ELECTRIC TANK HEATING
PT-501-1ELECTRICTANK HEATINGA GENERAL DISCUSSION CHROMALOX TRAININGFOR INTERNAL USE ONLYCopyright 1998, Wiegand Industrial Division, Emerson Electric
CHROMALOX TRAININGTANK HEATING- A General DiscussionDISCLAIMERThe facts and the recommendations made in thispublication are based on our own research and theresearch of others and are believed to be accurate.We cannot anticipate all conditions under which thisinformation and our products or the products ofother manufacturers in combination with ourproducts may be used. We accept no responsibilityfor results obtained by the application of thisinformation or the safety and suitability of ourproducts either alone or in combination with otherproducts. Users are advised to make their owntests to determine the safety and suitability of eachsuch product or product combination for their ownpurposes.Written ByAdam Heiligenstein&Hank NeubertChromalox IndustrialWiegand Industrial Div.Emerson Electric Co.701 Alpha Dr.Pittsburgh, PA 15238(412) 967-3800Revised 3/99Page 2Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
TANK HEATING- A General DiscussionCHROMALOX TRAININGINTRODUCTIONThe heating of tanks is a common industrial practice in many applications. Heatingmay be required to maintain pumping viscosity of heavy oil or resins, to preventcrystalline precipitation (sodium hydroxide), to facilitate production processes, for freezeprotection, and hundreds of other applications. Chromalox offers literally hundreds ofways of heating tanks of all sizes. Included in this guide is an overview of the types oftank heating approaches. The manual is not meant to be a complete guide to each ofthese heating methods, rather an overview of what is available. Once a specificmethod is selected, further investigation should be made into the suitability of theheater for the application. Finally, the manual is a detailed guide on sizing heaters forlarge tanks. This guide includes sizing details that are beyond the scope of the sizingguide presented in the general catalog.REQUIRED SIZING INFORMATIONFor any application it is essential that complete data be obtained and understood beforean evaluation and selection of a suitable heating system can be made. Specifically youwill need: Specific heat Heated material specific gravity and/or density Temperature rise or temperature to be maintained Heat up or temperature recovery times Process additions to tank Volume Incoming temperature Minimum low ambient temperature exposure Tank size, configuration, material of construction, and detail of nozzles andlegs Insulation Thickness k-factor Hazardous/non-hazardous service area Location - indoor/outdoor Wind conditions - velocity Environmental considerations Code requirements.Page 3Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
CHROMALOX TRAININGTANK HEATING- A General DiscussionTANK MARKETS AND APPLICATIONSNearly every major industrial process requires tank heating in some form or another.The major industries employing extensive tank facilities are: Refining and petrochemical operations Waste and environmental operations Terminal installations loading/unloading Pulp and paper operations Water storage and fire towers Utilities Mining operations Bulk storage, bins and silos Agriculture plants Food production plants Airports.COMMON HEATED MATERIALSA list of some materials commonly stored and heated in tanks is listed as follows:A. Liquids and aqueous based solutions: Liquid carbon dioxide Liquid chlorine Aqueous ammonia re towers Acids Solvents Resin and resin coatings.B. Food items: Vegetable cooking oils Molasses Syrups Sucrose (liquid sugar) Starch.Page 4Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
TANK HEATING- A General DiscussionCHROMALOX TRAININGC. Petroleum products: Benzene Naptha Paraffin Lubricating oilsCrank case (SAE 5 to SAE 50) Gear oils ASTM Asphalt compoundEmulsionsCut backsPenetration Fuel oilsNo 1 keroseneNo 2 (PS-100) Air craft fuels and domestic oil heatingNo 3 (PS-200) Air craft fuels and domestic oil heatingNo 4No 5 Heating oils for factory, commercial & mfg. process heatingNo 6 Bunker C Waste oils Synthetic and heat transfer oils.Page 5Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
