What is paper band filter and how it works

The paper band filter is the oldest and the simplest among all coolant filtration systems. A key feature that makes this system fairly low-cost is that it uses dirt to capture dirt and filter the coolant. To elaborate, dirt from the coolant builds up on the filter media over time to form a dirt cake. This dirt cake in turn works to capture additional dirt from the coolant being filtered. When the paper band filter is used to filer coolant from surface grinding machines,  a magnetic separator is used to improve the efficiency of the paper band filtration system. 

Explore the design and working of a magnetic separator

Paper band filtration system working principle

The dirty coolant is first passed through a magnetic separator to remove up to 95% of all ferrous particles in it. Next, it is introduced into the paper band filtration system. Here, all the non-ferrous impurities such as brass, aluminum or steel particles, and grit are are blocked by the paper filter while the fluid coolant moves on. 

As more and more dirt is caught in the paper filter, this dirt itself forms a cake and becomes a filter that catches more impurities. As more and more dirt is caught in the paper filter, the level of the coolant inside the paper filter rises. This rise triggers the floating switch which prompts the motor into action. The motor then pulls forward a new paper and the older one is discarded. 

Key factors to consider

Failsafe mechanism

 In case the floating switch fails to function properly, the paper band filter also has a timer mechanism to change the paper. Here, a timer sends a signal to the motor at a set time to change the paper. The paper can also be changed manually by using the control panel of the machine. Apart from this, a limit switch is installed within the paper band filtration system, which senses when the paper roll needs to be replaced. 

Particulars of the paper

In such types of systems, the porosity of the paper is an important factor. There needs to be a balance between the porosity and the width of the paper

Flow rate

The desired level of filtration of the coolant is impacted by the flow rate of the coolant which must take into account the rate at which the cake forms. 

Span Associates has over 40 years of experience and expertise in design, production and installation of paper band systems of various capacities. For more information, reach out to us!  


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