Document OzDK29VZ5b5z3ZV5eXw6Y2NJv

TOWOLDMONOQ22062 V. S. Pat. Off. 1248 009668 7 TOWOLDMONOQ22063 ................................h.is been used successfully since 19-11 as a liquid phase heat transfer ineduuti a! atmospheric pressure and temperatures up to fi(K) F. The compound, essentially tetraehlorobiphenvl, is a fire-resistant and non corrosive liquid, which does not crystallize at low temperature's. Handled properly, in well-designed forced circulation heat exchangers which avoid localized overheating damage, the fluid gives satisfactory continuous service for many years without replacement. Most significant. Aroclor 1218 is practically non-llainmablc. In one in stallation oi record, a ruptured pipe spewed the hot fluid into gas llamcs: the fluid l.liled to ignite! Tor general heat transfer, Aroclor 1248 has several other important qualities: it is highly mobile and can be readily pumped at temperatures as low as .50 F. If cooling is necessary, the heat transfer fluid can be put through a water cooler and used as a coolant. Aroclor 1218 transfers heat (up to 600 F. ) as a lifjuul. This liquid phase heat transfer makes it unnecessary to use the expensive pressurized equipment required by a heat transfer medium that operates as a vapor. Aroclor 12 IS operates safelv and efficiently with gas-fired, oil-fired, or electrical heat sources. It is used siiccessfulh in the following txpes of applications .... 0096688 I 5 i 2 Chemical processing equipment, particularly for reacting flammable materials Cooking of alkyd resins, varnishes, waxes Plastics molding, extruding, calendering Rubber processing Heating asphalt Food processing, including potato chip and doughnut frying in vegetable oils Processing titanium, magnesium, other non-ferrous metals Fabrication of magnesium and aluminum honey-comb structures for aircraft Indirect heating in dyestuff manufacture Heating of corrugating rolls Indirect heating of distillation equipment Saponification of fats Calcining ovens Impregnation and lamination of fibrous materials 0096689 TOWOLDMONOQ22065 T\ni,r. i Appearance Absolute density, g. ml. Absolute viscosity, centipoises Thermal Conductivity, Btu. 'hr.'Sq. ft./F./ft. Spec. Volume, ml. g. Practically colorless mobile liquid. Temperature Centigrade Fahrenheit 1.44 30 86 1.41 60 140 1.37 100 212 1.27 200 392 1.17 300 572 112.0 30 86 17.5 60 140 4.2 100 212 0.99 200 392 0.47 300 572 0.0571 30 0.0564 60 0.0555 100 0.0534* 200 0.0512* 300 * Extrapolated Data 86 140 212 392 572 0.696 0.709 0.728 0.787 0.860 30 60 100 200 300 86 140 212 392 572 CONTINUED 0096690 TOWOLDMONOQ22066 Spec. Heat. cal. g. TC. Vapor Pressure, mm. Hg. Distillation Range. ASTM D-20 Flash Pt., Cleveland Open Cup. ASTM D 92-45 Fire Pt.. Cleveland Open Cup. ASTM, D 92-45 Pour Pt.. ASTM, D-97 Average Coefficient of Expansion cc. cc. F. 0.283 0.297 0.326 0.355 0.00037 0.16 2.9 18.0 350.0 'Centigrade 50 100 200 300 37.8 100 150 200 300 'Fahrenheit 122 212 392 572 100 212 302 392 572 345-385 652-725 193-196 379-384 None 0.00037 0.00038 0.00041 0.00044 0.00047 0.00052 7 19.4 17.8 to 37.8 37.8 to 93.3 93.3 to 149 149 to 204 204 to 260 260 to 316 0 to 100 100 to 200 200 to 300 300 to 400 400 to 500 500 to 600 PHYSICAL CHARACTERISTICS of AROCLOR 1248 A complete knowledge of the physical characteristics of heat transfer media is highly essential to their satisfactory application in a heat exchanger. These physical constants have a major bearing on the equipment design, its mainte nance, and its operation. The following figures and charts give basic physical data on Aroelor 1248. 0096691 TOWOLDMONOQ22067 TEMPERATURE DKNSITY OF AliOCFOR 124S l op a\K. II,v in. ft.; hotlom axis. Hin. ml-1 600 500 400 300 ?00 100 0 100 TOWOLDMONOQ22068 TEMPERATURE VISCOSITY OF AROCLOR 1248 TEMPERATURE WATER,CENTIPOISES S s 8 S VISCOSITY UNITS 0096693 TOWOLDMONOQ22069 VISCOSITY OF AROCLOR 1248 (Saybolt Universal Seconds) 100.000 VISCOSITY, SAYBOLT UNIVERSAL SECONDS 35 I -30 -20 I I I I II I I I I III I I II l 33 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 350 Figure 3 TEMPERATURE, DEGREES EAHRENHEIT 009669'. f TOWOLDMON0022070 A HEAT CAPACITY and Its Relationship to Density Systematic errors exist in the various accepted pro cedures for making specific heat determinations. Consequently values may vary depending upon the procedure used. In practical operation, it frequently appears that the values for Aroclor 1248 shown in Figure 4 are somewhat low. Consequently, although these values have been accurately determined, they may be regarded as conservative. When comparing the specific heat values of Aroclor 1248 with corresponding values for other heat transfer fluids, it is important to note that the density of Aroclor 1248 is much higher, relativelv. than the densitv of other liquids used for heat transfer. Accord ingly. when comparison of heat capacitv is made on a volume basis (which is most pertinent in equipment design and efficient operation) the heat capacitv of Aroclor 1248 shows itself to better advantage than In direct comparison of specific heat v alues. Although specific heat values are important, they represent only one of several important constants that enter into the equations for calculating over-all heat transfer efficiency. Through the use of these conservative heat capacity values, it is possible that equipment engi neered from such data might he slightly `'over designed." This may he one of the factors that accounts for the exceptionally good operating performance of a number of highly successful commercial applications. 