FREQUENTLY ASK QUESTION
Q : Why do we need compressed air purification?
A : Compressed Air purification is needed to:-

i. Remove atmospheric dust, smoke and fumes inducted by the compressor.
ii. Remove atmospheric bacteria and viruses (for food industry and pharmaceutical).
iii. Remove water droplet from the air compressor.
iv. Remove gases generated in the compressor.
v. Remove oil carried over by the compressor.
vi. Remove solid contaminants generated within the system.



Q : For refrigerant dryer, what are the reasons causing moisture carry over to the production lines?
A : i. High inlet temperature of compressed air.
ii. Not enough refrigerant in the system.
iii. Auto drain not functioning.
iv. Undersizing of dryers


Q : What is the main purpose of coalescing filters?
A : Oil is the most difficult contaminant to remove from the compressed air system. Modern techniques of oil separation use the principle of coalescing, which is a term use to describe the action of forcing aerosols to combine into droplet which become large enough and heavy enough to be drained away by gravity. There are three different processes occuring in a coalescing filter, depanding on the particle size:-
i. Diffusion
ii. Interception.
iii. Direct impact


Q : Why do we need to use 0.01 micron filtration for compressed air?
A : The facts are:

i. There are 140 million dirt particles in 1 cubic meter of air (sized from 4mm - 0.001 micron).
ii. Up to 80% of these particles are smaller than 2 micron.
iii. The major contaminant in compressed air, oil aerosol is in the range of 0.8 - 0.01 micron.


Q : Will a 0.01 micron depth filter choke up faster than a 0.1 micron depth filter?
A : The 0.01 micron depth filter will filtered up more contaminants than 0.1 micron depth filter. If these two filters have the same void volume, the 0.01 micron depth filter will choke up faster.

Due to the different technology used in filters construction, the void volume of different filters can be different. ultrafilter uses a patented thermal bonded borosilicate fibreglass where it has higher void volume up to 98% compare to other filters, which means that the filters is able to filter out more contaminants but still last as long as other filters.

Elements with glued fibres obviously have less void volume due to the space taken up by the glue.


Q : I usually have moisture carry over to my production lines during afternoon and evening when the ambient temperature is higher, Please advise.
A : High ambient temperature will lead to high compressor discharge temperature. Refrigerant dryer's performance decreases with inlet air temperature increase.

You can install a pre-cooler (water-cooled or air cooled) and a cyclone separator prior to the dryer. The air and water act as a cooling agent to reduce the inlet temperature, moreover, the cyclone separator removes moisture. The dryer will have less load and works better.


Q : How many sterilization cycles does ultrafilter guaranted?
A : Under the assumption stated in the process brochure - 100 sterilization cycles for a P-SRF filter elements.


Q : What is the difference between a heatless and a heat regenerative desiccant dryer and the criteria for selection either one of the technologies?
A : Heatless dryer: Regeneration is carried out by means of dry compressed air without additional heat.

Heat Regenerated dryers: Regeneration is carried by means of ambient air heated up by an additional electrical heater.

Criteria for selection: Investment and operating cost depending on flow rate, pressure drop, operating pressure and economical evaluation.


Q : What parameters are necessary for sizing and designing filter system?
A : Volume flow rate, minimum operating pressure, maximum acceptable differential pressure, air quality required (depending on application), type of compressor, central or decentralize purification.


Q : What is the difference between a depth filter and a membrane filter?
A : Depth filter : Contaminants are retained in the depth of the filter media.
Membrane Filter : Contaminants are retained on the surface area.



Q : Why there is water in the compressed air line during plant start up in the morning after the compressed air system is being shutdown for a night?
A : Most of the dryers are designed according to the rating of the compressor and sized according to the operating pressure. During compressor start up, it built up the pressure gradually from zero bar/g to a setting value. The flow volume through the dryer are much more higher that the volume that can be taken by the dryer due to lower operating pressure. So the dryer is overloaded and the moisture will carry over to production line. The longer time the compressor take to reach the setting pressure, more water will carry over to the production line. In order to avoid this, there is a "start-up device" designed to solve this problem.


Q : Can I install filter to remove moisture in the production site? I already have a dryer upstream at the main compressed air line.
A : The coalescence filter will remove water droplets, oil droplets and contaminants from the compressed air but not water vapour. By installing a filter will not solve your moisture problem at the downstream of your compressed air system. You need to check the dryer operating condition and measure the pressure dew point of your compressed air system.


Q : Where to install the receiver tank, up-stream of dryer or down stream of dryers?
A : In Malaysian scenario, almost 90% of the receiver tanks are installed before the dryer (As Installation A) and about 10% are installed after the dryer (As Installation B).

Installation A: Compressor --> Receiver Tank --> Dryer --> Production

Installation B: Compressor --> Dryers --> Receiver Tank --> Production


There is no right or wrong answer in this case, but increasingly, more compressed air system designers are going for "Installation B". To decide where to install the receiver tank, it is good to determine the advantages and disadvantages associating to the system installation.


Receiver up stream of dryer (Installation A)

Advantages:-

i) The receiver tanks will reduce the compressed air discharged temperature
by 2ºC to 4ºC before going into filter and dryer, this will reduce some
temperature loading on the filters or dryer.

Disadvantages:-

i) Corrosion takes place inside the receiver tank
- Regular maintenance/re-painting of receiver tank is needed and regular
maintenence on auto drain installed at receiver tank.

ii) Heat emitted from surface of receiver to the ambient/compressor room
- Poor working environment for equipment and human.

iii) Risk of overloading the dryer due sudden surge in demand from production
- Risk of oil and moisture carry over

iv) Fluctuating load flowing through dryer and filters
- More wear and tear on dryer and filters


Receiver down stream of dryer (Installation B)

Advantages:-

i) No corrosion takes inside the receiver tank
- Very minimum maintenence required on receiver tank and autodrain
installed.

ii) Stable compressed air flow through dryer and filters
- Longer servicing life.

iii) Less heat emitted from receiver tank
- Better working environment.

Disadvantages:-

i) Higher temperature loading on dryer and filters.