How to keep instruments insulated and protected from freezing in winter

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This post was last edited by hnan on 2016-1-10 at 18:15. How to take insulation and anti-freezing measures for instruments in winter: During winter, as temperatures drop, when the medium to be measured is transmitted through the measurement pipelines to the transmitter, freezing, solidification, and crystal formation can occur when the ambient temperature is too low. Since such low temperatures exceed the normal operating range of the instruments used, it affects the accuracy of the instrument’s measurements. For various instrument points such as those for pressure, flow rate, liquid level, and temperature, the medium being measured is usually liquid; exposure to low temperatures can lead to measurement errors, and in severe cases, it may cause safety incidents such as poisoning, fires, or explosions. In summary, it is particularly important to take measures to protect instruments and equipment from cold and freezing conditions. Some users of large-scale instruments and equipment took preventive measures well in advance; for example, power plants, water treatment plants, as well as industries in the oil and chemical sectors, all established anti-cold and anti-freezing procedures suitable for their own businesses. Next, let’s discuss how gauge users should take measures to prevent their gauges from freezing in winter. To prevent freezing of instruments and their measurement pipelines, heating and insulation are required mainly for transmitters installed within instrument enclosures, external float-type level transmitters or other types of level transduction units installed outdoors, as well as the detection and measurement pipelines for instruments such as pressure, differential pressure, and flow meters. Avoid such accidents through proper selection or other means. The measures typically taken include: selection, insulation and heating, maintenance (spot inspections, drainage), etc. I. Selection measures (1) Select instruments with insulation devices. Based on the category and purpose of the instrument, as well as the location where it is to be installed, the insulation and anti-freezing requirements for that instrument are determined, and these requirements are then submitted to the manufacturer for handling. (2) For remote signal transmitters and display meters, the requirements regarding tolerance to environmental temperatures must be taken into account; for those equipped with insulating fluid, the tolerance of the insulating fluid to environmental temperatures also needs to be considered. (3) Metal rotor flowmeters, electric target flowmeters, positive displacement flowmeters, mass flowmeters, etc. generally do not require separate heating. (4) When selecting a model, the primary considerations are generally the practicality and cost-effectiveness of the instrument. Practicality refers to ease of maintenance and accurate measurement, while cost-effectiveness simply means it being inexpensive. The two need to be combined; it is not appropriate to choose mass flow meters, metal rotors, electric targets, etc., solely for the sake of convenience and reduced maintenance. Therefore, selecting the right model is also a measure to prevent freezing and condensation. Furthermore, when installing instruments, due consideration must be given to preventing freezing and condensation; for example, the pressure transfer pipes should be as short as possible, regular inspections and cleaning should be carried out, and heating systems should be made available – otherwise, no matter how well the instruments are selected, it will be of no use. (5) In some areas in the north, the temperature difference between day and night is extremely large; temperatures can drop below -20 degrees at night. If this issue is not addressed through proper product selection, it would result in a poor cost-performance ratio, making it uneconomical. Choosing insulation and heat tracing, along with maintenance methods such as routine inspections and sewage discharge, are the best solutions to prevent freezing. II. Insulation measures: Use insulating materials for insulation, that is, wrap the parts of the instruments that are prone to freezing or sensitive to cold with such materials. When winter arrives, inspections should be carried out and waste should be removed regularly to prevent damage to the insulation material of the packaging. III. Heat tracing measures 1. Steam heat tracing measure, which involves using steam from pipes for heating and insulation. Before supplying steam for insulation in winter, check whether the steam insulation pipeline is unobstructed or blocked. It is best to keep the steam flowing 24 hours a day, at a temperature that is not too high. Sometimes it is also necessary to adjust the amount of steam supplied based on changes in weather and temperature, in order to prevent condensation inside the transmitter’s pressure tube from vaporizing due to high temperatures, which could affect the transmitter’s operation, or to prevent the condensation from freezing due to low temperatures, which could also hinder proper functioning of the transmitter. 