How do coalescing filters work using fiberglass material as the core of the filter element?

answer:

Air enters through the center of the filter element and oil droplets are collected by four mechanisms:

Gravity, inertial impact, direct interception, and penetration.

Gravity effect:

If the air velocity in the filter is low, most of the 20-50 μm diameter oil droplets will be captured by gravity free fall before reaching the filter layer, and the air stream will continue to fall and will be captured as air. Flow passes through the filter. .The faster the airflow, the less efficient it is. Inertial collision:

Suspended particles with diameters greater than 1 μm typically have high momentum. It does not necessarily match the path of the airflow. As a result, it becomes difficult to hit the fiber layer. The higher the airspeed, the higher the collision rate.

Direct interception:

Particles with a diameter of 0.3 to 1 μm move along the air stream and are mostly captured and separated by the 1/2 fiber layer of the filter element. The smaller the particle, the lower the capture rate.

Penetration:

Particles with a diameter of 0.3 μm or less. Due to its low mass, it no longer has the properties of a normal liquid. They move in an irregular Brownian motion. Does not match airflow path. This movement allows us to capture it with a finer filter layer. Particles become smaller. The stronger the Brownian motion, the higher the probability of capture.

What are the main features of HEPA filters? answer:

The diameter is 0. 3 μm particles are not captured mechanically or efficiently. Evaluating whether a filter is effective is to see if it can capture the maximum amount of particles of that size.

What is the simple working process for an efficient coalescing filter?

answer:

After compressed air enters the center of the filter element, it is collected in the filter layer by gravity, impingement, interception and osmosis. After the oil droplets are removed from the filter layer, they are first collected. Small oil droplets first coalesce into large droplets, and when the mass of the coalesced large droplets is large enough, they settle to the bottom of the filter sheet. It then flows into filter bags and is removed from the system by manual or automatic oil drainers.

What are the design requirements for an efficient coalescing filter?

A:

Fiberglass is water repellent, but not oil repellent. Oil forms a thin film on the fiber surface, which impedes collection and increases the working diameter of the screen element. For this, finer fibers should be chosen in the design.

The filter layer design mainly considers air flow control and the physical environment of the filter layer. Care should be taken to ensure that the material has enough surface area to keep air velocities as low as possible for more effective interception, impingement, and diffusion effects. On the other hand, the designed filter bed should be thick enough to allow the particles to have sufficient residence time. Finally, the filter element should not have too many layers of fibers. This impedes drainage, increases pressure drop and reduces filter efficiency.  

Collecting oil droplets is a physical process, and pressure, flow rate, humidity, and the physical properties of the contaminants themselves affect the coalescence results. Therefore, the choice of filter sheet configuration, placement, size, and type is also important.

Does the filter element of the coalescing filter have a service life?

answer:

yes. Theoretically, a filter sheet can remove liquid indefinitely and maintain its high efficiency. In fact, the increased pressure drop caused by the continuous collection of liquid through the filter screen during use translates into the useful life of the filter sheet.

Why do coalescer filter elements use a porous foam layer (or cover)?

answer:

The filter element construction of a typical coalesced filter employs porous foam layers or covers inside and outside the filter layer.

As oily air passes through the media layer, it radiates into the flexible porous foam inner jacket. On the one hand, it acts as an air flow diffuser, pre-filter and room stabilizer. On the other hand, a unique adjustment modifies the airflow (inflation or deflation) so that it can exert gentle pressure on the filter layer to ensure its integrity and effectiveness as it works. Oil droplets are trapped and collected as the air passes through the filter layer. After the oil builds up, it flows through the hard metal tube to the outer porous foam cover (covered by the metal tube outside). The outer porous foam cover has a large non-absorbent surface area, allowing oil to quickly coat its surface under the action of gravity. Downward flow prevents oil from re-entering the airflow. If oil pools at the bottom of the cover (no air dead zone), the foam holes will clog and the oil will drop into the sump. 

Lingyu coalescing compressed air filter for moisture removal