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Screw air compressor unit is composed of screw compressor host, motor, oil and gas separator, cooler, fan, water separator, electrical control box and gas pipe, oil pipe, regulating system。The compressor host body has a pair of precision machined Yin and Yang rotors meshing with each other。For direct-connected units, the motor drives the positive rotor directly through an elastic coupling, and for geared units, the motor drives the gear shaft through an elastic coupling, and then gears to the positive rotor。The injected oil is effectively compressed between the rotor grooves after mixing with the air, and the oil forms an oil film between the rotor grooves, avoiding direct metal-metal contact and sealing the gap between the rotor parts and absorbing most of the compression heat。The unit has no oil pump, and the oil pressure is sent to each lubrication point by the gas pressure in the oil and gas separator。The oil and gas mixture discharged from the compressor passes through the oil and gas separator, and most of the oil is coarse separated by the method of cyclone separation. The remaining oil passes through the oil separator filter for further fine separation and settles at the bottom of the filter。The oil at the bottom of the filter element is introduced into the compressor by the return pipe using the pressure difference, and the oil level gauge, minimum pressure valve and safety valve are installed on the oil and gas separator。Oil and gas separators also double as fuel tanks and gas storage tanks。

(1), selection to "need to shape"

Combined with the needs of customers, find the best operating economy, and expand the scale in the future need to make a lot of decisions。The basis of the decision is the use or use of compressed air process, focus on the calculation of air demand, reserve and room for future expansion, and pressure is a determining factor, has a great impact on energy consumption, different pressure ranges with different compressors may sometimes be economical。

(2) Calculation of working pressure

Compressed air equipment determines the necessary working pressure depends on the compressor, equipment, pipelines, the highest working pressure determines the necessary device pressure, and the pressure reducing valve is used at the gas consumption location to meet the equipment needs, in extreme cases, with a separate air compressor is not economical。

Working pressure: End user + final stage filtration + piping system + dust filter + dryer + compressor adjustment range

The higher the pressure, the greater the power consumption, it is necessary to consider the pressure drop caused by the size and length of the pipe。List the use of various types of machine pressure, if the use of pressure difference is too much, you must purchase different pressure air compressor, can not reduce the pressure use, in order to increase the cost of consumption。

(3) Calculation of air demand

Compressed air is a clean power that converts electrical energy into air potential energy and does work with the expansion of compressed air, but its consumption of electrical energy is also very large。Generally speaking, 1m3 of air is compressed to 0.The power consumption required for 7MPa is about 7kW。According to statistics, the energy consumption of air compressor station accounts for about 20% of the total energy consumption of the entire enterprise。This means that saving compressed air and using it properly will bring you new profit margins!

Air demand: all tools + machines + related process air consumption + leakage + wear + future gas + coefficient of use (standard value 20%)

(4) Determine the number and specifications of compressors

1.Depending on the degree of flexibility required + control system + energy efficiency

1), choose a large machine or choose a number of small machines?

Production downtime, power utilization, load (load) changes, cost of compressed air system, available floor space。For reasons of availability, only one compressor is used to supply all the air in a unit, so the system can provide a quick interface for a mobile compressor to be connected when in use, and an old air compressor can be used as an inexpensive backup power to provide a reserve air source。

2) Stability (always a very important topic);

3) Energy expenditureRoad leakage;

Gas demand fluctuates from moment to moment (this is the most overlooked and the most serious)

Output efficiency of a single machine (select the best range of output efficiency models)

4) Universality of spare parts

The optimal combination of multiple 110KW models may be the best choice for 40-160m3/min, gas range。

5) Operation analysis

It should be observed within a week, and more than 90% of the measured energy recovery is recovered。Working pressure in a certain period of time, often decrease the control system can be modified with reference to the change of production, improve the use of air compressor another factor to check whether air leakage。

Pay attention to the energy consumption ratio, in order to save power: the actual displacement/real motor power, the larger the value, the more power consumption。

2. Selection of frozen dryer

In order to remove water from the air, your company uses an adsorption dryer, which shows that the air quality requirements of the gas equipment and tools are very high。

