Application of Fork Liquid Level Switch in Pharmaceutical Extraction

Today, pharmaceutical technology is rapidly advancing and its production process becomes more and more complicated. With the increasing competition in the industry, higher production efficiency and automatic control of the production process are demanding. Generally, a complete pharmaceutical production process includes five steps: raw material storage, pretreatment, chemical reaction, separation and purification, and refining. Separation and purification is the most important step in the entire process because the technical level of separation and purification directly affects the amount of effective medicinal ingredients. And level measurement for liquid or material in this step has a direct impact on the smooth progress of the process. Let´s check out how the Jiwei Ring-11 Fork Liquid Level Switches were successfully applied in the process of separation and purification (mainly extraction) for liquid level measurement in a pharmaceutical plant.

1. Brief introduction of separation and purification process

There are many methods for separation and purification. The common one at present is liquid-liquid extraction. We know that a compound has different solubility in two incompatible solvents. We can use an extraction method to transfer a compound from one solvent to another. Through repeated multiple extractions, most compounds can be extracted. Let´s take the production process of polyoxymethylene as an example. In this process, the aqueous solution of paraformaldehyde is an intermediate reaction product. Benzene can be used as an extractive agent to separate paraformaldehyde from water because its affinity to paraformaldehyde is greater than water, its gravity density is less than that of water, and it is easier to be separated from water. During the extraction process, when the separation layer is formed, the upper layer is the mixture of paraformaldehyde and benzene, the lower layer is the mixture of water and other sediments. At this moment, level measurement for two different solvents in the separation tower is needed. The liquid level is controlled through high/low alarm to ensure efficient and smooth operation of the entire production process.

2. Technical requirements for level switch in extraction process

Flammable, explosive, poisonous, harmful and corrosive solvents are often used in the extraction process in the pharmaceutical industry. And the process temperature is usually high. Therefore, technical requirements for a fork liquid level switch used for level measurement in the separation and purification process are focused on wetted material, explosion-proof characteristics and high temperature resistance.

1) Wetted material： Due to the corrosive nature of the solvent, the fork body should be with high corrosion resistance. From weak to strong corrosive resistance, material of the fork body can be selected from carbon steel, 304ss, 316ss, 316L, stainless steel lined with PTFE, and Hastelloy etc.

2) Explosion-proof characteristics：There are many types of explosion protection. The common types are flameproof enclosure and intrinsic safety explosion protection. Flameproof enclosure explosion protection is to keep the flammable and explosive hazards from entering the interior of the instrument. It is a passive protection. Intrinsic safety explosion protection is to use energy-limited design in electric circuits, which means the instrument is safer to operate even if there are flammable and explosive hazards in the environment because the instrument does not have the possibility to actively ignite the flammable and explosive hazards in the environment. It is relatively safer.

3) High temperature resistance：High temperature resistance refers to the temperature of the measured material, not the environment temperature as one commonly thought. Required material temperature for different processes can range from minus tens to hundreds of degrees. Metal’s thermal conductivity is usually very high, and the temperature resistance of electronic components is usually up to 85ºC. Therefore, the high temperature resistance determines the service time of the level switch. High-temperature working conditions in the extraction process requires high temperature resistance of the liquid level switch.

3. Advantages of Jiwei Fork Liquid Level Switch

Higher technical requirements on the level switch are necessary because of special working conditions in the pharmaceutical extraction process. Last year， a pharmaceutical company in Inner Mongolia purchased dozens of Jiwei Ring-11 Fork Liquid Level Switches with intrinsic safety explosion protection after careful comparison of many level switch products in the market.

Jiwei Ring-11 Fork Liquid Level Switch was selected by the customer for liquid level measurement and control in pharmaceutical extraction process is because of its following advantages:

1) The wetted fork body is made of 316L with higher surface finish quality and better corrosion resistance.
2) Electronic circuit design with intrinsic safety explosion protection: Ex ia II CT6.
3) Designed with high temperature resistance，highest process temperature can be 250℃.
4) Based on detecting changes of vibration frequency, the measurable medium density can be as low as 0.5g/cm³，more accurate and higher reliability.

Obviously, the Jiwei Ring-11 Fork Liquid Level Switch fully meets the technical requirements for a liquid level switch in the pharmaceutical extraction process. Dozens of Ring-11 Fork Liquid Level Switches with intrinsic safety explosion protection have been operated in the separation and purification process in the pharmaceutical plant in Inner Mongolia with high accuracy, reliability and stability for a year. It shows Jiwei Ring-11 Fork Liquid Level Switch has been successfully applied in the extraction process in the pharmaceutical industry.