CHROMALOX TRAININGTANK HEATING- A General DiscussionTYPES OF STORAGE TANKSStorage tanks encountered vary in size depending upon their application. In general,they can be classified as follows:A. Medium tanks 500 to 1000 gallonsB. Large tanks of 1000 to 10 thousand gallonsC. Very large tanks 10 thousand gallons and over.There are many approaches to heating tanks of these sizes. The many solutions thatChromalox offers are reviewed in the next section.In addition to storage tanks, many other tanks are employed in manufacturingprocesses, such as:A. Finishing tanksB. Wash and rinse tanksC. Cooking vesselsOpen top tanks used in these applications typically employ over-the-side heatingassemblies as well as screw plug or flanged immersion assemblies. This manual maybe used for sizing small open top tanks. Please note, however, that this manualincludes much more detail than is typically required for sizing small process tanks. It isrecommended that you consult the P120 or the P2000 for some additional examples.Finally, a computer based calculation tool is available that is designed specifically forrectangular open or closed top tanks used in the finishing industry. Contactheadquarters for more information.Page 6Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
TANK HEATING- A General DiscussionCHROMALOX TRAININGAN INTRODUCTION TO TANK HEATING DESIGNSChromalox offers the broadest range of tank heating solutions in the electric heatingindustry. There are two main methods to tank heating; direct and indirect tankheating.Direct tank heating consists of placing the heater in direct contact with the heatedmedium by placing the heater directly in the tank or circulating the fluid directly throughthe heater.Indirect tank heating uses a heat transfer medium to apply the heat to the tank.Indirect methods can vary from external heating of the tank using the tank wall as theheating medium to utilizing a heat transfer medium to carry the heat to the tank.Some heaters or systems can be utilized in direct and indirect methods and appear inboth sections of this manual.DIRECT TANK HEATINGDirect heating places the heater in direct contact with the heated medium. The heatingelement is immersed in the process fluid utilizing various mounting styles.The advantage of heating directly is that the heaters are nearly 100% efficient with thismethod. This is because all heat that is generated is absorbed directly by the process.This helps to speed heat-up and eliminate thermal lag. There is no intermediate heattransfer medium that could result in heat losses.The disadvantages of direct heating include the element surface limitation of the heaterto deliver the energy. Large surface areas require more space for the heater. If thetank is small there may not be room for a properly sized heater. Additionally,consideration of the heater material must be made to insure that the element iscompatible and will not degrade due to corrosion or pitting from the process. Becauseof the efficient heat transfer with directly immersed heaters, the relative watt density istypically high in these applications. Therefore, the heater must be designed so that it isnot exposed to air while operating which could lead to heater failure due to highelement temperatures. Finally, the element must be protected from sludge build up inthe tank that could limit the elements ability to transfer the heat. Figure 2 is anexample of immersion heater mounting and demonstrates installation mounting positionabove sludge line and below fluid line.A review of direct heating methods with the application pictures are shown throughoutthe next pages.Page 7Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
CHROMALOX TRAININGTANK HEATING- A General DiscussionDIRECT HEATING USING SCREW PLUG IMMERSION HEATERSScrew plug immersion heaters are typically applied in small tanks or reservoirs requiringrelatively small amounts of heat. Many of the tanks are open top style and are used inthe finishing industry or industrial process tanks. Many screw plug heaters include abuilt-in mechanical thermostat, which can often control the heater without any additionalequipment. Chromalox, however, typically recommends the use of an over temperaturecut out and/or level control.Figure 1: Typical screw plug immersion heater installationsFigure 2: Mounting a direct heating styleimmersion heaterFigure 3: Mating a screwplug heater to the tankPage 8Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
