World of filtration- Part 2

Hihi, come again the part 2 of the filtration knowledge sharing... As per mentioned previously, Air filter is divided into primary, secondary, HEPA, ULPA and SULPA filter.

Today we may talk about the primary filter. Primary filter commonly available in the market is disposable type and washable type. This type of filter basically used to filter the bigger particles of the air stream (5um to 10um) and prolong the filter life for high efficiency filter.

Disposable type filter means as per its name. It is disposed after the final pressure drop of the filter is exceed. Therefore, this type of filter should be produced by environmental friendly material. It is proposed to the manufacturer that the proper disposable method of this kind of filter should be listed and presented to the user. This helps user to have proper dispose them into the environment. Basically, now the user usually just disposable into their rubbish bin. Do you know that this filter is made of the sythetic fiber as their media. And synthetic fiber will dissolve into powder after expose to the UV light (sun light). The powder of the fiber will travel along the environment by the wind, this will polluting the air. Perhaps, I may suggest to buried the media into the ground.

Next, this type of disposable filter frame is made by the moisture resistant card board because this filters are installed in the Air Handling Unit where the relative humidity is very high. But I can tell you that many manufacturers in the world are not practising this very well. They may only apply the simple card board for cost saving purpose. I also highly suggest that we can have a recycle used paper board for this purpose with reasonable price.

However, in the commercial issue, many manufacturers thinking of cutting cost and production process, many issue of the proper filtration is neglected. We have to know that pre filtration is very important to control the performance of high efficiency filter. If we are not taking good care of pre filtration, then the next stage (high efficiency filter) will be affected.

Oh.. Sorry.. Normally primary filters are allocated into G class (according to EN779 standard) or MERV 1-8 class (according to ASHRAE 52.2).

Besides that, for this disposable type filters, in commercial they are made by pleated media to increase the face area of the media, so that the life of filter can be prolonged.Perhaps, this also may reduce the initial pressure drop of the filter.

However, in the market today, some manufacturer plan to cut down the cost of production, the number of pleats for the filter is reduced to provide the lower cost to users. Such as 24 inches x 24 inches x 2 inches disposable type should have 28 pleats, they reduce the pleats into 15 pleats/ 21 pleats. This action is not offended but please take note that this will reduce the face area of media to filter the particles. Consequence reduce the life of the filter. Therefore, in this practice, you may have to frequently change the filters (however, in Malaysia, many companies don't constantly monitor their filter). Frequently change the filters may end up with higher maintenance cost (even though the initial cost is lower). The maintenance cost includes labor cost, filter cost, production shut down cost and others. If we insist to run the filter under its final pressure drop, we have to pay for the high energy cost on running the blower.

Today, until here lar...