Many systems are designed utilizing centrifugal pumps to move fluid through the system. Currently there is an effort to minimize operational costs by upgrading constant speed pumps with Variable Frequency Drives (VFDs) or providing an initial design using VFDs. Process Engineers and Control Engineers need to understand the proper application, operational requirements and constraints associated Read more…

Feed Forward Curve Fitting Using a Process Dataset 1. Curve Fitting to a Dataset: As a complement to my last whitepaper, Modeling And Scaling Feedforwards, I have written this paper to discuss one of the approaches toward creating feedforward models. Many times it is not possible or practical to develop a mathematical relationship between the Read more…

Modeling and Scaling Feedforwards Depending on the complexity and precision requirements of the process, the resulting control arrangement can range from simple “Process Value > Controller > Manipulated Variable control” to a feedforward or cascade control. In this paper I will discuss the considerations when to utilize feedforwards, cascades and the scaling associated with these control additions. Read more…

Density Compensation of Differential Pressure FlowMeters By Wayne Salo The most elegant programming or control configuration is wasted if the fundamentalphysics, chemistry or mechanics is not understood. If you cannot measure it properly,you cannot control it properly. (Garbage In, Garbage Out – GIGO) The control engineeror technician must understand the fundamentals of these most used Read more…

Power Plant Control Systems By Wayne Salo Over the past 40+ years I have been involved with the design, specification, installation, maintenance and tuning of boiler/turbine combustion control systems and plant auxiliary systems. Over the years I have observed that companies have not been hiring or replacing control engineers in a timely fashion to provide Read more…

Wayne Salo joined Excel Engineering in 2012 with over 41 years in the power industry. These include over 6 years with Combustion Engineering Inc. in Windsor, CT as a field service engineer providing checkout and start-up of boilers, fuel firing equipment, scrubbers and associated fuel interlocks and controls. Wayne was hired by Northern States Power Read more…

Definitions There are several common terms that we use in our normal conversation but do not necessarily know what they actually mean. These are Dry Bulb Temperature, Wet Bulb Temperature, Relative Humidity, Dew Point Temperature and Adiabatic Saturation Temperature. Several discussions in the recent past have caused me to explain to others what many of Read more…

Creating a control arrangement with constraints As we noted previously it is important to have a good measurement of the air flow through the system. We need to be able to accommodate the design criteria and respect the system limits. We will need to compensate for the inlet temperature but will not actively compensate for Read more…

Accommodating Process Dynamics Depending on the material being ground or pulverized, maintaining the through-flow of the ground product to its destination is important. Depending on the particular process, it may be of benefit to either maintain a constant flow of the product through the transport lines or you may need to dynamically change the amount Read more…

Analysis of the flow measurement As we noted in the Phase 1 of this series we need to maintain at least minimum air flows throughout the piping and grinding process to prevent dropout of particles in the transport piping or within the grinder/pulverizer. We must check the sensitivity of the measurement. Typically the flow measurement Read more…