minimum. Since askarel is more hygroscopic than insulating oil, greater care must be taken to prevent exposure of aska rel to moist air. Askarel should be sampled only on clear, dry days and when the askarel temperature is above the ambient air temperature. Top samples must be taken from the top surface, not just below the top surface. Many askarel-filled devices are equipped with sampling devices which facilitate obtaining samples from the top surface of the askarel. Before taking samples from an askarel-filled device or container that has been moved, it should be allowed to settle for at least 12 hours so that if there is any moisture, it will rise to the top. PERIODIC TESTS Since askarel is not subject to deterioration by oxidation as insulating oil is, it is only necessary to periodically test askarel for contamination and decomposition by an electric arcv It is not unusual to find askarel in electrical devices contaminated with bushing compound, pothead compound, varnish from transformer-winding insulation, matter dissolved out of gaskets of improper material and/or other foreign matter. RILG567 DSW 357988 7-9 STLCOPCB4086676 The probability of contamination of askarel with moisture depends on the design of the askarel-filled device, being greatest with free-breathing devices and least with sealed devices with nitrogen over the askarel. To insure against failure of askarel-filled electrical devices due to contamination or decomposition of askarel, periodic tests should be made on samples of askarel from all askarel-filled devices. Periodic tests on askarels should include the following: Color Dielectric Strength Power Factor Visual Examination - D-1702 or D-2129 - D-877 or D-1816 - D-924 - D-1702 If there is any possibility that the askarel is contaminated with insulating oil or any other petroleum product, Fire Point (D-92), or preferably Volume of Oil in OilContaminated Askarels (D-1808) tests should be made. In the event that askarel may have been exposed to an electric arc, tests should be made for Hydrolyzable Chlorides (D-1820), Neutralization Number (D-664 or D-974), and Scavenger Content (D-1701). Un der some conditions the Cloud Point Test (D-97) is a useful supplement to the Dielectric Strength and Power Factor Test for detecting moisture. The Pour Point (D-97) and Viscosity (D-88 or D-445) tests will indicate a change in askarel due to excessive evap oration of volatile fractions. TEST METHODS In addition to test methods included above, the following tests are also used for askarel for design purposes only: TEST Coefficient of Thermal Expansion - D-1903 Thermal Stability - D-1936 During tests on askarel, particular care should be taken to avoid askarel contam ination by askarel-soluble material, e.g. , cells insulated with phenolic material should not be used for Dielectric-Strength, Power-Factor and Resistivity Tests. In making Dielectric-Strength tests, only one shot should be made for each filling of the cup. Corrosion Tests and simple Fractional-Distillation Tests (D-20) are used by man ufacturers of askarel-filled devices to determine the quality of askarel. Unfortunately, methods of making these tests have not been standardized. The compatibility of askarel with gasket and other material can be tested as follows: 1. Measure the power factor of a sample of new askarel. (It should be 0. 05%orless). 2. Place about 0. 5% by weight of the material in question in the askarel. If the material is readily soluble, stir until dissolved and measure the power factor of the mixture. 3. If the material is not readily soluble, cover and let the mixture stand at room temperature. 4. After 48 hours, measure the power factor of the askarel. Note: Do not use a test cell or other vessel that may contaminate the askarel. 7-10 imm RILG567 DSW 357989 STLCOPCB4086677 o ^ < l J4 \ ; f //> f.l SCREENING TESTS It has been found that under some conditions it is advantageous to make periodic screening tests on askarel samples in the field to determine when askarel samples should be sent to a laboratory for more accurate and complete tests. Experience indicates that if the results of field tests of askarel samples for Dielectric Strength (D-877), Power Factor (D-924), and Visual Examination (D-1702) are satisfactory, other tests are not necessary, unless there is a possibility that the askarel is contaminated with some petro leum product. If contamination is possible, tests should be made for Fire Point (D-92), or preferably for the Volume of Oil in Oil-Contaminated Askarels (D-1808). The Doble-Type MH and Type MEU test sets have proven satisfactory and are rec ommended for determining