Saturday, 7 March 2015

REASONS OF HYDRAULIC HOSE FAILURE

REASONS OF HYDRAULIC HOSE FAILURE


We have discussed in previous post about hydraulic system overheating problems and we have also analyzed the true cost of hydraulic oil leaks.

For maintaining a hydraulic system, it is very important to care the basic and key component of hydraulic system in same way as we care a new born baby. 

In this post, we will discuss the reasons of hydraulic hose failure.

 
The actual service life of a hydraulic hose pipe could be predicted and it will have a finite future but the service life of a hydraulic hose might be reduced if we are paying less or no attention for the working condition of hydraulic hose.

There is more than one factor that influences the service life of hydraulic hose pipe. It is observed that if we consider each factor, which we will discuss here, during the installation of hydraulic unit and its hoses, we may increase the service life of hydraulic hoses.

Let us come to point to understand the various reason of failure of hydraulic hoses.

External Physical Damage

I have discussed with hydraulic hose manufacturer and I came to know that approximate 75 % hydraulic hose failure occur due to external physical damage due to crushing , pulling , abrasion and kinking . We must inspect all hose clamps carefully as well as we will have to be careful during the route selection of hose so that one hose may not rub other hydraulic hose. 

Hence routing of hydraulic hoses is very critical and if we have selected the route of hydraulic hoses properly, we can surely avoid unwanted downtime of machine.

Operating Pressure

Before replacement, we must have to check the rated permissible operating pressure of hydraulic hose and rated permissible operating pressure of hydraulic hose must be lower than the system pressure. 

Operating temperature

Hose pipes are designed to convey the pressurized hydraulic fluid up to a specified temperature. Temperature rating of hose means the maximum fluid temperature that could be conveyed by hydraulic hose easily without any adverse effect. 

Higher temperature of fluid will affect the hose rubber and will reduce the service life of hydraulic hose. We must remember, especially in cold atmosphere, we will have to consider the factor of lower temperature of fluid in respect of the efficiency of hydraulic system. 

 
We must have to avoid the application of hose at high pressure and high temperature and high pressure as continuous operation of hydraulic unit in such condition will reduce the service life of hoses.

Multi plane Bending

As we may see in following picture that hydraulic hoses are made by rubber and reinforcement wires, if hydraulic hose will be bent in more than single plane then it will damage the reinforcement wires of hydraulic hose and hence service life of hose will be reduced. 

It was concluded that if a high pressure hydraulic hose will be twisted in seven degree then service life of hose will be reduced by 85 to 90 %.
Twisting of hydraulic hose might be avoided if we have selected the correct route for hoses as well as proper clamping for each hose will also be required.

Ambient temperature

Service life of hydraulic hose depends over the ambient temperature as too much hot or cold ambient temperature will affect the service life of hydraulic hose.

Fitting

During the selection of hydraulic hose, we must have to consider the fitting of hose which is provided at each end of hose

 

Costing of failure of a hydraulic hose

Costing of replacement of a hydraulic hose will be less as compared to cost associated with failure of same hydraulic hose, let us see what types of cost are associated with hose failure?
  1. Machine downtime: If a hydraulic hose failure occurs, we will have to take immediate shutdown for replacing the hose and machine will be unavailable to use.
  2. Wastage of hydraulic fluid, cleanup costing, costing of top-up of fresh hydraulic fluid
  3. Damaging of any other component, due to failure of hydraulic hose, may increase the cost of restoring the health of machine. 
Hence, we must have to give more attention over the working condition of hydraulic hoses.

Let us move towards next post "Basic principles of hydraulic system" to understand the basic concepts that we must have to keep in mind during the analysis of a hydraulic problem.

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