TANK HEATING- A General DiscussionCHROMALOX TRAININGDIRECT HEATING USING FLANGED IMMERSION HEATERSBecause screw plugs havelimited element space flangedheaters are used for largerwattage applications. Flangedimmersion heaters are typicallyapplied in large tanks or whereprocess requirements dictatehigh wattage. Flange heatersprovide a high amount of wattagein a relatively small spacebecause of the large amount ofheating elements that can fit intothe flange. Flanged heatersFigure 4: Mounting a flangedrequire an appropriately sizedimmersion heaternozzle in the tank and typicallycannot be removed withoutdraining the tank. The size of the nozzle will limit how many elements can be put in thetank due to the flange size. A smaller nozzle will require a longer heated length ormultiple heaters if the watt density is to be held constant. Nozzle size must always beconsidered when sizing a flanged immersion heater application.Figure 5: Typical flanged immersion heater installationsPage 9Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
CHROMALOX TRAININGTANK HEATING- A General DiscussionDIRECT HEATING USING OVER-THE-SIDE IMMERSION HEATERSOver-The-Side immersion heaters provide heating solutions for tanks without openingsin the side of the tank for insertion of a heater. They also are beneficial in small tanksor where heater portability is required. They are typically applied as an after marketmodification to the tank. Another advantage to the Over-The-Side approach is theability to remove or install the heater without draining the tank. Finally, large tankswhere there is only a manhole cover at the top available for heater access are ideal forOver-The-Side style heaters with manhole construction like the deep tank heaters.Figure 6: Over-The-Side heaterexamplesFigure 7: Deep tankinstallationsPage 10Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
TANK HEATING- A General DiscussionCHROMALOX TRAININGDIRECT HEATING USING CIRCULATION HEATERSCirculation heaters are utilized in direct heating applications. The process fluid iscirculated directly through the heater. The reason you would choose a circulation heaterover an immersion heater directly installed in the tank is either due to space limitationsor watt density limitations requiring high fluid velocity over the elements to increase heattransfer. Furthermore, if the circulation heater is piped and valved properly, the heatermay be serviced without draining the tank. The circulation of the process fluid isprovided by a pump or natural convection. In a pumping design the process fluid ispumped from the bottom of the tank, through a strainer, the pump discharges throughthe heater, and the fluid is returned to the top of the tank. In convection tank heatingapplications the natural convection of fluid is used to circulate the fluid through theheater. This approach is often referred to as side-arm heating. This design requirescareful consideration of viscosity and watt density to prevent damage to heater or fluiddue to low-flow conditions. Another type of tank heating that uses a similar approach toside-arm heating is vaporization. This is applied on low boiling point applications suchas ammonia. The heater is mounted side arm style low enough on the tank to remainconstantly flooded and the natural convection draws the fluid through the heater. Theheater adds the energy consumed by the vaporization of the fluid. Again, carefulconsideration of watt density must be considered. Additionally, level control should beinstalled to cut the heater out on fluid low-level conditions. Finally, a circulation heatermay be used to heat the fluid on demand as it is drawn from the tank. This methodallows for the tank to be maintained at lower temperatures or even remain at ambienttemperature.Figure 8: CirculationheaterFigure 9: Side armheatingFigure 10:InstantaneousheatingPage 11Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
CHROMALOX TRAININGTANK HEATING- A General DiscussionDIRECT HEATING USING HEAT TRANSFER SYSTEMSHeat transfer systems can be designed to heat tanks directly. The best example of thisapplication is freeze protection or temperature maintenance of large tanks. In thisexample the fluid is drawn directly from the bottom of the tank, through the heat transfersystem and pumped back into the top of the tank. Consideration must be given to thefluid being heated and the process conditions so that the pump and heater may beproperly specified for the application. In this approach the process tank must bemaintained at levels high enough to provide sufficient static head. Additionally, thedepth of the tank must be maintained high enough over the outlet nozzle to preventvortexing of the fluid and drawing air into the heat transfer system. Two feet of depth inthe tank is recommended for every foot per second of velocity in the suction pipe exitingthe tank. Finally, the tank should be vented to prevent high pressure from damagingthe heat transfer system.Figure 11: Simplified sketch of heat transfer system directheating a tankPage 12Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
