Thursday, 20 July 2017

FILTER ELEMENT MATERIAL

We were discussing the basic concept of full flow hydraulic filter and proportional flow hydraulic filter in our previous post.

Today we will start here another important topic in hydraulic system i.e. filter element material 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. filter element material, we will understand here the various types of materials for filter element and their importance too 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.

Let us first brief here the 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 the 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.

Filter material for filter element

Filter element will be prepared with various types of filter material such as wire mesh, paper and metal fibre.

Following figure, displayed here, indicates the various types of materials for filter element.
Filter one is prepared with wire mesh, second filter is prepared with paper and third filter is prepared with metal fibre.

 
There will be a star shaped fold in the filter material and hence there will be enough filter area with small size element and better stability.

Filter element with wire meshing

Stainless steel wire will be used in such filter.

Paper filter

Such filter element will be prepared with paper fibre. There is one disadvantage of paper filter and that is such filters could not be cleaned and therefore such filters will be one time use filters. Filtration size of paper filter will be approximate 10μm.

Metal fibre filter element

Metal fibres are used here in order to prepare the filter element. Such filter will have capability to capture the multiple dirt and foreign particle over same filter area.

Such filter will have good service life and will have good inherent stability.
 
Do you have suggestions? Please write in comment box.

Reference:

Hydraulic system maintenance manual (Industrial hydraulic control)
Image Courtesy: Google

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Wednesday, 19 July 2017

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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Tuesday, 18 July 2017

FULL FLOW HYDRAULIC FILTER WORKING PRINCIPLE


Today we will start here another important topic in hydraulic system i.e. basic concept of full 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. full flow hydraulic filter and we will understand here the basic operation and importance too of full 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 full flow hydraulic filter

Full flow hydraulic filter usually has capability to provide more positive filtering action and it will offer greater resistance to the flow of hydraulic fluid, especially when hydraulic fluid will be dirty.

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 pass to the system through the outlet port of full flow hydraulic filter.

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

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

Inlet port

Inlet port will be provided in the body of full flow hydraulic filter. Hydraulic fluid will enter in to the filter through the inlet port of full flow hydraulic filter.

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 outlet port passing through the filter element.

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.

Hollow core

As name indicates, hollow core is basically the hollow portion of a filter. Hydraulic fluid coming through the filter element will flow to outlet port through this hollow core of filter.

Outlet port

 
Filtered hydraulic fluid will flow to the system via this outlet port of full flow hydraulic filter.

Bypass relief valve

Full flow hydraulic filter will also be associated with a bypass relief valve. In a case when full flow hydraulic filter will be clogged, bypass relief valve will allow the hydraulic fluid to flow directly from inlet port to outlet port by bypassing the filtering mechanism.

Contamination level indicator

Some full flow hydraulic filter will also have one contamination level indicator to indicate the hydraulic fluid contamination level. Contamination level indicator works on the principle of differential pressure across the filter.

Differential pressure across the filter, difference in pressure of hydraulic fluid at the inlet of filter and outlet of filter, will increase as the collection of dirt, foreign particles and tiny particles over the outer surface of filter element increases.

Once differential pressure across the filter increases and reaches to pressure setting level, signal will be displayed for indicating the requirement of replacement or cleaning of filter.

Let us see how full flow hydraulic filter work?

Hydraulic fluid will enter in to the filter housing through the inlet port of full flow hydraulic filter and further hydraulic fluid will flow to the hollow core 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 from hollow core of filter to the outlet port of full flow hydraulic filter.

Finally filtered hydraulic fluid will flow towards the system via outlet port.

Differential pressure across the filter will increase as the collection of dirt, foreign particles and tiny particles over the outer surface of filter element increases.

Once differential pressure across the filter increases and reaches to pressure setting level, bypass relief valve will be opened and it will permit the hydraulic fluid to flow directly from inlet port to outlet port by bypassing the filtering mechanism.

Once bypass relief valve will be operated, signal will be displayed for indicating the requirement of replacement or cleaning of filter.

 
Signal symbol and meaning will be provided by the filter manufacturer and hence we must have to follow the full flow hydraulic filter OEM instruction in order to secure the information for respective signal.

