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What is Heat Tracing?WHAT IS HEAT TRACING? Heat Tracing is essentially heating a process (normally in pipe but also applicable to tanks and equipment) with an external heat source in the form of a “heat tracer”. Whether the heat energy source is electricity, steam from a boiler, hot oil from a hot oil heater or any other heating medium (or cooling medium), the energy source travels through the tracer which often spans the entire length of the pipe to ensure the process inside the piping stays at a certain temperature. This can be as simple as electric heat tracing a short run of pipe for freeze protection or as complex as a fully designed steam tracing system to heat an entire Sulfur Recovery Unit, for example. Insulation is applied over the heat tracing to ensure the heat is transferred into the process rather than lost to the surroundings. There are many types of heat tracing from Steam Tracing, Hot Oil Tracing, Water or Water/Glycol Tracing and Electric Tracing. Even fully jacketed pipe can be considered heat tracing although its normally referred to as jacketed pipe. Related Articles: What is Heat Tracing (Video by nVent)? (5) Ways to use Electric Heat Tracing
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How do I choose among different tracing technologies?ELECTRIC TRACING Most commonly, electric tracing is made from polymer sheathed wires that generate a specific electrical resistance along the length of the cable. When voltage and current are applied to the cable the resulting power flow is dissipated as heat, intended to replace the heat lost from the process through insulation. [All tracing should be insulated to perform the intended function]. There are many types of electric tracing systems available ranging from simple, low-temperature freeze protection systems to extremely high-temperature, Mineral-Insulated cables that can heat processes well above 500 °F. Electric tracing does have limitations that must be understood. Electric tracing is generally intended to only maintain process temperature and is not advised for heating processes from ambient to process melting points. Because of the limited heat density of an electric tracer, it could take days or weeks to heat a product line where other types of tracing (such as steam or hot oil) can take hours. This is an important distinction that is often overlooked on a project specifying tracing. Another important consideration is that all electricity is a secondary energy source. Though electricity is assumed to be highly efficient, that may or may not be true, depending on where that electricity is made. Understanding how your electricity is generated is important in determining your carbon footprint. This should be compared to other energy sources available for tracing before a selection is made. STEAM TRACING Steam tracing, like electric tracing, is used to heat trace a process pipe or tank to maintain temperature. A stainless-steel tube tracer conveys steam and is in contact with the pipe, tank, and equipment. If rapid heat-up of the process is important, steam tracing offers a substantial benefit. Steam is a high-quality energy source because condensing steam transfers a large amount of energy for heating process lines. When used in conjunction with Aluminum Enhancers like QMax FTS, heat transfer can be truly maximized. Steam is normally an ideal source of energy when heat-up of the process lines is a main objective. Heating an asphalt header at a railroad offloading spur is a prime example of a process line that requires rapid heat-up. Steam tracing does require the use of a boiler which is normally heated with natural gas or another hydrocarbon. Though these boilers use hydrocarbons to convert potential energy to heat energy to boil water, the efficiency from one BTU of energy to a BTU of usable heat can be quite high. This may mean a boiler is a better choice for reducing the carbon footprint of your facility. The steam, generated from a boiler, and used to heat the process lines, returns as condensate through steam traps. The condensate is recovered and sent to the boiler to make more steam, thus lowering emissions. Steam tracing is often used in chemical plants and oil refineries where steam is generated for use within other areas of the plants. Often referred to as “free steam”, the use of excess steam can be very beneficial in lowering the carbon footprint of an entire facility. Steam tracing does have a specific temperature band for use because steam temperature starts at 20 psig saturated steam at 259 °F and becomes impractical above 150 psig saturated steam or 365 °F. Other strategies are available for heating processes using steam below 259 °F and above 365 °F that offer flexibility and performance. WHICH IS MORE ACCURATE? So, which tracing technology controls temperature most