Human Error Prevention Using Accuracy Controlled Enterprise 3T Mistake Proof Standard Operating Procedures

In an Accuracy Controlled Enterprise (ACE) work is done correctly, accurately time-after-time with ACE 3T Target-Tolerance-Test mistake proof procedures that ensure human error prevention

Eliminating human error stops most of your equipment problems and delivers immediate positive benefits to your operation. Such as far fewer repairs, reduced costs, reduced time losses, less rework (even no rework), stop materials and parts waste, higher plant availability, more production, less maintenance, smaller stock holdings and lower spares inventory levels


Human error prevention is the greatest opportunity that is in the control of organizations which will make them a world class performer. Research into decades of equipment failure history in nuclear power stations (The nuclear industry is required to keep full and impeccable records.) highlighted 72% of operating equipment problems and failures are caused by human error. In the aircraft industry it was found that 80% of failures were human error induced. By implication those results apply to all industrial organizations that use machinery and engineered equipment in their operation.


Imagine, no production problems week after week in your operation

It can be that good—failure-free plant and equipment. It becomes possible if you use equipment health monitoring coupled with proactive maintenance done using ACE 3T standard operating procedures. Some 80% of failures can be eliminated by using mistake proof, human error prevention focused ACE 3T Standard Operating Procedures (SOPs).

When you have the right mistake proof systems and methods in place you consistently get the right results. It is not good luck, or fate, or the ‘right people’ that get equipment running reliably and producing at full capacity day after day. Good operating results happen because the right processes and methods are in-place and in-use. You can turn a poor performing operation into a star performer simply by error proofing the processes and practices used by its people. Anyone can do it once they know the right things to do and have got a sound and reliable method to introduce the necessary mistake proof changes into their operation.

In a Plant Wellness Way EAM System-of-Reliability you use ACE 3Ts – Target, Tolerance, Test – to error proof work. The 3Ts are the core of the ACE defect elimination method. It is the way of the expert. It is how a ‘master’ does their work and guarantees faultless quality. With the 3Ts imbedded into your operating and maintenance processes through your work procedures the scrap, losses and wastes disappear. All the savings go straight to the bottom-line as bankable profits.


Prevent failure, control ‘chains of events’ and get 100% right-first-time results

When you use ACE 3T mistake proof SOPs you can expect to:

  1. discover where and how defects, failures and error enter your business
  2. deliver tight statistical control over all work (like in the distribution curve of the Figure 1 below), so you can stop failure incidents and manage risks in every activity of your business.
  3. eliminate the devastating corporate-wide impact of failures, both the occasional large ones that everyone knows of and, most importantly, those many annoying, repetitive small failures that you brush past all the time, which add-up to bucket-loads of lost profit.
  4. permanently eliminate defects and prevent failures in their operating plants, facilities and work processes.
  5. bring necessary change into your business which your people support, promote and inculcate into newcomers.
  6. involve your people in testing and proving 3T failure prevention, defect elimination and error-proofing practices in your operation. And because your people improve the procedures themselves, the dreaded ‘not invented here’ disease does not take hold.


Figure 1 – Accuracy Controlled Enterprise ACE 3T Mistake Proof Procedures deliver Statistical Control over Work Activities


ACE is a sure and certain statistical quality management improvement technique that stops work defects, failures and errors from entering your business and then snowballing throughout your operation.

This scientifically sound approach is an outstandingly successful human error prevention work quality control technique. It prevents mistakes because it uses accuracy and precision to stop people introducing defects that later become plant maintenance and operating problems.

Moneys that are now lost on unnecessarily wasted costs and efforts will become new profits. Rework and scraped jobs will stop. The ACE 3T way of failure prevention and defect elimination permanently improves productivity and delivers new production and profits because losses disappear as more jobs go 100% right-first-time.


How ACE 3T SOPs permanently eliminate defects and prevent failures in operating plants, facilities and work processes

Let’s compare the learning and advice on human error prevention in the book, ‘Why We Make Mistakes,’ from J. T. Hallinan (published in 2009 by Broadway Books, New York) to the Accuracy Controlled Enterprise 3T format for creating mistake proof work procedures.

1) Replaces Feedback Control with Feed Forward Control
On Page 181 Hallinan discusses the role of feedback loops in controlling human error. He says, “Feedback sends back to the user information about what action has actually been done and what result has been accomplished. Feedback is a well-known concept in the science of of information and control theory; it’s why phones have dial tones and make those little beeps when you push the buttons—the feedback lets you know whether you’ve done something correctly.”

