How to do a good job in winter maintenance of instruments

In winter, as the temperature gradually decreases, when the measured medium is transmitted to the transmitter through the measuring pipeline, freezing, solidification, precipitation and crystallization often occur when the ambient temperature is too low.
Using the normal working temperature range of the meter directly affects the accuracy of the meter's measurement display
.

For pressure, flow, liquid level, temperature and other instrument points, the measuring medium is mostly liquid, which is more likely to cause measurement errors due to the influence of low temperature.

In summary, the cold-proof and anti-freeze work of instruments and meters is particularly important
.

Some large-scale instrument and meter users have already made countermeasures early.

Objects of measurement instruments and instrument lines for freezing process, it is necessary with heat insulation is installed in the main instrument incubator level transmitter unit within the transmitter, the outer float level transmitter or other forms of open-air installation, Test pipelines and measurement pipelines for pressure, differential pressure, flow and other instruments
.

Avoid such accidents through selection or other means

1.
Selection measures

(1) Choose the instrument with heat preservation device
.

According to the type and purpose of the instrument and the geographical location to be installed, put forward the insulation and antifreeze requirements of the instrument, and then submit it to the manufacturer for processing

(2) For remote signal transmission instruments and display heads, the environmental temperature resistance requirements must be considered, and the environmental temperature resistance requirements of the isolation fluid should be considered when the isolation liquid is installed
.

(3) Metal rotor flowmeters, electric target flowmeters, positive displacement flowmeters, mass flowmeters, etc.
generally do not require separate heating
.

(4) The most important consideration when selecting a model is the practicability and economy of the instrument.
Practicability refers to the convenience of maintenance and accurate measurement.
The economy means cheapness
.

The two must be combined with each other, and mass flow meters, metal rotors, electric targets, etc.

(5) In some places in the north, the temperature difference between day and night is too large, and it can reach more than -20 degrees at night.
If it is solved from the selection, the cost performance is quite uneconomical
.

The best solution to prevent freezing is to choose heat preservation and maintenance (point inspection, sewage discharge) and other methods

2.
Insulation measures

Use heat preservation material to keep warm, that is, use heat preservation material to wrap the part of the meter that is easy to freeze or afraid of freezing
.

When winter comes, check and discharge pollution frequently to prevent damage to the packaging insulation materials

3.
Heat tracing measures

1.
Steam tracing measures

Even use pipe steam heating for heat preservation
.

Check whether the steam insulation pipeline is unblocked or blocked before heat preservation and steam delivery in winter

2.
Measures for insulation protection box

a.
The electric heating tube heat tracing incubator is composed of three parts: the box body, the heater, and the instrument bracket.
Its structure is the same as that of the protective box.
The difference is that the box is equipped with an electrical heating device.
The structure is shown in the figure.
The electric heating device is composed of an electric heating tube and a temperature controller.
The side of the box is equipped with a socket.
When the power is turned on, the box is heated to the required temperature, and then 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 the constant temperature heater:

⑴, rated voltage 200V.
50Hz

⑵, rated power 300～500W

⑶, the control temperature can be set by the user

⑷, constant temperature heater can also be made into explosion-proof type

⑸ There are three types of electric heating tube materials: copper tube, carbon steel tube, and stainless steel tube
.

b.
Steam pipe heat tracing incubator.
The heat tracing pipe is made of metal pipes in an S-shaped structure.
The upper and lower parts of the box are welded with welded through plate joints and heat tracing pipes.
Circulation in the lumen to achieve the purpose of heating
.
Heat tracing pipe materials are generally divided into two types, namely copper pipes and seamless steel pipes (carbon steel)
.

c.
Add another layer of insulation cotton to the key instrument box, and add glue to seal the door of the insulation box and the inlet and outlet pipelines to achieve better insulation and antifreeze effect of the instrument system
.

3.
Electric heating belt measures

Electric heat tracing heat preservation technology is a new type of heating technology that directly converts electrical energy into thermal energy
.
Install thermal insulation cables, 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 should be economical and moderate)
.

Suitable for heating, antifreeze and heat preservation of pipelines, valves and pumps, or for maintaining the process temperature of instrument pipelines.
The heating per unit length is constant, and the output power is not changed by the change of the ambient temperature.
The length and power of the use are In proportion, it can be spliced ​​arbitrarily during installation, but there must be a heating section (that is, at least 2.
5m).
The outer braid has the function of heat transfer and heat dissipation, and can be used as an anti-static safety ground
.
It is mainly used for antifreeze and heat preservation of various pipelines and instruments, and the highest temperature can be maintained at 150℃
.
Note: Heat tracing and heat preservation of liquid pipelines that require strict temperature control (a temperature controller must be used)
.

There is also a product on the market, which is a soft-packed electric heat tracing protective cover, which is specially used for heating and explosion-proof instruments in a relatively small space.
It is mainly installed at the pressure pipe and valve of the instrument
.

Four, maintenance measures

1.
Installation measures

Reasonably choose the installation location: a dry place without rain and snow drips
.

2.
Check measures

When conditions permit, a dedicated person shall conduct technical confirmation and technical disposal on whether the insulation material is damaged or the steam pipeline is blocked on a daily basis
.

3.
Alarm measures

If possible, a small sound and light alarm device for steam leakage or power failure can be installed to facilitate the discovery and timely rectification of hidden dangers of heat preservation and antifreeze measures
.

4.
Inspection measures

The person in charge of regional instrument maintenance shall conduct regular inspections according to the scheduled inspection route
.
To check the insulation inspection pipeline valve is normal, normal incubator, hydrophobic means is normal, insulation materials packaging is intact, the electrical component is normal heating power and the like
.
Carry out key inspections of the easy-to-freeze device meters and make patrol inspection records, conduct dry, complete and clean maintenance of the meters and their insulation and anti-freezing measures, and solve the problem of heat preservation and heat tracing on the spot in time
.