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COMMON PROBLEMS IN HYDRAULIC SYSTEM

We have discussed in previous post about causes of hydraulic system overheating and we have also analyzed the cost of hydraulic oil leaks as well as we have studied various "Reasons of hydraulic hose failure". 

Today we will discuss the common problems in hydraulic system .As we have discussed in my last post “Basic principle of hydraulic system” that we must have to start to find out the root cause of a hydraulic problem from its basic principles. 

There are basically following common problems in hydraulic system and it is very interesting to discuss these problems and process to secure the root cause analysis as well as fixing the problems.

1. Abnormal Noise
2. Slower operation
3. Hydraulic system overheating

Let us discuss each problem and its solution. 

Abnormal noise 

Cavitations are the basic reason behind the abnormal noise in hydraulic system. The basic reason of cavitations or aeration is the entry of air in hydraulic system. When air enters in hydraulic system, it will be compressed and de-compressed during the operation of actuators. 

Cavitations are not only the reason of producing the abnormal noise but also quality of oil will also got affected and various components life will also get affected due to cavitations or aeration. 

If one section of hydraulic circuit needed higher fluid quantity but let us assume supplied fluid volume is lesser as compared to required volume of fluid, in this situation absolute pressure at the section of hydraulic circuit will be lower than fluid vapor pressure. 

Hence there will be formation of vapor bubbles and these vapor bubbles will be collapsed during operation and hence abnormal noise will be produced due to such hammering effect. 

Such hammering effect i.e. cavitations will be very dangerous for system components as cavitations may damage the various component of system and hence hydraulic oil will also got contaminated. Cavitations normally occur at the pump. 

Now the question is normally being asked, how will air enter in hydraulic system?


There are three main causes of air to enter inside the hydraulic system, let us see. 

1. Air might enter through suction line of hydraulic pump; hence we must take care of suction line of pump to avoid any air trapping through pump suction line. 

2. Hydraulic oil level inside reservoir must be as per recommended level, because low hydraulic oil level will lead the entry of air in hydraulic system and will lead the knocking and hence there will be abnormal noise in hydraulic system. We must maintain the recommended oil level to avoid the problem of abnormal noise in system. 

3. Air might enter through hydraulic pump shaft seal if seals will be damaged, hence we must check the pump shaft seals periodically as well as any leakage oil from system. 

4. Suction filter must be cleaned because if suction strainer will be clogged then it will help the fluid to vaporize.

Slower operation

I have seen one crane driven by hydraulic system and one day I have secured one complaint by operation team about increment in operating cycle duration. This is the indication of reduction in productivity of crane. 

We will start to find the root cause with the "basic principle of hydraulic system", as we know that actuator speed depends on fluid flow not on pressure. We are losing the speed of actuator that means fluid flow is not suitable and we will have to search that why is system not securing required fluid flow. 

There might be various reasons of lower flow of fluid in system, let us understand one key reason i.e. Internal leakage in actuators, pump and valve. As we have discussed in "basic concept of hydraulic system" that if there is any internal leakage there will be drop in pressure and heat will be produced due to loss of pressure energy because lost pressure energy will be converted in to heat energy. 

Let us consider that we have one hydraulic cylinder and this cylinder is not holding the load and its rod is coming back. What you will think about the root cause? 

There is internal leakage in hydraulic cylinder and this is the reason that cylinder is not holding the load. In order to make confirm we must have to check the cylinder whether cylinder is overheated or not.  

We may use infrared thermometer to secure the temperature and if cylinder temperature is higher as compared to normal temperature, it shows that there is internal leakage in cylinder that’s why cylinder got heated due to conversion of lost pressure energy in to heat energy. 

But in practical, it is not always feasible to use infrared thermometer to measure the temperature of each component for securing the location of internal leakage in system and in that condition we will have to use a flow measurement device such as flow tester. 

Higher fluid temperature will reduce the viscosity of oil and internal leakage will be more if viscosity of oil got reduced, it will create one cycle because internal leakage means loss of pressure energy in system and loss in pressure energy means creation of heat energy or increment in fluid temperature. Hence, we must have to take care of efficiency of heat dissipating device in hydraulic system.

Hydraulic system overheating

We have already discussed various causes of hydraulic system overheating and solutions and process that we must follow to avoid the overheating problem. 

Please visit my post “Causes of hydraulic system overheating” for securing the key information to avoid the hydraulic system overheating situations.

Let us move towards next post,

Keep reading ….

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