Dying to Learn!

Copyright Rory S. McLaren 2017

I took the photograph (above) moments after the accident. This is what happens when the jacks (outriggers) on a crane, drilling-rig, aerial platform, etc, fail. I am pleased to report that the crane's operator escaped unscathed.

While OSHA continues to look the other way regarding the issue of stored hydraulic energy, and hydraulic system designers continue to take advantage of the situation, I regret to report that I have learned of yet another accident related to stored hydraulic energy - with many more to come.

Preface

I am confident most industries envy the fluid power industry. While OSHA holds every industry listed in OSHA's Control of Hazardous Energy (Lockout/Tagout), Title 29 Code of Federal Regulations (CFR) accountable, and therefore they must invest heavily in safety, the fluid power industry gets away scot free. Here's just another example of the carnage OSHA, and irresponsible design engineers, leave in their wake.

This accident involved an untrained "journeyman," and apprentice mechanic, and an inherently unsafe drilling-rig. As you will learn, the accident could have claimed the lives of two people, and wrecked a multi-million dollar drilling rig. Not that I care too much about the drilling rig. What "blows my mind," is how the owners of these machines manage to get them insured. It's just as well insurance companies are as naive about the situation as the owners are.

The accident involved a massive blast hole drilling rig (similar to unit in photo) that was resting on “stilts,” which were located at each corner of the machine. I refer to them as “stilts" for the sake of simplicity. They are huge hydraulically operated jacks, which are used to stabilize the drilling rig. They also level it should it be working on uneven ground. In the photo of the drilling-rig you can see the "stilts" resting on the ground in front of the tracks. When a drilling rig is being readied for operation the operator uses the "stilts" to raise the drill-rig off the ground. The "stilts" stabilize the drill, and they also level it if the surface it is standing on is uneven.

If one of the flexible transmission lines connected to each jack’s cylinder unexpectedly fails, it could cause the giant drilling rig to topple over, and/or, snap the spinning drilling rod. As a critical safety measure, drilling rig designers typically install locking valves in the cylinder ports, which literally lock the oil in the cylinder (s) should a hydraulic hose fail.

Allow me to use the hydraulic schematic below to give you an idea of how the holding valve "locks" the oil in the cylinders in the event of an unexpected transmission line failure. Imagine that the holding valve (yellow) is attached directly to the cylinder, and the green "load" represents the drilling rig. If the oil transmission line, which connects the directional control valve to the holding valve/cylinder bursts, the holding valve "locks" the oil in the cylinder, thereby preventing the load from dropping.

There is typically a distinct flaw in the hydraulic system’s design: if the hydraulic pump is disabled for any reason, there is no way to safely lower the drilling rig to the ground. Well, actually there is, but designers won’t use the safety device because, when it comes to hydraulics, safety devices are only needed if OSHA says so! Moreover, it’s always easy to overlook safety when you are never going to be the person that’s in “the line of fire.”

Anyhow, the pump was disabled, and the drilling rig needed to be lowered to the ground. It's blatantly obvious that neither the journeyman mechanic, nor the apprentice, knew what they were about to get into, because the journeyman foolishly tasked the apprentice to remove the locking valves from the cylinders.

To give you some sense of what this “mechanic in training” was tasked to do, I want you to imagine that a giant artillery gun is loaded and ready to fire. Its entire weight is sitting on four supports; one at each corner. A person is tasked to simultaneously remove one of the supports, and pull the trigger while moving about in front of the gun's muzzle. It's the hydraulic industry's version of Russian roulette.

As you can imagine, this procedure is almost certain to severely injure or kill the person performing the task in one, or more, of three ways: One, the shell hits you directly between the eyes. Two, the giant artillery gun topples over on top of you and crushes you to death, and three; the shell hits you between the eyes, and the giant artillery gun topples over on top of you. Sounds like an episode from the roadrunner show!

The obedient, and obviously very ignorant, “mechanic in learning” approached the holding valve; wrench in hand. He slowly screwed the holding valve out of the cylinder, not realizing that the oil pressure within the cylinder was akin to the powder in an artillery shell, and unbeknownst to him, he was busy lighting it! After several rotations of the valve, there was an explosion. He opined that the force of the steel "missile" (holding valve) ripped the wrench out of his hand, propelling it past his face, and high into the air. He began to run as the giant drill rig suddenly listed to one side. He thought it was going to topple over. Thankfully it didn't!

He opined that he never recovered the socket he was using to loosen the holding valve. However, after searching for a while he found the holding valve approximately 75 feet away from the drilling rig.

