How to maintain and use differential pressure transmitter in cold area

In severe cold areas, when the measured medium is transmitted to the transmitter through the measuring pipeline, it often happens that freezing, solidification, crystallization and other phenomena will occur when the ambient temperature is too low, which exceeds the normal working temperature range of the instrument used because of the low ambient temperature, which directly affects the accuracy of the instrument measurement and display. Therefore, it is necessary to conduct anti-freezing treatment for instruments and instrument measuring pipelines. The objects that need heat tracing and insulation mainly include differential pressure transmitter installed in the instrument incubator, external buoy type liquid level transmitter or other forms of liquid level transmission unit installed in the open air, and detection pipelines and measuring pipelines for instruments such as pressure, differential pressure and flow.

A, differential pressure transmitter selection measures:

Choose the instrument with thermal insulation device. According to the category, use and geographical location of the instrument to be installed, the thermal insulation and anti-freezing requirements of the instrument are put forward, and then submitted to the manufacturer for processing.

In some places in the north, the temperature difference between day and night is too large, which can reach more than -20 degrees at night. If it is solved from the selection, it is quite cost-effective and uneconomical. Choosing heat preservation and heat tracing, maintenance (spot inspection, sewage discharge) and other methods are the best solutions to prevent freezing.

Second, the differential pressure transmitter insulation measures:

Use thermal insulation material to keep warm, that is, use thermal insulation material to wrap the parts of the instrument that are easy to freeze or afraid of freezing. When winter comes, it is necessary to check and regularly discharge pollutants to prevent the insulation materials of packaging from being damaged.

Three, differential pressure transmitter heat tracing measures:

1. Steam tracing measures

That is, the pipe steam is used for heating and insulation. Check whether the steam insulation pipeline is unblocked or blocked before sending steam in winter. Zui good steam is available 24 hours a day. Don't be too hot. Sometimes, the amount of steam for heat preservation should be adjusted according to the weather temperature change, so as to prevent the condensate in the pressure-inducing tube of the transmitter from vaporizing and affecting the transmitter's operation, or the condensate in the pressure-inducing tube of the differential pressure transmitter from freezing and affecting the transmitter's smooth operation due to the low temperature.

2. Measures for heat preservation and protection box

(1) The electric heating tube heat-tracing incubator consists of three parts, namely, a box body, a heater and an instrument bracket. Its structural form is the same as that of the protective box, except that the electric heating device is installed in the box, which consists of an electric heating tube and a temperature controller. A socket is installed on the side of the box body. When the power supply is turned on, when the box is heated to the required temperature, the temperature controller turns on the power supply to continue to heat up. The temperature in the box can be kept within a certain range through repeated work. The main parameters of its constant temperature heater are:

The rated voltage is 200V.50Hz

Rated power 300 ~ 500 w

The control temperature can be customized by the user.

Constant temperature heater can also be made into explosion-proof type.

There are three kinds of electric heating pipe materials: copper pipe, carbon steel pipe and stainless steel pipe.

(2) Steam pipe heat tracing incubator, the heat tracing pipe is made of metal pipe in an S-shaped structure. The upper and lower parts of the box are welded with the heat tracing pipe by welded plate-piercing joints, and the heat tracing pipe is installed in the box to go up and down, and the heating purpose is achieved through the circulation of steam in the tube cavity. Generally, there are two kinds of materials for heating pipes, namely, copper pipes and seamless steel pipes (carbon steel).

(3) Add a layer of thermal insulation cotton to the key instrument box, and add glue to seal the door of the thermal insulation box and the inlet and outlet pipelines, which can achieve better thermal insulation and antifreeze effect of the instrument system.

3. Measures for electric heating belt of differential pressure transmitter

Electric heat tracing insulation technology is a new heating technology which directly converts electric energy into heat energy. Install insulation cable, wrap the tracing tape around the instrument, or stick it inside the instrument cabinet (but pay attention to the length of the tracing tape, which should be economical and moderate).

Single-phase constant-power electric heating belt is suitable for heat tracing, anti-freezing and thermal insulation of pipelines, valves and pumps, or for maintaining the process temperature of instrument pipelines. The calorific value per unit length is constant, and the output power is not changed by the change of environmental temperature. The service length is directly proportional to the power, and it can be spliced at will during installation, but a heating node (i.e. at least 2.5m) must be reserved. The outer braided layer has the functions of heat transfer and heat dissipation, and can be used as a safe grounding for anti-static. It is mainly used for anti-freezing and heat preservation of various pipelines and instruments, and the ZI maintains a high temperature of 150℃. Attention: Heat tracing and heat preservation of liquid pipeline with strict temperature control (temperature controller must be equipped).

Four, differential pressure transmitter maintenance measures:

1. Reasonable installation location: a dry place without rain and snow dripping.

2. When the spot check measures are available, the specialist shall make technical confirmation and technical disposal on whether the thermal insulation material is damaged and whether the steam pipeline is blocked every day.

3. Inspection measures shall be regularly inspected by the person in charge of regional instrument maintenance according to the scheduled inspection route. During the inspection, it is necessary to check whether the valve of the insulation pipeline is normal, whether the insulation box is normal, whether the hydrophobic device is normal, whether the packaging of insulation materials is intact, and whether the power supply components of electric heat tracing are normal. Focus on the inspection of the instrument of the easy-to-freeze device and make inspection records, and carry out dry, complete and clean maintenance of the instrument and its thermal insulation and anti-freezing measures, so as to solve the problem of thermal insulation and heat tracing on site in time.

4. Alarm measures If conditions permit, an acousto-optic alarm device can be installed in the state of steam leakage or power failure, so as to facilitate the discovery of hidden dangers of heat preservation and anti-freezing measures and timely rectification.

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