009669^ 8 TOWOLDMONOQ22071 SPECIFIC HEAT OF AROCLOR 1248 {Btu. per lb. per degree F.) tSsdiM ._ ____................................ JMM ' - :rS*. --nzn *y - V-fk .._. . .......................... ......................... ninniiniiiiii&ii&^ ... .; iHMnnmH niimgn^yg .. . . ..400 iMa^ t :g TEMPERATURE Sl isi te &4 a& ail -- ---- "" siffiKsl IfitlSts^Iig Igtl&siMJIII .... i sL* S HHHHHiHllllll^il^ mimmmmmi&xir:-''s**..,usa&. mmmmmmm^^ *> 0 35 0.34 0.33 0 32 0.31 0 30 0.29 0 28 SPECIFIC HEAT Btu lb. F. 0 0 27 00V66V6 TOWOLDMONOQ22072 Temperature X. X. 0 32 10 50 38 100 66 150 93 zoo 121 250 149 300 177 350 204 400 232 450 260 500 288 550 316 600 TABLE II HEAT CONTENT of Aroclor 1248 Specific Heat Btu./lb./F. .269 .272 .280 .288 .295 .303 .311 .319 .327 .335 .343 .351 .359 Heat Content Btu./tb. 0.0 4.85 18.65 32.85 47.43 62.38 77.58 93.48 109.66 126.21 143.17 160.52 178.27 0096697 TOWOLDMONOQ22073 THERMAL CONDUCTIVITY and VISCOSITY The thermal conductivity values of Aroelor 1248 are shown in Figure 5. The curve shows this value over the operating temperature range, from 50'K. to 600 F., of Aroelor 1248. As freshly charged into a heat exchanger, Aroelor 1248 has an initial viscosity of 74 (S.U.S.) at 130F. which corresponds to a viscosity of approxi mately 5000 (S.U.S ) at 50F. -- which temperature is assumed for practical purposes to be about the limit at which Aroelor 1248 can be conveniently pumped with a centrifugal pump. The following table shows a comparison of the initial viscosity and the viscosity after a year's con tinuous service at 600F. in a LaMont forced circu lation heater: TABLE III Appearance Specific Gravity, 65" C. Viscosity, S. U. S. at 130 F. Original Colorless Liquid 74.0 After one Year of service at 600"F. Oark Brown Liquid 83 5 Although Aroelor 1248 tends to darken in use. this darkening is not harmful and does not indicate decomposition. In actual use at Monsanto, it has not been found necessary to replace the fluid after seven years of continuous use; additional fluid is onlv added as necessary to make up spills or leaks. In Figure 6, the horizontal line indicating vis cosity limit of pumpability at 50 F. shows that the rate of viscosity increase based on a year's continuous service should permit Aroelor 1248 to serve approxi mately four years before increased viscositv mav inter fere with its pumpability when cold. In practice. Aroelor 1248 has given satisfactory pumpahihtv for much longer periods. A simple S.U.S. viscosity deter mination by the ASTM-D-SS method can he used inr periodic checks on the fluid. 00^6698 11 TOWOLDMONOQ22074 600 500 TEMPERATURE cl 300 200 100 5 I l i * i 12 i_ _ _ _ _ Figure THERMAL CONDUCTIVITY OF AROCLOR 1248 (Dotted extension indicates extrapolated data) 0096699 TOWOLDMONOQ22075 EXPECTED MINIMUM SERVICE LIFE IN A FORCED CIRCULATION HEATER VISCOSITY. SAYBOLT SECONDS, at 130F. Figure t> YEARS OF USE AT 600 F 0096700 TOWOLDMONOQ22076 I 14 STABILITY Aroclor 1248 is an extremely stable chemical com pound. Tests over long periods of time have shown that 600 F. is a safe maximum temperature for continuous operation in heaters that are properly designed and operated to eliminate intense, localized overheating. At this temperature the fluid is 52 F. below the initial temperature of its boiling range, and consequently re mains a liquid. Near its boiling point Aroclor 1248 tends to dehydrohalogenate to a very slight but measurable degree. If this occurs as a result of accidental over heating. the small amount of HC1 gas evolved tends to pass through the vent tank without harm to the equipment provided that the system is dry. Experimental observations using ideally-suited heat exchangers operating at a temperature of 650F. with imposed nitrogen pressures of 30 and 70 psig. showed that application of pressure did not prevent this small amount of thermal decomposition, which also occurs when the material is heated above 600' F. at atmospheric pressure. When heated continuously at 650 "F. under nitrogen pressure a gradual increase in the viscosity of the fluid occurs indicating that its service life would be limited to about 6 months to one year. Results of operating at 600"F.. however, with out imposed nitrogen pressure indicate Aroclor 1248 can be heated continuously at this temperature for about 4 years before any viscosity increase could be expected to interfere with its pumpability at 50CF. which is slightly below normal room temperatures. Provision should be made to prevent water contamination of the system. If the system becomes contaminated with water, any HC1 liberated by local ized overheating may dissolve in the water film which will float on top of Aroclor 1248 in the expansion tank. The acidic solution thus formed can cause corrosion. It is recommended that moisture be eliminated from the expansion tank by installing a moisture trap or by sealing the tank and applying 15 to 30 psig. of nitrogen gas. With exception of the expansion tank, the system should be kept full of Aroclor 1248 at all times to pre vent formation of air pockets where moisture may condense when the system cools off between periods of operation. ' Many years of practical operating experience have shown that Aroclor 1248 is virtually non-corrosive to valves, piping, tanks, and jackets made of cast steel, steel, or stainless steel. In actual use. brass valves have been used satisfactorily. OQ 9 TOWOLDMONOQ22077 SAFETY of OPERATION Aroelor 1248 can be considered a non-flammable liquid; no fire point is obtained by the Cleveland Open Cup method on heating to its boiling point (650F.). The spontaneous ignition temperature*2* is 