What standards do hygienic pressure transmitters need to meet?

Hygienic pressure transmitters are an important component for process monitoring in food and pharmaceutical production equipment. With the increasing improvement of China's production technology and technology, the sanitary transmitter industry has also made great progress, and its quality and performance are gradually approaching the international level. However, due to the late start of China's pressure transmitter industry, the design standards of pressure transmitters are relatively backward and lacking, especially the hygienic design of sanitary pressure transmitters is still in a relatively blank stage.

Therefore, it is of great practical significance to carry out research on the hygienic design of pressure transmitters and put forward specific indicators.

Hygienic standards. Regarding the hygienic standards for transmitters, the "3-A Sanitary Standards" of the United States and the "EHEDG Standards" of Germany are the main ones, of which the "74-06" in the "3-A Sanitary Standards" of the United States is mainly for the hygienic standards of sensors and their accessories and connectors. These two standards organizations undertake the services of testing, certification and re-inspection of health indicators for equipment products and manufacturers with health requirements in all countries around the world, and issue hygiene certification certificates (3-A certificate and EHEDG certificate) to products that meet the requirements.

At present, many foreign pressure transmitter companies have obtained these certificates. With the increasingly stringent hygiene requirements for transmitters in China, major domestic transmitter production and use enterprises are also striving to obtain these certificates.

Hygienic design. Hygienic design refers to the design that prevents food and drugs from being contaminated by harmful substances in all aspects of production, harvesting, processing, transportation, storage, and sales. The purpose of the hygienic design of the pressure transmitter is to meet the cleaning requirements of the production site, that is, to ensure that the cleaning meets the cleanliness requirements, to ensure that the product is not contaminated by secondary pollution, and to meet the hygiene requirements.

Contact surfaces vs. non-contact surfaces.

The hygienic design of pressure transmitters inevitably involves two concepts: contact surfaces and non-contact surfaces. Contact surfaces are all surfaces that come into contact with the product being tested, or that have the potential to be discharged, leaked, diffused, or entered by the product being tested.

A non-contact surface is one that does not discharge, leak, diffuse, or enter any product being tested.

A pressure transducer is a device or device that can sense the pressure signal and convert the pressure signal into a usable output electrical signal according to a certain law.

A pressure sensor usually consists of a pressure-sensitive element and a signal processing unit. According to different types of test pressure, pressure sensors can be divided into gauge pressure sensors, differential pressure sensors and absolute pressure sensors.

Pressure sensor is the most commonly used sensor in industrial practice, which is widely used in various industrial automatic control environments, involving water conservancy and hydropower, railway transportation, intelligent buildings, production automation, aerospace, military industry, petrochemical, oil wells, electric power, ships, machine tools, pipelines and many other industries.

Pressure transmitters.

The method of selecting the scope of application and the range of the range is as follows:

Look at the degree of corrosion of the measuring medium, according to the size of the degree of corrosion to choose the corresponding transmitter, generally speaking, non-strong acids and strong alkalis can use stainless steel as the isolation unit of the transmitter, otherwise you can only choose titanium alloy designed for corrosion.

and other special transmitters.

It is necessary to look at the viscosity and cleanliness of the measurement medium, if it is very viscous (such as the flow is very slow), it is necessary to choose the transmitter of the hard isolation unit to determine the measurement range and measurement method, and generally consider the actual measurement range and overpressure measurement range when selecting the measurement range, and the selection range is subject to the measurement range, and the size of the overpressure measurement range is considered.

If differential pressure is to be measured, a differential pressure transmitter must be selected.

Determine the accuracy range, compensate the temperature range, and use the temperature rangeAccording to the minimum accuracy you need to measure, the differential pressure transmitter product that is slightly higher than the minimum accuracy required is generally selected.

At the same time, the long-term stability index should also be considered when selecting the pressure transmitter, the so-called compensation temperature range is the temperature range of the measurement medium during normal operation, and the use temperature range is the temperature range that may occur during the use process, which is slightly larger than the required temperature range when selected. Determine the pressure interface, electrical interface, mechanical dimensioning, etc. Determine whether explosion protection is required, protection against electromagnetic interference is required, and environmental indicators for waterproofing the enclosure.

