Causes and treatment methods of insufficient exhaust volume of air compressor

The compressor is a general-purpose mechanical device, and is now widely used in various fields. Due to the power of the motor and the length of the main shaft, the displacement of the compressor will vary. The following is the phenomenon of insufficient displacement of the compressor proposed by the customer. Simple analysis:

1. The selection is too small

Many users do not know the specific gas consumption of their own production at the beginning, so they blindly select models according to their own estimates, resulting in exhaust pressure that cannot be increased, lower than the rated exhaust pressure, and cannot meet the normal gas consumption of the factory.

You can first check whether there is an air leakage point in the pipeline, and close the valve behind the gas storage tank. If the unit can quickly increase the pressure, open the valve, the pressure will drop quickly, and finally reach a pressure point, then you can Confirm that the selection of the compressor unit is too small, and the displacement of the unit is less than the actual gas consumption of production.

The solution is to add a new unit so that the displacement of the compressor is 10% to 20% more scientific than the gas consumption.

(1) Selection of working pressure (exhaust pressure):

When the user is going to purchase an air compressor, first determine the working pressure required by the air end, add a margin of 1-2 bar, and then select the pressure of the air compressor (the margin is considered from the installation of the air compressor. The pressure loss of the distance from the site to the actual gas end pipeline, according to the length of the distance, the pressure margin should be properly considered between 1-2 bar). Of course, the size of the pipeline diameter and the number of turning points are also factors that affect the pressure loss. The larger the pipeline diameter and the fewer the turning points, the smaller the pressure loss; otherwise, the greater the pressure loss.

Therefore, when the distance between the air compressor and each gas end pipeline is too far, the diameter of the main pipeline should be appropriately enlarged. If the environmental conditions meet the installation requirements of the air compressor and the working conditions permit, it can be installed near the gas end.

(2) Selection of volumetric flow rate:

① When selecting the volume flow rate of the air compressor, you should first understand the volume flow rate of all gas-consuming equipment, and multiply the total flow rate by 1.2 (that is, enlarge the margin by 20%);

② New projects can be selected according to the flow value provided by the design institute;

③ Learn about the volume flow parameters of the gas equipment suppliers from the gas equipment supplier for model selection;

④ Air compressor station reconstruction can be selected by referring to the original parameter values combined with the actual gas consumption.

Appropriate selection is beneficial to both the user and the air compressor equipment. If the selection is too large, it is wasteful, if the selection is too small, it may cause the air compressor to be in a loaded state for a long time, or the air consumption is not enough, or the pressure cannot be increased.

(3) The relationship between power, working pressure and volume flow:

In the case of constant power, when the speed changes, the volumetric flow and working pressure also change accordingly. For example: for a 22kW air compressor, the working pressure is determined to be 7bar at the time of manufacture, and the speed is calculated according to the technical curve of the compressor host, and the displacement is 3.8m3/min; when the working pressure is determined to be 8bar, the speed must be reduced (otherwise The driving motor will be overloaded), at this time, the displacement is 3.6m3/min. Because, the speed is reduced, the exhaust is correspondingly reduced, and so on.

The power selection is under the condition of meeting the working pressure and volume flow, and the power supply capacity can meet the power of the matching driving motor.

Therefore, the steps for selecting an air compressor are: first determine the working pressure, then determine the corresponding volume flow, and finally the power supply capacity.

2. Compressor unit failure

If there is no leak point in the compressed air line, it is a problem with the compressor unit itself. The lack of displacement of the compressor unit has the following problems:

(1) Whether the maintenance is timely

The displacement of the compressor has decreased. After excluding the above possibilities, first check whether the compressor has been maintained? How long has it been maintained? If the environment is not ideal, check if the air filter is clogged after the compressor runs for 2000 hours. If it is light, you can use compressed air to remove dust; if the blockage is serious, replace it with a new air filter.

In many cases, the displacement of the compressor decreases, and there is no major problem. It is caused by the customer’s neglect of maintenance, and the air filter of the compressor is blocked. After replacing the new air filter, it can be used normally.

In addition, in addition to the air filter, the lubricating fluid and other filter elements are also critical. Check whether the lubricating fluid is within the standard range. If it is missing, please add it appropriately.

(2) Whether the intake valve is fully open

The displacement of the compressor has dropped, check the unit, if it has just been maintained, eliminate the third filter and oil problems, at this time first check the compressor intake valve, remove the intake hose, turn on the compressor, and observe the opening of the intake valve Is it normal. Generally, the theoretical design service life of the intake valve is 100,000 operations. Because each manufacturer uses different brand batches, the quality is also different, so the failure of the intake valve may cause the exhaust volume of the unit to decrease.