Usually there will be following three types of signals as mentioned here

Green signal indicates that full flow hydraulic filter is clean
Yellow signal indicates that full flow hydraulic filter is in partial bypass condition
Red signal indicates that full flow hydraulic filter is in complete bypass condition

So, we have discussed here every aspects, components and working of full flow hydraulic filter. We will discuss the working principle of proportional flow hydraulic filter in our next post.

Do you have suggestions? Please write in comment box.

Reference:

Hydraulic system maintenance manual (Industrial hydraulic control)
Image Courtesy: Google

Also read

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Sunday, 16 July 2017

DIFFERENCE BETWEEN HYDRAULIC FILTER AND STRAINER

We were discussing hydraulic actuators, hydraulic flow control valve, pressure relief valve, direction control valve in our previous post.

Today we will start here another important topic in hydraulic system i.e. Strainer and filter with the help of this post. Further, we will classify the filters and we will also see the working of each type of filter in detail in our next post.

So let us come to the main topic

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. There is one specific unit of measurement for contamination level in hydraulic fluid i.e. NAS value.

 
We will discuss the topic related with determination of NAS value and significance of NAS value, in a hydraulic unit, later in detail.

Hydraulic system must be operated with clean hydraulic fluid as according to some estimate, 75% of all hydraulic system failure occurs due to contamination problems.

Why hydraulic fluid will be contaminated?

There are lots of reasons for contamination of hydraulic fluid, but let us see here some examples to secure the brief idea for the contamination of hydraulic fluid.

With continuous operation of hydraulic system for completing the desired tasks, there will be normal wear of hydraulic valves, hydraulic pumps and other hydraulic components. As a result of such normal wear of hydraulic components, there will be produced tiny metal particles which will be measured in microns and these tiny metal particles will be mixed with hydraulic fluid and will cause increase in the contamination level of hydraulic fluid.

Hydraulic fluid will also be contaminated due to entry of foreign particles in to the hydraulic fluid or in to the hydraulic system.

Foreign particles may enter in to the hydraulic system during pouring of new hydraulic fluid in hydraulic reservoir. 

There are some more examples of sources of hydraulic fluid contamination and these are as listed here

1. Builtin foreign particle or dirt
2. Foreign particle already present during initial charging of hydraulic fluid
3. Foreign particles may enter in to the hydraulic system through loose air-breather cap and cylinder oil seals
4. Rust and paint flakes of reservoir may also mix with the hydraulic fluid. Therefore after preparing the reservoir it is very important for sandblasting of reservoir and also selection of suitable paints for painting of reservoir.
  
Therefore strainers and filters are used in hydraulic units as filtering device to remove the foreign particles and tiny metal particles from hydraulic fluid and provide clean hydraulic fluid as much as possible to the system. 
In simple, we can say that strainers and filters are used in hydraulic unit to secure the hydraulic fluid free from contamination.

Strainer

Strainer is basically used in hydraulic system to remove the large foreign particles from hydraulic fluid. 

 
Strainer will provide less resistance to the flow of hydraulic fluid as compared to resistance provided by the filter to flow of hydraulic fluid.

Screening action of a strainer will be less effective as compared to the screening action of a filter.
Strainer will be basically installed at the inlet of the hydraulic pump and will be inside the hydraulic fluid in reservoir.

A strainer will have one metal frame which will be wounded or wrapped by fine mesh wires to provide the screening action for removing the large foreign particles.

Filter

Filter is basically used in hydraulic system to remove the quite small tiny foreign particles from hydraulic fluid. 

A filter will provide high resistance to the flow of hydraulic fluid as compared to resistance provided by the strainer to flow of hydraulic fluid. 

Screening action of a filter will be quite good and effective as compared to the screening action of a strainer.

Filter might be installed at the inlet of the hydraulic pump, in return line, in pressure line, in reservoir or at any other location as per OEM instructions.

There are basically two types of filters used in hydraulic system as mentioned here.
Full flow filters
Proportional flow filters

 
So we have seen here the importance of filtering action and we have also differentiated the strainers and filters.

