The following discussion is part of an occasional series showcasing the ISA Mentor Program, authored by Greg McMillan, industry consultant, author of numerous process control books, 2010 ISA Life Achievement Award recipient, and retired Senior Fellow from Solutia, Inc. (now Eastman Chemical). Greg will be posting questions and responses from the ISA Mentor Program, with contributions from program participants.
Mike Laspisa has spent 37-plus years working in the instrumentation and control (I&C) discipline, including 32 years as a lead I&C engineer or manufacturing plant staff I&C engineer. Mike’s primary motivation is to advance the automation profession by sharing knowledge gained from plant experience as seen in the Control Talk columns, “Instrument specification: Where we are and where we should be,” “I&C Construction scope,” and “Instrument Index Insights.”
Instrumentation specification expertise is somewhat of a lost art and vendors can only quote what is on the submitted device ISA datasheet with no direct access to process data or P&IDs. They cannot see the device application specifics or intended installation .... it makes me wonder if instruments and control device installations have suffered. The specification phase usually includes the thought process of the installation requirements that are part of device selection. This would cover everything from d/p cell transmitter impulse lines, filling tees, condensate pots, above/below process tap mounting, device upstream/downstream requirements, full pipe requirements for flow up and/or back pressure methods, pH probe insertion and full pipe requirements, magnetic flowmeter grounding straps/rings (in lieu of ground electrode), materials of construction compatibility, etc. Has anyone noticed an increase in installation related issues over the last 10 years related to either device selection or improper installation?
I have definitely seen things go downhill, even at large engineering companies. They are tossing the instrument specifications to vendors so there are no knowledgeable staff engineers shepherding the installation. The number of mechanical and electrical installation errors on the For Construction packages are significant. Unfortunately, many clients lack any kind of internal automation staff, so I am often hired to serve the role of client instrument engineer and review the packages for them. I can only imagine what a mess the startup would have been had the mistakes gone unnoticed.
For years operating companies have adopted a strategy of relying on outside help to provide technical support. While vendors and EPC companies have many and varied skills in product and process design, project execution and management, they typically do not have the knowledge that experienced and skilled in-house technical support have, regarding the operating environment, operating practices, reliability requirements and maintenance practices, that might, and usually do, dictate design requirements. This can, and often does, result in remedies being required at site under adverse conditions, that add to direct cost, cost due to delayed start-up, and risk.
Interesting topic. We see more and more contracts to engineering firms or experts to review their installations, and not only for new projects. Often, just walking on the plant floor is sufficient to view flowmeters installed between 2 elbows, a thermowell not installed properly, or a positioner inserted between pipes where it is not accessible for maintenance.
Lack of engineers? Lack of knowledge? Low cost engineering? Lack of instrument technicians? Increase in complexity? An amalgam of all of those.
In my early years as an instrument and electrical design and construction engineer, I helped a very seasoned engineer develop instrument installation details that became a Standard for Monsanto Projects. While my involvement was only a few months, the standardization effort persisted for almost an entire decade. I wish I had kept a copy of all the instrument installation details developed.
I have a vintage copy of API RP550 Second Edition 1965 Manual on Installation of Refinery Instruments, and a 3-part short course on “Thermowell Design for Process Piping” (Part 1: Procedures for Piping Designs; Part 2: Installation and Specifications; and Part 3: Selection of Thermowell Insertion Lengths) published in Hydrocarbon Processing in February 1964.
I expect there are much more recent and comprehensive sources of instrument installation details. The ISA book Control System Documentation has a Chapter 10 – Installation Details. The Control Talk columns, “Prevent pressure transmitter problems” and “Your DP problems could be a result of improper use of purges, fills, capillaries and seals” alert users to key installation considerations.
Control valve selection, sizing, and pressure drop allocation are persistent troubling problems. The Control Talk Column “Responsible Valve Response” with the Annex A proposal link for the ISA 75.25.02 Technical Report on Valve Response provides insights as to the sources of the problems, including examples of fixes and specifications to help guide the practitioner. The emphasis of low cost, tight shutoff, and future capacity has lead to many poor choices as to control valves. Some of the consequences may be reduced by tuning, signal characterization, special algorithms, and smarter positioners, but many have a remaining serious detrimental effect.
Device Selection issues might be less of a problem now due to the increased rangeability of digital electronics, improved sensors, low conductivity devices, and the expansion of measuring method technologies. We used to have to specify limited capsule ranges and even scales on analog indicators/controllers. Also, digital positioners and advanced control strategies can overcome some control valve limitations.
Two issues stand out to me:
Correct device selection and sizing which includes understanding the application, reviewing, and validating the process data, and determining if the device is located properly in the process pipe or vessel.
Providing the Piping designers with information for insertion device fitting make-ups, flange sizes/ratings, flowmeter upstream/downstream diameters and orientation requirements, and vessel connection sizes and orientations. Face-to-face device dimensions may also be required for piping isometrics, especially on large bore off-site fabrications.
I hope that it might at least influence a young engineer to look into some of these issues when specifying devices and executing installation details and vessel connection reviews.