Document ZB99LjkMj5wvn0dxB0wRZ70Mp

AIEE No. 76 Dec. 1958 Proposed Guide for MAINTENANCE OF TRANSFORMER ASICAREL (Published for trial use) Published by AMERICAN INSTITUTE OF ELECTRICAL ENGINEERS 33 West Thirty-ninth Street, New York 18, N. Y. OS\N 357968 STLCOPCB4086656 AIEE No. 76 CONTENTS PAGE I Introduction ............ ....................................................................................... ................... . 5 II Economic Factors ........................................................... ...........................................'............. 5 III Classification of Used Askarel ..........................-............................................................-- 5 IV ASTM Askarel Tests and Their Significance .......................................... --.................... 6 V Other Criteria Which May Be Helpful in Evaluating the Quality of Askarel in Service ............................................................................................-............... -................. 7 VI Sampling .................................................... -........................................................ ................... 7 VII Testing Procedures ................................................................................................................ 7 A. Field Screening B. Laboratory Screening VIII Methods of Reconditioning and Reclaiming Used Askarel ............................................. 8 A. General B. Treatment After Exposure to High Temperature or an Electric Arc C. Reconditioning of Askarel D. Reclaiming of Askarel IX Addition of Scavengers ................ ................ ......... -- X Special Considerations ................................................ A. Askarel Used Under Light Arcing Conditions B. Hazards C Personnel D. Storage and Handling of Askarel 9 10 DSW 357969 STLCOPCB4086657 ACKNOWLEDGMENT The Institute wishes to acknowledge its indebtedness to those who have so freely given their time and knowledge, and have conducted experimental work on which many of the AIEE publications are based. The work of preparing this Guide was carried out by members of the Insulating Fluids Subcommittee of the AIEE Transformers Committee. The members of the subcommittee are: C. P. Xenis, Chairman R. G. Call W. H. Meade F. C. Doble J. C. Parker J. G. Ford E. L. Raab E. E. Gilcrease W. W. Satterlee R. B. Kaufman C. E. Welsh L. M. Limpus 1i !i f' :i i t DSW 357970 . '( i STLCOPCB4086658 PROPOSED GUIDE for MAINTENANCE OF TRANSFORMER ASKAREL I INTRODUCTION The term askarel generally describes a widelyused, broad class of non-flammable synthetic halogenated hydrocarbon insulating liquid. As treated in this Guide it applies solely to askarel used in transformers, reactors, and accessory equipment operated at power frequencies. Certain essential properties must be retained if askarel is to perform reliably its dual role of electrical insulation and heat-transfer agent. It must have adequate dielectric strength to withstand the electric stresses imposed in service. It must retain a sufficiently low viscosity so that its ability to circulate and transfer heat is not impaired. The dielectric losses should not become excessive. It should not be allowed to become so deteriorated or contaminated that it adversely af fects other materials in the apparatus. This guide attempts to assist the power equip ment operator in his efforts to maintain askarel in serviceable condition. It recommends standard ized tests and evaluation procedures. Methods are outlined for reconditioning and reclaiming askarel whenever necessary. II ECONOMIC FACTORS In Section III of this Guide askarel is classified on the basis of significant characteristics. Many of the undesirable characteristics of used askarel can be corrected by reconditioning or reclaiming, if economic considerations justify it. The alternate choice is to replace with new askarel. A review of the experiences of many users of electric equipment reveals a wide variation in the actual cost data involved in the reconditioning or reclaiming of askarel. This variation can be at tributed to the amount and condition of askarel involved, laboratory and shop facilities, whether the work is performed at one central or several distant locations and the availability of qualified personnel. Askarel that contains water and insoluble con taminants can be reconditioned by mechanical means using a conventional filter press. If soluble and/or colloidal contaminants are present in the askarel, reclaiming can be done with a special filter press that uses minerals such as activated clay, activated alumina or aluminum hydroxide. These processes can be operated at a cost of from 2 to 10 cents per gallon for reconditioning and at a higher range of costs for reclaiming, de pending on the quantity involved and the facilities available. To determine if reconditioning or reclaiming of askarel, where possible, is economically justifiable, a number of factors must be considered. Some of these factors arc as follows: 