TANK HEATING- A General DiscussionCHROMALOX TRAININGDIRECT HEATING USING SUCTION HEATERSSome tank heating applications can benefit from the use of suction heating assemblies.They consist of a flanged immersion heating unit mounted in a heating chamber withone end open so the liquid may be heated as it is pumped from the tank. Thiseliminates the need to maintain the total storage tank at process or pumpingtemperature. This simple design results in less piping required and lower installationcosts over a circulation heater design. Suction heaters are generally employed forheavy fuel oil and other viscous mediums. Capacity sizing is based on the pumpingrate and temperature rise required to obtain proper pumping viscosity. Suctionassemblies have the added advantage, through the use of proper valving and valveaccessories, of allowing the removal of the flanged immersion heater for maintenancewithout draining the tank. If the material is highly viscous the piping between the heaterand the pump may need to be heat traced to maintain the temperature of the processfluid at pumping temperatures in periods of downtime.Figure 12: SHO style suction heater piping andinstallation configurationPage 13Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
CHROMALOX TRAININGTANK HEATING- A General DiscussionINDIRECT TANK HEATINGIndirect heating uses a heat transfer medium to transfer the heat to the tank. Indirectmethods can vary from external heating of the tank using the tank wall as the heatingmedium to utilizing a heat transfer medium to carry the heat to the tank. In addition,pipe insert heaters have been included in this category because they use an air spacebetween the element and the process to convey the heat.There are various advantages to indirect heating. The biggest advantage is that theheater can typically be serviced without draining the tank. Second, indirect heatingoften allows watt density exposed to the process fluid to be lowered by spreading theheat over a larger surface. Finally, overheat conditions can be limited in manyinstances by simply limiting the temperature of the heat transfer medium.There are a few minor disadvantages to indirect heating that may be critical to yourprocess. The primary disadvantage is the thermal lag caused by using a heat transfermedium to carry the heat. The delay is caused by the fact that the heater must firstheat the heat transfer medium before the heat transfer medium can heat the process.If there is a large mass of heat transfer medium, larger heating capacities will berequired to raise temperatures.INDIRECT HEATING USING HEAT TRANSFER SYSTEMSHeat transfer systems are utilized inindirect heating by using a heatexchanger near or in the tank. The heattransfer fluid is circulated to the tank bythe heat transfer system where the heatexchanger transfers the heat from thefluid to the process.The heatexchanger may consist of a jacketedvessel or a heat exchanger immerseddirectly into the process fluid. The mainadvantage to this heating approach is theprocess fluid is never exposed totemperatures higher than the heatFigure 13: An example of atransfer fluid temperature.This ispackaged heat transferimportant in fluids that could be damagedsystemby high temperatures.A commonjacketed vessel application is the heating of chocolate. Chocolate, when melted, is veryviscous and susceptible to damage from even moderately high temperatures. Meltingand heating chocolate indirectly through the use of a water bath or jacketed vessel isnormally recommended. The water bath allows for the use of a higher watt densityheater to heat the water and subsequently a smaller heater without subjecting thePage 14Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
CHROMALOX TRAININGTANK HEATING- A General Discussionchocolate to the relatively high element temperatures normally associated with highwatt densities in a viscous liquid. Therefore, by using a double boiler or jacketed vesselapproach the process is protected from high temperatures. Finally, this approach isuseful when the process may not be compatible with a standard heater. Instead ofdesigning a custom heater that will withstand the harsh process a heat transfer fluid isused to transfer the heat from a standard heat transfer system.Figure 14: A simplified heattransfer system utilizinga jacketed vessel as theheat exchangerFigure 15: A simplified heat transfersystem utilizing a coil inthe tank as the heatexchangerFigure 16: A simplified heattransfer systemutilizing a coil externalto the tank as the heatexchangerPage 15Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
