Copyright Rory S. McLaren 2017

Isn’t it amazing that the same companies that implement a lockout, tagout, tryout safety protocol for their electrical systems; which they police vigorously, have a similar protocol for locking out their hydraulic systems; only, it has a slightly different twist. It’s called lockout, tagout, guess! It’s Russian roulette, except the guns are hydraulic systems, which are loaded with liquid bullets.

Copyright Rory S. McLaren 2017

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When it comes to hydraulic safety, the fluid power industry doesn’t get into all that offensive “lockout, tagout, tryout,” nonsense, we take; as President Bush once said, a kindler gentler approach: we use the “buddy” system. I also like to refer to it as the “trust me” system.

Ever tried working alongside a colleague on a machine that has only one lock on the breaker; and the safety officer approaches? Try telling the safety officer that there is only one lock on the panel because your colleague “trusts you.” Of course, you will be looking for a job!

Here’s is an example of how the “kindler gentler” approach works – or doesn’t:

Here is an excerpt from a company’s internal accident report:

A mechanic suffered an oil injection injury when he was repairing an oil leak in the steering system on a Caterpillar 793D. The truck was shut down and isolated, however, the hydraulic system did not automatically “drain and depressurize” as designed due to a faulty solenoid. As the mechanic began to loosen the fitting with a wrench the pressurized hydraulic hose blew off the fitting spraying the mechanic with hydraulic oil. Subsequently, the mechanic noticed his thumb swelling and saw what looked like a puncture mark in the soft area of tissue below his thumb. He was transported to the hospital.

The key words in the report are “drain” and “depressurize.” There is no mention of “verification.” Therein lies the problem.

It’s a well-known fact that hydraulic systems have the inherent ability to store energy, post shutdown. Unlike an electrical system, a single hydraulic system can store energy in over 30 “zones,” or “pockets.” However, post lockout an electrician can verify if an electrical system is isolated with a voltmeter. All mechanics have-to go by is “guess” and, believe it or not, OSHA and MSHA are perfectly happy with the status quo.

The fluid power industry utilizes two components for de-energization, and they are both notoriously unreliable: accumulators and solenoid valves. With respect to accumulators, mechanics are told to move levers until the actuator (s) stop moving, and then it’s safe – trust me!

With respect to solenoid valves; as in this case, a solenoid is supposed to activate within a pre-determined time post shutdown, which automatically discharges stored energy from the accumulator (s) – trust me!

The post accident contributing factors/learnings report, written by the company's safety manager, epitomizes how far out of touch safety managers are with regard to hydraulic safety (see my comments, in italics, below each factor).

• Anytime work is performed on a hydraulic system that has been energized - a check of the system status should be made. In this case, a hydraulic pressure gauge could have been used to determine that the system was de-pressurized before work began.

I beg to differ. It would have been necessary to breach the pressurized hydraulic system to install the pressure gauge. Bear in mind that a hydraulic system can store energy in individual "zones" throughout the system. Moreover, if there is a pressure gauge at the pump, it cannot be used to confirm the status of energy elsewhere in a hydraulic system.

• Proper isolation of any piece of equipment should include the de-energizing and "try-step" of associated systems where stored energy exists.

This is wishful thinking on the part of any safety person. It has already been established that Caterpillar's hydraulic system was allegedly unsafe by design because the mechanic could not verify that the solenoid failed to de-energize the hydraulic system. Tryout may work with electricity, but it does not, and cannot, work with hydraulics.

• A safety "stand-down" has been conducted with all the mobile maintenance teams to discuss this incident and confirmation of a zero state for any system before the work begins.

This is a feel good statement that might appease the company's executives, and MSHA, but it makes absolutely no sense. The subject company employs hundreds of hydraulic systems. There isn't a single one that has been modified to bring about a permanent solution to the stored hydraulic energy problem.

Recommendations:

1. The truck was reportedly “shutdown and isolated.” In the world of hydraulics, isolation means “assumed safe.”

2. NEVER trust a manufacturer when it comes to hydraulic system de-energization. We (USA) have the technology to mitigate the problem. However, engineers won't use it because it's not mandatory. It's easy to ignore safety devices when your children's lives aren't on the line.

3. Just because OSHA, MSHA and hydraulic systems designers ignore the problem of stored hydraulic energy, doesn’t mean it can’t severely injure, maim, or kill you.

4. Treat hydraulic systems with the same respect you treat electrical systems. If you cannot verify, with an instrument, that a hydraulic system is de-energized, have a chat with your company’s LOTO expert about stored energy. The quickest way to solve the problem is to have your LOTO expert demonstrate how to de-energize a hydraulic system by loosening a connector, and discharging high-pressure oil to atmosphere. If you find a LOTO expert that has the intestinal fortitude to de-energize to atmosphere, don't forget to film the event.

5. If a hydraulic actuator (cylinder or motor) doesn’t move when you activate the actuator’s control valve, DO NOT assume the system does not contain enough stored energy to severely injure or kill you.

6. Solenoid valves are notorious for seizing, especially when they are under constant pressure, and they have a low operating frequency – NEVER TRUST THEM! Designers should only use mechanical devices, if they are not going to make provisions for verification.

7. Remember, the only reason why you are going to get severely injured or killed while working on a hydraulic system is because the valve needed to give you the ability to verify if a hydraulic system contains stored energy, post shutdown, costs a measly $20.00. The treatment of an oil injection injury averages $75,000.00.