Conclusions:

1. The OSHA standard for The Control of Hazardous Energy (Lockout/Tagout), Title 29 Code of Federal Regulations (CFR) obviously doesn't apply to hydraulic systems, even though OSHA says it does. As you can clearly see, Part 1910.147, addresses the practices and procedures necessary to disable machinery or equipment, thereby preventing the release of hazardous energy while employees perform servicing and maintenance activities. The standard outlines measures for controlling hazardous energies—electrical, mechanical, hydraulic, pneumatic, chemical, thermal, and other energy sources.
2. Regardless of what machinery and equipment manufacturers recommend, NEVER attempt to remove a hydraulic oil transmission line, or any hydraulic component, unless you can verify there is no stored energy.
3. If you ever suffer a high-velocity oil strike (anything other than residual pressure), you have had an accident. Write a report. Hand a copy to your supervisor, and another to your company's safety manager. Don't forget to keep a copy at home.
4. If you work on hydraulic systems, and you don't have formal training in hydraulics, stop working on hydraulic before it's too late.
5. If you attend a lockout and tagout safety training course, have the presenter take the group out to a hydraulic system to demonstrate how to "carefully" loosen a hydraulic connector, which is under pressure.

In the electrical world it's a case of lock, tag, and try. In the hydraulic world it's simply lock, tag, and possibly die!

Help Me Make Sense Of Title 29 of OSHA's Code of Regulations (CFR) Part 1910.147

I am seeking advice from LOTO experts, and lawyers.

I was recently hired by a global mining company to conduct a hydraulic safety workshop for the company's hydraulic training instructors. One of the most controversial topics I cover whenever I conduct a hydraulic safety workshop is the matter of stored hydraulic energy post LOTO. The matter is controversial because it runs head on into Title 29 of OSHA's Code of Regulations (CFR) Part 1910.147. Part 1910.147, addresses the practices and procedures necessary to disable machinery or equipment, thereby preventing the release of hazardous energy while employees perform servicing and maintenance activities. The standard outlines measures for controlling hazardous energies—electrical, mechanical, hydraulic, pneumatic, chemical, thermal, and other energy sources. 

The fact is, there is no way, as OSHA puts it, to "prevent the release of hazardous hydraulic energy" while employees perform servicing and maintenance activities on hydraulic systems. There isn't now, and what's more, there never has been!

The day after I covered the topic of stored hydraulic energy one of my students handed me a document titled "824H Wheel Dozer System Pressure - Release," and asked me to explain it to them. This is the part of my job that I dislike the most because the discussion never ends well.

Accordingly, I am appealing to safety professionals, LOTO experts, and lawyers to weigh in on this controversial topic. Please read the following procedure, and my comments, and let me know how I should respond to my students.

Here is what the manufacturer recommends (in italics):

Personal injury can result from hydraulic oil pressure and hot oil.

Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system.

Make sure all the work tools have been lowered to the ground, and the oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.

WARNING

Escaping fluid under pressure, even a pinhole size leak, can penetrate body tissue, causing serious injury, and possible death. If fluid is injected into your skin, it must be removed

NOTICE

Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluid.

1.  Permit only one operator on the machine. All other personnel should be kept away.

2.  Move the machine to a smooth, level surface. Move the machine approximately ten feet in the forward direction. Then, move the machine approximately ten feet in the backward direction. Park the machine. Connect the steering frame lock so that the machine cannot articulate. Power down the lift linkage to raise the front wheels off the ground. Then, raise the lift linkage to lower the front wheels to the ground. Lower the bucket to the ground.

3.  Turn the engine Start switch to the off position.

4.  Engage the parking brake. Place blocks in front of the wheels and behind the wheels.

5.  Depress the brake pedal repeatedly. This will relieve any pressure that may be present in the braking system.

6.  Move the steering wheel several times in both directions to relieve the pilot pressure in the steering system. If you are servicing the steering cylinders, the steering valve, or the steering hoses, slowly crack the lines to purge any trapped oil that may be in the steering system.

7.  Turn the key switch to the on position. Do not start the engine. Move the implement control levers several times through the full range of travel. This will relieve any pressure that may be present in the implement hydraulic system. Turn the key start switch to the off position.

Note: There may be some pressure that is trapped in the tilt cylinder circuit. Relieve this pressure before servicing the implement hydraulic system. To relieve this pressure, slowly crack the hydraulic lines to the tilt circuit. This will remove any trapped oil pressure in the tilt circuit.

Now, let’s deal with the controversial points:

Step 5 – Notice, there is no reference to any type of instrument that confirms the brake pressure is relieved.

Step 6 – Again, there is no reference to an instrument to confirm that the pilot pressure in the steering system is relieved.