We will discuss full flow filters and proportional flow filters in our next post.
Do you have suggestions? Please write in comment box.

Reference:

Hydraulic maintenance manual (Industrial hydraulic control)
Image Courtesy: Google

Also read

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Thursday, 13 July 2017

LIMITATIONS OF EULER'S FORMULA IN COLUMNS

In our previous topics, we have seen some important concepts such as concept of eccentric loading , Assumptions made in the Euler’s column theory and difference between long column and short column with the help of our previous posts.

Today we will see here one very important topic in strength of material i.e. limitations of Euler's formula in columns with the help of this post.

Limitations of Euler's formula in columns

Before going ahead to see the limitations of Euler's formula in columns, we must have to understand here the significance of crippling stress and slenderness ratio of column first.

 

Crippling stress

When a column will be subjected to axial compressive loads, there will be developed bending moment and hence bending stress in the column. Column will be bent due to this bending stress developed in the column.

Load at which column just bends or buckles will be termed as buckling or crippling load.

Crippling stress, developed in the given column due to crippling load, could be easily determined by securing the ratio of crippling load to the area of cross-section of the given column.

Crippling stress = Crippling load / area of cross-section

Slenderness ratio of column

Slenderness ratio of column is basically defined as the ratio of effective length of the column to the least radius of gyration. Slenderness ratio will be given in numbers because it is one ratio and hence slenderness ratio will not have any unit.

Slenderness ratio is usually displayed by Greek letter λ
Slenderness ratio = Effective length of the column/ Least radius of gyration
λ = Le / k

 

Let us come to the main topic i.e. limitations of Euler's formula in columns

We have seen above the formula for crippling stress, where slenderness ratio is indicated by λ. If value of slenderness ratio (λ = Le / k) is small then value of its square will be quite small and therefore value for crippling stress developed in the respective column will be quite high.

For any column material, we must note it here that value of crippling stress must not be greater than the crushing stress. If crippling stress exceeds the crushing stress, in that situation, Euler's formula will not be applicable for that column.

Therefore there must be one certain limit of slenderness ratio for a column material so that crippling stress could not exceed the crushing stress.

In order to secure the limit of slenderness ratio for a column material, we will have to follow the following equation.
Crippling stress = Crushing stress,

This equation is only written for securing the limit of slenderness ratio for a column material, we will equate the crippling stress with crushing stress.

Example for better understanding of limit of slenderness ratio for a column material

Let us see here one example and let us solve for limit of slenderness ratio for a column material.
Let us consider that we have one column AB of mild steel with hinged at both ends carrying a crippling load P. For mild steel, column AB

Crippling stress = 330 MPa
Young’s modulus of elasticity, E= 2.1 x 105 MPa

Now we will follow the above mentioned equation in order to secure the limit of slenderness ratio for a column material.
Crippling stress = Crushing stress
From here, slenderness ratio will be approximate equal to 80 or we can say it is 80. Now what is the importance of saying that limit of slenderness ratio 80?

 
From here we will conclude for a column AB of mild steel with hinged at both ends, if slenderness ratio falls below 80 then in that case crippling stress will be high as compared to crushing stress and therefore in that case Euler's formula will not be applicable for that column AB.

Do you have suggestions? Please write in comment box.

We will now discuss Rankine's formula for columns, in the category of strength of material, in our next post.

Reference:

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

Also read

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SLENDERNESS RATIO OF COLUMN

In our previous topics, we have seen some important concepts such as basic concept of eccentric loading , Assumptions made in the Euler’s column theory and difference between long column and short column with the help of our previous posts.

Today we will see here one very important topic in strength of material i.e. slenderness ratio of column and its importance with the help of this post.

Slenderness ratio of column

 
Slenderness ratio of column is basically defined as the ratio of effective length of the column to the least radius of gyration. Slenderness ratio will be given in numbers because it is one ratio and hence slenderness ratio will not have any unit.

Slenderness ratio is usually displayed by Greek letter λ
Slenderness ratio = Effective length of the column/ Least radius of gyration

Importance of Slenderness ratio

In designing of structure, slenderness ratio plays a very important role. Columns are classified on the basis of slenderness ratio.