Pressure Transmitter SelectionThe pressure transmitter is suitable for the measurement of gauge pressure, differential pressure, negative pressure and absolute pressure of various fluids (liquid and gaseous). For various pressure forms and high temperature, high pressure, high viscosity, corrosion, crystallization (scale), suspended solids and so on, there are corresponding specifications and models.

and the way of application corresponds to it;

When selecting the measuring range, the normal value, value, and minimum value of the measurement object should be selected in advance.

Generally speaking, the range selection should meet the following requirements:

1. The lower limit of the measurement range should be lower than or equal to the minimum value;

2. The upper limit should be higher than the value;

3. The normal value is within the range of 1 2 4 5 in the whole range.

The range of the range is determined according to the actual operation of the place of use, the general normal operation pressure is not higher than the upper limit of the instrument range of 2 3, not less than the upper limit of 1 3, the pressure shall not exceed the upper limit of the instrument, otherwise the instrument will be damaged, of course, the normal choice may not be so standard.

, the measurement medium

Second, the accuracy level

Each electronic measuring meter will have an accuracy error, but because the accuracy level of each country is different, for example, the accuracy of China and the United States and other national standards is the best score of the sensor, that is, we usually call the accuracy between 10% and 90% of the measurement range; The accuracy of the European standard is the best score for linearity, which is what we usually call the accuracy between 0 and 10% and 90% and 100%. If the accuracy of the European standard is 1%, then the accuracy of the cover and the Chinese standard is.

Third, range

Generally, the maximum range measured by the sensor is 70% of the full range of the sensor is the best, that is, to measure the pressure of 70 bar, we should choose the range of the pressure transmitter should be 100 bar.

Fourth, the material of the nuclear state liquid

What should be considered is the medium measured by the pressure transmitter, and the material of the contact medium of the general pressure transmitter is 316 stainless steel. If your medium is not corrosive to 316 stainless steel, then basically all pressure transmitters are suitable for your medium pressure measurement. If your medium is corrosive to 316 stainless steel, then we need to use chemical seals, which can not only measure the pressure of the medium, but also effectively prevent the contact between the medium and the liquid part of the pressure transmitter, so as to protect and prolong the life of the pressure transmitter.

Object staring. Fifth, the temperature of the medium

Because the signal of the pressure transmitter is converted through the electronic circuit, so in general, the temperature of the measuring medium of the pressure transmitter is -30 to +100 degrees, if the temperature is too high, we generally use the condensation bend to cool the medium, so that the cost of producing a high-temperature resistant pressure transmitter for you will be reduced a lot.

Sixth, output signal

At present, due to the needs of various acquisitions, there are many kinds of output signals of pressure transmitters on the market, mainly 4...20ma,0..20ma,0...

10v,0...5v and so on, but the more commonly used is 4....20ma and 0....

10V two. Of these output signals, there are only 4...20mA is a two-wire system (the output we are talking about is a multi-wire system without grounding or shielding wires), and the others are three-wire systems.

Seventh, other factors

After we have determined the above five parameters, we also need to confirm the process connection interface of your pressure transmitter and the supply voltage of the pressure transmitter; If it is used in special occasions, it is necessary to consider the explosion-proof and protection level.

The pressure transmitter is suitable for measuring gauge pressure, differential pressure, negative pressure, and absolute pressure of various fluids (liquid and gaseous). For various pressure forms and high temperature, high pressure, high viscosity, corrosion, crystallization (scale), suspended solids, etc., there are corresponding specifications, models and application methods;

When selecting the measuring range, the normal, maximum, and minimum values of the measurement object should be specified in advance. Generally speaking, the range selection should meet the following requirements:

1. The lower limit of the measurement range should be lower than or equal to the minimum value;

2. The upper limit should be higher than the maximum value;

3. The constant value of the panicle of the positive ascendant is in the range of 1 2 4 5 in the whole range.

Thoughtfully attached to the LEEG hygienic pressure transmitter design standard, take away no thanks