1,299F. hi actual use, the following reported accident in a heating system demonstrates the fire resistance of Aroelor 1248 and the freedom it offers from the hazard of fire propagation. An operator's failure to start the circulation pump when the gas heater was on resulted in excessive coil temperatures. The line containing Aroelor 1248 sagged into the fire chamber. A weld rup tured and Aroelor 1248 poured into the red-hot fire chamber in contact with the flame. Dense smoke and fumes arose from the heater but there was no external fire. After the gas flame was cut off, the smoking stopped. Insurance authorities allow the use of Aroelor 1248 heaters in many locations with a minimum of protection. No fire walls are required to isolate the heaters. Aroelor 1248 has a low v apor pressure. In sys tems that employ a vented expansion tank, the loss due to ev aporation is not measurable. If Aroelor 1248 in the expansion tank would reach a temperature of 266'F., the vapor pressure of the fluid won! : e only 1 mm. of Hg. SAFETY OF HANDLING Aroelor 1248 is an inert, unreactive liquid. If it is Med on the skin, there are no noticeable ill effects. It i* advisable, however, to wash the skin with soap and water after contact. A skin burn resulting from accidental contact with hot Aroelor 1248 should be treated in the normal manner for hot oil burns. Any liquid adhering to the burned area need not be removed immediutelv unless treatment of the burn demands it. If the burn must be cleaned, soap and water or repeated washings with a vegetable oil (olive oil) may be used. The vapors emitted by Aroelor 1248 heated to elevated temperatures are injurious on prolonged exl>osure and should not be breathed. It is indicated that 2.0 mg. of Aroelor 1248 per cubic meter of air is the maximum safe amount permissable in workrooms. In commercial heat transfer installations, it is presumed that Aroelor 1248 will be used in a closed system free from leaks. Accordingly, there should be little or no opportunitv for workers to come in contact with Aroelor 1248 vapors. 0046707 HEATER The most significant factor to remember when selecting or de signing a heat exchanger for Aroclor 1248 use is this: Aroclor 1248 transfers heat while in liquid form, at the maximum recommended temperature of 600"F. for continuous operation, which is approximately 50'F. below the boiling point. Conse quently, Aroclor 1248 does not form vapor to accelerate convection circulation. Ordinary fire-tube or water-tube heaters which depend solelv upon convection perform satisfactorily only at relatively low temperatures. When temperatures of 500-600cF. are required, a forced circu lation type heater is recommended. A satisfactory type of heater design would consist of a specified number of tubes in parallel, properly orificed to provide a high velocity fluid flow of 8 to 10 feet per second. These should be spaced to permit uniform heat absorption throughout their entire length. A typical construction is shown in Figure 7. In its fabrication, the heater should be ASME Code all-welded construction, conforming to state and local ordinances. Tube joints, which in an ordinary steam heater would be the expanded type, must be sealwelded to prevent leakage. All connections larger than %" should be flanged connections, since ordinary threaded pipe connection is not suited for Aroclor 1248 service. Spiral-wound stainless steel and asbestos com bination is recommended for sealing joints and plugs. Drain valves should be installed at all low points on the heater and the vah s must conform with ASME requirements for "blow down valves. 0096703 TOWOLDMONOQ22079 Since a heater operating on Aroelor 1248 is completely filled with liquid, costly liquid-level controls and condensate return pipes, fittings, traps, etc. are completely eliminated. Heaters can be provided with any desired kind of firing. Portable and small size stationary units are frequently elec trically heated; larger units may be gas- or oil-fired. In installa tions where an open flame presents a fire hazard, to meet insurance requirements the heater may be installed in a sepa rate building with piping carrying the hot Aroelor 1248 to the point of use. Properly constructed transmission pipes may ex tend for hundreds of feet. HEATER EFFICIENCY Forced circulation heaters with integral economizers will show an efficiency of from 75 to 80%. Heaters of the straight con nector type show efficiencies of 65 to 75%, depending upon the discharge temperatures. HEATER CAPACITIES Heaters using Aroelor 1248 (gas- or oil-fired) art* available in output capacities ranging from approximately 250.000 Btu. per hour to large units rated over 10 million Btu. per hour. A heat flux density (or heat energy input) ot approximately 5,000 Btu. j)er hour per square foot of tube surface is regarded as satisfactory. For lower output rate, electrically-heated units arc favored, einphn ing watt densities of 12 to 16 w atts per square inch of element area. 009670"* TOWOLDMON0022080 THE USERS The "users" or recipients of the heat at the point of processing can be any type of heating pan, platen, jacketed kettle, or coils of steel or stainless steel construction. Ordinary low pressure construction is satisfactory, since the pressure imposed on the Aroclor 1248 seldom exceeds 50 psig. In the user, however, it is important that all-welded construction be used. Threaded connections may allow leakage of the hot fluid. As in the heater, all connections %" and over should be flanged and all joints sealed with i spiral wound stainless steel and asbestos gasket