the power factor of askarel in the field. The use of ASTM Method D-924 for the determination of the power factor of askarel in the field seems im practical, but can be performed conveniently in the laboratory by use of the Doble-Type M-O test set. Each supplier of askarel or askarel-filled devices has an askarel testing service for consumers who do not have the necessary facilities. Many consumers find it advan tageous to make screening tests in the field and utilize the manufacturer's service for the necessary laboratory tests. TESTS RECORDS To obtain the best results from an askarel test program, it is essential to keep complete askarel test records. These records should contain the results of each accept ance and periodic test, all special tests and the date each test was made. Without such test records, it is impossible to follow the change of the properties of askarel in service. SIGNIFICANCE OF TESTS GENERAL The results of tests on askarel are significant only when made under definitely prescribed conditions. It is difficult and often impossible to compare results of tests made by different methods. The significance and limits of test values which follow are based on samples taken and tests made in exact accordance with all applicable ASTM Methods. Where the significance of askarel tests is the same as for oil tests in Section Three, it is not repeated in this Section. " ARC-FOR MED GASES An electrical arc in askarel will produce combustible gases if it is not properly compounded by the producer or if it is contaminated with petroleum. This test, which has not been standardized by ASTM, is normally used as a specification requirement for new askarel. For used askarel, the test for the Volume of Oil in Oil-Contaminated Askarel (D-1808) is preferred. ' CHLORIDE COMPOUNDS, HYDROLYZABLE (D-1820) This method provides a quantitative measure of the stability of the askarel to hydrolysis. Unstable compounds in excess of the acceptable limit may be deleterious to askarel-filled apparatus. _ RILG567 SW 357990 7-11 STLCOPCB4086678 CHLORIDES. INORGANIC (D-1821) In the presence of water, inorganic chlorides can ionize and result in corrosion of metals. CLOUD POINT (D-97) The cloud point of an askarel is the temperature at which matter begins to pre cipitate from askarel under prescribed test conditions. Cloud Point Tests have been used to supplement Dielectric Strength and Power Factor tests for detecting moisture. Care should be used in interpreting the results of this test, since some hydrogen-chloride "scavengers" give a rather high Cloud Point temperature. COLOR (D-21Z9) The color of an askarel is a useful indicator of contamination. A change in color of an askarel in service indicates contamination. Additional tests should be made on any askarel whose color has changed appreciably. A new askarel with a color appreciably darker than normal should be checked for contamination. Since askarel is normally a water-white liquid, ASTM Method D-2129 is far more sensitive than ASTM Method D-1500, used for insulating oils, to changes in color. DIELECTRIC CONSTANT (D-924) The dielectric constant of an askarel is the property which determines the elec trostatic energy stored per unit of volume for unit potential gradient. The results of this test are used only for design purposes. If the dielectric constant of askarel or an oilaskarel mixture is changed due to contamination or the addition of insulating oil, it may result in an operating hazard. DIELECTRIC STRENGTH (D-877) The dielectric strength of an askarel is the minimum voltage at which electrical failure occurs under prescribed test conditions. It indicates the ability of an askarel to withstand electrical stress without failure. Low dielectric strength indicates contamina tion with water, solid-conducting particles, and/or other foreign matter. High dielec tric strength is no indication that an askarel does not contain contaminants. The con taminants causing low dielectric strength can usually be removed with a filter press. Askarel with a dielectric strength of less than 30-kv is usually considered an operating hazard. This is the most popular acceptance and periodic test for askarel. FIRE POINT (D-92) The fire point of a liquid is the temperature at which the liquid supports combus tion under prescribed test conditions. Since askarel has no fire point, this test is only of value for determining whether the askarel contains a large amount of combustible con taminant. The test for the Volume of Oil in Askarel (D-1808) is preferable for this pur pose. CAS CONTENT (D-831) This test is used only for determining the gas content of askarel for cables and capacitors where de-gassed oil is essential. The use of ASTM Method D-1827 for de termining the gas content of askarels has not been investigated by ASTM Committee D-27. 