Basic knowledge of the hottest pressure switch

2022-08-04
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Basic knowledge of pressure switch

1 Overview

pressure switch is a device combined with electrical switch. When the preset fluid pressure is reached, the switch contact acts. It is mainly used to output alarm or control signals on industrial equipment such as power plants, petrochemical and metallurgical industries. It has important applications in the industrial field. It can prevent the phenomenon that the indication error within certain range is out of tolerance in some frequently used tension tests, and the damage of important devices in production engineering, so as to avoid major production accidents

2. Main sensitive elements of pressure switch

2.1 Bourdon tube

features: common pressure switches adopt such sensitive elements, which are mainly made of stainless steel, phosphor bronze, etc., with a wide measurement range. The measurement range of Nagano pressure switch ranges from 10Pa (CL12) ~100mpa (jm11)

2.2 bellows

features: the durability and vibration resistance are better than Bourdon tube, and the connection and disconnection difference can be adjusted in a large range. The main materials include stainless steel, phosphor bronze, etc, The price is relatively high, but the measurable pressure range is small. The maximum pressure is 15MPa (cb33)

2.3 diaphragm

features: it has excellent corrosion resistance. The main materials are NBR, fluororubber, etc. such sensitive elements are used in CS, CL series, etc

nbr: gasoline, mineral oil, benzene

fluororubber: hot oil, steam, air, inorganic acid, halogen, etc.

3 Related terms of pressure switch

3.1 accuracy: refers to the value of equipment accuracy, including linearity, tolerance, hysteresis, repeatability, etc. At present, the highest accuracy of Nagano pressure switch can reach 0.5%f.s, and the model is cb33

3.2 maximum pressure (max.p): the maximum value of the pressure range

3.3 full scale (F.S): the difference between the maximum and minimum values of the pressure range

3.4 connection and disconnection difference (dead zone): refers to the difference between the set action value and reset value of the switch. For example, when the set value is 1MPa and the actual reset value is 0.9mpa, the connection and disconnection difference is 0.1MPa

3.5 operating temperature: it means that the internal mechanism and sensitive elements of the instrument will not be continuously deformed during operation. In order to improve the drug absorption capacity of the corneal contact lens, siddarth Venkatesh et al. Used molecular imprinting technology to synthesize poly (AA co am co NVP co HEMA Co PEG200DMA) hydrogel material with specific recognition function. It was found that the absorption capacity of the corneal contact lens made of this material to ketotifen fumarate was 6 times higher than that of the control material, The continuous release time of the drug can reach the temperature range of up to 5 days. The recommended working temperature range of general pressure switch is -5~400c. If the medium temperature is too high, it can be considered to add an accessory siphon (filling) to achieve the purpose of cooling

3.6 s.p.d.t (single pole double throw): it is composed of a normally open contact, a normally closed contact that can be confirmed to be able to conduct 30C rapid charge and discharge and a common terminal

3.7 d.p.d.t (double pole double throw): it is composed of a symmetrical left and right common terminals and two groups of normally open and normally closed terminals

3.8 upper limit one contact (normally open): when the pressure rises to the set value, the contact acts and the circuit is connected

3.9 lower limit one contact (normally closed): when the sub force drops to the set value, the contact acts and the circuit is connected

3.10 upper and lower limit two contacts HL: it is a combination of upper limit type and lower limit type, which is divided into two types: independent action of two contacts (double setting and double circuit) and simultaneous action of two contacts (single setting and double circuit)

3.11 upper limit 2 Contact: two upper limit forms are combined, which are divided into two types: independent action of two contacts (double setting and double circuit) and simultaneous action of two contacts (single setting and double circuit)

3.12 lower limit 2 Contact: two lower limit forms are combined, which are divided into two types: independent action of two contacts (double setting and double circuit) and simultaneous action of two contacts (single setting and double circuit)

3.13 withstand voltage: the maximum pressure that the pressure switch can withstand to maintain its normal performance. However, when the pressure switch is used in an overvoltage situation, the sensitive element will continue to deform. At this time, the pressure setting value will change, and the pressure switch will not play its normal performance or may even be damaged

3.14 IP (degree of protection): it is a standard drafted by the International Electrotechnical Association (IEC) on the dust-proof and moisture-proof characteristics of lamps. Refer to comprehensive sample P4 for specific meanings

4. Nagano pressure switch

4.2.2 explosion proof type (the explosion-proof grade of Nagano pressure switch is generally d2g4)

pressure proof explosion-proof structure: d

explosion-proof grade: 2 (the gap depth is greater than 25mm, the gap should be greater than 0.4mm and less than 0.6mm)

ignition degree: G4 (the ignition point is between 1350c and 2000c, and the temperature rise limit outside the container should be 700C)

applicable to hazardous places: the first place or the second place (as shown in the table)

applicable objects: petrochemistry, chemical fiber, synthetic resin, liquefied gas, electric furnace, pharmaceuticals, coatings, sulfur safety, ethylene, methanol, soda, sodium hydroxide, etc

4.3 pressure on "Li Chao also believes that the type selection of Guan

4.3.1 is necessary for explosion-proof: the explosion-proof form is divided into explosion-proof type and intrinsically safe type, and most of Nagano products are explosion-proof type, such as CD series

4.3.2 whether it is necessary to carry instructions: according to the customer's instructions

4.3.3 number of contacts: one contact (one output) or two contacts (two outputs)

4.3.4 determination of setting value and pressure range: the recommended setting range is between 30% and 65% of the pressure range, and the settable range is between 15% and 90% of the pressure range

4.3.5 form of connection and disconnection difference: adjustable or fixed

4.3.6 whether there is pulsation: if there is pulsation or vibration in the pressure, a throttle valve shall be provided to restrain the damage of pulsating pressure gauge

4.3.7 occasions with diaphragm: when determining corrosivity, high viscosity or high temperature, it is necessary to select diaphragm. The basic model of diaphragm is SC series, in which SC10 is threaded installation, SC2 □ is i-flange installation, and SC3 □ is single flange installation

the above points are used as a reference for model selection, and the specific model selection is specified according to customer requirements

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