Feedback control in typical standard operating procedures used in industry comes at the end of a series of major activities, as shown in Figure 2, and is done far too late to prevent defects. These tests tell you that you have a problem, which you then spend more time and money to fix.


Figure 2 – Quality Checks are Typically Done at the End of Many Steps


Each Test activity in an ACE 3T Target – Tolerance – Test procedure is a feedback requirement to prove that the task just done was inside its minimum standard, i.e. within its Tolerance range. Because the 3Ts require that each critical activity be tested as it is done, each Test is also a feed forward requirement on the input to the next step in the procedure. The next activity is only done when the input into it is proven right. Figure 3 shows how 3T procedures are used to control process outcomes. They feed forward information on the input to the rest of the job while also confirming that the prior work was done right.



Figure 3 – ACE 3T Quality Checks are Done at Each Critical Step


2) Limits Overconfidence: The Illusion of Being in Control
People prefer to guess than to go looking for the right details. We use made-up mental models of what we think are right. Hallinan writes on Page 161—”they think they will perform much better than they do. So strong is our belief in our own abilities that we often believe we can control even chance events, such as flipping a coin or cutting a deck of cards.” We dismiss the evidence and trick ourselves into thinking we are better than we are.

Hallinan tells a frightening story on Page 176 of a trial where 24 adults were asked to wire a household electric plug using the instructions provided. During the test, “Only ten of the twenty-four bothered to look at the instructions. And of those ten, seven consulted the instructions only to check the color coding for the electrical wires; the rest of the information was ignored. Not surprisingly, most people flunked this test. Of the twenty-four adults, only five wired the plugs successfully.” It turns out that the more you think you know about a subject, the less respect you have for your ignorance of what you do not know. It is the same for both novice and expert—once we think we are right about a thing our minds become set. Even clear proof to the contrary may not make us change our wrong thinking.

In an ACE 3T human error prevention procedure the exact details are always in the document. But unlike written instructions, an ACE 3T error proof procedure uses multiple ways to pass on the right information; words, drawings and pictures are combined to explain what needs to be done. When people scan a procedure few will read the words but they will see many images of how to do the job right. The right information is in an ACE 3T mistake proof procedure, so that when users stop the job to get the facts the right details are in the instructions. And when people do not bother to read the instructions they still have plentiful visual management guidance to look at.

This YouTube video takes you into greater details about the ACE 3T error proof method and how to apply it in you standard operating procedures: The Value Gained by an Accuracy Controlled Enterprise Using 3T in SOPs (19 min 16 sec)

For overconfident people the checklist imbedded in ACE 3T mistake proof procedures and instructions makes them step through their work task by task. Unless every task on the checklist is signed off by its Doer the job is immediately suspected of containing errors.

ACE 3T uses the checklist to get people to pay active attention and control their overconfidence! In an ACE 3T error proof procedure every task must be signed off by the person who did the task. This is what is done in aircraft maintenance and nuclear submarine maintenance and it greatly improves the odds of good work being done.

3) Removes Uncertainty and Puts Constraints in Place
In Hallinan’s book, Why We Make Mistakes, he provides suggestions to reduce human error. One of them is to use constraints, which he says on Page 183 are “simple mental aids that keep us on the right track by limiting our alternatives.” He tags them as “error blockers” and their job is to remove uncertainty in the right way to do a thing. He gives the example of how scissors are designed. Their handles are shaped so that the fingers can only go through the one elongated hole. Their design ‘nudges’ you to use them in the right way.

Affordances is another type of constraint Hallinan discusses. They are “clues to how a thing can be used”. His door example on Page 184 will strike a chord in many of us. “Have you ever walked up to a glass door in an office building and not known whether you should push or pull it? That’s because the door lacks proper affordances.”

To stop human error you need to signal to people what is the right thing to do. You cannot presume that people will ‘work it out for themselves’. Hallinan says to “strip out complexity and build in constraints”.

ACE 3T procedures help remove uncertainty with use of visual indicators and check tests imbedded in the procedure. The checklist is a constraint that no one using an ACE 3T mistake proof instruction can bypass

The design of ACE 3T procedures creates a target to hit—the first T in the 3Ts is Target. It makes us include a bullseye in every task that acts as an affordance to guide our work.



Figure 3 – ACE 3T Job Procedures Build-in Statistical Process Control


Make use of ACE 3T procedures when you want to deliver practical and valuable contributions to improve workplace productivity, reduce errors and mistakes by up to 100 times (10,000%), or solve those operating performance and quality problems.