Ensuring safety in process design and operation
By Steve Blair
Ever since the Deepwater Horizon accident in 2010, safety and risk management has become the subject pushed to the forefront of every business operating in the oil and gas sector.
This increased safety emphasis occurs against a backdrop of technological innovation, which has resulted in the general de-manning of process plants and the requirement for engineers to have broad skill sets to cover a wider range of responsibilities. As a consequence, there is a growing requirement for instrument manufacturers to apply their knowledge and expertise to on-site safety and operational assessments.
A hazard and operability study (HAZOP) is a structured and systematic examination of a planned or existing process, conducted to identify and evaluate problems that may represent a risk to personnel or equipment or prevent efficient operation. This increased drive to review safety processes can be reduced to two fundamental questions: whether a process is safe; and how an operations team will know if a specific process is not operating correctly.
These two questions are generally translated into terms relevant to specific industry sectors and processes. In process gas analysis, for instance, this relates to whether a user can "trust" their measurement-and what will happen if anything goes wrong with a measurement process. While process plant operators are best placed to determine what happens at the macro level of plant operations, the safety requirements at the micro level for safe gas analysis are increasingly being devolved to process analyzer manufacturers.
Maintaining the example of process gas analysis, consider the case of a high-pressure toxic process being regulated to provide a low-pressure sample to an oxygen gas analyzer. If there is a catastrophic failure of the pressure regulator, the high pressure will be forced into the gas analyzer. Whether the analyzer contains the excess pressure or ruptures to release potentially lethal gas is a question for which only the analyzer manufacturer is likely to have specialist knowledge and experience. What is important to note is this is primarily a safety issue; whether the analyzer continues to function correctly after the accident is a secondary issue when compared to maintaining plant safety.
As a consequence, manufacturers across a wide spectrum of instrumentation and control are increasingly integrating the safety requirements of their customers into their products and long-term support. Manufacturers and suppliers are more aware of what the effects of failure will be on their systems, so they are now required to participate more closely in HAZOP studies.
Consider a recent example where excess flare gas was being routed to make power via gas turbines. The primary analysis requirement was for monitoring oxygen levels to ensure complete and efficient combustion, but there was a significant side effect of the process: the sample gas contained a variable level of hydrogen sulphide, sufficient to cause harm if released into the atmosphere.
The inclusion of the manufacturer in the HAZOP study quickly determined the production of high pressure in upset conditions would not affect the analyzer itself, but could force high pressure gas containing hydrogen sulphide back down the utilities unit used to supply air and nitrogen. Having identified this potential danger, a utilities unit designed to contain the pressure was supplied, and the threat effectively neutralized.
Anticipating possible dangers, rather than simply reacting to established threats, has also been key to the development of safety systems such as Safety Integral Level analysis.
The striving for the minimisation of "undetected failures" (i.e., unsafe plant conditions) has resulted in instrumentation, analyzers, and systems being fitted with sensors that provide as much diagnostic information as possible on a range of measurements, as well as the relative health of that measurement. With digital communications allowing more sophisticated data to be transmitted to a control room, information can be quickly analyzed remotely and appropriate steps taken.
The combination of improved remote diagnostics and the ability to involve proven process experts continues to make a wide range of industries increasingly efficient and more profitable. It is making plants and operations safer than ever. On that basis, a relationship that brings the expertise of the manufacturer closer to the needs of the user can only be encouraged.
ABOUT THE AUTHOR
Steve Blair joined Spectris in May 2011 as Business Group Director and has responsibility for the In-line Instrumentation and Industrial Controls business segments. Blair has significant experience in the industrial controls sector and, prior to joining Spectris, was at Invensys, where he held the position of President, Invensys Operations Management for North America.