material. Alloy bolts i should be used to secure flanges. A typical system with several users is ( j shown in Figure 8. ii 18 Figure 8 0096705 TOWOLDMONOQ22081 THE PUMP For most systems, cast-steel centrifugal pumps with watercooled stuffing box and bearings are to be preferred. However, high temperature centrifugal pumps with mechanical seals are now available which give excellent performance. In some in stallations, immersion pumps have been used. Whatever type is selected, the pump capacity and pressure head must be sufficient to circulate the volume of fluid at the rate the particular installation demands. To avoid shaft trouble and leakage at the seals, it is important to provide adequate expansion joints and to support the piping in a manner to avoid stresses on the body of the pump. Direct-connection pumps driven by 1,750 rpm. motors are most commonly used. Each pump should be fitted with a positive differential control to switch off the burner in case of pump failure. When a new system is first put into operation, a slight leakage may be noticed at the pump. It is not advisable to tighten the pump gland, however, until the system has heated up close to the temperature of operation. PIPING LAYOUT The most important factors in the piping layout for Aroelor 1248 systems are (a) proper sizing for the required flow rate and (b) minimizing pressure drop. Because the sys tem will undergo temperature changes, adequate expansion joints and loops to relieve expansion and contraction stress are essential. Preferably, all pipe lines and connections should be of extra heavy or Schedule 80 welded construction meeting A.S.M.E. requirements. However, Schedule 40 welded pipe construction is often employed. Flanged joints should be used as sparingly as possible to minimize potential leak points. All valves and controls should be cast steel construction with stainless steel seats. Pipe lines should be well insulated and those exposed to temperatures below 70 F. should be steam jacketed. All high points in the piping system should be provided with vent valves: all low' points should have drain connections. Piping should be well anchored at frequent intervals particu larly near expansion loops, to prevent vibrations. Figure 9 shows a typical piping diagram that illustrates the important features of an Aroelor 1248 piping system. These may be varied to suit the installation. 0096706 TOWOLDMONOQ22082 THE EXPANSION TANK Ilir expansion tank should hr large enough to accom modate about 20~ of the total volume of tin.' entire svstem. including the fluid content of tin* heater, piping, and all heatiixei'x. Tank should he sized to he ]4-fuII when svstem is cooled to 7b h. and "j-fuit when system is at maximum operating tem perature. Expansion tank should he fitted with a sight glass at the "full range and a float-ojx'rated low-level switch to shut off burner in case of accidental fluid loss in the system. The expansion tank should he mounted on a platform high enough to support the liquid reservoir at least six feet higher than the highest point in the piping svstem. THE FEED and DRAIN PUMP To eliminate manual filling and draining of the heating system, it is recommended that a small 2-to-5 gpm. positive displacement pump be installed at some convenient point to pump the Aroclor 1248 into or out of the system. CONTROLS Controls for heating systems using Aroclor 1248 should he installed both on the heater itself and on the heat-using units. A wide variety of thermo-operating controls are available and any reliable standard equipment is satisfactory. Heater controls should he installed to regulate the firing mechanism in direct proportion to the required output. These controls should increase or decrease the heat in-put to main tain the Aroclor 1248 at the operating temperature required by the heat-demand of the user. Small units may be operated satisfactorily by relatively simple "on-off" or "high-low" con trollers; larger units may operate more uniformly if equipped with modulating temperature controls. lTser Controls should he installed to regulate the flow of the heat transfer fluid in direct proportion to the heat-con sumption of the heat-using equipment. In a multiple-user svs tem. separate controls should be installed on each consuming unit, to assure the proper hoat-deliverv. Safety Controls. In addition to activating controls, tlx* heater must also he fitted with the proper safetv controls to meet the A.S.M.E. requirements. Safetv controls should include: 1. A high temperature limit control operating at the heater outlet to shut off the burner in the event of an excessive temperature rise. 2. A suitable low-limit temperature control to hold the burner at low fire until the Aroclor 1248 in the svstem reaches a temperature level of 180`F. The low limit temperature control is essential because the viscosity of Aroclor 1248 is rather high at normal room tem perature. To avoid localized overheating upon start-up. it is not advisable to apply full heat from the burner until all the fluid in the system has attained a viscosity that allows good flow and unimpeded circulation. Cold start-ups require slow up-heats. Burners should be equipped with automatic ignition controls and flame failure controls. In wide-range firing opera tions. an over-fire draft control will increase the economy of operation. Induced draft fans are another factor which should be considered as a means of avoiding the expense of high chimneys. Where they are needed throughout the system, good quality recording or indicating gauges should be installed. COOLING EQUIPMENT Where fast reduction of temperature is required, suitable air- or water-cooling installations may be used. If the cooler is to be a water-type unit, it is suggested that stainless steel tubing be used for the coils to avoid corrosion on the water side. If a cooler is installed in the system, low temperature limit con trols should also be installed to avoid excessive cooling that might raise the viscosity to the point of impeding the circulation in the svstem. 