CHROMALOX TRAININGINDIRECT HEATING USING BOILERSBoilers are used as heat transfersystems for indirect heating.Instead of a liquid, steam is used totransfer the energy to the process.Again a heat exchanger is used inthe process to transfer the energyfrom the steam to the process. Thismay be in the form of a jacketedvessel or a heat exchanger directlyin the tank (see Figures 14-16).The advantage of steam is it cantransfer large amounts of energy tothe process efficiently.Thedisadvantage of steam is the highercost of piping materials required bythe high pressure associated withTANK HEATING- A General Discussion250Pr 200e150ss100ur 50e0212 267 298 320 338 353 366 378 388 397 406Temperature (Fahrenheit)Graph 1: Temperature vs. pressure.Note the high pressure required toachieve 400FFigure 17: Typical boiler installation showing required accessories for acomplete boiler heat transfer systemPage 16Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
TANK HEATING- A General DiscussionCHROMALOX TRAININGhigher temperatures. Operation above 350 F can become costly due to the associatedpiping materials required to operate at high pressure (125PSIG). Higher temperaturesand pressures may require using 300# construction of pipes and flanges instead of150# construction materials resulting in higher installation costs.However, whenoperating below these temperatures the boiler may be the most cost effectiveapproach. The steam heat exchanger can typically be sized smaller than an equivalentliquid heat exchanger due to the higher efficiency of condensing steam to transferenergy to the process.PIPE INSERT HEATERSThere are many approaches to pipe insert heaters utilizing various heaters. A pipeinsert heater uses an element inserted into a sealed pipe. The advantage to the pipeinsert heater is that the element is isolated from the process. This allows the elementto be removed without draining the tank, isolates hazardous or corrosive materials fromdeteriorating the element, and if sized properly may allow for the heat to be distributedover a larger surface area reducing the watt density exposed to the process.Consideration of element expansion both in length and the element supports on theinner diameter must be considered when designing a pipe insert heater. The internalheaters of pipe insert heaters consist of screw plugs, flanged heaters, or open coilelements (OCE) inserted into a pipe. Turnkey examples of these heaters with the pipeincluded are the RSTO and FXTH. Pipe insert heaters must have a separatetemperature controller mounted outside of the pipe to regulate the process temperature.An overtemperature device should be installed and attached to the top of the pipe atthe highest point. Packaged Systems offer a control panel with the necessary switchgear and temperature controls along with the heaters.Figure 18: Pipe insert heater utilizing a screw plug heater(MTO-LT). Flanged heaters are often used.Page 17Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
CHROMALOX TRAININGFigure 19:TANK HEATING- A General DiscussionFXTH heater assemblyFigure 20: Installing an FXTHheater in anunderground tankFigure 21: RSTO heater shown installedin a tank. The RSTO shipscomplete with a panelPage 18Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
TANK HEATING- A General DiscussionCHROMALOX TRAININGESTIMATING HEATING REQUIREMENTSA procedure for estimating a large tank heating requirement with calculations is detailedbelow. The first step in any application is to gather information on the application.INFORMATION REQUIRED FOR SIZING Determine tank characteristics and the nature of the material contained in thetank Bulk, liquid or other compound, etc. Acid or alkaline Specific heat Specific gravity or density Viscosity. Tank size Diameter Height Capacity (U.S. gallons) Length and width (rectangular tanks) Determine tank surface area, side and roof (sq-ft.) (A1 and A2) Determine tank bottom area in contact with ground (sq-ft.) (A3). Temperature Tank temperature contents to be heated from and to, or maintained,(T2 F) Ambient temperature tank surface is exposed to (T1 F) Ambient temperature of ground under tank (T3 F). Heat-up or temperature recovery times Process Additions to tank Volume Incoming temperatures. Insulation Thickness Type k-factors. Environmental Conditions Wind velocity Location classification Indoors/outdoors. Code requirementsPage 19Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