2. Measures for insulation protection boxes: a) Electric heating tube-based insulation boxes consist of three main components: the box body, the heater, and the instrument mounting bracket. Their structural design is similar to that of ordinary protection boxes; the difference lies in the presence of an electrical heating device inside the box. As shown in the structural diagram, the heating device is made up of electric heating tubes and a temperature controller. There are sockets on the sides of the box body, and once power is supplied, the temperature inside the box rises to the desired level. Once this temperature is reached, the temperature controller continues to supply power to keep the temperature high. Repetitive operation is used to keep the temperature inside the box within a certain range. The main parameters of its constant temperature heater are as follows: (1) Rated voltage: 200V, 50Hz; (2) Rated power: 300–500W; (3) The control temperature can be set by the user; (4) The constant temperature heater can also be designed as an explosion-proof version; (5) There are three types of materials for the heating elements: copper tubes, carbon steel tubes, and stainless steel tubes. b. Steam pipe heating insulation box: The heating pipes are made of metal tubes in an S-shaped configuration. The top and bottom of the box are welded to the heating pipes using welded plate joints; these heating pipes are installed inside the box with steam entering from the top and exiting from the bottom, and heating is achieved through the circulation of steam within the pipe channels. Heat tracing tube materials are generally divided into two types: copper tubes and seamless steel tubes (carbon steel). c. Adding another layer of insulation material to the key instrument cabinets, and sealing the openings of these cabinets as well as the inlet and outlet pipelines with glue, can achieve a better insulating and anti-freezing effect for the instrument system. 3. Electric heating strip measures: Electric heat tracing insulation technology is a new type of heating technology that converts electrical energy directly into thermal energy. Install insulated cables; wrap the heating tape around the instruments or stick it inside the instrument cabinet (be careful to choose a length for the heating tape that is appropriate and cost-effective). A single-phase constant-power electric heating tape suitable for use in heating, anti-freezing, and insulation of pipes, valves, and pump bodies, or for maintaining the process temperature of instrument pipelines. It has a constant heat generation per unit length; its output power does not change with variations in ambient temperature. The length required for use is proportional to the power output. It can be cut at will during installation, but at least one heating section (i.e., 2.5 meters) must be retained. The outer woven layer serves to transfer and dissipate heat, and it also functions as a safe grounding element to prevent static electricity. It is mainly used for anti-freezing and insulation of various pipes and instruments, with a maximum maintainable temperature of 150°C. Note: Heat tracing and insulation for liquid pipelines where strict temperature control is required (a temperature controller must be used). There is another product available on the market: a soft-packaged electric heat tracing jacket, designed specifically for heat tracing of instruments in spaces with limited space. It is explosion-proof and is mainly installed on the pressure transfer lines of instruments as well as at valves. IV. Maintenance Measures 1. Installation Measures: Select an appropriate installation location – a dry place free from rain, snow, and water leakage. 2. When conditions permit, a dedicated person shall conduct daily technical checks and take necessary actions to determine whether the insulation materials are damaged or whether the steam pipelines are blocked. 3. Where conditions permit, sound and light alarm devices for steam leaks or power outages can be installed to facilitate the detection of potential issues related to insulation and anti-freezing measures, as well as their timely correction. 4. The inspection measures are carried out regularly by the regional instrument maintenance responsible person along the predetermined inspection routes. During inspections, it is necessary to check whether the valves of the insulated pipelines are functioning properly, whether the insulation boxes are in good condition, whether the drain devices are working correctly, whether the insulation material is properly packaged, and whether the components responsible for electric heating are functioning properly. Conduct thorough inspections of the instruments in the freeze-proofing equipment and keep records of these inspections; maintain the instruments as well as the insulation and freeze-protection measures in a dry, intact, and clean condition, and address any issues related to insulation and heating that arise on site promptly.