The human factor

The operator’s confusion over which button to push was a classic example of human machine interface (HMI) issues, one of the principle focuses of human factors engineering (HFE). ‘HFE is a multi disciplinary science that integrates the human operator into a mechanical system’, said Hollaway, the Human Factors Engineering Manager for ABS Consulting, Inc., a Houston based firm.

When a petrochemical plant or refinery is being built or modified, design engineers ensure that the facility operates as efficiently as possible. HF Engineers, on the other hand, are plant safety experts who determine potential HMI danger spots.

The origins of HFE date back almost a century, to the early 1920s. At the time, biplanes began carrying mail around the country. In the space of five years, over 100 pilots were killed. Cognitive scientists were brought in to investigate the situation, and they learned that pilots would fly into bad weather and not know which way was up. They would suffer gravitational illusions and think they were flying level, when they were not. Plane manufacturers began to put gauges into the planes so they would know altitude, direction and orientation. This resulted in improved safety which exists today; the same basic HFE concepts integrated into a plane in 1930 still exists in a Boeing 737.

Currently, there are approximately 10 000 HF engineers worldwide. Most of them are usability engineers; they work with software firms, for instance, to see how a client would burrow down through their software applications.

In addition to HMI, HF engineers examine ways in which human physical and mental limitations affect operations, staff levels of training, and conduct of operations (COO), i.e., the way that a company runs its processes. ‘Our members believe that safety is everyone’s responsibility throughout the entire organisation and therefore topics that help promote safe operation like conduct of operations, operational discipline, human factors and human reliability are discussed at a variety of committee meetings, workshops, and conferences’, said Lara Swett, the American Fuel & Petrochemicals Manufacturers (AFPM) Director of Health and Safety Programs. ‘A COO program, for instance, reduces operational risk, helps promote a strong safety culture, and ensures that all employees perform their duties safely and consistently. The result is an organisation that has safety as a core value, less incidents occurring, improved safety performance, and most importantly every employee and contractor going home safely every day’.

 Ideally, HFE is incorporated right from the beginning of a project, when it is relatively inexpensive to classify and verify safety and optimise operations and maintenance. Hollaway was recently consulting on a project where an operator had three associated valves that were set into an offshore processing facility; a 5000 psi, a 7500 psi and a 10 000 psi. ‘If you were to open the 5000, then the 10 000, there would be no problem, but if you opened the 10 000 first, there would be a serious problem. I noticed this in the design stage and recommended they interlock them so that the 10 000 could not be operated incorrectly’.

Usually, however, HF engineers are called in during the construction phase, when the plant is already taking shape. They look at a number of basic factors to ensure safety. The location of emergency buttons is a priority. ‘Manual alarm call (MAC) is a button that sets off a loud warning sound that alerts everyone to evacuate an area when there is danger’, said Hollaway. ‘We were investigating a situation where a human error possibly led to an explosion. Prior to the explosion, the control room operator heard a rumbling and knew there was going to be an explosion, but he did not hit the emergency stop button before he ran away. When asked, he said that the MAC was not on the way out, it was in the direction of the hazardous event’.

In an emergency situation, the MAC should be located near an exit, noted Hollaway. ‘Even then, the location of the MAC is very important, because when people are caught in an emergency, their spatial perception contracts to the point where it seems they are looking through a toilet roll, they only see what is immediately in front of them’.

The design of worker access, such as scaffolding and ladders, can make significant difference in safety. ‘There are a lot of injuries due to the force of gravity’, said Hollaway. ‘You may think that it is easy to lift a 20 lb object, but not if it is 4 ft beyond the access point. For every worker killed, there are far more injured. There were 127 fatalities in the offshore Gulf of Mexico from 2003 - 2010 (Bureau of Labor Statistics), but there were 1400 career ending injuries’.

HF engineers analyse emergency escape and rescue, an issue that first gained prominence after the 1988 Piper Alpha tragedy (in which a North Sea platform caught fire and exploded, killing 167 workers). ‘Whenever you are dealing with hydrocarbons, there is always the possibility of a fire or explosion’, said Hollaway. ‘If it happens on an offshore platform, are there enough lifeboats for all the crew? Is there more than one way to reach them if access is cut off in a certain direction? Are there pathways that lead to a blind trap instead of an emergency exit?’

Proper alarm management strategy is key when an emergency arises. Accident investigators have delineated it as a factor in numerous tragedies, including the Three Mile Island nuclear meltdown and the Air France crash in the Atlantic Ocean near Brazil. The problem becomes acute when a score of alarms go off simultaneously and the operators have no idea where to start in terms of dealing with them. Studies show that people generally react in two ways; the first is that they freeze due to cognitive overload. The second is that they react to the alarm that is easiest to address, instead of the most critical. One solution is to design an alarm system so that the problems are identified in descending order of criticality.

Problems

While HFs are typically incorporated into elements of a plant design through applicable codes and standards, a broad look at the HF issues associated with the entire plant layout is often overlooked.  Whether due to time, cost or resource constraints, companies often fail to reap the benefits of this broader HFE examination.

Yet, according to Hollaway, the sector can fix the problem through relatively simple, inexpensive human factor measures that pay for themselves. ‘Through a human factors analysis, for instance, you might reduce the time it takes to do a task. If it used to take three workers 10 hours to change out a valve, and you show them how to do it with three people in 5 hours, you have just made a 50% savings. It is the same with safety training, only the returns are much greater’.

 Written by Gordon Cope.

Adapted for the web by Emma McAleavey.

The full article can be viewed in the December issue of Hydrocarbon Engineering.