0096707 TOWOLDMONOQ22083 FILTERING EQUIPMENT When heating systems operated on Aroclor 1248 are mn continuously near the recommended maximum temperature of operation (600*F.), it is advisable to provide a filtering device that can be attached to the drain line of the storage tank. In this way discrete particles of dirt that may get into the system can be filtered out periodically. This is an advisable maintenance step since it will eliminate the danger of dirt clogging the valve seats or lodging in parts of the control mechanisms. A small portable filter such as those manufactured by Honan-Crane Corporation (Lebanon, lnd.) or Sparkler Manu facturing Company (Mundelein, 111.) is quite satisfactory. CONNECTIONS and GASKETS To minimize the possibility of Aroclor leakage, welded rather than threaded screw connections should be used. All connections Va-inch and over should be of the flanged type, fastened with alloy bolts; spiral-wound gaskets of corrugated stainless steel and asbestos should be used with flanged con nections. For three-inch lines, 300 pound flanges fitted with eight three-quarter inch bolts should be employed. As a joint compound, a product like "Q" Seal* has been found useful. In ail cases, steel connectors are recommended for all instruments and controls. TESTING THE SYSTEM When a new system has been installed it is essential to test for leaks. Testing with air should be avoided because of hazard of rupturing pipes or jackets. Testing with water is not recom mended because it is difficult to remove residual moisture from the system which should be kept dry. Halogen Testing for leaks is the recommended pro cedure. Introduce one pound of Freon F-12 or F-22 for each fifty cubic feet of volume of the heater and sys tem. Carefully introduce air not exceeding 10 psig. of pressure. With up to 10 psig. of air pressure, the con centration of Freon will be sufficient to give sensitive test results. Attach a halide torch to an acetylene tank and light it. Using the Va inch host- as a probe, explore for leaks by passing the end of the hose along seams and joints. If a leak is present, the escaping Freon will be drawn * A produc t ill Quicklcy Co., Inc., 5(> \V. 115th St . New. York. \. Y into the acetylene flame turning it green. A large leak will produce a violet color. CLEANING THE SYSTEM After testing for leaks and making any required repairs, the system must then be cleaned. A new system will contain dirt, mill scale and other foreign particles. Unless removed, these particles will be sus pended by the Aroclor. They may then lodge in valves, con trols and mechanical equipment and cause faulty operation. Purchasers of the heating equipment should request their suppliers to clean the equipment as thoroughly as possi ble, using brushes and wiping rags. Where state or local codes require hydrostatic testing and cleaning with water, the procedure described by card No. 1 may be used. However, it is not easy to remove residual mois ture from the system. Since moisture is not desired in the system, testing and cleaning with water should be avoided whenever it is possible to do so. Testing for leaks should be done as described above using Freon. After repairing any leaks, fill the system with Aroclor 1248, warm the fluid and circulate it thoroughly. The Aroclor will serve better than water for hydrostatic test ing and cleaning and will keep the system free from excess moisture. Since the Aroclor will pick up dirt and extraneous particles, it will be necessary to clean the fluid by filtration. To prevent filter arrangements, including screens from interfering with the required flow of Aroclor through the system, the filters must not be installed permanently in the line of How. Tempo rary strainers in the suction side of the pump should be inspect ed frequently during initial start-up and removed when the system has proven clean. The Aroclor should be cleaned thorouglily using a by-pass filter, either a platten frame press fitted with dry filter paper and a thin bed of Attapulgus earth, or a convenient portable earthen cartridge type filter. Periodic use of this filtration equipment should assure that the Aroclor and the heating sys tem are clean at all times. In the event that the engineer chooses to earrv out testing and cleaning using water, it is very important that all moisture be purged from the system during the early hours of operation. Details are given on Card No. 1. Following hydro static testing, periodic use of the filter equipment referred to above1 is desirable to keep the fluid and svstem clean. 0096708 TOWOLDMONOQ22084 GENERAL RECOMMENDATIONS for Operation and Maintenance The following recommendations are primarily guides for the manner of using Aroclor 1248 in an operating svstem. They are .supplemental to the equipment manufacturers own recommendations for operation and maintenance that relate to the heaters or the heat-using installations themselves. The recommendations for start-up. shut-down, precautions in event of power failure, and periodic check-ups on the fluid and equip ment apply as generally accepted practice on all tvpes and sizes of systems. By following these recommendations, the troublefree service life of the heat transfer fluid will be increased. START-UP When systems have been shut down for week-ends or over-night and the fluid is cooled to room temperature, follow this start-up procedure: 1. Start the circulating pump and check the expansion tank to make certain the Aroclor 1248 is at the proper cold-start level (Tank should be Vs-fitll.) 