7-12 l-iyp RILG567 DSW 357991 ---------------------ff STLCOPCB4086679 INTERFACIAL TENSION (D-971, D-1902, D-2285) The interfacial tension of water against askarel is the force necessary to move a platinum ring through a water-askarel interface and is expressed in dynes per centimeter. Although this test has been widely used for oil, it is rarely used for askarel. NEUTRALIZATION NUMBER (P-664, D-974) The neutralization number of an acidic askarel is the number of milligrams of KOH required to react with 1 gram of askarel under prescribed test conditions. In case of a basic askarel, the neutralization number is the number of milligrams of KOH equiv alent to the acid required to react with 1 gram of askarel under prescribed test conditions. The neutralization number is of importance as a quality index of purity of new askarel. The neutralization number of new askarel should not exceed 0.010 mg KOH/gm. Since askarel is not subject to oxidation, a small change in neutralization number will indicate contamination. Decomposition of askarel may be indicated by a large change in neutralization number. A low neutralization number does not prove that there are no contaminants in the askarel. POUR POINT (D-97) The pour point of an askarel is the temperature at which it just flows under pre scribed test conditions. A low pour point is important, particularly in cold climates, to insure that askarel will flow in cold weather and serve its purpose as an insulating and cooling medium. An increase in the pour point of an askarel is an indication of the loss of volatile fractions of the askarel. POWER FACTOR (D924) The power factor of an askarel is the cosine of the dielectric phase-angle between a sinusoidal alternating potential applied to an askarel and the resulting component of alternating current having the same period as the potential difference. Power factor in dicates the dielectric loss in an askarel; thus the dielectric heating. Power factor is widely used acceptance and periodic test for askarel. The power factor of new askarel should not exceed 0. 05 per cent at 25 C. High power factor of used askarel indicates contamination with moisture, carbon or other conducting matter, asphalt base material, varnish, glyptal, gasket materials and/or other foreign matter or deterioration products. It is well to investigate used askarel having a power factor in excess of 0. 5%. When used askarel is found to have a power factor of 2. 0% or more, the cause of the high power factor should be determined. If the high power factor is caused by water or other con ducting matter, free chlorides or high neutralization number, the askarel is probably an operating hazard. If the high power factor is not due to these causes, it is probably not an operating hazard; except that when the power factor is quite high, it may result in excessive heating of the device in which it is used. High power factor due to askarel contamination may mask out other defects in askarel-filled devices. REFRACTIVE INDEX (D-1807) The refractive index of an askarel is the ratio of the velocity of light in a vacuum to its velocity in askarel. It is an indicator of the composition of an askarel and the na ture and amount of contaminants in solution. Periodic refractive index measurements have been used as a check for contamination by petroleum products. . RILG567 DS\N 357992 7-13 STLCOPCB4086680 SLUDGE Since askarel does not oxidize, this test is not used for askarel. SPECIFIC GRAVITY (D-1810) The specific gravity of an askarel is the ratio of the weights of equal volumes of askarel and water determined under specified conditions. The specific gravity of an askarel is used for converting the net weight of askarel to volume at 60F. It has little value in determining askarel quality or the suitability of askarel for electrical applica tions. Periodic specific gravity tests are rarely made except for correcting interfacial tensiometer readings. VISCOSITY (D-88) Viscosity is the resistance of askarel to flow under specified conditions. The viscosity of an askarel used as a coolant in an electrical device is a principal factor in the dissipation of heat by convection in askarel. An increase increase in viscosity of an askarel indicates the loss of volatile fractions. This test is not generally made on used askarel. TESTING ASKAREL-FILLED TRANSFORMERS Power-factor tests are as valuable in determining the condition of insulation in an askarel-filled