In terms of non-toxic and harmless requirements, different grades of stainless steel materials (304L, 316L) are selected according to different conditions; The quietly selected polymeric materials, rubber elastomer materials, adhesives, lubricants, measuring conduction liquid materials, thermal isolation materials, external plating materials, etc. shall not contain toxic and harmful components, and shall not have toxic and harmful components leaching or seeping;

In terms of structure, the surface is required to be smooth and clean, no dead ends, not easy to accumulate scale, not easy to pollute, easy to rinse (often using quick-open clamp interface) and easy to sterilize and disinfect;

In terms of anti-infection and anti-staining, strict sealing and isolation are required to prevent toxic, harmful and contaminants from entering and leaking, and resistant to high-temperature disinfection and sterilization; In terms of processing, Ziyun Sakura requires a certain degree of finish and weldability;

In terms of maintenance, suitable cleaning agents, easy cleaning of internal and external surfaces, easy cleaning-in-place (CIP) and sterilization-in-place (SIP) are required.

1. The medium of measurement.

2. The scope of measurement.

3. Installation method.

4. Display form.

It mainly depends on the power and where it is used.

The application range and range selection method of the pressure transmitter are as follows:

1. Determine the measurement medium.

Generally speaking, non-strong acids and alkalis can use stainless steel as the isolation unit, otherwise you can only choose special transmitters such as titanium alloys designed for corrosion protection.

2. Measure the medium.

It is necessary to see whether the measurement medium is viscous and clean, if it is very viscous (such as the flow is very slow), it is necessary to choose the transmitter of the hard isolation unit to determine the measurement range and measurement method, and generally consider the actual measurement range and overpressure measurement range when selecting the measurement range, and the selection range is subject to the maximum measurement range, and the size of the overpressure measurement range is considered.

3. You need to choose the right measurement method.

If the differential pressure measurement must be selected to determine the accuracy range, compensate the temperature range, use the temperature range according to the minimum accuracy you need to measure, generally choose a differential pressure transmitter product that is slightly higher than the minimum accuracy required.

Xi'an Huaheng Instrument is a professional manufacturer engaged in the instrumentation industry, we warmly welcome you to buy our company's products with exquisite technology and high-quality products; If you have any questions about related instrumentation, please get in touch with us in time!

Signature: Pressure transmitter manufacturer.

1. According to the working principle of the sensor, it can be divided into resistance, capacitor, inductance, semiconductor, etc.;

2. According to the classification of sensor chips, it can be divided into ceramic, diffusion silicon, sapphire, etc.;

3. Classified from the measurement range, it can be divided into differential pressure, gauge pressure, absolute pressure, etc.;

Do not use a voltage higher than 36V to the transmitter, resulting in damage to the transmitter;

Do not touch the diaphragm with a hard object, resulting in damage to the diaphragm;

The measured medium is not allowed to freeze, otherwise it will damage the sensor element isolation diaphragm and cause damage to the transmitter, and if necessary, the transmitter should be temperature protected to prevent freezing;

When measuring steam or other high-temperature media, the temperature should not exceed the limit temperature of the transmitter, and above the limit temperature of the transmitter must be used, a heat sink device must be used;

When measuring steam or other hot media, heat pipes should be used to connect the transmitter to the pipes and use the pressure from the pipes to transfer to the transformer. When the measured medium is water vapor, an appropriate amount of water should be injected into the heat pipe to prevent the superheated steam from directly contacting the transmitter and damaging the sensor.

In the process of pressure transmission, the following points should be noted: 1. Do not leak air at the connection between the transmitter and the heat pipe;

2. Before starting to use, if the valve is closed, the valve should be opened very carefully and slowly when using, so as to avoid the measured medium directly impacting the sensor diaphragm and damaging the sensor diaphragm;

3. The pipeline must be kept unblocked, as the sediment in the pipeline will pop out and damage the sensor diaphragm.

What do I need to look out for?

First of all, figure out the parameters of the products you use!

Just use it according to the regulations!