2. Start burner at minimum flame setting and continue full circulation until Aroclor 1248 is heated to 180"F. when measured on the return side of the heater. 3. Turn heater up to full heat. SHUT-DOWN The following procedure will eliminate overheating of the fluid when shutting down: 1. Shut off burner completely with circulating pump still oper ating. Continue to run the circulating pump at full head for at least \k hour to dissipate high residual heat in the com bustion chamber of the burner. 2. Shut off circulating pump at the end of hour and sw itch off all heater electrical controls. PRECAUTIONS IN COLD WEATHER When heat exchanger is exposed to ambient tempera tures below 50 F.. it is recommended that unit not be shut down. It is recommended that the burner be turned low and the fluid circulated continuously at about 2(X)'F. The unit will then be "at ready for immediate high temperature operation. PRECAUTIONS IN CASE OF POWER FAILURE In case of power failure, the burner circuit is interrupted by the heater controls. When power comes on. the circulating pump should first be run for a few minutes to eliminate ativ vapor pockets that might have been formed bv the fluid's being held static in the hot combustion chamber. If there is no knock ing in the piping system, full-fire may he resumed immediatelv. if the fluid temperature is above 180 K. PERIODIC CHECK-UPS The regular maintenance inspection schedule should include the equipment manufacturer s recommendations and also inspection of the heat transfer fluid. The following is a listing of check points. 1. Lubrication of moving parts. 2. Operating fidelity and accuracy of readings of safety controls and temperature limit controls. 3. Inspection of heater tubes, burner, refractory linings. 4. Periodic cleaning of heater surfaces. 5. Inspection of water cooling at the circulating pump. 6. Regular repacking of stuffing boxes according to the manu facturer's recommendations. 7. Semi-annual or annual sampling and analysis of Aroclor 1248. Under normal operating conditions not affected by fre quent power failures or accidental oxerbeating, when Aroclor 1248 is operated at 600~F. it should not be necessary to check oti the condition of the fluid more often than once or twice a year. The analysis for fluid condition is a simple determina tion of viscosity. The information given in Figure 6 serves as a guide to estimate the condition of the fluid, according to vis cosity values. Most users do their own testing; some have the viscosity determination made by an outside laboratory. Customers can have their fluid tested bv Monsanto free of charge. A one-quart sample is required, and sample should be earefullv packed to avoid breakage in shipment. Samples should be shipped to: Monsanto Chemical Company Organic Chemicals Division Industrial Fluid Sales St. Louis 24. Missouri ABOVE INFORMATION APPEARS ON POCKET CARDS INSIDE BACK COVER 0096 ?09 TOWOLDMONOQ22085 Designing or purchasing equipment for a heating system to he operated with Aroelor as a medium to deliver heat into a process requires consideration of heat transfer characteristics of both tin* user and the heater. The actual heat winch can he absorbed by a user, for example, depends upon the over-all heat transfer coefficient, heat transfer area, and a mean tem perature difference between Aroelor and the material being heated, both overall heat transfer coefficient and mean temperature difference are. in turn, affected by the flow rate of the Aroelor. This inter-relation of flow rate, heat, and temperature is usually solved by a trial and error procedure as covered in standard reference texts. The approach of Granetr) may be used to minimize or eliminate trial and error. The following tables and graphs of physical properties and engi neering data are provided as an aid in layout and design calculations for systems to be operated with Aroelor 1248 as a heat transfer fluid in the liquid phase. Table IV lists properties useful in heat balance calculations by which the flow rate is related to the heat transferred ami the temperature change of the Aroelor. This relation is also shown graphically in Figure Id. The over all heat transfer coefficient for the heater or user may be estimated by the methods outlined in the texts of MeAdamsC) or Kern(')- This is usually done by combining the individual film coefficient of the Aroelor with other coefficients and conductivities to yield the over all coefficient. Table V contains physical properties of Aroelor as a function of temperature which are needed for calculating the Aroelor film coefficient. Table \ 1 gives typical film coefficients for Aroelor flowing through a 0.81 inch i.d. tube. These are listed as a function of temperature and flow rate in a tubular heat exchanger. Other tube sizes would, of course, require a correction for the diameter in the Kevnolds and Nusselt group of the equation (from McAdams) given at the top of Table VI. ('oirelations for estimating film coefficients for \arious materials that might he processed by indirect heating may be found in the texts cited (*). (') and elsewhere in the literature. For sizing pipe* lines and pumping requirements. Figure 11 shows pressure drop vs. flow rati* ami pipe size tor Aroelor 1248 at temperatures over 800 F. Above this temperature Aroelor 1248 flows licelv like water. 