In today’s guide, you will learn both the basic and advanced concepts of return line filters.
It will help you choose the best return line filter for your system, preventing costly and unnecessary system contamination.
Among the key things, you will learn here include definition, symbol, function, installation, and criteria for selecting a return line filter.
Let’s have a look.
Return Line Filter Basics
This section covers the most basic concepts of return line filters.
Even before you think of buying return line filters, here are a few things you should know:
· What is the return line filter?
Return line filter refers to a type of filter that is common in open loop applications.
They serve the function of filtering the fluid before it flowing back to the hydraulic reservoir.
Return line filter – Photo courtesy: Modern industrial hydraulics
By doing this, return line filters help in keeping the reservoir clean by removing all the dirt particles.
Also, filtering the fluid before it flows into the hydraulic system enhances the operational efficiency of your application.
· Return line filter symbol
Return line filter symbol offers a clear representation of every component and their function.
It is, therefore, crucial to understand these symbols since they will aid in understanding return line filter components and how they work.
These symbols are essential in depicting the fluid flow on the return line filter as well as the components that make up a return line filter.
Thee symbols need to adhere to the industry standards such as DIN24300, ISO1219-1, and ANSI Y32.10.
Here is a look at these symbols for better understanding.
Return line filter symbol
Return line filter consisting of a bypass valve and an electrical clogging indicator
There are different characteristics that a return line filter represent.
That is, the function, the number of connections, the operating principle of the return line filter as well as the switching position
It is therefore vital that when coming up with a return line filter, you consider all the components.
Also, the function of the bypass valve is to prevent the fluid from flowing backward before filtration takes place.
· Return Line Filter Function
As we have seen earlier, the essential function of a return filter is to filter the fluid before it returns to the hydraulic reservoir.
However, a return line filter serves other functions including:
· Filtration of your fluid
There are several contaminants present in your fluid which can hurt the fluid performance.
Some of these contaminants are small in size to be seen by the naked eye.
However, you can increase the performance of your fluid through filtration by using a return line filter.
The availability of different filter element sizes for your return line filter makes them ideal for fluid filtration.
· Ensures the smooth flow of your fluid
Imagine how many times you would have to stop your hydraulic system from removing the contaminants that hinder its operations.
Perhaps it will take you long to finish a particular task.
However, you can eliminate these disruptions by using a return line filter which filters all these contaminants.
This results in a smooth flow of your fluid in a hydraulic system.
· Protection of the hydraulic system
A return line filter protects your hydraulic system by filtering unwanted particles from your fluid.
This has the effect of extending the productive life of your hydraulic system.
Where to Install a Return Line Filter
There are several factors that you need to consider before selecting where to install your return line filter.
They include the hydraulic system cleanliness requirements and the location of the component that needs protection.
Return line filter with by-pass valve
You may also consider the pressure of your application before deciding where to locate your return line filter.
Different types of return filters are available for different location points.
However, in practice, you can install your return line filter either on the inside of your reservoir or in-line with your reservoir.
Always consult with your manufacturer before deciding on the perfect location of your return line filter.
Types of Return Line Filters
Even though return line filters have a basic working principle, there are different types that you can find in the market.
You, therefore, need to select the model that best fits your application.
Return line filter with clogging indicator
For better understanding, let’s have a look at the different types of return line filters available.
· Tank mounted return line filters
As the name suggests, the design of tank mounted return line filters allows for the installation and fitting on hydraulic fluid tanks.
Here, their primary function is to filter solid particles from the fluid ensuring clean fluid flow.
Alternatively, a tank mounted return line filter can function as a bypass filter for your hydraulic system.
A tank mounted return line filter consists of various components which work in hand to ensure smooth filtration of your hydraulic fluid.
These components include a filter bowl, a cover, filter element, bypass valve, a maintenance indicator, and an electronic switching element.
Also, depending on the size of your tank mounted return line filter, you may have a breathing filter, a surge protection unit and a return pipe.
The working of these components is similar to that of a regular return line filter.
· Double tank mounted return line filters
Double tank mounted return line filter is a type of filter that consists of two return filters joined together using a bypass valve.
These filters are ideal for mounting on hydraulic fluid tanks with a large operating capacity.
They function just like any other return line filter with the only difference being their operational capacity.
The fact that they double to allow for simultaneous filtration of your fluid ensuring continuous operation of your application.
When clogging happens on one return line filter, the bypass valve closes directing the fluid to the other filter.
This allows you to clean the clogged return line filter while the operation of your application continues.
Double tank mounted return line filters are ideal for an application that requires a continuous flow of fluid or larger applications.
· T-types return line filters
T type return line filter gets its name from its shape which is like a T.
