The technical knowledge of these three types of screw air compressors must be mastered by sales engineers

The technical knowledge of these three types of screw air compressors must be mastered by sales engineers

Sales engineers need to understand the basic principles of air compressors. I believe that the company has given a brief introduction after joining, so I won’t repeat them. If you still don’t understand, you can consult books. There is no need to master the complex technology of the host, such as the molding problem. It is not necessary to explain clearly in three or two pages. If you want to learn by yourself, you can refer to related books. After grasping the overall situation, if you are interested, you can learn more about the mold line, contact line, leaking triangle, 4:5 teeth, 4:6 teeth, etc.

　　 Air compressor (the following refers to screw air compressor) roughly, there are three main lines: air circuit, oil circuit and circuit. Everyone should start to understand from these three aspects, and then comprehensively after z*, the structure of the air compressor is basically clear.

Gas line

　　 Let's talk about the whole process in a complete way. Some manufacturers may cut corners and have no relevant parts. You can compare our products:

Filter (some industrial environments are relatively poor, such as corrosive gases, then the air compressor inlet must be set in a harmless and clean place, some user companies will build air clean rooms)-air filter (Some manufacturers only have filter elements but no assembly)-intake valve-main engine-check valve (some use mechanical valves, some use solenoid valves, and some do not)-air tank (vertical Straight gas storage tanks have partitions, while horizontal gas storage tanks generally don’t)-oil and gas separators (both spin-on and barrel-mounted)-minimum pressure valve (actually a combination valve of pressure valve and check valve)- —After cooler — air-water separator (some manufacturers directly “save away" the air-water separator and the comb valve, ask yourself what effect this will have) — outlet valve.

There are also solenoid valves used to control the intake valve. In addition, different manufacturers have differentiated control methods (generally international brands pay attention to differentiation, domestic products are highly homogenized, and the competition is not quality, but cost and flicker ability. ), this is discussed in the final control part.

　　 The above are the basic components of the air path of the air compressor. The pipes connected in the middle do not need to be elaborated. In order to "saving materials", some manufacturers directly connect the air filter element directly to the intake valve. This is a very inferior design. For salespeople, this is one of the places that may be attacked by opponents. As a sales engineer, you must know your own products as well as those of your opponents. This is just a basic requirement. Only on this basis can we make a sales strategy that is conducive to ourselves and achieve the purpose of maximizing strengths and avoiding weaknesses.

　　Oil road

Gas storage tank (lubricating oil is installed here, this is different from other mechanical equipment, think about why it is designed this way)-temperature control valve (this valve is very important, but some manufacturers also give this "saving" The temperature control valve determines its flow direction according to the temperature of the lubricating oil. If the lubricating oil temperature is relatively low, the lubricating oil does not pass through the oil cooler; if the lubricating oil temperature is medium, some of the lubricating oil passes through the oil cooler and does not pass through the oil cooler. The cooled lubricating oil works together; if the lubricating oil temperature is relatively high, it will all pass through the oil cooler.

　　Think about it, if there is no such component, what problems will happen to the machine: under what circumstances will the problem be minor and under what circumstances will the problem be serious? )-Oil filter-pressure regulating valve (most of which do not have)-oil cooler-main engine (the flow direction of the main engine part of the oil-injected air compressor and dry oil-free air compressor is different: for For gear-driven air compressors, in addition to lubricating bearings and gears, oil-injected air compressors mainly act on the compression chamber; for dry-type oil-free air compressors, in addition to lubricating bearings and gears, they also pass through the inside of the main casing The oil jacket takes away the heat generated by the screw compression, and some manufacturers use cooling water jackets).

　　 There is also a small branch is the oil return pipe, which drains the remaining lubricating oil in the bottom groove of the oil-air separator in time. The best of this design is SULLAIR, which is not only visual (very friendly for maintenance and repair), but also a dual-circuit design. Another better design is KOBELCO. They set up iron absorption stones at the bottom of the gas storage tank, so that some very small metal particles can be absorbed and extend the life of the oil filter.

　　 The above is the basic composition of the oil circuit. The materials and structure of the parts selected by different manufacturers will be different. For example, oil pipes, some choose high-pressure oil pipes (the materials are also different), some use copper pipes, and some use stainless steel.

　　 circuit

　　 There are frequency conversion and industrial frequency, some frequency conversion with industrial frequency control, some without. Some frequency conversions use frequency conversion motors, and some use permanent magnet motors.

