Noise analysis and treatment of air compressor

Noise analysis and treatment of air compressor

A compressor manufacturer's statement: The noise level guarantee is +3dBA, which means that its noise level will be twice or one half of the declared noise level.

Two units operating at different speeds may have the same noise level, but they sound completely different. One may be harsher than the other. This is because noise forms dBA based on the sum of all the frequencies in the spectrum.

In order to measure the noise level, the noise of each scale band is measured, and the number of answers (dBA) is obtained by inverse evaluation with "A" and comparison and addition. mechatronics tells you what all this means:

1. This means that we cannot place a compressor in a room due to reflection and expect to have the same noise level as in the open field conditions.

2. We cannot make a clever guess about the noise level with two different units (with different speeds, different drives, different components and different enclosures). The only way to measure noise is to use a sound measuring device.

How do we overcome obvious differences in noise levels?

1. By accurately measuring the noise level

2. By knowing how the noise level is composed, sensibly specify the frequency difference and harshness factors.

3. Know that two units have the same noise level, but the noise of the unit with different frequency characteristics causes the same damage to the ears, even if one of them does "sound" lighter.

How can we further reduce noise?

1. Ensure that all joints in the machine body are safe, the forklift holes are closed, and the base body of the machine body on the ground is solidly sealed.

2. Transport air intake and exhaust through pipelines.

3. Reduce reflected noise.

Sound and noise measurement is at best a very imprecise science. The discussion on this topic hopes to avoid field problems, the large cost of field corrections and user dissatisfaction.

1. All noise level measurements use the ANSLS51 standard. This is an industry standard. We should use this standard to refer to the noise level used for citation. In short, the standard requires open field measurements (without reflecting walls and roofs), multi-point measurements around the unit, and an average of the measured values. It should be measured one meter away from the unit, 1.5 meters above the ground and foundation level. Any single-point measurement can reach the quoted A noise level. As long as the average reading can meet or fall below the reference level. In addition, the measurement used is the average value of the measured noise that should be broadband. When frequency band analysis is required or given, some mid-band readings can, and usually do, are higher than the noise measurement average. Once again, this is what the standard accepts.

2. There is no tolerance given and applicable in the standard structure

3. Units that have not been placed in the field should be placed in the open field. In fact, the noise level in regular locations is always higher because of reflections from nearby walls and/or roofs and nearby equipment.

4. The noise level data that may be submitted is the actual measurement when the measurement should be made for a specific compressor, and repeated operation of a compressor of the same type under the same conditions can be interpreted as a typical noise level.

Pay attention

For any multi-point measurement or repeated compressor measurement, there is a certain error link. These errors indicate that in order to ensure that the noise level is a problem for a particular compressor, 3 decibels should be added to the total dBA measurement. When guaranteeing a user's noise level, it is absolutely necessary to comply with the above requirements.

Empirical formula

A 0.7MPa air compressor produces 0.1416M3 gas per horsepower

Every 0.007MPa pressure drop is equal to 0.5% power

The thermal load of the air-cooled compressor=HP×2545BTU/hour (1BTU = 1.055KJ)

GPM of water-cooled compressor (liters of water per minute)

HP × 2545

500×△T water

Or, if △T water = 11.1℃ (closed loop), it is HP/4

Such as △T water = 22.2℃ (urban water supply system) is HP/8

65% of the condensed water has been removed after passing through the aftercooler

96% of the condensed water has been removed after passing through the refrigerated dryer

When the exhaust temperature increases by 11℃, the water content will double

Every 0.028M3 = 7.48 gallons = 28.31 liters = 1 cubic foot

The air compressor needs to be equipped with 133.5 liters of cylinder air storage capacity for every M3 air intake

Pumping formula derived from the ideal gas law

Volume (m3) × pressure rise (MPa)

Time (minutes) =———————————————

      Air volume (cubic meter) × 0.1013 (MPa)

          Motor pulley size (inch) × compressor speed (RPM)

Motor pulley size (inch) =------------------------------------

         Motor speed (RPM)