0096710 TOWOLDMONOQ22086 |j| gSgS85s<RB2=s5333551g3S?333?25S=232siiil5Iisisi2sS2S2Ii*3 JI 2:!:!!SSi5l|iiSSS3||PgSS|g|l||S|5g|SS|ggsS|SlP||SSSSSS5S I S||||||2|1553|2i|il5|3|gS31!lli!i3lll!!il3i|HiligggSiS5s3S32 J| ! SSSS32g5Si=S3S|SgSS55SSSSSggSSgsiSSSSSSS55SS233SS2353SS5SS22S | !ISI8ll!I!!lS!SSlIS!IS!!IISlSllllS5IISIIiSISIIl!!sil!l8SSSI8 } issiiiaiiijiiiiiiiiiiiiiiiii! j j5|!|!!i;!?|!!!!j|iiij / ''2-~R~S3SSSS;=CS!"s!sS=5SS52S2SSEgggSsg2gRggsssssSsgsggs22gRg J " ! ssssssSSS2SSSgSlggggSsgggsgsgSassss|Hggiggg?iHSgSsssss|gg 00<*>1VV TOWOLDMONOQ22087 FLOW RATES FOR AROCLOR 1248 TEMPERATURE DIFFERENTIAL F OF AROCLOR ENTERING AND LEAVING THE USER FLOW RATE GALS PER MIN 0096712 TOWOLDMONOQ22088 Temperature TABLE V THERMODYNAMIC PROPERTIES of ABOCIOR 1248 P R A N DTL Absolute Viscosity Hr. Ft. Thermal Conductivity Ft. Hr. eF. ("crT LkJ Temperature F. aC. Absolute Viscosity Lbs. Hr. Ft. k Thermal Conductivity Btu. Ft. Hr. 'F. Cp/t k [> i 32 0 0.0577 320 160 3.53 .0542 20.6 3.35 ! 40 4 .0576 330 166 3.34 .0541 19.6 3.29 1' 50 10 0.575 340 171 3.14 .0540 18.5 3.22 60 16 2060 .0574 9844 39.5 350 177 2.95 .0539 17.5 3.15 : 70 21 960 .0573 4430 28.7 360 182 2.78 .0537 16.7 3.08 : 80 27 485 .0572 2353 22.3 370 188 2.66 .0536 16.1 3.04 | 90 32 278 .0570 1361 17.9 380 193 2.54 .0535 15.4 2.99 i 100 38 160 .0569 789 14.4 390 199 2.42 .0534 14.8 2.94 i no 43 114 .0568 566 12.6 400 204 2.32 0532 14.3 2.90 ` 1?0 49 77.5 .0566 388 10.8 410 210 2.20 .0531 13.7 2.85 jI 130 54 58.0 .0565 293 9.7 420 216 2.10 .0530 13.1 2.80 |: 110 60 43.5 .0564 221 8.7 430 221 2.03 .0529 12.7 2.76 < 150 66 33.8 .0563 173 7.88 440 227 1.93 .0527 12.3 2.73 i 160 71 26.6 .0562 137 7.15 450 232 1.83 .0526 11.7 2.68 1I 170 77 22.0 .0560 115 6.68 460 238 1.76 .0525 11.3 2.64 j! 180 82 18.2 .0559 95 6.18 470 243 1.71 .0524 11.0 2.61 jj 190 88 15.2 .0558 80 5.78 480 249 1.64 .0523 10.7 2.58 f' 200 93 12.6 .0557 67 5.38 490 254 1.57 .0521 10.3 2.54 i: 210 99 10.6 .0555 57 5.05 500 260 1.51 .0520 10.0 2.51 1 220 104 9.45 .0554 51.1 4.83 510 266 1.45 .0519 9.67 2.46 ; 230 110 8.10 .0553 44.1 4.55 520 271 1.38 .0518 9.26 2.43 i 240 116 7.26 .0552 39.8 4.36 530 277 1.33 ,.0516 9.00 2.40 j 250 121 6.48 .0550 35.9 4.18 540 282 1.28 .0515 8.72 2.37 | 260 127 5.76 .0549 32.1 4.00 550 288 1.22 .0514 8.36 2.34 270 132 5.03 .0548 28.2 3.81 560 293 1.18 .0513 8.14 2.31 ! 280 138 4.75 .0547 26.8 3.73 570 299 1.13 .0512 7.85 2.28 j 290 143 4.40 .0546 25.1 3.63 580 304 1.09 .0510 7.63 2.25 1 300 149 4.07 .0544 23.4 3.53 590 310 1.04 .0509 7.33 2.22 i 310 151 3.83 .0543 22.2 3.45 600 316 1.01 .0508 7.16 2.20 00q TOWOLDMONOQ22089 FLOW RATE, 6PM F. 1.0 2.0 150 200 44.9 250 33.5 58.5 300 40.5 70.1 350 45.3 79.0 400 49.0 85.5 450 53.3 93 500 56.3 98 550 60.5 105 600 64.2 112 TABLE V] HEAT TRANSFER DATA for AROCLOR 1248 FILM COEFFICIENTS P2k-| roG"|0.8rcP/no.4 h-UiJx0-O23L^J LtJ fMcAdamsj Based h flaw tbreafii Ml' I. D. tube (1' 0. 0. 113 tO expressed Bta./sq. ft /hr / F 3.0 63,4 80.9 97 109 118 128 136 145 155 4.0 78.7 102 122 137 149 162 171 183 195 5.0 94.0 122 146 164 178 193 204 219 233 6.0 83.2 109 141 169 190 206 224 236 253 269 7.0 86.2 124 159 191 215 232 253 267 286 305 8.0 93.8 138 177 212 239 259 282 297 319 339 9.0 103 151 195 233 262 284 309 327 350 373 10.0 114 164 212 254 286 309 336 356 381 405 Calculations lor other pipe sizes can be made usinf the data found in Tables IV and V. No film coefficients were calculated for flow rates where the Reynolds number was less than 2100. 11.0 123 179 229 274 309 334 363 383 411 437 12.0 130 191 245 294 331 358 388 411 441 469 0096 71 A TOWOLDMON0022090 HEAD LOSS, FT. PER 100 FT. 30,000 FRICTION LOSSES IN SYSTEM PIPING AROCLOR 1248. ABOVE 300 F. 2S 00^^71^ TOWOLDMONOQ22091 TYPICAL HEATERS USING AROCLOR 1248 A 200,000 8tu. (right) and a 300,000 Btu. heater, both ga$-fired, have been in use at Monsanto tor over 14 years for organic chem icals reactions. The heaters have operated near 600 F. with the same charge of Aroclor 1248 for periods of 7 years. 0096716 TOWOLDMONOQ22092 t insulated Aroclor return 1i An Aroclor dram port (Optional) A steam outlet from the to a steam trap with a bypass around the trap (Optional) A steam inlet line ir for heating cold Aroclor Arvclor Heater: Each heater consists of fire brick-lined walls and bottom inside a steel shell with steel baffles to force the hot combustion gases over the Aroclor coil for three passes. The top is a steel plate. Channel rron supports to ratse the bottom of the heater above floor level The Aroclor outlet from the cooler ties into the main line above the picture Right side water outlet Left side water inlet Cooler: Two-stage shell and tube construction with the Aroclor 1248 on the outside of the tubes. The two stage cooler is piped so that one stage can be used on each Aroclor healer or both stages can be used on either Aroclor heater. 009671T TOWOLDMONOQ22093 RIGHT A 40,000 Btu. per hour electrically heated portable heat exchanger used to heat vessels of about 50 gallons working capac ity. This unit was built for a variety of small scale chemical reactions. It was initially designed to vaporize approxi mately 200 lbs., hr. of an organic com pound which has a heat of vaporization of 150 Btu. per pound; a 30% heat loss was allowed for. Experience with the heater indicates that a horizontal rather than the vertical mounting of the immer sion heater (at operator's left) would have been more satisfactory. FAR RIGHT A 4,000,000 Btu..hr. forced circulation International LaMont heater. RIGHT Control panel for a 3,000,000 Btu.. hr. International LaMont heater that oper ates the 3,500 gallon, glass-lined kettle shown on the left. This kettle is the largest of its kind in the United States. FAR RIGHT Commercial heaters operating on Aroclor 1248 are available in any capacity desired. This is a 1.200,000 Btu./hr. installation. 