Comparison Metabo BASIC 250-24 W 24 L vs Remeza SB4-24.VS204 24 L

The criterion for separating compressors according to this parameter is whether oil is necessary for the normal operation of the device.

— Oily. Compressors that use oil during operation have a high motor resource (due to the fact that friction in their mechanism is reduced due to the presence of lubrication) and a lower noise level than oil-free ones. On the other hand, they are much more difficult to maintain and more expensive to operate. the oil supply has to be replenished periodically; and during operation, such a unit should be located on a flat horizontal surface. In addition, the outgoing air contains tiny drops of oil. Therefore, oil-based devices are poorly suited for certain types of work — for example, in the food industry, where such impurities are unacceptable, the use of special fine filters will be required.

— Oil free. The main advantage of oil-free models can be called the purity of the exhaust air — it does not contain oil droplets and in most cases does not require additional purification. This makes these compressors perfect for medical, food and paint applications. In addition, they are simpler in design (respectively, in repair), do not require the hassle of providing lubrication, and can work in almost any position. On the other hand, high friction of parts significantly increases wear, which accordingly affects the resource.

The speed of rotation of the compressor motor shaft in normal operation. This parameter, usually, does not affect the efficiency of the unit — the main indicators are still the performance and nominal pressure (see above). At the same time, it allows you to evaluate the design features of the compressor and its durability. The fact is that a higher rotation speed allows the use of fairly simple and inexpensive working mechanisms, but it increases the wear of moving parts and reduces the motor resource. Therefore, a model with a lower number of revolutions is likely to cost more than the "high-speed" version, but it will also last longer (ceteris paribus characteristics — performance, pressure, drive type, design; see all above).

The number of cylinders provided for in the design of the compressor; by definition only indicated for reciprocating models (see "Compressor type"). This characteristic is primarily associated with performance indicators (see above). For example, values above 400 L / min among single-cylinder units are rather rare exceptions; therefore, if you need a high performance reciprocating compressor, you should look into multi-cylinder models. The second application for multiple cylinders is a multi-stage operation scheme (see "Number of stages").

Air tanks, or receivers (for details, see "Receiver volume") for modern compressors are usually made in a shape close to cylindrical, and can have both horizontal and vertical arrangement. Each option has its own characteristics:

— Horizontal. Such receivers require quite a lot of space on the floor (or other surface), but this moment also has a “reverse side” — the area of the upper part of the tank is also quite large, and belt-driven mechanisms can be placed on it without problems (see "Drive") . In addition, the horizontal arrangement allows the use of tanks of almost any volume, from small to very capacious, and the compressors themselves are very stable — it is almost impossible to accidentally overturn such a device. Therefore, this option is by far the most common and is found in the vast majority of models.

— Vertical. The main advantage of such receivers over horizontal ones is the relatively small amount of space required for installation. On the other hand, the vertical layout imposes serious restrictions on the maximum volume of the tank, and a small amount of space on top is usually only suitable for direct drive systems (see above). And the stability of such structures is somewhat worse. Therefore, this option has not received wide popularity, and it is worth specifically looking for a vertical compressor only if the situation does not allow the use of a horizontal model.

— Is absent. Models supplied without any receiver at a...ll.

The main advantages of tankless units are compactness, light weight and relatively low cost. However the air flow from them is relatively uneven, but in many cases this is not a drawback; in addition, various solutions can be used in the design, to some extent compensating for this drawback, and some compressors without a receiver are even positioned as devices for the same airbrushing.

— Frequency converter. This function is used to automatically control the power of the motor in the compressor (see "Motor type"), more precisely, to adjust the speed to the current air consumption and maintain a constant pressure.

In electrical units, in addition to reducing wear and tear and eliminating current surges in the network, such systems provide the most stable air pressure at the outlet, and energy is spent more rationally. At the same time, frequency converters are expensive and take up quite a lot of space; and the advantages mentioned are relevant for heavy professional-grade equipment. Therefore, this function is found mainly among industrial compressors with an operating voltage of 400 V and based on internal combustion engines.

— Dehumidifier. The purpose of such devices is already clear from the name: they are designed to dry the air at the compressor inlet, that is, to remove excess moisture from it. The need for such a procedure is primarily due to the fact that high humidity adversely affects the state of the compressor: it leads to condensate settling, and it, in turn, contributes to corrosion and the formation of various emulsions, due to which the channels become dirty and the wear of the entire unit increases .

— Tandem. Devices created according to the "tandem" scheme are actually two compressors on one receiver, connected...in parallel. This allows you to turn on both compressors at once, or only one of them — in this way you can adjust the power and performance even in those models where special regulators such as a frequency converter (see the relevant paragraph) are not provided at all.

Among the disadvantages are heavy weight, bulkiness and high cost. In addition, the tandem operation scheme is mainly suitable for powerful performant units — otherwise the individual compressors would have to be made too small, and this does not make sense.

— Wheels for transportation. The presence of special transport wheels in the design of the compressor. Modern compressors can be of considerable weight, which would require the participation of several people when carried; wheels, on the other hand, allow you to move even rather weighty devices without problems by the forces of one, in extreme cases — two people.

The maximum noise level produced by the compressor during operation. When evaluating it, it must be taken into account that the decibel used to evaluate noise is not an absolute value. In fact, this means that noises, for example, 20 dB and 40 dB differ in level not by a factor of 2, but by 100 — it is this multiplicity that corresponds to a difference of 20 dB; a twofold increase corresponds to a 3 dB increase. Therefore, to assess noise levels, it is worth referring primarily to comparative tables. For values found in modern compressors, this table would look something like this:

70 dB — loud conversations at a distance of about 1 m;
75 dB — scream;
80 dB — motorcycle engine with silencer;
85 dB — loud scream;
90 dB — freight train car at a distance of 5-7 m;
95 dB — noise inside the subway car.

Anyway, the lower the level of noise produced by the unit, the more comfortable its use, the less it will “hit on the ears” and increase the volume of the entire set of working instruments.

The sound pressure level in decibels at a certain distance between the noise source and the ear of the compressor equipment operator. Since people do not work in the immediate vicinity of the compressor, the parameter will be useful for estimating the noise level at a distance. It is most often measured at a distance of 7 m from a working installation, less often at a distance of 1 m.