The hard-boiled tribologist
Evan Zabawski | TLT From the Editor April 2011
Or The Case of the Sticky Servo.
What could take down a hydraulic system but escape detection with fairly routine oil analysis?
My name is Slick. I’m a private investigator. I have two magnums in my desk: an unloaded gun and a bottle that keeps me loaded. I have eight slugs in me, one is lead and the rest are whiskey. It’s barely noon and I’ve only been awake for half an hour.
My door bursts open to reveal a tall, blond drink of water. She says she has a case for me. With a pile of overdue bills on my desk, I decide to take it. She starts to tell me her story.
It seems she’s looking for some answers, but I haven’t even heard the questions yet. She wants to find out who or what bumped off her hydraulic system. I ask her if this isn’t something she can just take to the boys at the lab. She says she has and that they came up dry. Speaking of dry, I take another pull from my bottle.
She tosses some reports across the desk to me. She seems like the pushy type, the kind who’d either break your heart or your arms. I give the reports my full attention. They tell me the oil’s clean, at least according to the spectrographic data, the particle count, the Karl Fischer water and the acid number. What am I missing?
When I look up, I see that she’s gone. I decide to visit where the victim worked—maybe I can find some clues. I step out into the rain and review the facts. There aren’t many. Questions pour down like the rain. What could take down a hydraulic system but escape detection with fairly routine oil analysis? Which part failed and tripped the system? What was I expecting to find?
I arrive to find forensics pulling the system apart like a pair of surgeons. The pump comes out first (no sign of cavitation). Next is the suction strainer (clean as a whistle). I need a clue and a drink, but I only know where to find the latter. When they get around to the servo valve, they find the spool stuck firmly.
Will the valve snitch? I’ve got to get it to tell me something. I decide to introduce it to one of my two buddies, who travel light and are fun to have around. One travels in a holster, the other in a hip flask. I try pouring a little 80-proof down into the valve body to see if it will loosen up. No go! I guess I can’t pin this case on varnish.
Forensics is now working on the reservoir. The fluid looks about as dark as the alley where I meet my bookie. I’ve got to figure what’s darkening the fluid. The filter must be working, the particle count was fine. I ask them to pull the filter anyway.
From the outside, it all looks copacetic but I’ve learned to always look inside, too. Aha! Uncompressed diamonds! Seems this hydraulic system isn’t dealing on the up and up. I decide to call my client with the news, but she’s not answering the phone.
I swing by her building only to find the front door open. I hear noises upstairs that sound like screaming. I don’t like the way this story is shaping up, so I decide to write a new ending with my .357 as co-author. I race up the stairs expecting action, and then I remember I didn’t load my piece. I burst into the office to find the blond with her head down on her desk, crying into her crossed arms. The rest of the room is as empty as my gun.
I console her as best I can, but the guilt has gotten to her. She says she didn’t think I would solve this case and was hoping I would come up with the usual conclusion and pin it on the oil.
I tell her that carbon deposits on the clean side of a filter usually indicate electrostatic spark discharge. Her simple upgrading of the filter to a lower micron rating increased the restriction creating the necessary potential. The carbon produced by this phenomenon is small enough to escape detection by particle counting and not an element typically measure by spectrometry. A nearly perfect crime, but she didn’t get away with it.
(With much respect to Bill Watterson and his highly influential Calvin and Hobbes’ character, Tracer Bullet, celebrating 20 years this month).
Evan Zabawski, CLS, is manager of training and education services for The Fluid Life Corp. in Edmonton, Alberta, Canada. You can reach him at evan@fluidlife.com.