0096718 31 TOWOLDMONOQ22094 (Photo Courtesy Union Iron Works) FAR LEFT A pilot plant resin processing vessel operated on indirect hejf transferred by Aroclor 1248. Vessel and hotter are mounted together m one unit. LEFT This 500.000 Btu. hr. forced circulation heater is electrically heated and designed for a liquid temperature of 500' F. The construction is similar to a double pipe heat exchanger with the electric heating elements in the inner pipe: the Aroclor 1248 circulates through the annular space between inner and outer pipe. The liquid Aroclor 1248 is delivered from the heater at a temperature of 500' F. and heats the contents of a jacketed kettle with a batch capacity of 1.000 gallons. This design for a forced cir culation heater was de veloped by Cleaver Brooks Company. UTKKAUKK CITKI) 1. Monsanto Chemical Co.. St. Louis. Mo.. Application Data Bulletin O-P-115 (1954). 2. Sullivan. M. \ ., Wollc. |. K.. and Zisman. W. A., "Indus. Eng. Chrin.." 59. 1607 (1917). 3. Granet I.. Heat Transfer Performance Curves'*. Chemical /.'rig/jirer/rig. P. JS7-I90. March. 1955. 4. McAdams. W. II,, "lleat-Transmission". McCraw-lIill Book Co.. Inc.. New York. ( 1942). 5. Kern, D. Q., `Process Ileal Transfer", McCraw-I Jill Book Co.. |,h-.. \,-w Ymk: ( 1950). 0096719 TOWOLDMONOQ22095 POCKET CARDS SUMMARIZING INFORMATION ON PAGE 22 HANDY FILE TAB Tara forward and up arodor LIQUID HEAT TRANSFER MEDIUM For temperatures up to 600 F. Long-lasting, trouble-free service Fire-resistant, non-corrosive Operates in un-pressured, minimum cost equipment Monsanto supplies troclor 12 tti. but not the heut exchangers. Monsanto a ill be happy to reconinienil sources of supply. 0096720 TOWOLDMONOQ22096 1 TESTING and CLEANING aroclor New or overhauled svstems must he TESTED FOR LEAKS and THOROUGHLY CLEANED OUT. This can be done in one operation as follows: Fill the empty system with cleaning solution (5 lbs. caustic soda and 5 lbs. of soda ash in each 1000 lbs. or 120 gal. of water). Thoroughly vent the system to insure complete filling. Close the vents and start the circulation pump. Start the burner at low fire, heat liquid to 180F. Circulate solu tion at least 24 hours, During this time, periodically drain off from a low spot some of the solution and replace this volume with clear water. Do this until the fluid in the system is clear. This takes about 24 hours. When clear, raise the exit fluid temperature to 215-225F., then turn the burner and pump off. Next drain the entire system and open all vents. Residual heat will dry out the moisture. When inspection shows the system is thoroughly dry, close all drains and vents. Now fill the system with Monsanto Aroclor 1248 until the expan sion tank gauge reads 1/4 full. Start the circulating pump and turn the burner on at low heat, Heat the fluid to 2509F. (return temp.) over a two-hour period. During this time, vent the lines every 10-15 minutes to allow any residual water vapor and air to escape. Reinspect the entire system for leaks while fluid circulates. Again inspect the expansion tank to make sure it is 1/4 full. Finally, set the burner for full heat. Bring system up to normal operating temperature. Adjust all controls for full modulation. Examine all pipelines for expansion, adequate bracing and leaks. Proceed with normal operations. 391-04SS-44 LITHO IN U S A. (over) OOS 6 7 ^1 TOWOLDMONOQ22097 Card No. 2 of 3 on operation of Arocior 1248 heat transfer systems, GENERAL RECOMMENDATIONS FOR .. nmWl248OPERATION and MAINTENANCE HEAT TRANSFER SYSTEMS The following instructions apply to all Arocior heating systems and are supplemental to manufacturers' recommendations for the equipment proper. Start-up Procedure 'follow these instructions any time a system lias been shut down long enough for the Arocior to cool below 180F.). ll.Sturt circulation pump and check expansion tank (should he 1/4 full). ^jstart burner on lowest heat and maintain full circulation until return fluid temperature reaches 1S0*F. 0Sct burner for full heat. Resume normal operation when fluid reaches proper temperature. Shut-down Procedure | (follow these instructions to pres ent localized over-heating when system is being shut down). H Shut burner off but maintain full circulation for at least 1/2 hour to dissipate high reskKiaT heat in combustion chamber. Qir air temperature is under 50F., keep fluid circulating constantly at 200F. Rower failure automatically interrupts the burner operation. When power resumes, start the circulation pump to get rid of any vapor pockets that may have formed in the heater tubes. If fluid is still hot (above 180F.), full heat may lie resumed when pipe knocking (if any) has stopped. It returning fluid lias cooled below 180F. during power failure and initial circulation, follow Start-up Procedure above. _ For more details, consult Monsanto's booklet on ' "Arocior 1248 Heat Transfer Data", or contact >0 o o MONSANTO CHCMICAL COMPANY--Organic Chamicoli OlvUion I n d u I r I o I Fluid! So I *i, t. O. Box 4 7 8--St. Unit, Minouri TOWOLDMONOQ22098 Cafcl No. of 3 on operation of Arocloc 1248 heat transfer systems SYSTEMS TOWOLDMON0022099 TOWOLDMONOQ22100