Their design allows them to be a perfect fit for filtration of fluid with low pressure.
The reason for this is because fluid flows into the return line filter creating a high pressure which aids in fluid filtration.
There are different sizes of T type return line filters available for selection depending on the size of your application.
It is vital that you select one that fits your application to avoid incidents of not having enough pressure for filtration to take place.
Criteria for Selecting Return Line Filter System
There are several return line filters available for your selection depending on your application.
However, you need to consider several factors before picking one.
Return line filter design – Photo courtesy: Hydac
Among these considerations include:
· Maximum pressure
The maximum pressure a return filter can handle during the filtration process is a vital factor when selecting your return line filter.
Too much pressure past the given limit has the effect of causing rupture to your filter element.
Also, it may have the effect of your pocket filter not filtering well as a result of too much fluid passing at a given time.
As such, when selecting a return line filter, you need to ensure that the pressure of your return line filter matches that of your hydraulic system.
· Flow rate
The flow rate of your return line filter is a crucial factor that you must take into account.
Different return line filters have different flow rates.
When selecting a return line filter, you need to ensure that it has the same flow rate as that of your hydraulic system.
A flow rate ensures uniform flow of your fluid at a given point over time which maximizes the filtration process.
By having the correct flow rate for your return line filter, you can ensure maximum filtration of your fluid.
· Size of your return line filter element
The size of the return line filter element plays a vital role in determining which return line filter to select.
As you know, not all the contaminants have the same size; as such, you need to pay attention to the size of the filter element.
The size of the filter element will determine the filtration level of the fluid.
· Filter ratings
Every return line filter has a rating that determines how effective it is at filtering your fluid.
You need to consider this when selecting a return filter for your fluid.
This is what will determine the effectiveness of your filtration and also have an impact on the flow of your fluid.
· Dirt holding capacity
The dirt holding capacity is another consideration that you need to consider when purchasing your return line filter.
Dirt holding capacity – Photo courtesy: Eaton
It is vital to note that a larger dirt holding capacity minimizes the number of times you have to stop your application for unclogging purposes.
On the other hand, a small dirt holding capacity return line filter implies that you will have to interrupt your application frequently.
It is therefore vital that you select a return line filter that has the correct dirt holding capacity for your application.
· Type of your fluid
Fluids have different characteristics which you must consider when selecting your return line filter.
These characteristics affect your return line filter.
For instance, the viscosity of your fluid affects your return line filter since it affects the flow.
You, therefore, need to ensure you either have a return line filter that has a large filter element of has high pressure.
Also, the temperature can affect your return line filter.
You need to ensure that your return line filter meets the given temperature of your hydraulic fluid.
If the temperature of your fluid is high, it is advisable that you select a return line filter that has a higher temperature than that of your fluid.
The purpose of this is to prevent the filter element from rapturing which may lead to malfunctioning of your return line filter.
It is therefore vital that you select a return line filter that matches the characteristics of your fluid.
Return Line Filter Assembly – Understanding Return Line Filter Designs
Understanding the components of a return line filter is crucial in knowing its assembling process.
Through this, you will be able to know how the different parts work together in ensuring the efficiency of a return line filter.
Different types of return line filters – Photo courtesy: Fluiden
Here is a look at these components in detail.
· Return line filter head
This refers to the topmost of the return line filter that is portable.
It serves as the mounting pad while installing on a machine.
· Inlet and outlet points
On the filter head, you will find the inlet and outlet points.
They are crucial points during the filtration of your fluid since they serve as points through which the fluid enters and exits the filter.
Dirty fluid flows through the inlet for filtration to take place and clean fluid leaves via the outlet.
· Filter housing
The filter housing refers to the outer casing that holds the components of the return line filter together.
Different materials make up the filter housing.
However, an effective filter housing material is one that can withstand the environmental stress in which it operates.
· Filter element
The filter element refers to the inner part of the return line filter where actual filtration takes place.
As fluid flows through the return line filter, it passes through the filter element where filtration of contaminants takes place.
· Dirt holding bowl
After filtration, clean fluid flows out of the return line filter via the outlet while the contaminants flow to the dirt holding bowl.
This happens continuously until the clogging takes place on the filter element.
· Discharge valve
At the bottom of the return line filter is a discharge valve that serves as the exit point of the contaminants.
After filtration, you need to clean your filter to remove the unwanted particles.
· Bypass valve
A bypass valve is a valve located between the inlet and the outlet on the filter head.
The function of the bypass valve is to protect the system in case your filter is clogged.
This allows you to clean your return line filter.
Working Principle of Return Line Filters
The basic principle of how a return line filter works is quite easy.
