The capabilities where Collaborative Controls engineers can assist during startup are extensive, although we only assist in direct operations when developing or adjusting control schemes. The services normally provided prior to and during unit startups are:
Field Instrument installation evaluations
This normally involves a unit walk-through to punch listing all installations which may cause errors in measurement accuracy. Improper flow transmitter or flow element mountings can cause zero offsets, which can prevent safety trips, or cause inaccurate readings. Too often flow transmitters are installed for ease of maintenance compromising instrument accuracy. Analyzer installations are evaluated. Improper valve or positioner mountings create mechanical stress and maintenance problems
All operating graphics, including unit overviews, and graphics navigation hierarchy, are evaluated. Depending upon the project scope the graphics may be redesigned and rebuilt for clarity of operations. The goal is to facilitate the operation with consistent and logical workflows,
Pretuning of PID controllers
Default tuning (from the DCS system) will almost never function to control a process. Initial tuning of PID controllers involves reviewing the control schemes, determining the goal of each scheme, estimating the settling time (from experience, equipment size, trays, etc.) and then setting the gain, integral time, and derivative time. Pretuning the controllers enables a smooth startup and acclimates the operators to using automatic controls.
The full scope of process startup assistance depends upon the unit size and the needs of the site’s control staff. It may involve a few hours of targeted assistance, a few weeks of on-site consulting, or months of assistance prior to and during the unit startup.
