In the mid-18th century, there was a common theory from sailors that dolphins are a mariner’s best friend. It had come from stories of those who had fallen overboard close to shore—they felt dolphins saved their lives by pushing them towards shore when they had no clue what direction to swim. Sailors thought these creatures of the sea were looking out for them.
Today this story is often used in discussions about the quality of scientific data by illustrating cherry-picking of data clusters. In this case, only people who survived falling overboard are “submitting the data.” If someone fell overboard and the dolphin pushed that person out to sea, he would not live to tell the story and the data would be excluded. Perhaps it is only a coincidence they were being pushed to shore, and that these ocean-loving mammals actually hate humans! Examining only the good data and excluding the bad happens all the time—including with flange sealing maintenance practices where results only include half the data.
FACTS, NOT FALLACIES
In today’s data-driven world it is important we look at maintenance training that is based on facts, not fallacies. Many plants do not have specific training based on good bolting practices that could increase overall plant performance and safety by reducing leaks. It is critically important to review a plant’s training program to ensure it is examining more than partial data when analyzing its effectiveness. One of the ways to do accomplish this is to view training as a continuous improvement process.
To enhance a flange sealing training program, use good sources for technical information. Consider the Fluid Sealing Association (FSA), founded in 1933, which is an international trade association. Member companies are involved in the production and marketing of a wide range of fluid sealing devices primarily targeted to the industrial market and are a trusted technical resource to industry.
The FSA, for example, reviewed a hundred gasket failures and after doing a root cause analysis realized that 68% of the failures were due to under-compression of the gasket. In that same study, 15% failed because the wrong product was used in the wrong application. With these facts in hand, it seems important that bolt tightening skills be included in any part of a good maintenance training program. However, as seen in the field, bolt loading training is not taken as seriously as it should be. For example, not having a plant standard anti-seize, used by all employees and contractors, so all torque calculations can be used with the same Coefficient of Friction (K Factor). Many times, journeymen at a plant are using “torque tables” to get the torque for a bolted connection. In small print at the bottom of these tables, it states the K factor they were designed around—but they have not been updated based on the K factor of the anti-seize being used in the plant.
It’s also important to review the condition of the bolting in a bolted connection. The lack of under-compression results from poor transmission of load. This can be seen from not realizing the bolt condition is one of the most important factors in bolting. Torque is not tension. This is a mantra that comes to mind during any tightening process. Too often people will interchange the words—thinking they mean the same—but they do not. Torque is the force applied to the bolt that in perfect conditions will result in a certain amount of stretch (tension) on the bolt. The relationship also must deal with other factors including bolt condition, coefficient of friction, and torque wrench accuracy, just to name a few.
A real-life example of the other issue regarding incorrect materials happened a few years ago. At 4:15 pm, Sunday, Nov. 25, 2018 (Thanksgiving Weekend), ethylene oxide (EO) was accidentally released into the air from an EO plant in Delaware. The Delaware Memorial Bridge was closed for five hours as a precautionary measure because of the potentially hazardous nature of EO, which is flammable and toxic. No injuries to plant personnel, responders, or nearby residents were reported but shutting down one of the most traveled roads in America during one of the most traveled days of the year inconvenienced thousands. Investigations by the company and the state determined the release was caused by a failed flange gasket on the water reboiler piping servicing the purification column. The gasket used was of a material not suitable for the operation. This is another example of how critical gasket selections are in hazardous service.