1. Value of askarel being considered for process ing 2. Cost of processing materials 3. Total cost of process vs quality of end-product 4. Equipment maintenance and amortization 5. Cost of collection and storage 6. Labor and transportation costs 7. Laboratory cost 8. Loss of askarel during reprocessing 9. Cost of scavengers and make-up chemicals if addition is necessary and desirable 10. Cost of disposing of processing material and scrap askarel. Ill CLASSIFICATION OF USED ASKAREL It is extremely difficult, if not impossible, to indicate the value of specific tests and recom mended test limits for all possible existing appli cations of askarel. It should also be recognized that with the present state of knowledge no one test can be used as the sole criterion of condition of askarel. It is possible, however, to summarize the value and importance of current tests and to suggest methods of treatment for the askarel being examined, such methods being based on cur rent industry experience. Askarel may be placed in the following classifications based upon com posite evaluation of significant characteristics and on field and laboratory screening tests. (Refer to Section VII--Testing Procedures) GROUP I This group contains askarel which is in satis factory condition for continued use. GROUP II This group contains askarel which requires only minor reconditioning for further service. (Re conditioning is the removal of moisture and in soluble contaminants. The usual method employed is dry paper filtration.) (Refer to Section VIII-- Methods of Reconditioning and Reclaiming Used Askarel) GROUP III This group contains askarel in poor condition. It should be reclaimed or discarded depending upon economic considerations. (Reclamation in volves the use of methods and processes which result in a beneficial chemical change in the askarel. Possible means employed are treatments DSW 357971 T STLCOPCB4086659 with adsorption agents, aqueous extraction or washing procedures, alkali treatments, etc.) (Re fer to Section VIII--Methods of Reconditioning and Reclaiming Used Askarcl) GROUP IV This group contains askarel in such poor con dition and requiring such drastic treatment that it is not feasible either technically or economically to attempt reclamation. An example of such a condition would be excessive oil contamination of an askarel. 3. Neutralization Number--D 901, D974, and D 664 Neutralization number for used askarel is, in general, a measure of their acidic constituents and is measured as the milligrams of potassium hydroxide required to neutralize one gram of askarel under prescribed conditions. Askarel, un like insulating oil, does not oxidize even under severe service conditions. Consequently, this test will indicate an acid condition obtained either by electric arcing or by contamination from other materials or sources. t IV ASTM ASKAREL TESTS AND THEIR SIGNIFICANCE There are a number of tests than can be applied to transformer askarel as a basis for their clas`ification as indicated in the foregoing. It is recom mended wherever possible that tests be the latest revisions accepted as standards or tentative stand ards by ASTM. These tests and their significance are as follows:-- Test ASTM Designation 4. Viscosity--D 901, D 88, and D 445 The viscosity of an askarel is its resistance to uniformly continuous flow, without turbulence, inertia, or other forces, and is usually determined by measuring the time of flow of a given quantity of the liquid, at a given temperature (37.8C (100F) unless otherwise specified), under con trolled conditions. Viscosity is an intrinsic prop erty of askarel dependent upon basic chemical composition and type. Under certain conditions, i 1. Dielectric Strength........ D 901, D 877 significant changes in viscosity of askarel in ! 2. Free Chlorides............. . D 901 service may indicate evaporative losses of volatile i 3. Neutralization Number.... D 901, D 974, D 664 components or contamination from other sources 4. Viscosity.............. ......... D 901, D 88, D 445 (i.e. mineral oils, sealing compounds). 5. Pour Point...................... D 901, D 97 6. Volume of Oil (percent) D 901 5. Pour Point--D 901 and D 97 7. Fire Point ...................... D901, D 92 The pour point of an askarel is that temperature 8. Specific Gravity.............. D 901 at which the liquid just flows under prescribed 9. Refractive Index............ D 901 conditions. The pour point has little significance 10. Color .............................. D 901, D 155 with respect to minor contamination or deteriora i 11. Power Factor ............... . D 901. D 924, D 150 tion but may be useful for type identification. 12. Dielectric Constant ........ D 901, D 924, D 150 6. Volume of Oil in Askarel--D 901 i 1. Dielectric Strength--D 901 and D 877 This method covers a procedure for the de The dielectric strength of an askarel is the termination of the percentage, by volume, of oil average voltage gradient at which electric failure in askarel. In evaluating used askarel, this test or breakdown occurs under prescribed conditions. has considerable significance in maintaining pre This test is made to determine whether an askarel scribed nonflammability characteristics where oil has adequate electrical strength and may, in cer contamination has been indicated by other test tain instances, reveal the presence of deleterious procedures. contaminants but is not necessarily an indication of its other properties. 7. Fire Point--D 901 and D 92 i !1 2. *Free Chlorides--D 901 Askarel may contain free chlorides as a result of imperfect refining or contamination from other sources. Such free chlorides are undesirable be cause of their possible corrosive action or other deleterious effects in the presence of moisture. Aside from extraneous contamination, free chlo rides may also result when the material is sub jected to an electric arc or heated above a limit ing temperature of 200C if the askarel does not contain a scavenger. This test indicates the pres ence of these free chlorides. The wording of the current D 901 pertaining to free chlorides requires revision in order to recognize the general industry usage of scavanger agents. The fire point of a material is that temperature to which the material must be heated in order to support combustion when exposed to the atmos phere under prescribed conditions. Askarel, as such, has no fire point. The test is only of value, therefore, in showing whether the material has the non-flammable characteristics required of an askarel or has a large amount of combustible con taminant. 8. Specific Gravity--D 901 The specific gravity of an askarel is the ratio of the weights of equal volumes of askarel and water at 15.56C (60F). Specific gravity may be useful for type identification or to determine marked compositional changes. \ ) 6 DSW 357972 i ik+u.a,-. .. STLCOPCB4086660 9. Refractive Index--D 901 The refractive index of an askarel, in common with all light-transmitting substances, may be de fined as the ratio of the velocity of light in a vacuum to its velocity in the substance, under prescribed conditions. The refractive index of an askarel varies with its composition, and with the nature and amount of contaminants held in solu tion. Changes in refractive index on askarels in service may be useful in estimating compositional change and degree of soluble contamination. 10. Color D 901 and D 155 The color of an askarel is determined by trans mitted light and is expressed by a numerical value based on comparison with a series of color stand ards under prescribed conditions. Color is chiefly significant as an indicator of soluble contamination in askarel. However, color in itself has limited value as a measure of serviceability since it maj or may not correlate with physical and electrical characteristics of the liquid. 11. Power Factor--D 901, D 924 and D 150 Power factor is the ratio of the power dissi pated in the askarel in watts to the product of the effective voltage and current in volt-amperes, when tested with a sinusoidal field under pre scribed conditions. Since askarel is not subject to oxidation, an increase of power factor value of the askarel in service may be attributed to the presence of moisture or other contaminants. Depending upon type of apparatus and applica tion, high power factor due to contamination other than by moisture seldom impairs the serviceability of the askarel, however, the high power factor may result in excessive heating of the device in which it is used. 12. Dielectric Constant--D 901, D 924 and D 150 The dielectric constant of an askarel is a mea sure of its relative ability to store electrostatic energy. It may be useful as an indication of com position and purity of an askarel. V OTHER CRITERIA WHICH MAY BE HELPFUL IN EVALUATING THE QUALITY OF ASKAREL IN SERVICE 1. Visual Condition This test indicates the presence of free water and sediment such as metal particles, carbon, dirt, solid insulation fragments, etc. Askarels con taining metallo-organic hydrogen chloride scav engers may show some precipitation of the scav enger at low temperatures because of limited solubility. Under normal operating conditions, such material readily and rapidly redissolves and does not impair serviceability. One method of visually examining an askarel sample is to observe a representative sample in a clear glass tube or bottle. If the askarel by visual examination is clear, then the appropriate tests should be ap plied to classify the askarel in the proper group as initially defined above. If insoluble contami nants are present, valuable information may be obtained by filtering the askarel and identifying the residue. The askarel filtrate should be ex amined and classified in the same manner as a clear askarel sample. A method for visual condition is currently under investigation by ASTM. 2. Water Water may be present in several forms. The presence of free water maj- be disclosed by visual examination in the form of an immiscible layer, separated droplets or a cloud dispersed through out the askarel. This type of water invariably results in decreased dielectric strength which may be restored by filtration or other suitable means. It is significant to note that free water, less dense than askarel, will separate at the top surface of the askarel. Water in solution cannot be detected visually and is normally determined by either physical or chemical means. One method under ASTM consideration is the Karl Fischer reagent method. 