accurately, steam, or electric? The answer is, well, both, and for different reasons. Electric tracing is normally equipped with a controller that can be adjusted for the application, even during operation. For this reason, electric tracing can be considered more accurate because the controller can be used to adjust heat input based on the process temperature, so long as the temperature sensor is functioning properly. Steam tracing, on the other hand can be more accurate if proper calculations are performed for the intended application. For example, if the goal is to heat sulfur to maintain at 280 °F with 50 psig saturated steam (298 °F), the amount of steam tracing can be calculated to maintain product temperature in the line. In this sense, steam tracing can be a “set-it-and-forget-it” system which always operates, if there are no steam or process upsets. HOT OIL TRACING Hot oil tracing is also used when processes need to be maintained at temperatures higher than is practical for steam. Liquid asphalt is a good example of a process that is often maintained about 365°F where steam would no longer be effective. Hot oil tracing is a similar concept to steam tracing, and the system is almost always “closed loop”. Hot oil is circulated through a hot oil heater powered by either electricity or hydrocarbon combustion, and then pumped through a facility to heat tanks and tracing lines. In this case, steam traps are not needed, however, proper controls are required to balance all users so they each get the hot oil flow they need to operate as intended. A balancing process is normally required to start up a hot oil heated facility. OTHER TRACING MEDIUMS Other common types of heating mediums are glycol, water, water/glycol mixes, and less commonly hot oil vapors. Regardless of the energy source and type of tracing that is selected, it is strongly recommended to consult with a company that understands all forms of tracing. Each type of tracing has a suitable place for a given applications. Choosing the optimal course of action is where experts can help.
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How do Aluminum Enhancers affect tracing?Why use Aluminum to Enhance the heat transfer? Using Aluminum Enhancers like QMax FTS in conjunction with steam, hot oil or electric tracing can have big benefits for little cost. These types of enhancers maximize the heat exchange between stainless steel tube tracers or electric tracers and what is being heated and offer consistent results. Used correctly, they transform the nature of a tracer from convection heat transfer through air to highly efficient conduction heat transfer through solids. Because of this, the heating surface area is greatly increased. For example, a single 1/2 inch tube tracer with steam has a single point of surface contact along a pipe so the heat must be transferred through the air space for the tracer to heat the pipe. The addition of a 2 inch aluminum enhancer (shown to the right) increases the heating surface area considerably and causes the heat to transfer through aluminum instead of air. This not only offers significant heat exchange performance, but it also allows for greater predictability of the actual heat exchange. Related Articles: Which Metals Conduct Heat Best? Does Aluminum Foil conduct heat well? Copper vs. Aluminum Heat Sinks, What you need to know.
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Why would rapid heat up be necessary?There are many reasons why a client would need rapid heat-up of a process inside of a tank or vessel. One reason may be to cause or control a reaction, in which case, generally fully jacketed vessels are used. Additionally, if a facility or a processing unit needs to be brought back online, rapid heat-up can cut down the time required to bring the system back to operating temperatures. Another example where rapid heat-up may be necessary is a process demand that cannot be accomplished with a traditional heat exchanger. If the process inside a vessel must be heated to a certain temperature and then maintained to replace heat that is lost naturally, then an internal or external heating system is used. There are many types of heating systems, both internal and external, using many types of energy sources.
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When is industrial tank heating used?Tank heating solutions are required when fluid processes inside tanks need to be stored at higher temperatures to maintain a particular viscosity. When process temperatures heat or cool out of the acceptable limits, processes can freeze, become viscous, or overheat. If the process does not flow properly, it can affect other processes up and down stream. Additionally, in industries dealing with corrosive substances, tank heating solutions serve to prevent the buildup of corrosive agents on the inner walls of tanks.
