Differential pressure switch is also called pressure differential switch or differential pressure controller by engineering and technical personnel. At ordinary times, people are not very familiar with differential pressure switch, and they are also at a loss when selecting and designing. How to choose a suitable differential pressure switch at ordinary times? What should be paid attention to in the selection and design of differential pressure switch at ordinary times? I think relevant technicians need to learn more about the differential pressure switch, and these problems need to be solved one by one. Only by solving the problem of differential pressure switch selection and design, can we know more about its various types in life, and it will be more convenient to apply.
1. Influence of dead zone (return difference) of differential pressure switch on process selection
Deadband, It refers to the difference between the action value and the reset value of the pressure switch. It is called dead zone in foreign countries. The so-called dead zone refers to the switch action value switching difference and reset difference. Some people call back the difference. For example, it is necessary to set a low alarm of 11mpa. If the dead zone of the switch is 1MPa, then the switch will reset when the pressure is at 12MPa. If the pressure does not reach 12MPa, then the pressure switch will always be In the alarm state, the switch cannot be reset. Therefore, when selecting the machine type pressure switch, it is necessary to consider the influence of dead time, especially in the differential pressure switch with double setting values. The maximum and minimum values of the standard deadband are determined according to the settings in the first line. If it is set at the low end of its adjustable scale, the deadband is also close to the minimum value; on the contrary, the deadband will be close to the maximum value in the label. Some models have fixed deadband and some models have adjustable deadband. Electronic differential pressure switch is usually adjustable in full range, so it is not important to consider dead zone, which is also the biggest advantage of electronic differential pressure switch.
2. Impact of maximum pressure and withstand voltage on the switch
The maximum pressure refers to the pressure that the switch can sustain without causing drift or relaxation of the sensing element at the set point. Withstand voltage: the maximum pressure that the sensing element may suffer sometimes. The switch will not be damaged but the setting value needs to be recalibrated.
3. Selection of diaphragm of differential pressure switch
The differential pressure switch is divided into three categories: diaphragm, bellows and piston. The characteristics of diaphragm switch are good universality, multiple selectivity and strong comprehensive performance. The advantages of welding stainless steel are zero leakage. The characteristics of bellows are small dead zone and high precision. The characteristics of piston are high pressure resistance;
4. Influence of temperature on selection of pressure switch
When we select the type, for example, the furnace temperature is 1000 ℃, but there is no pressure switch that can withstand 1000 ℃. When installing on site, we can consider adding the accessory siphon (capillary tube) to achieve the purpose of cooling. Therefore, temperature is not considered in general selection.
Through the above introduction of the design and selection of the differential pressure switch, we know what type of differential pressure switch should be selected, especially some influencing factors that need special attention. We should pay close attention to the relevant knowledge of the differential pressure switch, once it is used, it will not appear at a loss. We should pay attention to the selection and design of the differential pressure switch We need to pay attention to it all the time. We should never choose the model casually. There are regulations on what kind of model to use in any place.
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