The most dangerous aspect of steps 5 and 6 is that person performing the work must assume that depressing the brake pedal repeatedly, and moving the steering wheel several times, relieves the pressure. If there is a problem with either system’s accumulators, the results will be the same and leave the person facing a very grave situation. 

The most controversial aspect of the entire procedure is that Caterpillar allegedly defies their own warning that "escaping fluid under pressure, even a pinhole size leak, can penetrate body tissue, causing serious injury, and possible death," and recommends that a person perform a procedure that actually creates a pinhole leak in a hydraulic system while their hands, and face, are within inches of the leak.

Step 7 – Once again, Caterpillar recommends moving the levers several times through the full range of travel to relieve any pressure that may be present in the implement hydraulic system. However, there is some uncertainty as to whether the procedure relieved the pressure, so again, Caterpillar allegedly defies their own warnings, and recommends that the person slowly crack the hydraulic lines to remove trapped oil pressure in the tilt circuit.

When Caterpillar’s experts refer to “cracking the lines,” to relieve the pressure, they are allegedly recommending that the person performing the procedure loosen a hydraulic connector while it may be under sufficient pressure to cause severe injury or death. Ironically, the type of connector employed on the vehicle is a split-flange design, which, if loosened, while under pressure will cause the O-ring seal to unexpectedly burst.

This is a photo (non Caterpillar) of the type of connector the person has to loosen to relieve stored hydraulic energy. Note the four bolts, which retain the two flanges. There is an O-ring seal between the face of the fitting, and the face of the component.

Here are actual photos of a mechanic performing the identical procedure recommended by Caterpillar on a Doosan excavator. These photos were taken while the mechanic was "carefully" loosening the line to relieve stored energy. The top photo taken moments before the explosion. In the bottom photo, the high-pressure oil suddenly breaches the O-ring seal, and discharges a lethal dose of stored hydraulic energy to atmosphere.

Doosan's procedure for relieving the pressure mirrored Caterpillar’s. Moreover, the Doosan excavator was equipped with the identical connectors as those employed on the Caterpillar machine. As you can see from the photos, despite the fact the mechanic loosened the connector "very carefully" to "slowly" relieve the pressure, it is virtually impossible to have a different outcome with this type of fitting. If the mechanic's hand was in the path of the oil, the outcome would have been consistent with Caterpillar's warning: he could have suffered severe injury or death.

After the accident, I wanted to learn how much pressure remained in the Doosan excavator's hydraulic system if a person followed Doosan's recommendations for removing stored energy. I installed a Safe-T-Bleed device (a device for verifying, and removing, stored energy from a hydraulic system non-invasively) in the circuit, and proceeded to follow the manufacturer’s recommendations to remove stored energy. The lowest pressure I could achieve was 500-PSI. According to numerous medical studies, 500-PSI is sufficient pressure to cause a debilitating oil injection injury or death.   

According to my students the subject procedure for making the Caterpillar 824H Wheel Loader's hydraulic system "safe," is one of the most feared tasks mechanics undertake in the course of their work.

Here are my questions to the experts:

1.  Does Caterpillar’s procedure meet a manufacture’s duty of care?

2.  Is there a conflict between Title 29 of OSHA's Code of Regulations (CFR) Part 1910.147, and these recommendations?

3.  Is it reasonable for a manufacturer to warn mechanics about the consequences of discharging high-pressure oil to atmosphere, and then ask them to do it?

4.  Is it reasonable to ask a mechanic to loosen a connector to relieve stored hydraulic energy to atmosphere, even though connector manufacturers would never condone the practice?

5.  Would you permit a person in your company to loosen a line to remove stored hydraulic energy, knowing that it is impossible to control that energy?

6.  Does a person that is aware that loosening high-pressure lines could allegedly injure or kill them have a right to refuse to follow the manufacturer’s recommendations?

7.  If a person gets injured or killed while “loosening lines,” can the manufacturer be held liable, or is the manufacturer “off the hook” because the victim ignored the warnings?

8.  What advice should I give my students regarding this matter?

9. Do you have a suggestion for doing the subject task safely?

By the way, Caterpillar is not alone when it comes to the problem of stored hydraulic energy. ALL hydraulic systems have the same problem, and all people that work on hydraulics can be injured or killed while in the process of "carefully" removing stored hydraulic energy.

I encourage people from Caterpillar to help answer my students' questions.

I thank you in anticipation for your help.

Note: My opinions are based solely on the document given to me by my students, and their opinions about the procedure. Accordingly, I reserve the tight to change my opinions if I am given further information about the procedure.