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What is Steam Tracing?WHAT IS STEAM TRACING? Steam Tracing is an external heating source in the form of a tracer which utilizes steam flowing through it to heat a process. Steam tracing is used to heat trace a process pipe or tank to increase and/or maintain process temperature within the equipment. The energy from condensing steam within the tube tracer transfers a large amount of heat to heat the process equipment. When used in conjunction with Aluminum Enhancers like QMax FTS, heat transfer can be truly maximized. Steam is normally an ideal source of energy when heat-up of the process lines is a main objective. Heating an asphalt header at a railroad offloading spur is a good example of a process line that requires rapid heat-up. Other forms of heat tracing include Hot Oil tracing, water or Water/Glycol tracing and Electric tracing. Related Articles: Understanding Installation of Steam Tracing for Long-Term Success
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Can Superheated Steam be used for steam tracing?CAN SUPERHEATED STEAM BE USED FOR STEAM TRACING? Using Superheated steam can be detrimental in a steam tracing system. One of the biggest benefits of using steam in heat exchange is that condensing steam releases a tremendous amount of heat energy. Steam only condenses at saturated temperatures. So if steam that is superheated is used for steam tracing, the release of energy may not happen inside the stainless steel tube tracer. This must be factored into the calculations when determining the actual heat exchange. Another thing to consider is the internal film coefficient of steam in the overall heat exchange formula. The film coefficient or convection coefficient of condensing steam is 500 to 1000 BTU/hr ft^2 F. This can drive the heat exchange from steam to process. Superheated steam has a film coefficient of 1-10 BTU/hr ft^2 F which can actually hinder the heat exchange even though it is hotter than saturated steam at the same pressure. This is an interesting phenomena that is often overlooked. QMax always recommends de-superheating any steam that will be used for steam tracing. Related Articles: Types of Steam
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What is Steam and Superheated Steam?WHAT IS STEAM and SUPERHEATED STEAM? Steam is made by boiling water. At atmospheric pressure, steam is 212 Degrees F and turns to vapor. However, if kept under pressure, the temperature of steam is increased. The temperature of steam correlates directly to the pressure the steam is maintained. For example, 50 psig saturated steam is 298 Degrees F. Steam at 50 psig is held inside a system that must withstand internal pressures of at least 50 psig (pounds per square inch at gauge). Steam Table (each pressure correlates to temperature when steam is saturated): Superheated Steam, like the name implies, is steam that is heated above it's saturation temperature. This allows for higher steam temperature at lower pressures. The benefit of superheated steam is that water vapor is very unlikely to be present. For example, superheated steam is used in electrical power generation because saturated steam would carry water droplets that could damage process equipment. Note: Using superheated steam can be detrimental in a steam tracing system. The FAQ below explains this phenomenon. Related Articles: Types of Steam. What is Steam?
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What is the best Steam Trap to use with Steam Tracing?WHAT IS THE BEST STEAM TRAP FOR STEAM TRACING? The debate has gone on for a long time and will continue to be discussed. There are many steam traps which are suitable for steam tracing. However, there are factors that must be considered for each application. Consult with QMax or a steam trap company for individual attention to each application. What is a steam trap? A steam trap is a mechanism, normally at the end of a steam system, that maintains steam pressure upstream of the trap and allows condensate to flow through to be recovered. There are many types of steam traps on the market. Mechanical Steam Trap (Free-Float & Bucket Traps) - Thermodynamic Steam Trap - Thermostatic Steam Trap - Related Articles: Application of Different Types of Steam Traps Selecting Steam Traps
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Should I use Stainless Steel Tubing, Copper Tubing or Carbon Steel?STEAM TRACING - STAINLESS, COPPER OR CARBON STEEL? Related Articles:
