The information needed to successfully select and install instruments is spread out in articles, books, handbooks, papers, and vendor catalogs and in knowledgeable individuals who do not have the time or incentive to publish. Articles and papers tend to focus on success stories, with few details. The articles are designed more to sell than to [...]
In the 1970s, there was a concerted effort at the chemical company I worked for to provide extra process measurement connections throughout the plants for pressure and temperature measurement. These connections could be used as needed to help identify and solve unforeseen problems. The installation of a wired transmitter on a temporary basis was not [...]
When I am in an instrument and valve repair shop, I see many more control valves than instruments, particularly with the advances in sensor technology, transmitter intelligence, and asset management systems. Valves are mechanical devices and as such require more maintenance. Packings, seals, seats, and O-rings wear out. To ease maintenance, a control valve must [...]
I became sensitized to the importance of measurement location when I found the easiest way to keep a pH electrode from fouling was to install it in a pipe with a flow velocity of 5 to 7 fps, preventing the usual 100X deterioration in the speed of response that resulted from just a few millimeters [...]
When we did process control improvements in the 1980s and 1990s, the major limitation was the lack of a reliable field analyzer. None of the plants had field analyzers on raw materials. The specialty chemicals production units had very few field analyzers and were flying blind. Plants for chemical intermediate products had field analyzers on [...]
I never have quite understood why every raw material, utility, vent, reactant, recycle, and reagent flow rate and total is not ratioed to the product flow rate and total for each unit operation. The operator screens should display flow ratios (e.g., kg/kg or lb/lb), cost ratios (e.g., Euros/kg or $/lb), production rate ratios (e.g., kg/hr [...]
During my career, modeling has been an essential part of developing a better understanding of opportunities and a better control system. I have built simulations in IBM’s Continuous Simulation Modeling Program (CSMP), Raytheon’s Advanced Continuous Simulation Language (ACSL), Microsoft’s Visual Basic, Hyprotech’s HYSYS, Emerson’s DeltaV, and MYNAH Technologies’ MiMiC. most cases I focused on the [...]
The classic case for process control improvement uses a figure that shows the mean and standard deviation of a statistical distribution and the optimum of a process variable (PV). The optimum is often taken as the constraint on product quality. The case is made that if PV variability is reduced, the setpoint for the PV [...]
In the 1980s and 1990s, coriolis meters were expensive and were primarily relegated to critical measurements of small liquid streams. The meters were susceptible to vibration and errors from bubbles or solids. Since then the price and capability have improved. Coriolis meters can now be used on gas streams and can measure the percent bubbles [...]
Every instrument is well suited for some applications and perfectly awful for others. These next few tips discuss the more common types of flowmeters and provide an insight into how they work, when they should be used, and when they should be avoided. I will begin with a brief description of how each meter works, [...]
