What is piping heat tracing?
Pipeline heat tracing is a kind of constant temperature or heating method to prevent the material in the pipeline from crystallizing and solidifying or to meet the process demand, and to keep the material at a certain temperature.
Electric heat tracing system is the use of electrical energy into heat energy, for the pipeline insulation antifreeze, its has with high efficiency, easy installation and so on many advantages by the majority of users, but there are many users still do not know what pipeline need to use electric heat tracing insulation? Is the pipeline needs a certain temperature inside the medium to flow need to use insulation facilities, such as chemical pipelines need to react at a certain temperature to the media need insulation heat to normal operation.
Why does the pipeline need to accompany the heat insulation?
In the production, some easy to condense medium, such as crude oil, heavy oil, etc. in the pipeline transportation process, because the temperature decreases, viscosity will increase or even solidify and affect the normal operation of equipment, so this kind of pipeline must take insulation facilities to maintain a certain temperature. The insulation of electric tracing heat system is very simple, as long as you choose the corresponding model, and then the electric tracing heat tape is attached to the outer wall of the pipe. When it is needed, the electric heat tracing system is energized and starts working to provide the required temperature to the pipeline.
According to the pipeline parameters and the required temperature, you can choose different types of self-limiting electric heating cable, constant power electric heating cable, MI armored heating cable, heating cable, etc. Electric heating cable has been widely used in the pipeline and tank freezing insulation and maintenance of process temperature, etc.
Types of heat tracing system
Heat tracing systems can be divided into two main categories, electric and fluid.
Fluid heat tracing system
Fluid heat tracing systems use a heating medium at high temperatures to transfer heat to the piping. The fluid is usually contained in a pipe or small tube connected to the piping being traced. If steam is the tracer fluid, the condensate is either returned to the boiler or dumped. If an organic heat transfer fluid is used, it is returned to the heat exchanger for reheating and recirculation. Typically, heating of the tracer fluid can be provided by the combustion of waste heat from the process stream, fossil fuels, steam or electricity.
Electric tracer systems
Electric tracer systems convert electrical energy into heat and transfer it to the piping and the fluid it contains. Most commercial electric tracer systems in use today are resistive and take the form of a cable placed on the pipe. When an electric current flows through a resistive element, the heat generated is proportional to the square of the current and the resistance of the element to the flow of the current. Other specialized electric tracer systems use impedance, induction and skin conduction effects to generate and transfer heat.
Types of electric tracing heat for pipelines
Pipeline electric tracing heat classification: self-limiting electric tracing heat tape, parallel electric tracing heat tape, series electric tracing heat tape, high temperature electric tracing heat tape, silicone rubber electric heating belt, MI heating cable. The electric tracing heat system is composed of three parts: power supply system of heating cable, heating system of anti-freeze cable and electric tracing heat only control alarm system. Each electric accompanying heat circuit includes thermostat, temperature sensor, air switch, contactor, working state display, fault buzzer alarm and transformer and other circuits.
1. Self-limiting temperature pipeline electric tracing heat. As the temperature rises, the resistance of this tropical becomes bigger and the power becomes smaller. Due to the large starting current, the service length is generally within 100 meters, and the tropical area can be cut freely. No matter how long it is, the rated voltage is applied to heat up.
2. Parallel pipeline electric tracing heat. Tropical area two (or three) parallel insulated copper strands as power bus, winding PTC characteristic electric heating wire on the skeleton, service length is about 10-800 meters.
3. Series pipeline electric tracing heat. It has the same cross-sectional area, one end is reliably short-circuited, and the other end is connected to 380V (or design voltage) power supply, forming a star-shaped load. Joule’s first-order law: Q = 0.24IRT of electrical energy In fact, according to the need, the three phases of the electric heating area (single-phase) can be separated, but also can be integrated. The length of this heat tape used should not be too short. Generally, it is around 500-2500m.
4. High temperature pipeline electric tracing heat. This heat tape is made of glass fiber and other high temperature resistant materials, can withstand the temperature within 300 degrees Celsius, the length of 1-50 meters (can not just cut, need to find a professional manufacturer design).
- 1). thermal stability out of sex: from 10 degrees Celsius to 99 degrees Celsius after 300 round trips, the heat of the heat tape to maintain more than 90%.
- 2). bending radius: 25.4mm at 20 degrees Celsius, minus 30.
- 3). insulation resistance: when the pipeline electric accompaniment is 100m long and the ambient temperature is 20 degrees Celsius, the minimum value of insulation resistance (between wire and shield) is 20MΩ after 1 minute of swing test under 2500VDC.
- 4). starting current (10 degrees Celsius) is 0.4A per meter. 5、Maximum use length: below 100m.
Steam heat tracing
Steam tracing is the application of steam heat to pipelines and vessels to maintain the desired process temperature, anti-freeze, viscosity control or to obtain a temperature control point within the fluid for chemical interactions in the process.
Steam tracing is typically accomplished by running a steam line in direct contact with the piping or vessel to be heated.
