In the cold winter, the transmitter often freezes. This is because when the measured medium is transmitted to the transmitter through the measurement pipeline, it often occurs that the ambient temperature is too low, and solidification, precipitation and crystallization will occur. Too low and beyond the normal operating temperature range of the instrument used directly affects the accuracy of the instrument's measurement display. For this reason, the instrument and the measuring pipeline of the instrument must be anti-freezing.
How to protect the transmitter in winter? First of all, the objects that need heat tracing and insulation mainly include transmitters installed in the instrument insulation box, external buoy liquid level transmitters or other forms of open-air level transmitter units, pressure, differential pressure, flow and other instruments. Inspection pipeline and measurement pipeline. Avoid such accidents through selection or other methods.
The measures taken are usually: type selection, heat tracing, maintenance (point inspection, sewage), etc.
1. Selection measures
Choose instrument with insulation device. According to the type and use of the instrument and the geographic location of the proposed installation, the insulation and antifreeze requirements of the instrument are proposed, and then submitted to the manufacturer for processing.
The temperature difference between day and night is too great in some places in the north, and it can reach more than -20 degrees at night. If it is solved from the type selection, the cost performance is quite uneconomical. The best solution for anti-freezing is to choose heat preservation and heat tracing, maintenance (point inspection, sewage) and other methods.
2. Insulation measures
Insulation with thermal insulation material, that is, the thermal insulation material is used to wrap the parts that are easy to freeze or afraid of freezing. When winter comes, it is necessary to check and frequently discharge sewage to prevent damage to the packaging insulation materials.
3. Heat tracing measures
1. Steam tracing measures
That is, use tube steam heating to keep warm. Check the steam insulation pipeline for blockage or blockage before sending heat in winter. The best steam is 24 hours, not too hot, sometimes to adjust the amount of heat supply steam according to the temperature change of the weather, to prevent the temperature is too high to vaporize the condensate in the pressure pipe of the transmitter to affect the work of the transmitter or due to temperature Too low makes the condensate freezing in the pressure pipe of the transmitter affect the smooth operation of the transmitter.
2. Insulation protection box measures
(1) The electric heating tube heating insulation box is composed of three parts: the box body, the heater, and the instrument bracket. Its structure is the same as the protective box. The difference is that the box is equipped with electrical heating devices, and the electric heating device is made of electric heating. The tube is composed of a temperature controller, and the side of the box is equipped with a socket. When the power is turned on and the box is heated to the required temperature, the temperature controller is turned on to continue to heat up. Through repeated work, the temperature in the box can be kept within a certain range. The main parameters of its constant temperature heater:
â‘´, rated voltage 200V.50Hz
⑵, rated power 300 ～ 500W
⑶, the control temperature can be set by the user
â‘·, constant temperature heater can also be made into explosion-proof type
⑸ There are three kinds of electric heating tube materials: copper tube, carbon steel tube and stainless steel tube.
(2) Steam tube heat tracing insulation box, the heat tracing tube is made of metal tube with S-shaped structure. The upper and lower parts of the box are welded with a welded through plate joint and a heat tracing tube. The heat tracing tube is installed in the box for up and down, and the heating purpose is achieved by the circulation of steam in the tube cavity. The materials of the heat tracing tube are generally divided into two types, namely, red copper tube and seamless steel tube (carbon steel).
(3) Add a layer of thermal insulation cotton to the key instrument box, and glue seal at the door of the insulation box and the inlet and outlet of the pipeline to achieve better insulation and antifreeze effect of the instrument system.
3. Electric heating belt measures
Electric heat tracing insulation technology is a new type of heating technology that directly converts electrical energy into thermal energy. Install insulation cables to wind the heating cable around the instrument or stick it inside the instrument cabinet (but pay attention to the length of the heating cable used and it must be economically appropriate).
It is suitable for heat tracing, anti-freezing and heat preservation of pipelines, valves and pumps, or single-phase constant-power heating belts that maintain the process temperature of instrument pipelines. The heat output per unit length is constant. Proportionally, it can be spliced ​​arbitrarily during installation, but a heating section (that is, at least 2.5m) must be retained. The outer braid has heat transfer and heat dissipation functions, and can also serve as a safety ground for anti-static. Mainly used for anti-freezing and heat preservation of various pipelines and instruments, the maximum maintenance temperature is 150 ℃. Note: Heat tracing and heat preservation of liquid pipelines with strict temperature control requirements (temperature controller must be equipped).
There is also a product on the market, which is a flexible package of electric heat protection cover, which is specially used for heat tracing of instruments with relatively small space and explosion protection. It is mainly installed at the pressure pipe section and valve of the instrument.
4. Maintenance measures
1. Installation measures Reasonably choose the installation location: dry, free from rain and snow.
2. When the inspection measures are conditional, a special person shall perform daily technical confirmation and technical disposal on whether the insulation material is damaged or the steam pipeline is blocked.
3. The inspection measures shall be regularly inspected by the person in charge of regional instrument maintenance according to the predetermined inspection route. During the inspection, it is necessary to check whether the insulation pipeline valve is normal, whether the insulation box is normal, the drainage device is normal, whether the insulation material packaging is intact, and whether the heat tracing power supply components are normal. Carry out key inspections on the instruments of frost-free devices and make inspection records, perform dry, complete, and clean maintenance of the instruments and their insulation and antifreeze measures, and solve the heat tracing problems on the spot in time.
4. Alarm measures Conditionally, small sound and light alarm devices with steam leakage or power failure status can be installed to facilitate the discovery and timely rectification of hidden dangers of thermal insulation and antifreeze measures.
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