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How do I set up a leak-free steam or hot oil tracing system?MINIMIZING STEAM LEAKS IN STEAM TRACING SYSTEMS Steam is made by boiling water. At atmospheric pressure, water becomes steam at 212 Degrees F and turns to vapor. However, if kept under pressure, the temperature of steam can be increased. The temperature of steam correlates directly to the pressure under which steam is maintained. For example, 50 psig saturated steam is 298 Degrees F. Steam at 50 psig is held inside a system that must withstand internal pressures of at least 50 psig (pounds per square inch at gauge). That is a lot of pressure. Areas that are not sealed properly through welds, threads and other sealing surfaces can leak. Steam leaks are often very noticeable and can be very dangerous. They also represent large energy waste as steam is lost to the atmosphere. Therefore, any steam system should minimize leaks. Where can steam leaks occur? - Welds - Steam held in carbon and stainless steel piping and vessels are normally welded together. Makers of these parts should follow the appropriate code to fabricate and test to be able to maintain appropriate pressures. Carbon steel welds are more susceptible to internal and external corrosion than is stainless steel. However, stainless steel equipment is normally more expensive. - Connections - Between pieces of equipment containing steam, there are networks of piping, valves and control equipment. All of these pieces of equipment must connect together without leaking. These can be threads, flanges, compression fittings and welds. In all cases, proper fitment is important. In general, good practice is to use welds, flanges or compression fittings and to avoid using threads. Threads leak and cause other long-term, chronic problems. - Tubing/Fittings - Steam conveyed through Steam Tracing is normally connected using ferruled compression fittings linking tubes to tubes. These sealing surfaces can leak but are far less susceptible to leaks than threads or flanges. A best practice is to use a double ferruled compression fitting for steam to reduce leak potential. - Hoses - Flexible Metal Hoses are commonly used in process systems. These hoses are made from thin wall stainless steel with an overbraid for strength. Hoses are inherent weak points in any system and steam is no different. They often leak due to mistreatment or misuse. While in some cases they must be used, such as around a loading arm for movement, hoses should generally be avoided in steam systems due to the high leak potential. Other recommendations to mitigate steam leaks: - Fitting Connection Training - Most manufacturers of ferruled fittings provide training either written, video or in person. Take advantage of these training tools to know the proper ways to use the connection equipment. QMax can facilitate this training upon request. - Steam Tracing Training - Most manufacturers of steam tracing systems have approved installers and/or offer training to in-house installers. This training normally is brief and low-cost and is very valuable. QMax can facilitate this training upon request. Related Articles: Preventing Steam Leaks
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What is Gang Trapping and is it acceptable?WHAT IS GANG TRAPPING OR GROUP TRAPPING? Gang trapping or group trapping is a term that commonly refers to multiple steam lines being tied together before a single condensate trap. Often times it can cause unbalanced flow, lines can become flooded, and it can create problems such as steam lock or water hammer if not properly designed. When is Group Trapping Acceptable? Group trapping can be successfully implemented if a properly sized condensate header is used, such as a QMax Sub-Header. These can lower infrastructure cost by eliminating the need for additional tubing, fittings, condensate traps and manifolds. Engineers at QMax specifically design steam systems and sub-headers to ensure that proper condensate drainage is achieved. Related Articles: Group Trapping
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What is the typical circuit length for Steam Tracing?WHAT IS THE TYPICAL CIRCUIT LENGTH FOR STEAM TRACING? Industry Standard for circuit lengths of steam tracing before the need to trap condensate and resupply steam is approximately 150 linear feet of tracing, with a maximum of 50 linear feet of ViperLine (pre-insulated tubing) on each end of the circuit (totaling 250 linear feet). These circuit lengths should be validated for each application prior to use. For example, for high temperature differences between heating medium and process, the heat exchange could be higher than normal so the circuit lengths should be shorter. Consult with QMax with each application.
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Where should Steam Tracing Expansion Loops be installed?HOW OFTEN SHOULD AN EXPANSION LOOP BE INSTALLED ON STEAM TRACING? As a general rule, Expansion Loops should be installed every 50 feet of tubing to allow the steam tracing system to grow independently of the piping system. When using tubing, such as with QMax FTS, tubing expansion loops can be used. Expansion Loops should also be installed at flange breaks in the piping system. The connections should always be made outside the insulation so any steam leak is visible and does not saturate insulation.
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Why does the QMax FTS System come with ViperLine and what exactly is it?ViperLine is QMax’s brand of pre-insulated tubing, and it is used to connect your FTS tracing circuits to your heating/cooling medium supply and return. The tubing is covered with thermally insulated fiberglass material and a flexible, flame-resistant PVC jacket. This keeps your system at the temperature you want, while also providing personal protection from steam or hot fluids. For more information, click here.
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