In the actual working field, chemical instrumentation is essential monitoring equipment, chemical instrumentation on the one hand to maintain the smooth operation of the chemical production line function, on the other hand also play a role in the protection of life and property security. For the field instrument, long exposure, sun and rain, the instrument is prone to failure, then this requires us to do the work of anti-corrosion, anti-vibration and dustproof, strengthen the instrument management and maintenance not only to improve the accuracy of the instrument, but also to prolong the service life of the instrument, today vacorda will tell you how the field instrument is anti-corrosion, shockproof and dustproof.
The maintenance of anti-corrosion
1. Choose the material properly
Targeted selection of corrosion-resistant metal or non-metallic materials to manufacture the components of the instrument, industrial instrumentation is the fundamental method of anti-corrosion. For example, the instrument parts made of titanium and tantalum metal have strong corrosion resistance to chlorine chemical media, and the instrument parts and gaskets made of PTFE material are also widely used in various corrosive media environments.
2. Add the protection layer
A protective coating on instrument parts or components is a very common corrosion protection method in industry. According to the material and forming principle of the protective layer is different, can be divided into the following three kinds:
A. Metal protective layer. Including spraying, electroplating, hot dip, carburizing and so on.
B. Non-metallic protective layer. Such as paint, acid-resistant cement, rubber, plastic, enamel and so on;
C. Non-metallic protective film, chemical treatment on the metal surface, the formation of oxide film, phosphate film and other protective film;
3. Adopt the isolation fluid
This is an effective method to prevent the corrosive media from direct contact with the instrument. In the case of the failure to select the appropriate corrosion resistance instruments, use the isolation fluid solution can achieve the purpose of isolation. The isolation fluid is often used for pressure, flow, and level measurement in corrosive media. The liquid must not be miscible with the medium to be tested and chemically, and cannot be corrosive to the measuring parts of the instrument. The density of the isolation solution should be different about the density of the measured medium and the instrument working medium, and the density and viscosity should not change significantly when the ambient temperature changes, and it should also have good fluidity. In the event of an accident, when the separation fluid is mixed with the measuring line, it should not affect the use of the medium under test. For example, glycerol aqueous solution for oil, water gas, semi-water gas, C1, C2, and other hydrocarbons; ethanol is suitable for propane, butane and another medium; methyl silicone oil is suitable for various gases and liquids other than dehumidification chlorine gas.
4. Diaphragm isolation
The corrosion-resistant diaphragm is used to isolate the isolation solution or the filling fluid from the medium under test for corrosion protection purposes. It is suitable for strong corrosive media, difficult to use in-pipe isolation or container isolation, usually suitable for pressure measurement, not suitable for differential pressure measurement.
Isolation diaphragm should be flexible and impermeable, such as commonly used diaphragm pressure gauge, single flange anti-corrosion pressure transmitter and so on.
5. Air blowing method
This is the use of blown air (or nitrogen and other inert gas) to isolate the measured medium against the instrument measurement components of the corrosive effect. Air blowing method is usually used for atmospheric or low pressure liquid level measurement system, blowing into the gas should not be with the corrosive medium to be tested. According to the principle of constant pressure blowing method, the blowing liquid (water and other clean liquid) method is also used in the flow and liquid level measurement system. For example, the vapor condensate is blown to isolate the corrosion of the measuring parts of the instrument and to remove the blockage of the guide tube.
The maintenance of dustproof
The dust-proof method on the outside of the meter is for the protective cover on the instrument hood or in a sealed box.
For the measurement of the medium containing dust, impurities and particles, such as the protection, in addition to the use of dust reduction measures to prevent clogging, usually using a coarse intake tube, add dust collectors, add air blowing device and installed protective screen and other methods.
Coarse intake tubes are often used in combination with dust collectors and blow-washing devices. When using the orifice plate without annular chamber to measure the flow, it is possible to use the 1.5~2m's coarse intake tube directly in the pressure mouth, and add the plugging head, so as to make the cleaning hole during maintenance or as a vent. Liquid level measurement, in order to prevent the formation of the negative pressure tube crystallization, the negative pressure pipe can be used to steam condensate solution. For gas measurements with moisture, a water separator can be used, which is common in pressure and flow measurement.
The maintenance of shockproof
The vibration of instruments and equipment comes from internal and external factors. The internal vibration is the fluctuation of the measured medium, for example, the fluid from a single cylinder compressor can easily damage the instrument's elastic elements and affect the accuracy of the measurement. The external vibration is often caused by the operation of the material conveying, crushing, grinding and other power machinery, but also by the intense chemical reaction.
In order to reduce and prevent the impact of vibration on instrument components and measurement accuracy, the following methods can usually be used:
1. Add a buffer or throttle
The damper can be an empty container, which is installed between the pressure-taking point and the detecting instrument. After the pulsating pressure passes through the damper, the air pressure is stabilized, thereby reducing the influence of the pulsation of the measured medium. The restrictor can usually use a restrictor orifice, and the resistance formed by the orifice can reduce the pulsation of the gas or liquid medium pressure.
2. Install the rubber cushion to absorb the vibration
Adding rubber to the instrument support surface or the instrument is spring-connected and then fixed to the bracket. It is also possible to fix the entire instrument panel with a vibration-proof rubber washer on the foundation. These methods are effective in absorbing external vibrations.
3. Add a damping device
The damper device and the damper valve are used to form a RC, which can effectively reduce the pulsation of the medium.
4. Use vibration-resistant instrument
In addition to the above several vibration reduction methods, the vibration problem can be fundamentally solved in the design selection. For example, an anti-vibration pressure gauge is installed on the pulsation line of the pump outlet; in the case of pulse flow, a flow meter that is insensitive to the flow state is selected.