Do you know how to flush your hydraulic systems?

Have you ever attempted to clean a vacuum cleaner? It’s a big job. Even if you use a vacuum that comes with a bag, dust and grime seem to cover every nook and cranny. Over time, all that dust and dirt will build up and affect the efficiency of the machine. So, you end up spending your Saturday dismantling it and cleaning every little part on the inside.
Now, think of your hydraulic systems as a vacuum cleaner. Even with the most airtight system, dirt, debris, and contaminants will build-up, just like they do in your vacuum. One way to clean all that off is to take everything apart and clean it. But we’re talking about huge hydraulic systems, so that plan probably isn’t feasible. So, how do you clean a hydraulic system?

Flushing is the answer! Flushing is a process used by mechanics to clean out hydraulic systems. Depending on the type of hydraulic system and the method you choose, it can be a highly complex process. But it’s a great way to remove deposits, old lubricants and oils, and contaminants. The essential function of flushing is to introduce a new fluid into the system while pulling out the old fluid and deposits. There are a lot of different ways you can do this. Machinery Lubrication has outlined 11 different flushing strategies. Let’s review them.

  1. Drawdown Filtration/Separation: This milder flushing strategy relies on periodic filters to clean the oil and remove sediment and contaminants.
  2. High Turbulence, High Fluid Velocity, Low Oil Viscosity: This process relies on increasing fluid velocity and reducing the oil viscosity. You increase the speed of the new fluid going into the system, which reduces the thickness of the oil and pushes it out.
  3. High Flush Oil Temperature: This process increases the speed and temperature of the new fluid entering the system. The higher temperature helps remove stubborn deposits.
  4. Cycling Flush Oil Temperature: This strategy alternates the machine’s temperature between hot and cold as the system is flushed. The shift in temperature helps to break up deposits.
  5. Pulsating Oil Flow: This strategy relies on speed and movement by pulsing the oil as it’s fed into the system to break up deposits and remove contaminants.
  6. Reverse Oil Flow: This strategy is simple. You reverse the flow of the liquid as you flush it through, and it will remove deposits and sludge.
  7. Wand Flush Tool: Sometimes, you’ve just got to get in there and scrub! A wand flush uses a tool on the end of the flushing hose that you can manually direct while cleaning the system. Sometimes it even has a suction feature, just like a vacuum, so you can suck up all the dirt and grime! This technique is great for sump pumps, gearboxes, reservoirs, or tanks with accessible hatches.
  8. Charged Particle (Electrostatic) Separators: This process relies on electrostatic technology to remove contaminants from the surface.
  9. Solvent/Detergent Flush: Just like when you throw drain cleaner down a clogged drain, a solvent detergent flush causes a chemical reaction that breaks down contaminants and deposits. There are different types of solvents you can use, and you must watch out for compatibility issues and follow up with a rinse of the system afterward.
  10. Chemical Cleaning: Similarly, a chemical cleaning uses acid or another caustic chemical to break up deposits.
  11. Mechanical Cleaning: This tactic is most like cleaning your vacuum cleaner. You break out your brushes, scrapers, and tools to get in there and remove the deposits manually.

As you can see, the process of flushing is quite complicated. There are a lot of different techniques you can use. But how do you know when you need to flush your system? Here are some of the signs you want to watch for:

  • Oil Degradation: If you notice that the oil in your system is degrading or becoming contaminated, it’s probably time for a rinse. One way you can check the status of your il is to take samples of your equipment for oil analysis regularly. We offer an oil analysis program for our customers that helps them make maintenance and lubrication decisions based on how their machinery and lubricants are performing.
  • Filter Collapse or Failure: If your filters are starting to fail or become clogged, the chances are high that contaminants are already in your system, and it’s time for a cleaning.
  • Before bringing a machine back into service: If your equipment has been sitting idle for some time, then make sure you give it a flush before putting it back to work. This way, you can ensure that any contaminants that may have gotten into the system while it was out of use are removed.
  • If antifreeze gets into your oil. Antifreeze and oil don’t mix. So if antifreeze has gotten into your system, it will cause deposits, sludge, and acids to form.
  • Mixing lubricants: If you’ve mixed in lubricants or are adding a new lubricant without cleaning the system, you could cause chemical reactions that could damage your system. You always want to ensure that your lubricant supplies are compatible or remove the old lubricant from the system before introducing a new one.
  • Contamination: If you get water, dirt, or any other containment in the system, you need to give it a flush to maintain the integrity of your system.

So, now we know the different flushing techniques and when we need to flush the system, but how do you do it? Luckily the team at Machinery Lubrication has created a simple 11 step process that can guide you for most flushing processes. But a word of caution, your flushing procedure should always be designed for your equipment needs and done by a trained professional, but this is a basic process that may be helpful.

  1. Drain the system and replace filters.
  2. Use a clean rag to clean the reservoir of any sludge or deposits.
  3. Perform the flush.
  4. Drain the flushing liquid and replace filters. Then, inspect the reservoir and clean it again.
  5. Fill the system up 75% of the way and then bleed or vent the pump. Run the pump for 15 seconds with the pressure relief open. Repeat a few times to prime the pump.
  6. Run the pump with the pressure relief open. Stop and let it sit for one minute. Then run the system with the bypass closed for five minutes. Again, stop and let the system sit for five minutes.
  7. Start the pump and actuators one at a time and monitor the fluid moving through the system. When it’s gone through the whole system, shut it down. If your fluid levels drop below 25%, add more fluid.
  8. Refill the reservoir up to 75% and run the system for a few minutes. Shut it down and release the pressure, then run again. Repeat a few times and troubleshoot for any potential issues.
  9. Run the whole system at normal temperatures for 30 minutes. Then, shut it down and replace filters. Inspect for any signs of contamination. Repeat the process if you find any.
  10. Run the system for six hours, shut down, replace filters and test the oil.
  11. Continue sampling and testing the oil until you are satisfied that your fluid levels are correct.

Flushing your hydraulic system is a highly complex process. You should always follow the operator’s manual instructions or consult a professional mechanic for the proper way to do it. You can even hire a firm that specializes in flushing systems! But the most crucial principle of flushing your system is to clean your system thoroughly and remove any contaminations, deposits, and sludge that builds up. Eliminating these factors will increase the efficiency of your lubrication supplies and protect your machinery. Plus, flushing is way easier than taking everything apart and cleaning it manually, as you do with a vacuum! As your fuel and lubricants supplier, we want you to know we are here to help answer any questions about your flushing procedure!