I. Temperature Controller
A temperature controller, as the name suggests, is a device that adjusts and controls the temperature based on changes in the working environment. It plays an important role in many applications. Temperature controllers can be divided into several different types, and many people have questions about the working principle of each type. Let's take a look.
The snap-action thermostat is a new type of bimetallic thermostat, mainly used for overheat protection in various electric heating products. It is typically used in series with a thermal fuse, with the snap-action thermostat serving as primary protection. The thermal fuse then acts as secondary protection when the snap-action thermostat malfunctions or fails, causing the heating element to overheat. This effectively prevents damage to the heating element and any resulting fires.
Liquid expansion thermostats utilize the lever principle to actuate the switch, achieving a constant temperature. They feature accurate and reliable temperature control, small temperature difference between start and stop, a wide temperature control range, and high overload current. Liquid expansion thermostats are mainly used in temperature control applications in the home appliance industry, electric heating equipment, and refrigeration industry.
A pressure-type temperature controller is a component that regulates pressure and volume in a space by controlling temperature changes. When the set temperature is reached, the contacts automatically close via an elastic element and a rapid-acting mechanism to achieve automatic temperature control. It consists of three parts: a temperature sensing unit, a temperature setting main body, and a microswitch or automatic damper for opening and closing. Pressure-type temperature controllers are suitable for refrigeration appliances (such as refrigerators and freezers) and heating appliances.
Electronic temperature controllers (resistive type) measure temperature by resistance sensing, typically using platinum wire, copper wire, tungsten wire, or thermistors as the temperature sensing resistors.
The above introduces several common types of temperature controllers, categorized according to their working principles. Each type has its own characteristics and functions to regulate temperature, thereby protecting machine components. Once users understand the principles of different types of temperature controllers, they can choose the device that provides the greatest protection based on their specific needs and the intended use of the temperature controller.
II. Differential Pressure Controller
(a) Differential Pressure Controller
Differential pressure controllers are divided into oil differential pressure controllers and air differential pressure controllers, etc. The former maintains a certain pressure difference at the points requiring a differential pressure. For example, the discharge pressure of the compressor lubricating oil should be 0.1–0.2 MPa higher than the pressure inside the crankcase for the compressor to operate normally. The latter, when the pressure difference reaches a certain level, should trigger the next step of the program. For example, in an air conditioning system, when the inlet and outlet pressure difference of a wound-type air filter exceeds a certain value, it indicates that the filter media can no longer function and should be automatically replaced. This can be done automatically using a differential pressure controller.
(II) Debugging of differential pressure controller
(1) The direction of medium flow should be consistent with the direction of the arrow on the valve body;
(2) This type of valve should be installed on the return water pipe, with a pressure guide pipe connected to the valve. The other end of the pressure guide pipe is connected to the water supply pipe. It is recommended to install a 1/2" ball valve at the water supply end of the pressure guide pipe to activate the anti-blockage function.
(3) A filter screen should be installed on the water supply pipe before the pressure guide pipe to prevent the valve from losing its automatic adjustment function due to poor water quality;
(4) Pressure gauges should be installed on the water supply pipe and the return pipe before the valve to facilitate the adjustment and control of the pressure difference;
(5) If the system flow rate is found to be too high or too low, the possible cause is that debris from the installation of the pipeline components is stuck on the valve plug. You can close the 1/2" ball valve for 3-5 minutes. If it is a minor blockage, it will be cleared automatically. If it cannot be cleared, you need to disassemble the valve to check and remove the blockage.
(6) Differential pressure adjustment method: Adjust the pressure regulating valve rod counterclockwise. When the pressure gauge before differential pressure decreases by 0.01 MPa, the differential pressure will increase from the set 0.02 MPa to 0.03 MPa, and so on.
(7) The working pressure difference of the valve is 0.02-0.03MPa. If the working pressure difference is found to be greater than 0.3MPa after installation, a manual regulating valve should be installed on the water supply pipe to reduce the pressure difference between the supply and return water pipes at the heat inlet device. Otherwise, the pressure difference controller may only work at a small opening for a long time, which will generate noise and greatly reduce the service life of the valve.