The Need for Steam Tracing
The principle of how steam tracing works is very simple. When the product in the pipeline is at a higher temperature than the air around it, heat is transferred from the product to the surrounding air through the pipeline walls.
This heat loss will cause the temperature of the product to drop. Pipe insulation will significantly reduce the rate of heat loss, but unfortunately, no insulation is 100% effective.
Steam is a very effective heat carrier with a fixed relationship between pressure and temperature. It can transfer heat over long distances and release it at a constant temperature.
To compensate for the heat lost from the product piping, small diameter steam pipes or tracers are attached to the product line. The heat generated by the steam enters the product line and replaces the lost heat. The heat transferred, as well as the product temperature, can be easily controlled by a simple self-acting control system. The same type of control can be used for winterization applications, allowing steam to enter the tracer line only when the ambient temperature falls below a predetermined level.
In order to find the leak, hundreds of meters of pipe insulation must be removed. The costs are enormous and also related to scaffolding. Therefore, please keep this in mind and make sure that the steam tracing is installed correctly.
Types of Steam Tracing Heat
- Jacketed – Used in ultra-critical applications where the product temperature must usually be maintained at a high temperature at all times. The use of a steam jacket also allows for rapid preheating of the piping.
- Critical – Here, steam tracing is used to maintain the product at a temperature that will cure or deteriorate if its temperature falls below a predetermined level.
- Non-critical – Tracing is used to maintain product viscosity at optimal pumping levels.
- Winterized – Ensures that pipelines are not damaged by freezing in adverse weather conditions.
- Instrumentation – Small diameter steam tracer tubing, typically 10 mm, used to protect flow meters, control valves, sampling stations, pulse lines, etc.
Determining Tracer Requirements
To select the size and number of steam tracer lines required for a particular application, the heat loss rate of the product piping under worst-case design conditions must be determined.
This heat loss rate depends on the difference between the product temperature and the ambient temperature. Other factors such as the thermal conductivity of the insulation, ambient wind speed and the emissivity of the insulation surface will affect this loss rate.
Size and Length
The most common steam tracing diameters are 3/8 inch (9.52 mm) and 1/2 inch (12.7 mm) OD copper or stainless steel tubing. 5/8-inch (15.88 mm) and 3/4-inch (19.05 mm) OD pipe is used; however, this requires greater expense. 3/8-inch pipe is more likely to become clogged with deposits and/or debris and is therefore used less frequently. Copper is preferred for its heat transfer properties, while stainless steel shows better resistance in corrosive environments.
Advantages of steam tracing compared to other methods
While the advantages of each method can be debated, the table below shows the relative advantages and disadvantages of each system.
As energy costs continue to rise, one of the key areas of concern for plants is the reliability and energy efficiency of the tracer system. The high available heat content of steam offers many benefits over using thermal fluids for tracing, and is much more efficient than electric tracing.
Because steam consists primarily of water, it has minimal environmental impact when leaking into the atmosphere. It is estimated that the cost to clean up a one-liter glycol spill could be as high as $5,000.00. This cost includes the cleanup, reporting and documentation required in the event of a spill at an industrial site. Steam is inherently safe, which makes it a practical choice for most industrial applications where ignition sources must be minimized.
For these reasons, the use of steam tracing remains the preferred choice for temperature maintenance in most industrial and process applications.
What is an electric heat tape?
A ribbon heater that converts heat energy directly through electrical resistance, referred to as a heating cable (electric heat tape, electric hot wire).
How to solve the problem of uneven heat transfer temperature between electric heat tape and pipeline?
The working principle of electric heat tracing is relatively simple, which is to lay the electric heat tracing cable on the outside of the pipeline to energize the heat, and conduct the heat to the pipeline. Whether the heat can be enough and uniform heat transfer, to ensure that the effect of anti-freezing with heat, will not appear in the pipeline of the medium of freezing blockage problem. To solve the problem of uneven heat transfer temperature between electric heating cable and pipeline is the key. There are many problems that affect the uneven temperature of electric tracing heat tape, as follows.
- 1. Electric tracing heat brutal installation, electric tracing heat insulation damage, causing short circuit phenomenon, or excessive bending, PTC resistance value was destroyed.
- 2. Electric tracing heat installation more than the use of length. For example, the longest single self-limiting electric heating cable is not more than 100 meters. More than the length will appear not hot situation.
- 3. The outer insulation layer is not waterproof treatment, the installation thickness is not evenly caused by the heat loss difference is too big, heat loss too much.
- 4. The outer wall of the pipe has low thermal conductivity or uneven heating area. Electric heating auxiliary materials are indispensable, for example, aluminum foil tape can assist in accompanying heat temperature transfer and increase the heated area.
- 5. Power supply circuit or voltage problems, if there is a shortage of electricity, this time the user can set up an independent electric heating system power supply power point, to ensure sufficient power supply voltage.
- 6. Product quality problems electric heating tape production process is not qualified, resulting in uneven PTC organization or damage, please choose the regular electric heating tape manufacturers, solutions: please follow the qualified manufacturers of electric heating tape.