CHROMALOX TRAININGTANK HEATING- A General DiscussionEXAMPLE PROBLEMAssume a tank of 20 ft. diameter and height of 15 ft. containing 35,000 gallons of No. 6fuel oil is to be maintained at 100 F, minimum ambient temperature is 10 F, groundtemperature averages 40 F, wind velocity is 15 MPH, tank wall and bottom iscomprised of 5/16 inch thick carbon steel, roof construction is 12 gauge carbon steel ontruss supports. The dome is 4’ high. The tank is situated on a concrete donut shapedfooting extending below the frost line. Area inside the donut footing is filled withcrushed trap rock and sand. The tank has yet to be built, therefore, flanges and nozzlemodifications may be added to best meet the heating requirements of this tank. Condition (1) Bare tank, uninsulated Calculate steady state heat loss Assume a power brown out of three (3) days duration. Calculate KWrequired to bring tank and contents back to temperature through atemperature rise of 10 F. NOTE: Large tanks holding viscous materials rarely havetemperature drops of more than 2 to 3 F per day. Please seethe charts at the end of this text concerning the effects of tanksurface conductance and inside tank film build-up on heat loss.Specifically, the following factors come into play:A. Air surface conductance (fo). This factor is largelyinfluenced by wind velocity and tank surface emissivity.(i.e., tank loss is proportional to wind velocity for givenemissivity factor). Please see Table 1 for heat lossesversus wind speeds.B. Tank wall inside film build up is also a factor effecting therange of tank losses. This factor is influenced bythickness of film and temperature. Please see Table 2 atthe end of this text. Correction factors are employed toreflect this reduction in loss for tanks containing light toheavy oils, asphalt’s and other viscous materials. Seeheat loss data at the end of this text. Correction factorscan vary from 10 to 50%.Condition (2) Insulated tank with one (1) inch of fiberglass insulation. K 0.25 at50 F Calculate steady state heat loss Calculate heat-up kW for same brown out condition as condition (1).Page 20Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
TANK HEATING- A General DiscussionCHROMALOX TRAININGCALCULATIONSA. Tank Area’s Variables A1 is the area of the bottom of the tank (ft2) A2 is the area of the sides of the tank (ft2) A3 is the area of the roof of the tank (ft2) H1 is the height in feet of the sides of the tank h is the height of the dome in feet on the top of the tank D is the diameter of the tank in feet. Tank BottomΠD 2A1 4 Π x 202/4 314 ft2 Tank SideA2 ΠDH1 Π x 20 x 15 942 ft2 Tank TopΠ A3 D 2 4 h 2 4 A3 (Π/4) x (400 4 x 16)A3 364 ft2 Total surface area exposed to ambient airATOTAL (A2 A3) 942 364 1306ft2B. Estimated Uninsulated Heat Losses From Top and Sides of Tank (Condition 1) Variables T1 is the lowest ambient temperature tank surface is exposed to in F T2 is the tank temperature contents to be heated or maintained in F T is (T2-T1) in F UA is the heat loss factor in BTU/HR/SQ-FT/ F (See Table 1) LS is the total losses UA x T x ATOTAL Heat loss to ambient air condition at 15 M.P.H. and T (T2-T1) F 90 FUA 5.1 BTU/HR/SQ-FT/ FLS UA x T x ATOTALLS 5.1 x 90 x 1306 599454 BTU/HR x correction factor of 0.6 359672 BTU/HR 3412 105 KW/HR for tank side and roof.C. Estimated Heat Loss To Ground Variables T3 is the lowest temperature the tank bottom is exposed to in F T2 is the tank temperature contents to be heated or maintained in F TGround is (T2-T3) in FPage 21Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
CHROMALOX TRAININGTANK HEATING- A General Discussion K is the conductivity of the ground that the tank is supported on inBTU/HR/in/SQ-FT/ F X is the depth of the soil in inches UG Overall heat transmit rate in BTU/HR/SQ-FT/ F LG is the total losses to the tank foundation in BTU/HR Heat Loss To Ground TGround (T2-T3) 60 FUG 1 X K K Conductivity of foundationWhere, K 8.5 BTU/HR/in/SQ-FT/ F, sand at 4% moistureX 12 inches sandUG 1 X K Where, UG Overall heat transmit rate BTU/HR/SQ-FT/ FUG 11.41 0.71 BTU/HR/SQ-FT/ FLG UG x TGround x A1LG 0.71 x 60 x 314 13376 BTU/HR 3412 3.9 KW/HR It should be noted here that tank ground loss verse tank ambient lossis small3.9kW/105kW .037 or 3.7% of the total losses For very large tanks at temperatures under 100 F, ground loss may beignored for all practical purposes.D. Total Estimated Heat Loss (L) For TankL LS LG 105 3.9 108.9 KW/HRSafety Factor of 20% 131 KW/HR TOTALE. Estimated Heat Loss To Ambient Air For Insulated Tank (Condition 2) Variables T1 is the lowest ambient temperature tank surface is exposed to in FPage 22Copyright 1998, Wiegand Industrial Division, Emerson Electric Co.
