Wednesday, 19 July 2017

PROPORTIONAL FLOW FILTER WORKING PRINCIPLE

PROPORTIONAL FLOW FILTER WORKING PRINCIPLE

We were discussing the basic concept of full flow hydraulic filter, piston type hydraulic cylinder, and shuttle valve working principle in our previous post.

Today we will start here another important topic in hydraulic system i.e. basic concept of proportional flow hydraulic filter with the help of this post.

As we know very well that in order to secure the smooth and correct operation of each component of hydraulic system, hydraulic fluid must be clean as much as possible.

We have already discussed the various reasons and sources of hydraulic fluid contamination and therefore we will not repeat it again. We will directly come to the main agenda of this post i.e. proportional flow hydraulic filter and we will understand here the basic operation and importance too of proportional flow hydraulic filter in a hydraulic unit.  

 
However, we can refer here the post difference between hydraulic filter and strainer in order to secure the complete information in respect of various reasons and sources of hydraulic fluid contamination.

Introduction to proportional flow hydraulic filter

Proportional flow hydraulic filter, as name suggest, will have capability to filter a portion of hydraulic fluid in one cycle. But due to continuous recirculation of hydraulic fluid in the system, complete hydraulic fluid will be filtered with proportional flow hydraulic filter.

A portion of hydraulic fluid, which is going in to the system, will have to pass through a filtering element and therefore foreign particles and other tiny metal particles will be captured by the filtering element and filtered hydraulic fluid will return to the system via a passage provided to connect hollow core of filter with venturi throat.

Let us see here the various components of a proportional flow hydraulic filter

First of all we will see here the basic construction and components of a proportional flow hydraulic filter as mentioned here.

Inlet port

In case of proportional flow hydraulic filter, filtering action will take place in either flow direction. Port from where a portion of hydraulic fluid will be sucked inside the filter, will be considered as inlet port and it is shown in following figure. 
There are two passages for hydraulic fluid to enter in proportional flow filter as displayed in above figure.

Filter housing

 
Filter housing consist the filter element. Hydraulic fluid, which is going in to the system, will enter in to the filter housing and further hydraulic fluid will flow towards the venturi throat passing through the filter element i.e. towards outlet port.

Filter element

Filter element is a key component of any filter. Hydraulic fluid, which is going in to the system, will enter in to the filter housing and further hydraulic fluid will flow towards outlet port passing through the filter element.

During flowing through the filter element, dirt and other foreign particles will be left over the outer surface of the filter element and filtered hydraulic fluid will further flow towards the system via outlet port.

Outlet port

Filtered hydraulic fluid will flow back to the system via a passage connecting hollow core of filter with venturi throat. Hence a point from where filtered hydraulic fluid leaves the proportional flow filter and returning back to the system will be termed as outlet port of proportional flow filter.

Let us see how proportional flow hydraulic filter work?

Proportional flow hydraulic filter works on the principle of venturi. There will be a tube with narrow throat in order to increase the velocity of the hydraulic fluid flowing through it. Due to increase in velocity of the flowing fluid, there will be a pressure drop at narrow point.

A portion of hydraulic fluid, going in to the system, will enter in to the filter housing due to decrease in pressure. Further, hydraulic fluid will flow to the filter hollow core passing through the filter element.

 
During flowing through the filter element, dirt and other foreign particles will be left over the outer surface of the filter element and filtered hydraulic fluid will further flow towards the system via a passage provided to connect hollow core of filter with venturi throat.

Do you have suggestions? Please write in comment box.

We will now discuss filtering materials and elements, in our next post.

Reference:

Strength of material, By R. K. Bansal
Image Courtesy: Google

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