2. Air pressure sytems
2.1. Air consumption and compressors
The air consumption – especially the average air consumption - of a vibration system forms the basis for a calculation to determine the compressor size
The following table shows the air consumption of our pneumatic vibrators at an operating pressure of 2 and 6 bar in liters per minute.
The values can deviate by 10% due to manufacturing tolerances.
|Types||2 bar||6 bar||*||Types||2 bar||6 bar||*||Types||2 bar||6 bar|
|Types||2 bar||6 bar||*||Types||2 bar||6 bar||*||Types||2 bar||6 bar|
2.1.1. Calculation of avarage air consumption
1. Air consumption according to Table 2. 1 .: CONS = ....... liters / minute
2. Operating factor (on / off) × 100%: OPF = .........%
3. Average air consumption = CONS × OPF: ACON = .......... liters / minute
4. Total air consumption = ACON × number of vibrators
To calculate the average air consumption of different vibrators, the average air consumption of each vibrator needs to be added together.
To determine the size of the compressor – to be on the safe side – add on an additional 20% of the calculated total air consumption (as a recommendation). Leaks in the air system, other connected devices and probable future expansion needs to be taken into consideration as well to determine the size of the compressor.
There is another factor to consider: The highest possible air consumption caused by all units operating at the same time and the duration of this high capacity utilization period.
Highest possible air consumption = number of vibrators × CONS for ........... minutes
= .......................... liters / minute lasting for ........... minutes.
Both values (the amount of maximum air consumption & the average air consumption) should be taken into account when selecting the compressor.
Dry or not dry? This is an important question.
Generally, lubrication helps to increase the lifespan of moving parts as long as it reduces the friction. However, the lubrication of a ball vibrator is superfluous, as its lifespan is not extendable. For all turbine vibrators T-series (with unprotected bearings) lubrication is required. For GT types with encapsulated bearings, lubrication is not required.
Due to the special materials and coatings (Teflon) the friction is already extremely minimized. Even without lubrication the piston vibrators (FP-series) and the roller vibrators (DAR series) show excellent emergency running characteristics. Only after a while lubrication is necessary to avoid wear and tear.
There is no general answer how many drops of oil are sufficient and/or too much. It may be possible that the piston compressors discharge a sufficient amount of oil into the compressed air. Then an additional lubricator is not necessary. On the other hand, due to leaks, the same type of compressor could lose so much machine oil, which might cause to a reduction in the frequency and the force and / or oil bonding then an additional lubricator would be necessary (e.g. when using a vibrator of the DAR series). Air compressors with installed air dryers require a lubricator when using vibrators of T-, DAR-, and FP series.
Important to know for lubrication of any Findeva vibrators:
Use only oil with the following viscosity: ISO VG 15 with 15cST/40°C
Klüber Airpress 15 is recommended.
Alternatively usable is oil with the following viscosity: ISO VG 5 with 5cST/40°C.
The used oil should not tend to glue together. We have listed some varieties:
Shell Tellus Oil C5
Esso Nuto H5
Mobil Velocite No.4
BP Energol HP 5
for utilization in food industries: Mobil Whiterex 304 (vegetable base)
NOTE: Oil with other viscosities as listed here reduce frequency and power of the used devices. For piston vibrators (FP-series) applies: distilled water can be used instead of oil. The lubrication effect will be sufficient as long as the dosage is at least 10 drops / minute.
Check the silencers for traces of oil and adjust the oiler to a minimum of oiling (but not completely without oiling). Please avoid the reduction of performance of piston or roller vibrators by too much lubrication.
2.3. Air filter and pressure regulator
All compressors are fitted with air filters to protect the valves and pistons from wear and tear. This compressed air is sufficiently clean for all of our rotating vibrators. Remaining micro particles are passing through without damaging the vibrator. However, an air filter with particle passage of 5 mm or less is recommended. This helps to extend the lifespan of the vibrators.
Note: Always use air filters ≤ 5µm for any piston vibrator and knocker!
Recommendation for mounting: First the filter, then the regulator and finally the oiler.
2.4. Compressed air pipes
It is basically possible to control vibrators by changes in air pressure or air volume. However, please take care that the air pressure units are dimensioned correctly. If the diameter of the air pressure pipes is too small, the vibrator is not reaching its full capacity.
This applies in particular to the air outlet pipe. This should be as short as possible, as the volume of the exiting (expanded) air is many times greater than the pressure difference.
The corresponding formula is V (in) x P (in) = V (out) × P (out) as long as P is the absolute pressure and not just the excess pressure . This means a vibrator operating at 6 bar produces an air outlet volume which is 6 times larger than the air inlet volume.
Diagram for determining the diameter and the length of the air pressure pipes.
A too long or too small air outlet pipe prevents the air pressure in the vibrator from being completely converted into vibrational energy.
A silencer mounted directly on the vibrator is the best way to utilize as much power as possible.
In order to determine the sizes of the supply pipe, the diagram shown above can help to determine the required pipe diameter.
Example:- Air consumption = 900 ltrs. / minute with an air pressure of 4 bar- The pipe length is 10 meters.- Start at the right side with 900, continue left until you reach the 4 bar line. Now follow this line 45 ° upwards to the vertical dividing line, further on horizontally to the left until you reach the 10 meter line. Follow this line now 45 ° right up to the vertical line pressure loss in shown in bar. The required cross-section or diameter appears now horizontal on the left.Note: The loss of air pressure in the pipe should not be more than 0.5 bar. Anyhow, it is not useful to keep this value as small as possible, because this increases the size and cost of the pipes. A value between 0.1 and 0.5 bar is ideal.The required dimensions of the air outlet pipe can be determined the same way. Instead of the input pressure you now use the output pressure of the vibrator (this has to be a value between 0.2 and 0.5 bar).
2.5. Valves and pressure regulators
2.5.1. Pressure regulator
Using pressure regulators (e.g., needle valves), the vibrator can be adjusted to the optimum working torque. The adjustable volumetric rate of flow influences the frequency and power of the vibrator.
We recommend: Mounting of the regulator between air filter and lubricator, in order to achieve the best possible results.
2.5.2. Air pressure valves
For some applications, the vibrator only needs to operate temporarily e.g. emptying of hoppers and bunkers. To achieve this a solenoid valve may be connected after the oiler. The positioning in front of oiler and regulator is disadvantageous as the controller has to re-adjust itself at any pressure build up and the full air pressure is not available directly. This could lead to a functional failure at the vibrator. Therefore, it is also recommended to fix the valve as close as possible to the vibrator.
Important: Do not install air pressure units such as air filters, pressure regulators, oilers, etc. directly on the vibration system. The air pressure devices would not work properly then.
NOTE: Make sure that the inner diameter of the valve is large enough (please see our chart to determine the size of your air hosepipe). Otherwise it is not ensured that the vibrator can reach its full capacity, and / or the piston vibrator may start operating. Piston vibrators need a very quick starting impulse to start up operating (rapid onset pressure). For manual operation try to open the valve as quickly as possible or use solenoid valves.