3. Askarel Insoluble Matter '. Occasionally samples taken from equipment in service will show insoluble matter which might be composed of many types of material, i.e., fibers, dirt, water, carbon, insulating materials, etc. Under certain circumstances, it may be desirable to subject such residues to laboratory analysis. 4. Hydrogen Chloride Scavengers . Suitable quantitative methods for the estimation of the commonly used scavenger agents are avail able and at present are under consideration by ASTM. 5. Resistivity The resistivity of askarel is a measure of its electrical insulating properties under prescribed conditions of test. High resistivity reflects low content of free ions and ion forming particles and normally indicates a low concentration of con ductive contaminants. - VI SAMPLING The sampling of askarel is important from the standpoint of evaluating quality. Particular care must be taken to prevent samples of askarel from coming in contact with moisture or other materials which may contaminate it. It is important that the procedures and the precautions outlined in the latest revision of ASTM Designation D 901 pertaining to the sampling of askarel. be followed. VII TESTING PROCEDURES The procedures for testing askarel are quite DSW 357973 STLCOPCB4086661 similar to those for testing mineral oil and they . depend to some extent on the testing equipment available. Most users of askarel find that testing is accomplished best in adequately-equipped labo ratories. However, some users of transformers find it desirable to make "Field Screening Tests." Unlike mineral oil, askarel does not oxidize; con sequently, sludge tests are unnecessary. Standard methods for testing askrael have been assembled by the ASTM Designation D 901. (A) Field Screening Field screening tests are usually made to de termine which samples of askarel may require laboratory investigation. Since most tests of askarel can be done best with laboratory equip ment and trained personnel, field tests are usually limited to visual inspection and dielectric strength. No standardized procedure is available at the present time, for performing field tests on used askarel nor for classification.* Portable dielectric test sets have been available for some time and have proved satisfactory. Visual condition is at present a matter of personal opinion when the liquid is viewed in a glass container. (See Section V). In addition to the above tests, some operators with suitable field equipment and trained person nel may wish to gain additional information by use of a power factor test. In interpreting results of these tests consideration must be given to other characteristics of the askarel under test. . (B) Laboratory Screening Askarel requiring laboratory evaluation will vary widely in condition depending upon the . degree of contamination. There are many tests of a research nature which could be applied, but the general use of such tests would be impractical. The following tests, therefore, are believed to be adequate for classifying used askarel and when used should be performed in the order indicated. Visual Condition Water Content Dielectric Strength Free Chlorides Power Factor or Resistivity Neutralization Number Volume of Oil (percent) VIII METHODS OF RECONDITIONING AND RECLAIMING USED ASKAREL A. GENERAL Askarel can be reconditioned and reclaimed and restored to good operating condition in many instances. Since askarel does not oxidize the problem resolves itself to the removal of free moisture and other insoluble particles (recondi tioning) and to the removal of certain soluble or colloidal contaminants such as varnishes, gums, resins, certain plastics, rubber-like materials, etc. *To be determined by industry questinnaire. 8 (reclamation) with which the askarel may have come in contact. In addition askarel which has been exposed to temperatures in excess of 200C or to an electric arc will liberate hydrogen chloride gas and carbon. Special treatment is required, for askarel which has been thus exposed. There is no practical method of removing in sulating oil from askarel. Askarel contaminated with oil sufficiently to affect its non-flammable characteristics must be discarded. Only metallic hoses should be used in the handling of askarel since rubber and rubber-like compounds are attacked by it resulting in con tamination of the askarel as well as deterioration of the hose. When recirculation methods are used the askarel should be taken near the top of the tank and returned at the bottom since free water ancj most of the sediment are found near the top surface of the askarel. Since such a procedure