Under normal circumstances, only according to the flow of the air compressor, choose the dryer with a capacity that is or slightly greater than the flow of the air compressor。

For enterprises that have high moisture requirements for the air of the frozen dryer and do not need to use the adsorption dryer, the frozen dryer can be increased by one level or two dryers can be selected side by side。

3. Selection of adsorption dryer

1), no heat regeneration (PSA)

The desiccant tends to become saturated after a period of use，It must be dried and regenerated，The simplest and most common method is to draw a part of the dried air from the outlet of another tank，After reduced pressure expansion, the wet desiccant is blown dry，For dryers without heat regeneration，About 14% of the rated flow of air is required to regenerate it completely。

Suitable for small air flow regeneration process using compressed air, its gas consumption at 7bar working pressure requires 15-20% compressed air, pressure dew point is -40oC。The lower the pressure dew point of the dryer, the more air consumption is required。

2), heating regeneration (TSA)

In addition, if some heating devices are added to the drying tank, such as heating rods, etc., less recycled air can be used when the desiccant is regenerated to 200 ° C, saving a lot of energy consumption。Only 4% of the recycled air is required to achieve complete regeneration, saving about 10% of the compressed air volume。In general, heating regeneration is usually used in larger units or locations where compressed air flow is limited, although its initial investment is higher, but it can save more money under long-term use。

Heating regeneration is usually used in larger units or when the flow of compressed air is large。

3), micro-thermal regeneration

The micro-heat regeneration adsorption dryer is a compressed air adsorption dryer with Chinese characteristics, which is designed to reconcile the characteristics of non-heat and thermal dryers, and produce a dryer with a smaller gas consumption than the non-heat type and less heating power consumption than the heating type。

In the structure, the micro-thermal type is desorbed with dry air generated by itself, and the desorbed gas is specially micro-heated by external heat source。The aim is said to be to save energy。But theoretical research shows that the actual situation is not so ideal;A small amount of regas heated to a certain temperature after entering the regeneration tower, the temperature is immediately absorbed by a large number of adsorbents, in other words, to make the regeneration exhaust temperature reach the required value, first make the adsorbents in the tower reach this temperature, which will consume a lot of regas。

Conclusion: No matter which of the above three types is selected, compressed air is needed, and the regenerative air required by the suction dryer should be taken into account in the selection of air compressors。

4. Selection of tube filter

The selection of the tube through the filter is usually only based on the flow of the air compressor, select the filter that the capacity is or slightly greater than the flow of the air compressor。

The tube filter has different accuracy, and the choice of accuracy depends on the air quality requirements of the enterprise。At present, the air compressors used more in the market are mainly divided into screw air compressors and piston air compressors。Because the oil content of the compressed air of the piston air compressor is 25-150PPM，Tertiary filtration required，For screw air compressors, the oil content of compressed air is usually 2-3PPM，Therefore, the selection of filters generally passes two stages of filtration treatment to meet customers' requirements for air quality，当然，In special cases, we can also deal with it by adding active carbon filters。

5. Selection of gas storage tank

The usually simple method is 15-30% of the air compressor output (m3/min as a unit)。If you want to calculate, the following formula can be used。

V = 空气桶体积; Q = 空压机空量(m3/min);8 = 常数(一般用于7bar时);

△P = differential pressure (bar, usually set to at least 0.6-1bar)

In addition, in the selection, but also for customer needs, to determine the working pressure, both to meet customer needs, but also to save the cost of investment。

Screw compressor has the advantages of simple structure, easy operation, less wearing parts, convenient replacement of parts, low noise and safe and reliable operation, so it is more and more widely used in enterprises。However, if the maintenance measures are not correct or improper operation, it will lead to increased equipment failures and reduced life, thus affecting the normal operation of the unit。In order to maintain the normal and reliable operation of the compressor unit and long operation life, it is necessary to develop a detailed maintenance plan, perform regular operation, regular maintenance, regular inspection and maintenance, so that the compressor can be kept clean, oil-free and dirt free。Only a comprehensive grasp of maintenance common sense and familiar with the solution to the fault, in order to ensure the smooth operation of the compressor。