Once you have identified each part, you won’t fail it understand how it works.
Working of hydraulic filters – Photo courtesy: Machinery and Hydraulic
This is crucial not only when it comes to the operation of the device but also during its maintenance.
Here is a look at how this device works.
First, fluid flows into the return line filter via the inlet which is mostly at the top but depends on the design of your filter.
This flow is generally of high pressure that forces the fluid into the filter element.
As it flows through the filter element, the filtration takes place via the filter mesh.
It is therefore essential to consider the sizes of the filter mesh before selecting a return line filter for your application.
After filtration, the filtered fluid flows out of the return line filter via the outlet while the contaminants flow downwards to the dirt collecting duct.
There are different sizes of the dirt collecting duct for selection depending on the size of your application.
The bypass valve available minimizes the risk of having unfiltered fluid from flowing back to the hydraulic system.
The filtration process continues until clogging takes place.
At this point, you have to clean the filter element and the filter itself.
There are several ways of cleaning your return line filter.
However, the most common is the self-cleaning backwash option.
It involves allowing the flow of water in reverse through the filter element which removes all the contaminants.
The contaminants flow to the dirt holding duct and out through the drainage valve.
How to Install Return Line Filter System
After purchasing a return line filter and before it starts operation, you need to install it on your application.
If you are not an expert, installation implies that you will have to hire a professional which will add to your cost.
However, you can avoid all the inconveniences that come with hiring an expert by going through this section.
Here, I have simplified all that you need to know for a successful installation of your return line filter
Typically, there are two options; you may install a return line filter in an entirely new system.
Or install, as a way of replacing the current or worn out return line filter.
The first step that you need to follow is to switch off your machine to prevent leaking of your fluid.
It is vital to install the filter as close as possible to the reservoir.
The purpose of this is to filter the fluid before flowing into the hydraulic system.
You need to ensure the mounting point on the reservoir is clean.
Since the filtration of your fluid will take place, you don’t want to operate under dirty surroundings.
You can use a clean piece of cloth to clean the mounting point.
After that, you need to apply clean fluid to your return line filter as well as to the mounting base.
The importance of this is to enhance the two points when installing them.
Please, you need to avoid using Greece at this point since it will have a negative effect during the operation of your return line filter.
In some cases, the mounting base of your reservoir is threaded.
This aids in the installation of your return line filter especially if your return line filter is also threaded.
Fix the return line filter on the mounting base while ensuring you tighten it.
For a tighter fit, you need to ensure you have placed the return line filter correctly.
In the next step, you may start your engine. As the engine runs, you can check if there are any leaks.
In case of leaks, you need to tighten them before you start operating your application.
You may follow the same steps if you are replacing your return line filter.
However, you need to ensure that you have drained the fluid in both your reservoir and your return line filter before you start the process
Application of Return Line Filters
Different applications utilize return line filters for successful filtration of the fluid which enhances the efficiency of a hydraulic reservoir.
In this section, I am going to take you through the major applications that use return line filter in their operations.
Have a look.
· Construction industry
Different equipment in the construction industry function adequately due to the availability of the return line filter in them.
Such equipment includes excavators, graders, trenchers, loaders, bulldozers, and backhoes.
The return line filters available in these machines help them function appropriately by filtering the fluid.
The fluid is necessary for lubricating the moveable parts.
· Oil and mining industry
Oil and mining industry is yet another industry that utilizes return line filters for the smooth operation of activities.
Such equipment includes mining equipment, a dragline excavator, underground mining equipment and drills.
Mining industry machines
In these machines, the return line filters play a crucial role in ensuring in filtering the fluid which is necessary for the smooth operation of the machines.
· Agricultural industry
You will find various machines in the agricultural industry that use return line filter for smooth operations.
Such machines include tractors, ploughs, trailed sprayers, harvesters, dryers, and round balers.
Return line filters serve the purpose of filtering the fluid which is vital in ensuring the efficient operation of these machines.
· Automotive industry
Lastly, the importance of return line filters is noticeable in the automotive industry.
Here, various moveable parts utilize these devices for their smooth operation.
Audi car engine
These parts include; the power steering system, shock absorbers system and the brake system.
Contaminated fluid is the leading cause of failure of most hydraulic systems.
However, in most cases, you will find people replacing the pumps as a remedy instead of cleaning the fluid.
A return line file is an efficient way of ensuring your hydraulic system functions at an optimal level.
When selecting a return line filter, ensure you factor in all the considerations as per your application including fitting it appropriately.
From this guide, you can successfully purchase, operate and maintain your return line filter.
Go ahead and protect your hydraulic system by purchasing a quality and reliable return line filter.
Talk to us today for any questions on return line filters.