can introduce air into the askarel, sufficient time (two hours or more) should be allowed for the air to escape before reenergizing the apparatus. It is suggested that further detail be obtained from the manufacturer of the apparatus when desired. Con siderable savings can frequently be realized in processing used askarel if it is allowed to remain in its container undisturbed for at least 2-1 hours so that water and suspended solids can separate from the askarel. Because of the ease with which askarel can be contaminated by insulating oil, reconditioning or reclaiming equipment should be reserved solely for use with askarel. B. TREATMENT AFTER EXPOSURE TO HIGH TEMPERATURE OR AN ELECTRIC ARC When askarel has been exposed to an electric arc or high temperature, dry nitrogen should be bubbled through the askarel for four to six hours. Approximately 220 cubic feet of nitrogen should be used for each 100 gallons of askarel. The treatment should be started as soon as practical as any hydrogen chloride liberated in combination with moisture will quickly attack exposed ma terials in contact with the askarel. This procedure is recommended even though the askarel con tains a hydrogen chloride scavenger. The nitrogen should be admitted at the bottom of the tank or container and the container should only be vented sufficiently to allow the nitrogen to escape in order to prevent the entrance of mois ture and the formation of hydrochloric acid. Ex cept while treating with nitrogen, the tank or container should be kept sealed, to prevent the en trance of moisture, until the askarel is removed. When askarel has been subjected to.arcing or high temperature, samples should be promptly taken and tested for color, free chlorides, neutral ization number and visual condition. A laboratory check following recommended reclamation meth- DSW 357974 i. i. : y | ; s iir. i P iS r* i l 1j r i ] f i I n STLCOPCB4086662 6 ods oil a relatively small quantity of the askarcl will indicate whether it is practical to reclaim it C. RECONDITIONING OF ASKAREL The reconditioning of askarel, that is, the re moval of water and other insoluble contaminants may be accomplished with a conventional filter press. Filter presses vary somewhat in form, but are based upon the principle of forcing askarel under pressure through a series of absorbing materials such as paper. Filters of this type are capable of removing carbon, water, and other solid particles when they are in suspension but paper alone cannot remove them effectively when they are dissolved or in colloidal form. These devices will not remove air but in fact tend to aerate the askarel. . The water-removing ability of the filter press is dependent upon the dryness of the filter papers, and' consequently ovens must be provided to dry the paper before use. When filtering askarel con taining water the filter papers rapidly come into equilibrium with the water content of the askarel and from that time on the filtered askarel may contain water up to 100 percent of saturation at the temperature at which the filtering is done. Since the amount of dissolved water at saturation increases markedly with increasing temperature, filtering at low temperature is more effective in removing water. However, the temperature should not be so low that any hydrogen chloride scaven ger present is precipitated out of solution. The necessity of changing the filter papers is usually determined by an inspection of papers, an increase in input pressure, a lowering in the dielectric strength or a rise in water content of the filtered askarel. D. RECLAIMING OF ASKAREL Methods of reclaiming askarel to remove solu ble or colloidal contaminants involve the use of materials such as activated clay, activated alu mina, or aluminum hydroxide. While gravity or pressure percolation through activated clay has been used to some extent for reclaiming askarel, most askarel has been reclaimed using special filter presses in combination with activated clay. Figure 1 shows one such device in which a mixing tank is provided and a larger space is incorporated in the frames between sections of filter papers. About one fourth of the clay re quired to charge the press is mixed with a rela tively small quantity of askarel in the mixing tank and the filter then operated to recirculate the askarel and thus deposit a cake of clay on the surface of the paper. Additional clay and askarel are mixed and recirculated until the desired cake has been established. The filter press is then ready to be used for reclaiming the askarel. The arrangement shown in Figure 2 is similar except that the full charge of clay is placed in the auxiliary tank and the askarel is forced up through it. The askarel then passes through a wire screen prior to entering the filter press to remove practically all the clay. A relatively small quantity of askarel is used to fill the tank and wet the clay before the unit is ready to use. Periodic tests on the output of these devices for the characteristic being improved will deter mine the necessity