By Phil La Duke
There are a lot of useful things that safety professionals can learn from manufacturing, particularly Lean Manufacturing, yet surprisingly few safety practitioners—even within manufacturing—see the connection. Two of these concepts that have a profound value on safety and risk are cycle time and takt time. Takt time is generally defined as the maximum time per unit that it takes to produce something to fulfill the customer’s demands, and cycle time is the time it takes to do one job. Both terms are measures of capacity and key elements of efficiency.
That might not seem to mean much in terms of safety and risk, but it does.
Shorter takt times mean that providing goods (or services) to the customer is happening faster. This fact in itself doesn’t mean very much, but if you consider that to improve efficiency (for our purposes, efficiency will mean producing goods or services as quickly as possible without compromising cost, quality, or safety) you have to reduce your takt time, we start to see implications for safety. Few of you would argue that “haste makes waste” and in fact, rushing to complete a job introduces the risk of injury, and that is exactly what can happen if we try to reduce takt time simply by cracking the whip and force the workers to work faster.
Similarly, cycle time is the time it takes to do one job. In manufacturing, it is the time it takes to complete all the tasks at one station and this is typically described in minutes or seconds. Years ago when I built seats for one of the Big Three auto manufacturers my cycle time was 55 seconds, and our takt time was around 16 hours (the time it took for one car to go from hunks of metal, plastic, and cloth to a fully functioning automobile.) To improve the takt time you generally have to reduce cycle time. The key to both these activities is to eliminate waste. In the discipline of Kaizen there are seven kinds of waste, or muda as they like to call it, mainly so that there job feels like a cool karate class, but then I digress. The seven wastes are:
- Defects (and rightfully this should include injuries and damage to facilities or equipment, or environmental spills, from a process stand point, when a process fails, whatever the unintended consequence is waste)
- Overproduction (work done without an immediate order for it)
- Inventories waiting to be \processed
- Unnecessary movement of stock (like moving things around your operation)
- Unnecessary motion of employees (people having to walk farther than necessary, for example)
- Overly processing (quality checks or redoing job because it wasn’t done correctly in the first place)
- Waiting (workers standing idle because they have nothing to do)
All of these sources of waste introduce variation into the process and where there is variation there is risk of injury. So we want to eliminate waste and be sure that we preserve the safety of the workplace; sounds simple right? Well, predictably, it isn’t.
Apart from the obvious risks of rushing, let’s assume that there is an unidentified hazard in a job (for our purposes, it doesn’t matter if the job is taking orders at a logistics company, running a ride at a theme park, or building jet engines) if the cycle time is decreased it means that the job is done more times a day (assuming a steady flow of consumer demand) which means that the probability that the worker will be injured through interaction with the hazards grows proportionately. Think of like this let’s say you are a shoplifter (relax I know some of you aren’t really shop lifters) and you decide to steal a steak from your grocer. Two things come into play (actually more than two, but bear with me) the length of time to steal one steak (takt time) and the number of times you go back to the store to steal a steak (like any good shoplifter you go back to the same store over and over again because you know the layout and routines of the staff). Unlike the odds of say, flipping a coin that remain 50:50 each and every time you flip it, our scenario is a bit different. While the coin will never change in a way that will affect the probability our chances of successfully shoplifting are in almost constant flux (security measures are likely to get “beefed up”, the store staff is more and more likely to recognize you and suspect that you may be the thief (assuming you weren’t seen in the act). To reduce your risk you might decide to steal something else, something that reduces your takt time because it is closer to the exit, or you might decide to lower you cycle time to let things “cool down” before trying it again.
How is this important to safety? Well ergonomic strain can build to create the most costly injuries, and you don’t have to be swinging a sledgehammer to get one. A worker may be able to process invoices safely at three an hour, and might be able to ultimately increase his or her time to say, six an hour, without noticing any immediate discomfort. But after doing six invoices an hour, 5 days a week, 8 hours a day for a month, he or she may begin to show symptoms of a repetitive strain injury.
There are other exposure risks as well. Let’s say a doctor sees 4 patients an hour. Each time a sick person comes in for treatment (assuming it is a contagious disease and not a chronic complaint or injury) the doctor risks getting ill. If the doctor increases the number of patients (and in turn decreases his or her takt time) he or she increases the likelihood of contracting an illness. You can carry this example to working with asbestos or a radioactive activity. The more times you are exposed to a hazard the more likely it is that you will be harmed by it.
What this means in practical terms is that when we calculate probability we need to remember that: a) we are calculating not the chances that someone will interact with a hazard, but also the likelihood that that interaction will cause harm and b) both the number of times a worker interacts with a hazard and the duration of the hazard are important things to think about when considering probability.
The safety professional must be involved in these efforts to improve workplace efficiency not just to add value, although that is important, but also to ensure that the improvement effort doesn’t just trade one set of wastes for another, in this case, injuries.