transformer as they are in determining the condition of insulation in an oil-filled transformer. The procedures and instruments required for determining insu lation power factor of askarel-and oil-filled transformers are identical. Acceptable test values are of the same order of magnitude. Due to the limited data of tests on askarelfilled transformers, it is difficult to set exact test limits. It is practical to specify that the power factor of transformer-windings in askarel, with all bushings and the highvoltage switch in the circuit, shall not exceed three per cent when corrected to 20C. " TREATMENT The fact that the cost of askarel is approximately ten times the cost of insulating oil, and that the cost of reclaiming the two insulating liquids is about the same, insures that askarel can be economically reclaimed in relatively small quantities. Moisture and large particles only can be removed from askarel with a filter press. A filter press, having deep frames charged with fuller's earth, is preferable. To charge a filter press having deep frames with fuller's earth, thoroughly mix 800/300 mesh fuller's earth with a few gallons of askarel and circulate the mixture through the filter press, adding fuller's earth as required until cakes of fuller's earth of suitable thickness are evenly deposited on the surface of the filter papers. It is advantageous to have a source of clean dry air available for blowing the remaining askarel out of the fil ter press upon completion of filtering. A centrifuge is useless in treating askarel because of the high specific gravity of askarel. Moisture, dirt and other foreign matter, asphalt and asphalt-base materials, paint, varnish, gums, resins, rubber and rubber-like materials can be removed from askarel with fuller's earth. It is impossible to remove insulating oil and petroleum products from askarel with fuller's earth. ' DSW 357993 7-14 RILG567 STLCOPCB4086681 A number of devices are commercially available for treating askarel with fuller's earth. The three general types of fuller's-earth treating devices function as follows: a. Fuller's earth is mixed with the askarel which is later removed with a filter press. b. Askarel is pumped through a bed of fuller's earth, then through a filter press to insure that all fuller's earth is removed. c. Askarel is pumped through fuller's earth bound into blocks with a suit able bindefr. If clean fuller's earth blocks are used, a.filter press is not required. Devices used for filtering oil and treating oil with fuller's earth should not be used for filtering and treating askarel, since it is practically impossible to clean them sufficiently to insure against contamination of askarel with insulating oil. It is essential to use only thoroughly dried filter paper and fuller's earth in treat ing askarel. It should be remembered that dried filter paper and fuller's earth can re absorb in less than ten minutes two thirds of the moisture that they will absorb from the air. Neither fuller's earth nor filter paper can be effectively dried after once being sat urated with askarel. Treating temperatures should be as low as practical and, under no condition over 40C due to the rapid increase in the solubility of water in askarel with increasing temperature. When askarel is circulated from a tank through a treating de vice and then back into the same tank, it should be taken from the top and returned to the bottom of the tank, since water floats on askarel. Treating devices and procedures should be designated to reduce aeration of askarel to the least practical amount. Askarel can be removed from used filter paper and fuller's earth by placing them in a suitable container and just enough water to cover them. After standing overnight, the askarel can be drained from the bottom of the container and dried in the usual man ner. This is due to the fact that filter paper and fuller's earth have a greater affinity for water than for askarel. It is impractical for a utility to attempt to remove insulating oil or other petroleum products from askarel. Contaminated askarel may be returned to some manufacturers of askarel-filled devices for reclamation, provided the askarel is not contaminated with insulating oil and that the contaminant can be removed with fuller's earth. Askarel must be returned in sealed, clean, metal containers. The cost of such reclamation is usually about half the cost of new askarel. No appreciable quantity of the hydrogen-chloride "scavenger" will be removed by fuller's earth treatment of askarel unless excessive amounts of fuller's earth are used or the treatment is at an excessive temperature. TREATMENT