for changing the filter press . papers or recharging with clay. The clay must be thoroughly dried before being used and tempera tures ranging from 180C to 300C are recom mended. Excessive amounts of clay and a high reclaiming temperature should be avoided since the use of large amounts of highly-active clay at high temperature would be expected to selectively absorb scavengers or stabilizers which the askarel may contain. Amounts of clay up to 0.1 percent by weight of the askarel treated and temperatures up to 60C will have no appreciable effect on the scavenger content. To judge the sufficiency of reclamation, samples should be tested for color, free chlorides, neutral ization number, dielectric strength, water content and power factor or resistivity. After the askarel has been reclaimed it is advisable to test for un reacted and reacted scavenger content in order to determine if scavenger should be added. Much of the askarel left in the reclaimer can be saved by passing clean dry compressed air or dry nitrogen through the device at the end of the reclaiming operation. IX ADDITION OF SCAVENGERS As previously stated askarel which has been ex posed to temperatures in excess of 200C or to an electric arc will liberate hydrogen chloride gas some of which dissolves. In order to minimize the effect of soluble hydrogen chloride on appa ratus materials, askarel usually contains a small percentage of a certain chemical commonly called a "scavenger" or "getter," to mitigate the effects of the hydrogen chloride. Various manufacturers use different chemicals for this purpose, tin tetraphenyl and phenoxypropene oxide being the most common. Most askarel currently in use contains scavengers, however, there may be cases where the scavenger was not originally included or re quires replacement. Tin tetraphenyl is a white crystalline compound melting at 227C. Phenoxypropene oxide is a color less liquid at ordinary temperatures. Small con centrations can effectively minimize the damage to apparatus parts which might be caused by the formation of hydrogen chloride. Concentrations on the order of 0.1 percent to 0.2 percent are ordi narily used. These scavengers have good dielectric properties, are nonvolatile and introduce no ab normal fire or explosion hazard. 9 SVV 357975 ST LC6pCB4086663 Before any scavenger is added to an askarel the manufacturer of the apparatus in which the askarel will be used should be consulted as to the amounts and method of addition. It is extremely important that the scavenger be of approved purity and that it be added in the recommended proce dure. In general the scavenger is mixed with a small quantity of the askarel and then poured in the top of die apparatus. Extreme care must be taken to see that any containers, funnels, etc., (used) are clean, dry, and made of materials un affected by the askarel. X SPECIAL CONSIDERATIONS A. Askarel Used Under Light Arcing Condition Askarel is used, to some extent, in apparatus where it is subjected to light intermittent arcing such as in self-contained induction regulators, where operating switches are continually produc ing slight arcs, in transformer deenergizing switches etc. Under normal operating conditions deterioration of the askarel is very slight. How ever, improperly adjusted or defective switches in this type of apparatus can produce excessive and prolonged arcing with accelerated deterioration of the askarel. It is recommended that when aska rel is used under these conditions checks of the liquid condition in conformance with manufac turers recommendations be made more frequently than when it is used only as a cooling and insu lating fluid. Deterioration of this type is indicated by a blackening of the liquid. It can be recondi tioned as previously described. Special attention should be given to maintaining the scavenger at the appropriate level. B. Hazards (a) Askarel Under Fault Conditions or Excessive Temperature When askarel is subjected either to tempera tures in excess of 200C or to an electric arc it distintegrates and hydrogen chloride gas is formed. During this disintegration process, por tions of the liquid change into a gaseous state and abnormal pressures develop. Consequently it is recommended that, wherever possible, sealed askarel filled equipment be provided with pressurerelief devices. These devices must be large enough to provide immediate relief at a definite pressure and to prevent further build-up of pressure if de composition continues. It must be remembered that the presence of devices of this sort does not necessarily preclude the rupturing of containing vessels since pressure build-up can be extremely rapid under violent arcing conditions. Askarel in the uncontaminated state is, of course, non-flammable as is the hydrogen chloride gas that is generated during decomposition. How ever, if the askarel becomes contaminated with petroleum products flammable mixtures may re 10 sult. Under these conditions secondary fires may result if relief devices or containing vessels rup ture during