TANK HEATING- A General Discussion CHROMALOX TRAINING T2 is the tank temperature contents to be heated or maintained in F T is (T2-T1) in F UInsul is the heat loss factor in BTU/HR/SQ-FT/ F LS(I) is the total losses UInsul x T x ATOTALHeat Loss CalculationsUInsul 0.25 BTU/HR/SQ-FT/ F for (1 inch Fiberglass insulation)LS(I) 0.25 x 90 F x 1306 29385 BTU/HR 3412 8.6 KW/HRHeat Loss to GroundLG 3.9 KW/HRTotal estimated heat loss, insulated tankL(I) 8.6 3.9 12.5 KW/HRSafety Factor of 20% 15 KW/HR installedBy comparing the kW required to maintain a tank temperature of 100 F (for a T 90 F) it can be seen that the insulated tank kW is only 11.5% of the KWrequired for base uninsulated tank. If energy cost per kW*Hr is 0.05 cents,operating cost for insulated tank versus bare tank is: Bare tank loss 131KWEnergy cost 131 x 0.05 x 720 4716.00/month Insulated tank 15KWEnergy cost 15 x 0.05 x 720 540.00/monthSavings of 4176.00/month or 89% The cost of insulating a typical tank is 7.50 to 10.00 per sq-ft.Based on this assumption the cost to insulate subject tank can berealized in approximately three (3) months energy savings.F. Tank heat up, recovery for T 10 F Estimated weight of the tankWeight of 1 square foot of 5/16 steel (0.3125” thick)12.7 lb/ft2 (0.3125/12) ft x 487 lb/ ft3 22Side (A2) 942 ft x 12.7 lb/ft 11,963 lb.Roof (A3) 364 ft2 x 4.375 lb/ft2 1,593 lb.Bottom (A1) 314 ft2 x 12.7 lb/ft2 3,988 lb.17,544 lb. Weight of No. 6 fuel oilSpecific Gravity of No. 6 fuel oil 0.943Tank Volume is 35000 gal.35000 x 8.4 x 0.943 27,7242 lb. Specific heat of tank and oil:Specific Heat - tank 0.12 BTU/LB/ F- oil 0.44 BTU/LB/ F Tank heat up17544 lb. x 0.12 x 10 F 21053 BTUPage 23Copyright 1998, Wiegand Industrial
The disadvantages of direct heating include the element surface limitation of the heater to deliver the energy. Large surface areas require more space for the heater. If the tank is small there may not be room for a properly sized heater. Additionally, consideration of the heater
3- Differential surge tank: an orifice tank having a riser is called differential tank. 4- One- way surge tank: in a one way surge tank the liquid flows from the tank into the pipeline only when the pressure in the pipeline drops below the liquid level in the surge tank. 5- Closed surge tank: if the top of the tank is closed and there is
prevent tank uplifting, the following are minimum requirements for different types of common tank supports and surfaces upon which the tank shall be placed. Tank Supports – Tank supports shall be either (a) types that are included under the tank Listing (steel saddles welded to tank), or (b) 1.25" diameter
However, electric furnaces can accommodate central cooling easier than zonal electric heating, because the air conditioner can share the furnace’s ducts. Electric resistance heat can be provided by electric baseboard heaters, electric wall heaters, electric radiant heat, electric space heaters, electric f
Fin – Input flow rate of the tank F out – Output flow rate of the tank H - Total height of the conical tank. R - Top radius of the conical tank h - Nominal level of the tank r - Radius at nominal level Fig3. Mathematical modeling of a conical tank The area of the conical tank is given by (3.1) R
tank, this work was designed the refill sauce storage tank connection to the normal sauce storage tank to control level sauce in tank. m Fig.7. two liquid storage tank systems The purpose of this study is to control level in normal sauce tank. The apparatus, shows in Fig.7, consisting of normal sauce tank and one more refill sauce tank.
FOR INDUSTRIAL HEATING OF AIR AND GAS UP TO 800 C (1470 F) Traditional heating cassettes are commonly equipped with tubular heating elements as the heating source. The design of these elements limits the maximum reachable air/gas temperature to about 600 C (1110 F). With the state of art heating element design used in our Kanthal heating .
Figure 1: Screenshot of Tank Summary Worksheet in the Storage Tank Assessment Spreadsheet.xlsx. b. Complete Tank worksheet(s) for each individual storage tank i. Interpret maximum and minimum tank levels of each cycle with corresponding time and date for all tanks. Tank level data may be found in tabular or graphical form and reported in depth
variable. And level of conical tank is a control variable[3]. This can be achieved by controlling the input flow of the conical tank. Fin Fig2. Schematic diagram of conical tank Process operating Parameters are, Fin - Input flow rate of the tank F out - Output flow rate of the tank H - Total height of the conical tank.