AFTER EXPOSURE TO AN ELECTRIC ARC Immediately, not the day after an electrical arc-over in an askarel-filled trans former, dry nitrogen should be bubbled through the askarel for 4 to 6 hours using a 220 cu bic-foot cylinder of nitrogen for each 100 gallons of askarel. The nitrogen should be fed into the transformer drain valve and allowed to escape through a suitable vent above the askarel level in the transformer. A metal standpipe from the drain valve to a point above the askarel level should be used to prevent askarel contacting non-metallic hose or the ni trogen regulator. This procedure is essential to minimize the destructive effect of hydro chloric acid on the insulation and metal parts of a transformer, even if the askarel contains a hydrogen-chloride "scavenger." If this procedure is followed, it may be practical to re claim the askarel. . DSW 357994 RILG567 7-15 STLCOPCB4086682 Except while bubbling nitrogen through the askarel, the transformer should be kept sealed, with nitrogen over the askarel, from the time of failure until it is untanked. The transformer tank-cover should not be removed until hydrogen-chloride has been removed from the askarel by bubbling nitrogen through it. If the core and coils are exposed to the atmosphere before the complete removal of hydrogen-chloride, the mois ture in the air will dissolve the hydrogen-chloride, forming hydrochloride-acid, thus re sulting in greater damage to the core and coils. It is advisable to immediately advise the manufacturer of an electric arc-over in . an askarel-filled transformer, giving him the transformer rating, serial number and all available data on the arc-over in order to obtain his recommendations as to the procedure to be followed in repairing any damage to the transformer and in reclaiming the askarel. The manufacturer will, no doubt, want samples of the askarel. It is recommended that no work except bubbling nitrogen through askarel should be done except upon the advice of the transformer manufacturer. Even when the manufacturer is contacted for recom mendations on repairing a transformer after an arc-over in askarel, nitrogen should be promptly bubbled through the askarel. Bubbling nitrogen through askarel in a transform er is inexpensive; it can cause no damage and will minimize the necessary repairs and simplify the reclamation of the askarel. Samples of the askarel should be promptly taken and tested for Color, Free Chlo rides and Neutralization Number. A laboratory check on a relatively small quantity of the askarel will indicate whether it is practical to reclaim the askarel. In checking to see whether it is practical to reclaim askarel after an arc-over, particular attention should bd paid to the carbon in the askarel, particles of which are usually much smaller than those found in insulating oil. In case of a minor arc-over, the askarel can probably be reclaimed and also those parts of the core and coils not damaged by the arc-over may be salvaged. If se vere arcing has occurred, it may be possible to reclaim the askarel; however, it is . doubtful whether any part of the core and coils can be salvaged unless the askarel con tained a hydrogen-chloride "getter." This can be determined only by tests on the aska rel and careful inspection of the core and coils. Upon completion of the nitrogen bubbling process, the core and coils should be removed from the transformer tank and carefully inspected. If the damage cannot be repaired immediately, all parts of the transformer should be washed with good askarel and they should then be retanked. The tank should be filled with good askarel and sealed with nitrogen over the askarel. When all parts are available for repairing a transformer, transfer the askarel to a suitable metal container and remove the core and coils. Thoroughly clean the core, coils, and the inside of the tank and all other parts of the transformer with a solvent rec ommended by the transformer manufacturer. Carbon tetrachloride may be used on me tallic parts but must not be allowed to contact the coils or insulation. This cleaning op eration is necessary because askarel becomes quite tacky when exposed to the atmos phere. If metal parts are not immersed in askarel immediately after cleaning, a rust- preventative recommended by the transformer manufacturer should be applied to min imize corrosion. . Repairs should be made in the usual manner, the core and coils retanked and the transformer filled with askarel in the usual manner. The transformer should then be dried. 