When the pressure transmitter is used to measure oxygen, it needs to be deoiled and degreased, because the characteristics of oxygen make it dangerous to react with organic matter such as grease in some cases, and even cause an explosion. The reasons and scenarios for this process are explained in detail below.
Characteristics and risk analysis of oxygen
1. Strong oxidation of oxygen:
• Oxygen is a strong oxidizing agent that can react quickly with some fats and organic matter.
When the grease is present, the oxidation reaction may release a large amount of heat at a faster rate, resulting in local high temperatures and possibly even a fire or explosion.
2. Increased risk of pressurized environment:
• When the pressure transmitter is used in a high-pressure oxygen environment, the oxidation activity of oxygen is significantly enhanced, which increases the risk of contact with grease.
3. The role of particle pollutants:
In addition to oils and fats, some solid particles (such as rust or dust) may also act as catalysts for oxidation reactions, further increasing the risk.
The purpose of degreasing
1. Prevent oxidation reaction:
• Degreasing removes grease or organic matter from the sensor surface or internal channels to avoid contact between oxygen and grease.
2. Improve measurement security:
• The treated equipment can effectively reduce accidents caused by grease and improve the reliability and safety of system operation.
3. Ensure measurement accuracy:
• Grease residue may adsorb particles or lead to blockage of internal flow channels, affecting sensor performance and measurement accuracy.
The specific method of degreasing
1. Chemical cleaning:
• Clean the sensor with a special degreaser (e.g. Trichloroethylene, alcohol, etc.).
2. Ultrasonic cleaning:
• Ultrasonic cleaning of sensor components to remove stubborn grease.
3. High temperature drying:
• After degreasing cleaning, remove residual cleaning agent and moisture by drying.
4. Verification and inspection:
• After degreasing, the treatment effect can be confirmed by UV lamp, residual oil test paper or oxygen exposure test.
When is degreasing necessary
Special attention should be paid to deoiling and degreasing in the following scenarios:
1. The medium is pure oxygen or high oxygen concentration gas:
• High purity oxygen (usually purity >99%) or high concentration oxygen environment, oxidation is significantly enhanced.
2. High system pressure:
• When the oxygen pressure in the system is high (such as >1MPa), the reactivity of high-pressure oxygen is greatly improved, and it must be strictly degreased.
3. Medical or Aerospace applications:
The safety of oxygen in medical devices (such as ventilators) and aerospace environments is extremely high and must be free of grease contamination.
4. High ambient temperature:
• If the measured ambient temperature is high (e.g. >60°C), the increase in temperature will accelerate the oxidation reaction of oxygen.
5. There are highly sensitive parts:
• When there are components in the system that are susceptible to contamination or reaction, such as high-precision valves or coating materials.
Under what circumstances does degreasing not need to be done?
Deoiling and degreasing can not be performed under the following conditions:
1. The medium is air rather than pure oxygen:
• The oxygen concentration in the general air is low (about 21%) and the pressure in most systems is low, so the risk is relatively small.
2. Low system pressure and temperature:
• At low pressure (e.g., normal pressure or below 1MPa) and low temperature, the possibility of oxidation reaction is greatly reduced.
3. The system has low security requirements:
• In non-critical applications, the presence of small amounts of grease in the system does not significantly affect operational safety.
Brief summary
The deoiling and degreasing treatment when the pressure transmitter measures oxygen is to avoid the reaction of oil and oxygen and improve the safety of the system. The specific treatment requirements depend on the oxygen purity, pressure, temperature and application scenario. In high-purity, high-pressure oxygen systems and areas with high safety requirements, such as medical, aerospace, etc., deoiling and degreasing must be strictly carried out, while it is not necessarily required in ordinary air or conventional applications.
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