　　 First, let's talk about the ordinary power frequency control method. Basically, 380V voltage motors use the star-delta control method (the instrument control method will not be discussed, there are still on the old equipment, and now basically all use microcomputer control). The specific circuit is not provided here, you can look through your own drawings or check electrical books, network materials, etc. Let's talk a little about the control method, this is different, and it is also a place where sales engineers can have a good chat with customers.

　　 The following mainly talks about the core control method, as to whether the touch screen or the text screen is used; how many single-chip microcomputers are used in the core control chip, or 32-bit STM32 (based on ARM architecture), or chips based on other high-level ARM architecture, etc. Look at your own things for yourself, and then think about sales strategies.

　　 There are two representative control methods: switch control and capacity adjustable control.

On-off control method: It can be understood from the literal that the intake valve opens after the machine is turned on. When the pressure sensor detects that the pipeline pressure reaches the set maximum pressure, the unloading solenoid valve opens and the intake valve closes; when the pressure drops to When the minimum pressure is set, the intake valve opens again. If the pressure is always maintained at the set maximum pressure, the air compressor will stop when the set stop time is reached. When unloaded, the motor is constantly running and idling (this is more energy consuming, so engineers thought of control methods such as air intake capacity adjustment, variable compression section adjustment, and frequency conversion adjustment to save energy, as well as waste heat recovery technology).

　　Volume adjustable control mode: that is, the intake valve (some use butterfly valve, some use poppet valve) valve plate (core) can be fine-tuned, not the kind of on-off valve that only has two position modes: open and closed. In other words, the on-off valve has only two states, 0 and 1, and the capacity adjustable control mode can be adjusted between 0 and 1 (in actual use, it is only adjusted when it is close to 0 and close to 1). After starting, the pressure sensor continuously detects the pipeline pressure, and the controller receives the analog signal of the pressure sensor and converts it into a digital signal. When the pressure is close to the set maximum pressure (ie 1), the controller sends out a digital signal, which undergoes digital-to-analog conversion The converter converts the digital signal into an analog signal to control the intake valve actuator to close the intake valve valve plate (core) according to the designed ratio.

If the actuator is in place according to the program and the air pressure continues to rise, when the set maximum pressure is reached, the intake valve is closed, and the air compressor will unload and enter the no-load state; when the pipeline pressure drops to close to the minimum pressure (Ie 0 o'clock), the controller will require the actuator of the intake valve plate (core) to open according to the set ratio. Even if the intake valve is partially opened, the pressure will continue to decrease. When the pressure reaches the minimum value , The intake valve is fully open. The above-mentioned control method is electronically controlled, and the manufacturer uses mechanical adjustment (two pressure regulating valves respectively).

　　Adjustable capacity control method, if you want to exert the energy saving effect, the key is to choose the model. Only when the air compressor (or air compressor combination) is selected is very close to the actual gas demand, the advantage can be exerted.

　　 Another type of control method: frequency conversion adjustment and variable compression section adjustment.

　　Inverter adjustment, as the name suggests, is to control the motor through the inverter to achieve the purpose of constant voltage control, and to reduce the current to a corresponding level in proportion to achieve the effect of energy saving. Although they are all frequency converters, different designs can use frequency converters with different functions (frequency converters of similar quality, the stronger the function, the more expensive the price). If the inverter is controlled by the controller (with PID function) to achieve the control purpose, then the PID function can be omitted for the inverter. Although this increases the complexity of the controller program, it can effectively reduce the cost; if the inverter has With the PID function, the analog signal returned by the pressure sensor can be directly sent to the inverter, and the inverter can adjust with the pressure, so that the program complexity of the controller can be reduced, and the functional requirements will also be lower.

　　 Variable compression section adjustment is to mechanically adjust the effective compression length of the rotor according to the air consumption of the rear section of the air compressor, in order to achieve the balance of compressed air production and sales and achieve the purpose of energy saving.

　　 Frequency conversion adjustment and variable compression adjustment cannot achieve 0-100% adjustment. The frequency conversion adjustment must be set to the lowest frequency, otherwise it will damage the motor. The variable compression adjustment is generally used in conjunction with the capacity adjustment intake valve at the beginning of the design.

In order to achieve energy-saving effects for frequency conversion adjustment and variable compression section adjustment, the key is also the selection, and for the combination mode (more than 2 air compressors + 1 standby machine) mode, only one frequency conversion adjustment or variable compression section adjustment is required. Air compressor. In terms of configuration, this is optimal. But why do some people fool their customers to buy all inverters, and the inverter itself consumes energy? There are prerequisites for the use of the frequency converter, what is it?

　　The situation of the air compressor will be briefly mentioned here, but this is not all that the sales engineer should grasp, because the customer wants "qualified compressed air", and the air compressor usually cannot meet the customer's needs.