If the intake valve cannot be fully opened when the compressor is loaded, it can be concluded that the decrease in displacement is the fault of the intake valve, which should be removed for repair or replacement.

(3) Motor failure

After eliminating the faults of the intake valve above, the exhaust volume of the unit still does not change, and it should be considered whether the motor is faulty. Due to local short circuit in the motor coil, or bearing wear and motor shaft wear, the motor speed is lower than the rated speed, and the compressor discharge volume is reduced. The motor coil, bearing, etc. should be repaired, and the compressor discharge volume should be tested after repair. .

(4) The working pressure set by the pressure switch of the compressor is too low, and the pressure upper limit should be adjusted upwards

When debugging in the compressor factory, adjust to the specified pressure according to the customer’s needs, and then set a pressure difference. For example, the compressor starts to pump air into the gas storage tank. When the pressure reaches 10kg, the compressor stops or unloads. When the pressure reaches 7kg, the compressor starts again. There is a pressure difference. This process can make the compressor Take a break to protect the compressor.

Different compressor switches have different adjustment methods, one is that the pressure difference is fixed by the switch itself, and only the automatic shutdown pressure, the maximum pressure, is adjusted. This kind of switch has two knobs adjusted by a flathead screwdriver on the switch. The two knobs must be adjusted in the same way, otherwise they will stop when they start together, and start again after stopping, which will burn out the electrical appliances.

The other is to adjust the starting pressure (low pressure) and the stop pressure (high pressure) one.

Compressor pressure adjustment:

a. Turn the pressure adjustment screw clockwise to increase the closing and opening pressures simultaneously.

b. Turn the pressure adjustment screw counterclockwise, the closing and opening pressures decrease synchronously.

Compressor differential pressure adjustment:

a. Turn the differential pressure adjustment screw clockwise, the closing pressure remains unchanged, and the opening pressure increases.

b. Turn the differential pressure adjustment screw counterclockwise, the closing pressure remains unchanged, and the opening pressure decreases.

If the pressure switch of the compressor is faulty, the working pressure error will be caused. It is necessary to overhaul the pressure switch, and replace it with a new one if it cannot be repaired.

(5) The environment changes, resulting in a decrease in exhaust volume

It used to be used in inland areas. Because the factory was built in the northwest region, the compressor was used in the new factory along with other equipment. The altitude increased and the environment became humid, which may lead to a decrease in the exhaust volume of the unit.

The higher the altitude, the thinner the air, and the smaller the gas production per unit time; the moisture in the air is too large, and the compressed air contains a lot of moisture. In the post-processing, water vapor is precipitated, resulting in a decrease in the gas output.

(6) The belt driven by the compressor is too loose, resulting in a decrease in transmission efficiency

The transmission belt needs to be adjusted, and if it is damaged, replace it with a new one.

Choose the appropriate positioning method according to the cooperation between the pulley and the shaft, install the pulley on the shaft of the compressor head and the compressor motor, and fix and lock the pulley of the compressor head first.

For a loose transition fit, tap with a softer copper, aluminum or rubber hammer. For tight fit, it can be assembled by pressing in with a pressure plate or heating and red packing, and the heating temperature is controlled at 120-150°C. If the tolerance of the tapered sleeve pulley is slightly tight, the inner hole of the tapered sleeve can be slightly enlarged and installed on the shaft. Use a level ruler (accuracy ≤0.5mm) to measure the perpendicularity between the two pulleys and the same reference plane, and the allowable error is ≤0.5mm. If the verticality error is greater than 0.5mm, gaskets can be used to adjust the compressor head or the installation foot of the compressor oil and gas barrel to ensure that the vertical error does not exceed 0.5mm on the same reference plane.

Tighten the mounting bolts of the compressor head or compressor oil and gas barrel. Install the belt on the pulley according to the principle that the trademark code is at the same position. With the small pulley as the benchmark, use a ruler or a laser measuring instrument to measure the plane straightness of the two pulleys, and the allowable error is ≤0.5mm. Tension the belt with the compressor motor adjustment screw. Conversely, take the big pulley as the benchmark, recheck the plane straightness of the two pulleys, the allowable error is ≤0.5mm, and finally tighten the adjusting screws and nuts.

The replacement of the belt is the same as the adjustment of the belt, but it should be noted that if you want to replace the belt, you can’t just replace one belt, otherwise the new belt will be damaged due to the different tension of the belt; do not splash the lubricating oil on the belt or pulley, to prevent the belt from slipping. Check the belt after the first 30 hours of operation of the new machine. If the belt of the compressor is loose, it should be adjusted immediately.

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