For long column, Slenderness ratio will be more than 45
For short column, Slenderness ratio will be less than 45

Strength of column is also dependent over the slenderness ratio. With increase in slenderness ratio, column will have more tendencies to buckle. Hence, compressive strength of column decreases with increase in Slenderness ratio.

 
In simple, we can say that slenderness ratio of the column will be indirectly proportional to the compressive strength of the column. A column with lower slenderness ratio will have more capability to bear higher compressive load and will have more resistance against buckling.

Some important definitions in respect of slenderness ratio

We have already discussed here the basic concept of slenderness ratio and now we must have to understand here its two parameters i.e. Effective length of the column and radius of gyration.

Effective length of the column

Effective length of a given column is basically defined as the distance between successive points of inflection or points of zero movement. Effective length of the column will be dependent over the end conditions of the given column.

Radius of gyration

 
Radius of gyration of a body or a given lamina is basically defined as the distance from the given axis up to a point at which the entire area of the lamina will be considered to be concentrated.

We can also explain the radius of gyration about an axis as a distance that if square of distance will be multiplied with the area of lamina then we will have area moment of inertia of lamina about that given axis.
I = A.k2
Where, k is the radius of gyration of the given column
A is area of cross-section of the column
I =  Area moment inertia of the given column

Do you want the detailed post based on radius of gyration? Click here.

Do you have suggestions? Please write in comment box.

We will now discuss the limitations of Euler’s formula, in the category of strength of material, in our next post.

Reference:

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

Also read

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Tuesday, 11 July 2017

RELATION BETWEEN CRIPPLING STRESS AND RADIUS OF GYRATION

In our previous topics, we have seen some important concepts such as basics of eccentric loading and difference between long column and short column with the help of our previous posts.

Today we will see here one very important topic in strength of material i.e. crippling stress in terms of effective length and radius of gyration with the help of this post.

Before going ahead, we must have to understand here the significance of crippling load or buckling load, concept of effective length of the column and radius of gyration of the column too.

Crippling load

When a column will be subjected to axial compressive loads, there will be developed bending moment and hence bending stress in the column. Column will be bent due to this bending stress developed in the column.

 
Load at which column just bends or buckles will be termed as buckling or crippling load.

Effective length of column

Effective length of a given column is basically defined as the distance between successive points of inflection or points of zero movement. Effective length of the column will be dependent over the end conditions of the given column.

Radius of gyration

Radius of gyration of a body or a given lamina is basically defined as the distance from the given axis up to a point at which the entire area of the lamina will be considered to be concentrated.

We can also explain the radius of gyration about an axis as a distance that if square of distance will be multiplied with the area of lamina then we will have area moment of inertia of lamina about that given axis.
I = A.k2
Do you want the detailed post based on radius of gyration? Click here.

Now we will concentrate here with our main topic i.e. crippling stress in terms of radius of gyration and effective length of the column.

Crippling stress in terms of radius of gyration and effective length of the column

We know very well the formula given by Euler’s for buckling of a long column for any type of end conditions and it is given as mentioned here.
Where,
P = Critical buckling load
E = Young’s modulus of elasticity of the material of the given column
I = Moment of inertia
Le = Effective length of the given column with given end conditions

 
Formula given by Euler’s for buckling is also termed as formula for critical buckling load.

Crippling stress, developed in the given column due to crippling load, could be easily determined by securing the ratio of crippling load to the area of cross-section of the given column.

Crippling stress = Crippling load / area of cross-section
As we have already seen above the equation of area moment of inertia i.e. I = A.k2
Where,
A is the area of cross-section of the column
I is the least value of area moment of inertia
K is the least value of radius of gyration of the given column

We will use the value of area moment of inertia in equation of crippling stress displayed above and we will secure the formula for crippling stress in terms of radius of gyration and effective length of the column.
Do you have suggestions? Please write in comment box.

 
We will now derive expression for crippling load when one end of the column is fixed and other end is hinged, in the category of strength of material, in our next post.

Reference:

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

Also read

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