fault. Consequently some thought should be given to location of askarel-filled equip ment in order to minimize the hazard to person and property. C. Personnel It is generally accepted that exposure to askarel is not hazardous provided simple precautions are taken. Most people can handle askarel in the same manner as insulating oil without fear of toxic effects. As with insulating oil, some people are allergic to askarel and continued exposure may result in skin irritation, therefore, direct contact should be avoided where possible. Avoiding un necessary contact with askarel and its vapor, par ticularly when it is hot, and cleanliness of work men handling it should constitute adequate safe guards against such effects. Medicinal washes or detergents followed by an application of cold cream have been successfully used to eliminate irritation resulting from askarel coming into con tact with an open cut or skin abrasion. A drop of castor oil has been found to neutralize, in most cases, irritation caused by contact of askarel with the eyes. It is recommended that small quanti ties of cold cream, castor oil, soap and clean water be readily available when askarel is being handled. There is no evidence that ordinary ex posure 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. As with many volatile liquids, the vaporization of askarel increases rapidly with temperature. There fore, ventilation which is adequate for handling askarel at room temperature may not be adequate for handling askarel at elevated temperatures. The gases produced when askarel is disintegrated by very high temperatures or an electric arc in the presence of air or organic insulating materials contain a high percentage of hydrogen chloride and small percentages of carbon dioxide, carbon monoxide, oxygen and in some cases phosgene. Very small concentrations of this combination of gases are very unpleasant and irritating, thus giv ing ample warning of their presence. The all purpose gas masks available for use around oilfilled devices are also used for protection from gases liberated from disintegrated askarel. Indi vidual uses may require more detailed precautions in order to conform to local safety requirements pertaining to the specific operating conditions in volved. D. Storage and Handling of Askarel Transformer askarel is a fluid' and can be handled in much the same manner as transformer oil. Since askarel is somewhat more susceptible to contamination by moisture than transformer oil DSW 357976 i t? f: ?` I? STLCOPCB4086664 and also acts as a solvent on a large number of materials, considerable care must be exercised in its handling. The following general rules should be observed. 1. AH necessary steps should be taken to main tain the askarel in a dry clean condition. This in volves proper sealing, dryness and cleanliness of all storage containers and handling equipment. 2. Since askarel is a powerful solvent, care should be taken in the selection of materials to be used in contact with it. For example, con sideration should be given to such things as the nature and compatibility of gasket materials, pipe sealing compounds, container and tank linings (such as paints, varnishes, etc.) valve and pump packings and lubricants, the cleanliness and prior service of containers, storage tanks and trans port lines. Only metal hoses should be used in handling since rubber and rubber-like compounds are attacked by askarel. It is important to avoid contamination of askarel with mineral oil and similar soluble organic materials. Therefore, handling equipment should be reserved solely for their use. 3. In general, care should be employed in the handling and processing of askarel to maintain it at or near room temperature to prevent undue volatilization of certain compounds and minimize removal of special scavenger additives due to solu bility limitations or absorption on treating clays and to assure the most efficient removal of mois ture by filtration or other means. All necessary precautions should be taken to provide adequate ventilation and other protective measures to properly protect those working with these mate rials. 4. Askarel weighs approximately twice as much as transformer oil, consequently thought should be given to size and structure of containing vessels. 5. More detailed information on various phases of these subjects, as generally treated above, is available in manufacturers' instructive pamphlets. These publications should be freely consulted when askarel-filled transformers are used. E. Underwriters' Laboratories Reports The Underwriters' Laboratories have exhaus tively examined at the electrical manufacturers request the miscellaneous hazards involved in the use of askarel and askarel-filled apparatus. Re ports have been issued to the respective manufac turer covering the tradenamed askarel being con sidered. It is suggested that interested users of transformer askarel contact the manufacturers for this information. DSW 357977 STLCOPCB4086665  DSW 357978 i. ii jijuuyiijjpM^ *mf - STLCOPCB4086666