There are two main types of pressure switches, one is normally open, and the other is normally closed. The pressure switch has four main characteristics. The first is that the pipe threaded joint type and the installation structure and the installation structure of the welded copper pipe are very flexible and extremely convenient in use. No additional installation is required to fix the structure; second One feature is that the pressure switch has a plug-in connection method and a wire connection method for customers to choose; the third feature is that the pressure switch has a safe and reliable sealed stainless steel sensor, which customers can use with confidence; The last one is that within a certain pressure range, the customer can arbitrarily select a pressure value to let the pressure switch operate.
Classification of pressure switches:
The first type introduces the explosion-proof pressure switch. This type of pressure switch can be divided into explosion-proof and explosion-proof. The use grade ranges from ExdIICT1-T6. Imported explosion-proof pressure switches need to pass UL, CSA, CE and other international certifications. It can be used in explosive areas and strong corrosive atmospheres. The explosion-proof pressure switch can provide products with different pressure, differential pressure, vacuum and temperature range. Common applications include power, petroleum, chemical, metallurgy, boilers, food machinery, environmental protection equipment and other industries.
The second type of mechanical pressure switch is a micro switch action caused by pure mechanical deformation. When the pressure increases, the different sensing pressure components (diaphragm, bellows, piston) will be deformed and will move upward through the railing spring and other mechanical structures, and finally activate the uppermost micro switch to output electrical signals. The pressure switch setting method is divided into continuous displacement type and force balance type from the functional principle.
The third type of electronic pressure switch is also called smart pressure switch. The digital display pressure switch can be used to replace mechanical pressure switches and be used in systems with higher industrial control requirements. This type of pressure switch has a built-in high-precision pressure sensor, amplifies the pressure signal through a high-precision instrument amplifier, and collects and processes data through a high-speed MCU. Generally, a 4-digit LED real-time digital display of pressure is used, and the upper and lower limit control points can be set freely. Stable, low hysteresis, anti-vibration, fast response, stable and reliable, high accuracy (the accuracy is generally ±0.5%FS, up to ±0.2%FS), the use of hysteresis setting can effectively protect repeated actions caused by pressure fluctuations, and protect Control equipment is a high-precision equipment that detects pressure and liquid level signals and realizes pressure and liquid level monitoring and control.
common problem
Pressure switches are widely used in the high and low pressure protection control of household, commercial, and automobile refrigeration systems, steam conditions and power stations; accumulators, receivers, flash tanks, separators, scrubbers, oil refining devices. It can also be applied to high and low pressure protection control of various equipment and tools. But in the selection of pressure switch, the following points must be paid attention to:
1. The necessity of explosion-proof: explosion-proof forms are divided into explosion-proof type and intrinsically safe type. Most of Nagano products are explosion-proof type.
2. Whether you need to bring instructions: according to customer instructions.
3. Number of contacts: one contact (one output) or two contacts (two outputs).
4. Determination of setting value and pressure range: The recommended setting range is between 30% and 65% of the pressure range, and the adjustable range is between 15% and 90% of the pressure range.
5. The form of differential connection: adjustable or fixed.
6. Whether there is pulsation: If the pressure is pulsating or vibrating, a throttle valve is required to suppress the damage of the pulsating pressure to the instrument.
7. Occasions with diaphragm: When measuring corrosiveness, high viscosity or high temperature, it is necessary to choose diaphragm.
General failure of pressure switch
1. Failure phenomenon: The pressure switch has no output signal. Reason analysis:
(1) The micro switch is damaged
(2) The switch setting value is adjusted too high
(3) The wire contact to the micro switch is not connected properly
(4) The pressure-sensitive part is poorly assembled and stuck
(5) The pressure-sensitive component is damaged
Solution:
(1) Replace the micro switch
(2) Adjust to appropriate setting value
(3) Reconnect to make good contact
(4) Reassemble to make the action sensitive
(5) Replace the pressure-sensitive component
2. Fault phenomenon: poor sensitivity of pressure switch
Cause Analysis
(1) Poor assembly/excessive friction of the transmission mechanism (ejector rod or plunger, etc.)
(2) The contact stroke of the micro switch is too long
(3) Improper adjustment of adjustment screws, ejector rods, etc.
(4) Improper installation, such as uneven and inclined
Installation solution:
(1) Reassemble to make the action sensitive
(2) Reasonably adjust the contact stroke of the micro switch
(3) Reasonably adjust the positions of nails and ejector rods
(4) Change to vertical or horizontal installation
3. Failure phenomenon:
Pressure switch signals too fast
Cause Analysis:
(1) The oil inlet orifice is large
(2) The isolation diaphragm is broken
(3) System shock pressure is too large
(4) The electrical system design is wrong
Solution
(1) The size of the orifice should be appropriately changed, or a damping tube should be added to the control pipeline
(2) Replace the isolation diaphragm
(3) Add a damping tube to the control pipeline to reduce the impact pressure
(4) Design electrical system according to process requirements