In winter, the temperature gradually decreased, when the medium is measured by measuring the pipeline is transmitted to the transmitter when the ambient temperature is too low, often occurs when freezing, solidification and crystallization phenomenon, because the ambient temperature is too low and beyond the normal operating temperature range of the instrument, directly affect the measuring accuracy of the display. The pressure, flow, liquid level, temperature and other types of instruments, the measurement for liquid medium, low temperature impact, more likely to cause measurement errors, which may cause poisoning, fire and explosion accidents.
To sum up, the instrument of cold and antifreeze work is particularly important. Some large-scale instrumentation users are early to do a good job of response measures, such as power plants, water plants, oil, chemical industry, etc., have formulated their own enterprises cold, anti freeze work system. Next, let's discuss how winter meter users should do the instrument antifreeze work.
The instruments and instrument measurement pipeline freezing treatment, with the main object need thermal insulation are installed in the transmitter insulation box, an outer float type level transmitter or other forms of outdoor installation level transmission unit, pressure, differential pressure, flow meter tube line detection and measurement of pipeline. Avoid such accidents through selection or other means. Measures taken include selection, heat preservation, heating, maintenance (spot inspection, pollution discharge), etc..
Selection measures
(1) choose the heat preservation type instrument. According to the category, purpose and location of the instrument, the thermal insulation and antifreeze requirements of the instrument are presented and submitted to the manufacturer for processing.
(2) signal transmission meter, display meter to consider the environmental temperature requirements, with isolation liquid, to consider the isolation liquid environmental temperature requirements.
(3) metal rotor flowmeter, electric target flowmeter, volumetric flowmeter, mass flow meter and so on, usually do not need to be accompanied by heat alone.
(4) when selecting type, the main consideration is the practicality and economy of the instrument. The practicability is that the maintenance is convenient, the measurement is accurate, and the economy is cheap. The two must be combined with each other, not only for convenience and maintenance, but also for mass flow meters, metal rotors and electric targets. Therefore, the correct type selection is also a measure of anti freezing and anti coagulation. In addition, the instrument should take full account of the instrument's antifreeze, anti coagulation, such as the pressure pipe as short as possible, frequent inspection, sewage, to facilitate the accompanying heat, etc., otherwise, a good selection does not work.
(5) in some places in the north, the temperature difference between day and night is too great. At night, we can reach more than -20 degrees. If we solve the model selection, the cost performance will be considerable and uneconomical. The best way to prevent frost is to select the heat preservation, heat, maintenance (spot inspection, pollution discharge) and other rules.
Two, insulation measures
With insulation material insulation, that is, the use of insulation materials will be easy to freeze or cold parts of the instrument. When winter comes, it is necessary to check and regularly discharge the sewage so as to prevent the breakage of the packing material.
Three, accompanied by heat measures
1, steam heating measures
That is the use of tube steam heating insulation. Before winter heat transfer, check that the steam insulation line is unblocked or blocked. The best steam is 24 hours pass, not too hot, sometimes according to the weather changes in temperature to adjust for the insulation of steam temperature is too high, in order to prevent the transmitter pressure in tube condensation liquid vaporization effect of transmitter or because the temperature is too low the transmitter pressure coolant condenser transmitter smooth effect.
2, thermal insulation box measures
A, electric heat pipe heat insulation box, composed of three parts of body, heater, instrument bracket, its structure and the same protection box, the box is equipped with electric heating device, the structure form of figure, the electric device is composed of electric heating tube, a temperature controller, the side of the box with a socket, when the power is turned on after the required temperature to the heating, the temperature controller is switched on to rise. The temperature in the cabinet can be kept within a certain range by repeated work. Main parameters of its constant temperature heater:
The rated voltage of 200V.50Hz
The rated power of 300 ~ 500W
The temperature control can be set by the user
Finally, it can be made into explosion-proof type constant temperature heater
The electric heating tube, the material has three kinds: namely copper, carbon steel, stainless steel tube.
B, the steam pipe heat insulation box with heat pipe is a S type structure with a metal box under control. Using welded joints and the wear plate with the heat pipe is welded with the heat pipe installation is in progress under the box, and achieve the purpose of heating by steam in the lumen of the cycle. Heat transfer tube material is generally divided into two kinds, namely copper tube, seamless steel tube (Tan Gang).
C, adding a layer of insulation cotton to the key instrument box, adding glue and sealing at the entrance of the incubator and the inlet and outlet, can achieve better insulation and anti freeze effect of the instrument system.
3, electric heating belt measures
The technology of electric heat tracing is a new heating technology, which directly transforms electric energy into heat energy. Installation of insulated cables, with the tropics attached to the instrument, or glued to the instrument cabinet (but be careful with the length of the accompanying tropics, be economical).
Applicable to the pipeline, valve, pump body and heat insulation, and antifreeze or maintain instrument piping process temperature Dan Xiangheng power band, the calorific value per unit length is constant, the output power is not affected by environmental temperature change, and power is proportional to the length of use, can install any splicing, but must retain a fever section (at least 2.5m), an outer woven layer with heat transfer and heat dissipation effect, and can be used as antistatic safety grounding. The utility model is mainly used for frost proof and heat preservation of various pipelines and meters, and the maximum maintenance temperature is 150 DEG C. Caution: the accompanying heat of a liquid line that is strictly controlled by temperature
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