Hydraulic Grenading - what to do next
In hydraulics, “grenading” is the cataclysmic internal failure of a pump or motor, where components break apart and distribute small bits of metal through the system almost instantaneously. You’ll normally know about it, because it gives off a loud noise, almost like a massive knock, just as it’s about to fail. It’s seriously destructive - and the whole system normally stops within minutes.
What actually happens
When internal rotating parts (gears, pistons, bearings, running surfaces), are severely worn out, or broken, they will eventually fragment into chips and shrapnel.
Unfortunately, because these metal fragments mix with the oil, and hydraulic fluid is so good at moving through the system, it carries these hard particles throughout the entire circuit, contaminating valves, cylinders, pretty much everything. They can seize a system that was running perfectly fine ten minutes earlier. It’s seriously bad news.
When a hydraulic pump or motor lets go in a big way, it leaves you with a mix of headaches.
Hard particles: Metal bits turn clean oil into grinding paste, and even tiny stuff will score valves and pump surfaces.
Soft junk: Pieces of seals and elastomers can plug or partially plug ports and screens, so the symptoms don’t always scream “contamination” straight away.
Heat and burn‑off: If things got hot or you had cavitation, you’ll often see dark oil and sticky varnish starting to form, which can make valves hang up later.
Bottom line: that shiny new pump or motor is only as safe as the system you’re about to bolt it into. So be careful. An experienced Hydraulic Service Tech should probably be involved at this point.
First hour: don’t make it worse
Treat the system like it’s still live, even though it’s stopped.
Shut it down properly, lock it out, and isolate what you can. Debris keeps moving as long as oil can circulate, so isolate the bad circuit if there are multiple loops.
Grab an oil sample before you top up or add anything. That “before” sample tells you if you’re mainly fighting particles, water, cooked oil, or a mix.
If you can, cut open the return filter. If it’s full of shiny metal or rubber bits, you know the failure isn’t local and you’ll need to clean harder and deeper.
Drain, flush, or just filter?
People call everything a “flush,” but there are really two different tools.
Off‑line filtration: Great for pulling particles out and keeping oil clean, but it won’t magically scrub junk out of long pipe runs, coolers, or manifolds.
High‑velocity flushing: This is what actually scours the plumbing, moving oil fast enough to lift debris and carry it to a filter or catch point.
Most big failures need some of both. A practical way to tackle it:
Drain and clean the tank if it’s ugly. If you can see metal, sludge, or it smells burnt, clean the bottom and walls, otherwise you’re just polishing oil in a dirty reservoir.
Bypass or remove sensitive parts before you flush. Precision valves, new pumps, and tight‑tolerance gear shouldn’t be used as flushing tools.
Flush key pipe runs with dedicated filtration in the loop, so you’re not just relocating the dirt.
Keep an off‑line filter unit running afterwards. Use particle counts if you can, or at least a consistent inspection method, so you know when you’re actually “clean enough.”
Where the junk likes to hide
Even good maintenance crews miss the same spots after a ‘grenading’.
Coolers and heat exchangers are great at trapping particles and then slowly feeding them back if they’re not cleaned or swapped out.
Manifold blocks can hold contamination in cross‑drilled passages; sometimes you can clean them in place, sometimes they need to come off and be stripped.
Hoses and suction lines can hang onto debris, especially if the liner is damaged, and any restriction or air leak on the suction side just sets you up for cavitation and a repeat failure.
Bringing it back online without killing the new gear
Once you’ve done the cleanup, the restart is where you either win or lose.
Pre‑fill and prime the new or rebuilt pump or motor. A dry start is a great way to wreck fresh hardware in minutes.
Start gently. Bring it up low and slow, watch temperature, listen for odd noises, and keep an eye on pressure. If you’ve got case‑drain flow readings, use them - they’re a quick tell‑tale for internal leakage.
Final Thought
Post grenading recovery is part troubleshooting, part clean up, part precision work. Flotek has dealt with post failure recovery on countless occasions. We can help flush, determine the right filtration strategy, replace the necessary hydraulic components and hoses, to get the system back online without repeated failures. Our hydraulic fault finding expertise is unmatched in Melbourne.