7-16 RILG567 DSW 357995 STLCOPCB4086683 DRYING ASKAREL-FILLED TRANSFORMERS It is advantageous to dry askarel-filled transformers completely assembled, filled with askarel and sealed, using the short-circuit method with continuous circulation of askarel through a filter press or, preferably, through a fuller's earth treating unit. In circulating askarel, it should be removed from the top of the device and returned at the bottom, since water will float on askarel. If the transformer is not sealed and the aska rel circulation and treating system sealed, there will be a loss of volatile fractions of askarel due to evaporation. Drying will be slower than with an oil-filled transformer be cause of the greater difficulty in transferring water from cellulose insulation to askarel and in removing water from askarel. In drying askarel-filled transformers by this method, 125 to 150 per cent of full load current should be applied until the top askarel temperature reaches 60C. Then the current should be reduced to the following maximum values: Per Cent Full Load Current Maximum Top Askarel Temperatures 80 75 75 80 50 85 If the above currents or temperatures are exceeded, the transformer insulation may be damaged by excessive temperature at hot-spots in the windings. Under no condition should the top askarel temperature be allowed to exceed 90C. The cover of the transformer should be lagged to prevent condensation. It is advisable to blanket the transformer tank during drying with a suitable insulating material to reduce temperature differences in the transformer, and thus minimize the condensation of mois ture on the inner surfaces of the tank. Under some conditions, it may be advantageous to operate the filter press or ../. , treating unit intermittently to reduce the temperature differences between the transfo'riwfer winding and the top askarel. CONCLUSIONS Askarel is not hazardous to handle. Although more care is required, it may be handled, stored, sampled, tested and treated in a manner similar to insulating oil. Com plete, separate facilities are advantageous for askarel. Transformers filled with oil or askarel may be applied, operated, loaded, tested, and inspected in a similar manner. The principle difference is maintaining askarel-filled transformers is the procedure after an arc-over in askarel. The disadvantages of askarel are compensated for by the elimination of fire and explosion hazards and its long trouble-free life in sealed electrical devices, under normal operating conditions. RILG567 DSW 357996 7-17 STLCOPCB4086684 t fc lt T- _ \ ; "X.JHt.l s ' 1. REFERENCES u. S. Patents 1931373, 1931455. and 2041594. 2. Underwriters Laboratories Reports on "Liquid Dielectric and Cooling Mediums" Miscellaneous Hazard No. 2581. One dated September 29, 1934, another dated December 18, 1937, and a third dated March 16, 1944. 3. Dielectric Strength of Non-Inflammable Synthetic Insulating Oil by F. M. Clark, A. I. E.E. Transactions, Volume 56, 1937. 4. Water Solution in High-Voltage Dielectric Liquids by F. M. Clark, A, I. E.E. Transactions, Volume 59. 1940. 5. Characteristics of Chlorinated Impregnats in DC Paper Capacitors by L. J. Berberick, A. I. E. E. Transactions, Volume 63, 1944. 6. Performance Characteristics of Askarels and Discussion by F. M. Clark, A. S. T. M. Special Technical Publications No. 95. 7. Practical Aspects of Testing Submersible Askarel-Filled Network Transformers, John C. Parker and R. D. Barrett, Minutes of the 15th Annual Converence of Doble Clients. 8. * Installation, Care, and Operation of Chlorextol Liquid-Filled Transformers, Allis Chalmers Manufacturing Company. 9. Instructions - Pyranol Transformers, including Pyranol-Immersed, CurrentLimiting Reactors, GEH-1093 A, General Electric Company. 10. Moloney Askarel Transformers, Instruction Book No. 488, Moloney Electric Co. 11. Westinghouse Inerteen Transformers, I. B. 5802-B Filing No. 00-200, Westinghouse Electric Corporation. 12. Inerteen Insulating Fluid for Electrical Apparatus, Instruction Book I. B. 44-860-1, Westinghouse Electric Corporation. 13. Instructions for the Conversion of 7336-7 Inerteen to 7336-8 Inerteen, Engineering Data Letter 1337-A, Westinghouse Electric Corporation. 14. Instructions for the Conversion of Inerteens No. 7336-1 through No. 7366-7 to Inerteen No. 7336-9, Engineering Data Letter 1337-B, Westinghouse Electric Corporation. 15. Preparation of Oil-Filled Transformers to use Inerteen and Preparation of Inerteenfilled transformers to use WEMCO-C oil, Engineering Data Letter No. 1236-A, Westinghouse Electric Corporation. 16. , The maintenance of Askarel Used in Transformers by John C. Parker, Minutes of the 19th Annual Conference of Doble Clients. 7-18 DSW 357997 RILG567 STLCOPCB4086685