Unusual erratic noise from hydraulic pumps (Hitachi EX300)

[MKF1]

Hi everyone!

We are hearing an unusual noise from the hydraulic pumps of our Hitachi EX300-1. It has twin axial piston pumps.

The noise is difficult to describe but it is erratic/random and the pumps sound stressed (Attached is a short video of the pumps making the noise).

It does not sound to me like the typical cavitation noise which I understand is more of a high-pitched screeching/whining sound, or gravel passing through the system.

While doing a hydraulic oil change (after noticing the noise), we found metal debris stuck to the hydraulic suction screen in the tank (Video attached). It looked like brass debris. Around one fourth of the suction screen was covered with this stuff and the oil had some debris in it as well. The excavator was recently fitted with additional piping for a hydraulic breaker and we suspect the debris entered the tank due to faulty workmanship during the piping installation. Though we cannot be absolutely certain if the debris came from our own pumps' cavitation, which is certainly a possibility, the hydraulic return filter was found to be clean when removed. Today, we drained the system of oil, cleaned the tank, changed the oil and filters but the noise still persists.

The machine was run with a bucket attachment for around 20 hours after fitting of the hydraulic breaker lines was completed. We have noticed that the machine is working slightly slower than before the noise appeared. However, we have not noticed any large or constant vibrations in the hydraulic hoses nor were the pumps heating up excessively.

I understand that an inlet restriction is the most common cause of pump cavitation. It could very well be that the damage has already been done, but I wanted to positively assess how bad the situation is, and whether we now need to get the pumps disassembled and repaired; any advice on the possible way forward would be greatly appreciated.

I was reading on another forum (

What is Cavitation in Pumps? Learn the Causes and Cures

What causes cavitation in pumps and how can it be prevented? Understand the causes, cures, and considerations.

www.pumptec.com

) which said and I quote "Because of their lower flow rates, plunger pumps typically have fewer cavitation issues". So I am really hoping the partial inlet blockage did not have a detrimental impact on the pumps. Extremely stressful situation!

Thank you

Muneeb

 

[IceHole]

There's no video. Load it to YouTube

 

[MKF1]

Will do. Thank you for pointing that out!

 

[MKF1]

Hi everyone

I have uploaded the videos of the hydraulic pump noise and the debris found in the suction screen on YouTube for ease of viewing.

Links can be found below:

1) Pump noise Video 1 (

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2) Pump noise Video 2 (

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3) Pump noise Video 3 (

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4) Debris found in suction screen (

)

 

[92U 3406]

When was the last time that strainer was checked?

If its got a case drain filter pull it off and cut it open. If you've got brass and debris in there then you've got pump problems.

 

[LACHAU]

It looked like brass debris. Around one fourth of the suction screen was covered with this stuff and the oil had some debris in it as well. The excavator was recently fitted with additional piping for a hydraulic breaker and we suspect the debris entered the tank due to faulty workmanship during the piping installation. Though we cannot be absolutely certain if the debris came from our own pumps' cavitation, which is certainly a possibility, the hydraulic return filter was found to be clean when removed. Today, we drained the system of oil, cleaned the tank, changed the oil and filters but the noise still persists.

In the entire hydraulic system of the machine. Only one component is made of brass. Those are piston shoes.
I don't know what the other technicians thought, but for us, when we discovered brass debris in the filter, we had to disassemble the main pump for inspection immediately.

 

[LACHAU]

...The excavator was recently fitted with additional piping for a hydraulic breaker and we suspect the debris entered the tank due to faulty workmanship during the piping installation.

Usually, when you install a breaker, you should install the accumulator with compatible specifications. Otherwise, your main pump will encounter the same situation as you just mentioned because the hydraulic pulses caused by the breaker will create very harmful impacts on the main pump of the machine.

 

[MKF1]

Thank you everyone for your replies.

The last time the strainer was checked was a few days before the breaker installation and it was clean. This model does not have a case drain filter.

 

[IceHole]

In the entire hydraulic system of the machine. Only one component is made of brass. Those are piston shoes.
I don't know what the other technicians thought, but for us, when we discovered brass debris in the filter, we had to disassemble the main pump for inspection immediately.

View attachment 309707
View attachment 309706

What i was thinking as well but never been in a 300, just a 200. Pilot pump have brass wear plates as well?

 

[Coaldust]

Thank you everyone for your replies.

The last time the strainer was checked was a few days before the breaker installation and it was clean. This model does not have a case drain filter.

Interesting coincidence, ferrous contamination appeared immediately after fabrication. Hmmmm. And, that’s a lot of debris on the screen. Now, the pumps are screaming? Perhaps, check the case drain flow to see how healthy the pumps are.

I would consider performing or hiring a contractor to kidney loop it and clean it up.
Meanwhile, contemplate pump repair.

That’s a tough decision. Clean it up now, and hope the pumps don’t fail, or fix the pumps and then clean it up?

Few people take contamination control seriously.

 

[MKF1]

Interesting coincidence, ferrous contamination appeared immediately after fabrication. Hmmmm. And, that’s a lot of debris on the screen. Now, the pumps are screaming? Perhaps, check the case drain flow to see how healthy the pumps are.

I would consider performing or hiring a contractor to kidney loop it and clean it up.
Meanwhile, contemplate pump repair.

That’s a tough decision. Clean it up now, and hope the pumps don’t fail, or fix the pumps and then clean it up?

Few people take contamination control seriously.

Thank you for your reply and advice.

We will check the case drain flow. The pumps certainly sound like they have taken a hit. It really is a tough decision but we would prefer to fix them rather than waiting for them to fail on us.

The debris looks quite fine and a lot if it must have passed through the suction screen and reached the control valves and cyllinders.

I was speaking to a technician today who said that if the debris has flown through to the valve blocs and cyllinders, the machine would be more or less lost since it is very difficult to clean the whole hydraulic system. That would be an absolute disaster!

 

[Coaldust]

It’s cleanable. That’s why I mentioned a kidney loop filtration system. There are companies that offer that service that will come right to your door.

I’ve also disassembled everything after a catastrophic failure and cleaned them that way.

 

[MKF1]

It’s cleanable. That’s why I mentioned a kidney loop filtration system. There are companies that offer that service that will come right to your door.

I’ve also disassembled everything after a catastrophic failure and cleaned them that way.

That's very reassuring! I will try to see if I can find a company to that that for us followed by the pump repairs.

Thank you!