In winter, especially winter in the north, with the reduction of the temperature when the measured medium by measuring the pipeline for a transmitter, often appear the environment temperature is too low freezing, coagulation and precipitation crystallization occur, due to environment temperature is too low and beyond the normal working temperature range of instrument used, directly affect the accuracy of the meter display.The pressure, flow, liquid level, temperature and other types of instrument points, the measurement medium is mostly liquid, affected by low temperature, more likely to cause measurement errors, serious may cause poisoning, fire, explosion and other safety accidents.
So every year into the winter, the cold and frost prevention work of instrumentation is particularly important.And some large instrument and meter users are prepared to deal with in advance, such as power plants, petroleum, chemical industry, water plant, etc., have developed a system suitable for their own enterprise's instrument anti-cold anti-freeze work, and the instrument of anti-freeze, sewage treatment and other aspects of the work.Today, we will discuss the instrument users how to carry out the winter instrument anti-cold anti-freeze work.
1. To do a good job in the anti-freezing of instruments and meters, the selection of product type is a key, in the early stage of installation of instruments, instrument users should consider the working condition of the instrument, choose the instrument with thermal insulation device.According to the category and use of the instrument and the location of the proposed installation, put forward the thermal insulation and anti-freezing requirements of the instrument, and then submit to the manufacturer to deal with.
The following are some Suggestions on the selection of models given by users:
1) the signal remote transmission instrument, display head to consider the environmental temperature requirements, with the isolation fluid to consider the environmental temperature requirements.
2) mass flowmeter, metal rotor flowmeter, electric target flowmeter, volumetric flowmeter and so on generally do not need separate heat tracing.
3) first of all, when selecting the model, the general consideration is the practicality and economy of the instrument. Practicality refers to convenient maintenance and accurate measurement, while economy, in other words, is cheap.The two should be combined with each other, not only for convenience, maintenance free selection of mass flow meter, metal rotor, electric target.Therefore, I think the correct type selection is only a measure to prevent freezing and coagulation.When installing the instrument, the anti-freezing and anti-coagulation of the instrument should be fully considered. For example, the pressure guide pipe should be as short as possible, and the pollutant discharge should be inspected frequently to facilitate the heat tracing.
4) in some places in the north, the temperature difference between day and night is too large, which can reach -20 degrees or more at night. If the problem is solved in terms of type selection, the cost performance ratio is quite large, which is not cost-effective.And the choice of heat preservation, maintenance (point inspection, sewage) and other methods is the best solution to prevent freezing.
2. Insulation measures
Use insulation material insulation, namely insulation material will be easy to freeze or afraid of freezing parts of the instrument.Winter to check, often sewage, to prevent packaging insulation material damage.
Heat tracing measures
1, steam heat tracing measures: that is, the use of pipe steam heating insulation.Check whether the steam insulation pipe is smooth or blocked before sending steam in winter.Had better steam is 24 hours pass, do not want too hot, adjust to provide heat insulation steam quantity even according to weather temperature change sometimes, in order to prevent the temperature is too high to make the condensate vaporization inside the pressure guide pipe of the transmitter affects the transmitter to work or because the temperature is too low to make the condensate cold freeze inside the pressure guide pipe of the transmitter affects the transmitter to work smoothly.
2, insulation protection measures: a, electric heat pipe thermal insulation box, the box body, a heater, instrument bracket three major components, such as its structure form and protection case is the same, the difference is in the box is equipped with electric heating device, a thermal device is composed of electric heat pipe, temperature controller, body side with socket, when switched on, the heat in the oven to the required temperature, then by the temperature controller connected to the power supply continues to heat up.The temperature in the box can be kept within a certain range through repeated work.Main parameters of its thermostatic heater:
(1) rated voltage 200v.50hz;2, the rated power is 300 ~ 500W;3, the control temperature can be set by the user;Of, thermostatic heater can also be made of explosion-proof;Electric heat pipe material has three kinds: namely copper pipe, carbon steel pipe, stainless steel pipe.
B. Steam pipe heat tracing insulation box, the heat tracing pipe is made of s-type structure by metal pipe. The upper and lower parts of the box are welded with the welded plate connector and the heat tracing pipe.Heat pipe materials are generally divided into two kinds, namely, copper pipe, seamless steel pipe (carbon steel).
C. Add another layer of insulation cotton to the key instrument box, and add glue seal at the door of the incubator and the inlet and outlet of the pipeline to achieve better insulation and anti-freezing effect of the instrument system.
3. Maintenance measures
1. Installation measures: reasonable selection of installation location: dry, no rain and snow leakage.
2. When the spot inspection measures are available, the technical confirmation and disposal of whether the insulation material is damaged or not and whether the steam pipeline is blocked shall be carried out by a special person every day.
3, alarm measures conditional can be equipped with steam leakage or power off the state of acoustic and optical alarm small device, in order to facilitate the discovery of hidden dangers of insulation and anti-freeze measures and timely rectification.
4. Inspection measures shall be regularly inspected by the regional instrument maintenance person in accordance with the predetermined inspection route.During the inspection, check whether the thermal insulation pipeline valve is normal, whether the thermal insulation box is normal, whether the hydrophobic device is normal, whether the thermal insulation material packaging is intact, whether the electric heat tracing power supply components are normal, etc.Focus on the inspection of the instruments of easy to freeze and make inspection records, carry out dry, complete and clean maintenance of the instruments and their thermal insulation and anti-freeze measures, and timely solve the on-site thermal insulation and heat tracing problems.
Users users warm tips
1) check whether the insulation pipe is smooth before steam delivery.In addition, it is necessary to check frequently in winter, often discharge pollutants, to prevent the insulation pipe from blocking, once there is a blockage, it is very easy to be frozen, then it will be a big trouble, ha ha.Sometimes according to the temperature change to adjust the steam supply, to prevent the temperature is too high to make the transmitter pressure pipe condensate vaporization affect the transmitter work.Caution is the best policy.
2) in the north, the winter is the most important problem is the problem of instrument equipment insulation, as a maintenance personnel at the grass-roots level, we are just days before the arrival of winter, advance the overall comprehensive check all instrument equipment with thermal dissipation of heat preservation and for the calendar year in winter often because of the heat preservation heat tracing fault instrument equipment, collective report to workshop, everybody together to discuss and research the solution, consider above all is completes the thermal insulation layer, and good company hotline, as for the electric heating and steam heating or water heating in low temperature, depending on the particular case is particular analysis.If the thermal insulation and heat tracing are done, the instrument is still out of order, then consider replacing the measuring instrument, such as replacing the original buoy with double flanges and so on.So that the instrument equipment can be normal and smooth through the winter.In this way, the workload of instrument maintenance workers is small, and the production is stable. Everyone is ok.
3) personal opinions:
Excluding the temperature range required by the instrument itself (note: electronic components are divided into military, industrial and civilian products, the vast majority of which can only be about -20 degrees) and the heating and heat tracing adopted, the most commonly used is the heat tracing of the sampling pipe road.Measuring pressure, differential pressure or the dominant position in the form of diaphragm box, know that the shorter the sample tube, the better, but also to have a valve, to facilitate maintenance, it must be from the pipe corridor to the ground, pressure pipe heat is essential.Winter operation, mainly rely on instrumentation inspection, encounter frozen, coagulation circuit, the use of external steam belt blowing + knocking pipeline method, very primitive, very tired, there is no good way.
In addition, as a clean energy, the cost of electricity is the highest;In my original unit electric heat tracing is very little, unless there is no heat tracing pipe nearby;Notice, big factory has heat exchange station, waste heat heating, heat, spend a few money.And electric heat tracing explosion - proof difficult.