Recent news reports have alleged that operators at the generic drug manufacturer Mylan Labs in Morgantown, West Virginia had been regularly bypassing “Red Screen” alarms, designed to indicate when tablets or capsules might fail to meet hardness, thickness or weight requirements, and, thus, fail to deliver the correct dose of medication to patients.
Whether or not these specific allegations prove to be true, they point out serious manufacturing issues that can, and often do, exist in any manufacturing plant in any industry.
Sadly, most of the discussion surrounding such scenarios fails to address root causes and effective action. Companies generally respond with management changes (which have reportedly already begun at Mylan). Management blames workers, workers blame the production equipment, and the production equipment designers insist that their product is sound. New “band-aid” policies and procedures are then typically implemented that may only cover serious wounds.
This article will briefly examine why problems like this occur, and what actions should be taken to make meaningful changes while preventing future repetitions of the same mistakes.
First, let’s consider the reasons why production workers may ignore alarms:
- The alarms do not provide adequate warning.
- Workers are distracted.
- Operators are subject to so many alarms that they can’t prioritize actions.
- The required action is ambiguous or improperly understood. Intentionally circumventing Red Screens or warnings that stop production, however, is a far more serious problem than unintentionally ignoring warnings.
Except for sabotage and revenge, workers will intentionally ignore or circumvent warnings when:
- They know or believe that the sensors generating the warnings are faulty.
- They believe that warnings are not important, and that the product is still fit for the intended purpose.
- They are rewarded for ignoring the alarm.
Since each of these can and should be prevented in the design of the production equipment, some elaboration is helpful.
Sensor accuracy and precision can degrade as the sensor ages, and sensors can fail. When most Red Screen warnings are traced to faulty sensors, workers are trained to believe that warnings are useless. Because of the critical nature of “Red Screen” warnings, it is unacceptable to allow faulty gauges to generate these warnings.
There are several ways to prevent this problem. The first is preventative maintenance, in which the life of each sensor has been characterized or its performance tracked, and the sensors are replaced long before they generate faulty readings.
Where preventative maintenance is not adequate, redundant gauges should be used with voting, as NASA does in its space missions. Where only two sensors are used, it is often impossible to tell which sensor is faulty, since voting schemes often require at least three gauges. Where two sensors are used and one indicates an out-of-tolerance condition, the first warning and actions should be to replace one or both sensors rather than a Red Screen. Ideally, equipment should be designed so that sensors can be safely and reliably changed while the equipment is operating.
A third strategy is to select and use sensors, sensor configurations, and circuitry that enable active sensor monitoring that detects faulty sensor conditions such as a ground fault, or circuit break or changes in sensor performance. Naturally, all of these strategies can be combined, where needed.
Overuse of Alarms
Invalid warnings are worse than no warning at all. Consider the case where the response time of the sensor is longer than the available measurement time. Even if perfectly calibrated, these sensors may produce out-of-tolerance warnings, even when careful measurement of the product, after the fact, shows that all of it is within specification. The product may be perfectly fit for use, despite the “Red Screen” warning.
How production performance is monitored turns out to be extremely critical, and simple changes can provide more effective control solutions without requiring frequent or immediate shut down of the process. Consider the case where one cavity in a frame or wheel is not being properly filled and the weight of pills formed in this cavity is only 60% of target weight. If 100 pills are weighed at a time to check conformance, this defect may never be detected, yet it is a far more serious problem than the case where all pills are 0.4% under the nominal target weight.
On the other hand, if the entire process is shut down every time there is problem with a single cavity, the line will be down regularly.
Instead of generating a “Red Screen” alarm for out-of-tolerance conditions, it is far better to detect and remove each defective item without shutting down the line, unless the defect fraction becomes excessive. For example, passing pills or capsules over an air stream may separate over- and underweight parts from acceptable product without requiring an interruption of production.
Lessons From Potato Chip Makers
Food processors and, notably, potato chip makers often weigh or sense features on each individual item, and then remove each defective item individually. For example, a jet of air combined with sensors can remove every overcooked or blemished potato chip without a warning or stopping the line where hundreds of millions of chips are produced every day.
Potentially the worst quality violation is creating an environment that rewards workers for bypassing warnings, thus contradicting policies and procedures. Workers, supervisors, and managers who are paid for meeting production goals will bypass warnings if they believe that these are not causing any real harm because they are being personally penalized for stopping and fixing quality problems.