Lock Out Tag Out

The more technology progresses, the greater the chances we're gonna get hurt. Process safety is an important theme in any workplace, which is why I have decided to blog about a very important concept within process safety, called Lock Out Tag Out.

When working in any plant, automated machinery often works on hazardous sources of energy--electricity, hydraulic energy, high pressure pneumatic energy etc. Since hydraulic and pneumatic energy are high pressure fluids, this concept of lock out tag out is very relevant to this blog. As an introduction, I will ask an important question: When multiple people are working on the same machinery, how do you create a system where one person's mistake does not hurt someone else, and compound the issue even further?

To further illustrate the problem the above question brings to attention, lets suppose 10 workers are working in a plant that manufactures diapers. The diaper has many parts to it, and making parts of it require, other than electricity, strong vacuums and air power as well. The machine needs to be cleaned and shuts down. 9 of the 10 workers finish cleaning their parts of the machine. It's been a long day they just want to start the machine again, because their bosses will be mad if they don't. The 9 workers look at each other, think everyone is done and start the machine back up, forgetting to count the 10th worker. The 10th worker is still inside the large diaper making machine, while it turned on. The pneumatic energy and electrical energy are now both active and the 10th worker's life is in serious threat.

To prevent a situation like this, there needs to be a system where if any worker is working on the machine, its electrical and pneumatic energy cannot be activated. This system is lock out tag out. In factories like the one above, when any worker shuts the machine down, they must lock the on/off switch so nobody but them can open it. Each worker has his/her own set of locks. Thus, in the situation above, the 9 workers would not be able to turn the machine on because the 10th worker's lock would still be on the on/off switch. Many workplace incidents are caused due to failure to lock out, and is a serious safety violation for most companies. Workers often think its okay to just quickly finish a job without locking out, which is why companies must give the biggest disincentive for such behavior.

Example of proper locking

Random Explained

I still don't really get turbulence. I know it can be quantified with average velocities, but why does it happen? While we may not have all the answers, the below video narrated by Robert W. Stewart, of the University of British Columbia, does a great job of explaining this perceived randomness. Stewart smokes his pipe, and lets us know that Turbulent flow is not necessarily random as we think.

Like in my transport class, he goes over the Reynolds number and why turbulent flow is about high Reynolds numbers (much greater than 2000). He also defines turbulent flow has having disorder, vorticity, and efficient mixing. For a video that seems to have been made half a century ago, the illustrations and experimentation were very clear. As viscosity was decreased, the flow turned turbulent and the pressure gradient increased. He also explains that this increase in pressure is due to the Reynolds stress, or the additional stress in turbulent flow compared to laminar flow.

But the part that I found cool was that if a funnel was put in at the entrance, the flow was laminar for a greater Reynolds number (around 8000). The video says that the funnel makes the flow smoother and less mixing happens, making more laminar flow. Thus, once again, turbulent flow is not random, and the number 2000 is not random either; it applies to specific geometries. Further, as Stewart says, random implies some sort of Gaussian distribution, which is not the case with turbulent flow. So the idea of randomness is not accurate--its more like we don't know.

The last cool part of this video is the dye illustration part, and how basically turbulent flow makes a blob bend and thin until it has enough of a surface area increase to go through molecular diffusion very fast. This mixing would really make sense for chemical reactions that require mixing in order to go to completion. As a chemical engineering major, this makes a lot of sense to me.

The video really helped clear up my concepts about turbulence, so definitely give it a watch! While I cannot promise the lips will be synced to the dubbing in the video, Stewart does an excellent job defining turbulence as best as possible (50 years ago).