Instrument steam tracing tube

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I. Characteristics of instrument heating tubes: 1. They have a single function, which is to provide heating. 2. The material is single; once selected, the entire system uses only one type of material, namely ordinary carbon steel or copper. 3. The medium is singular; without exception, it is all low-pressure steam, with a typical pressure of 0.2 MPa. 4. The pipe diameter is fixed; once selected, the entire system uses only one specification, namely seamless steel pipes or copper pipes with dimensions of 14x2, 18x2, 10x1, or 8x1. 5. The installation requirements are not high. Except for the accompanying pipes inside the insulation box, which need to be bent neatly and aesthetically, all other parts are covered by insulating material, so the installation requirements are not high. II. Precautions for the installation of heat tracing pipes 1. Medium of the heat tracing pipes: Determine whether the heat tracing pipes are used for direct heating or indirect heating. The purpose of the heat tracing tube is to ensure that the medium with a high freezing point in the pipeline remains in a flowing state at all times. For this reason, with media having a lower boiling point, it is sufficient to ensure that they do not solidify and flow normally; there is no need to vaporize the medium. As a result of medium vaporization, significant errors can occur in flow measurement and pressure measurement. This type of medium belongs to indirect heat tracing, also known as light heat tracing. However, for media with a low freezing point, such as when the heating temperature is insufficient, it will affect the fluidity of the medium. Such media must be provided with direct heating, also known as forced heating. Re-insulating involves pressing the heating tube tightly against the pressure guiding tube, and the insulation also needs to be carefully checked. Light tracing involves leaving a gap of about 10 mm between the tracing tube and the pipe being traced. It depends specifically on the physical properties of the medium inside the tube and the pressure of the low-pressure steam. It is important to distinguish between direct heating and indirect heating, as it directly affects the proper monitoring and control of the system. And this issue is often overlooked by the constructors. 2. Determine the location for introducing low-pressure steam. On the control diagram, low-pressure steam is usually introduced from the nearest source. But sometimes, there is no low-pressure steam nearby. The best way to solve such problems is to install a low-pressure steam distributor in areas where the accompanying pipes are concentrated, and introduce low-pressure steam there. Then, it is connected out from the distributor. This is more convenient than introducing it directly from the low-pressure steam main into the companion pipe. 3. Condensate water should be discharged in a centralized manner; this issue is often overlooked by designers. ““Discharge on-site” is the easiest way to put it. The result of discharging directly on site is that steam appears everywhere first (the traps may be damaged), followed by water, and finally ice. The condensation water that accumulates on the frame platform turns into ice, posing significant difficulties for the operators. Centralized discharge, with the liquid being poured into gutters or drains in separate amounts, makes the setup much neater and also facilitates operation for the workers. 4. After the heat tracing pipes are installed, pressure testing must be carried out. The pressure testing requirements for these pipes are the same as those for steam pipes. The strength test pressure is 1.5 times the working pressure. The pressure test of the heat tracing pipe is conducted only for strength testing; there is no need to perform tests for tightness or airtightness. During strength testing, the valve and trap should be tested together. If a thermal insulation box is connected, the heating tubes (elbows) inside the box also need to be tested. Special attention should be paid in case this pipe leaks, as it could affect the proper operation of the instruments inside the incubator. During pressure testing, the instruments should be removed to prevent damage. The support for the heat tracing tube can move along with the pressure guiding tube it accompanies. 5. Handling of valves and instruments during the installation of accompanying pipes: The heat tracing pipes must not have any breaks in them, as otherwise the section with a break is prone to freezing. The areas prone to disconnection are the instrument valves and the root valves of the orifice plates. Whether the valve is directly or indirectly heated, it can be placed closely without causing the liquid inside the valve to vaporize. If not pressed tightly, it will affect heat retention. For the heat tracing tubes of instruments, only the part in contact with the medium is considered. For transmitters, considering the pressure guiding tubes that lead to them, there is one pressure transmitter, while there are two differential pressure transmitters for flow and level measurement. In special cases, heat tracing for the positive and negative pressure chambers can be considered. For pressure gauges and indicating level gauges (such as glass plate level gauges), it is sufficient to provide heat tracing pipes up to the instrument connections. 6. Insulation of the heat tracing tubes – The insulation of heat tracing tubes is an important process. The instrument pipelines are quite thin; using insulation material will make these small pipes larger. Poor insulation can turn what were originally neat and aesthetically pleasing pressure guide tubes into bulky clumps of cotton. Therefore, it is necessary to choose the right insulation material and ensure proper insulation. Common materials used for instrument insulation are asbestos rope and glass fiber cloth. Wrap the heat tracing tube around the pipe to be heated using asbestos rope, then cover it carefully with glass fiber cloth and tie it up with thin iron wire. Finally, apply the finishing paint as required by the design. The insulation material used in insulated boxes is usually foam plastic panels; these porous plastic panels provide excellent thermal insulation.