November 2001

Bonus Report: Instrumentation

Using a single final control element to regulate two process variables

This analysis showed the loops would be stable

Needham, M. J., Technip Upstream

Fig. 1 is a diagram of the control loop that uses a centrifugal pump to both hydraulic decouple inflow surges into the surge tank and also decrease inflow to the free water heated knockout (FWO) as the oil/water interface level increases. When our client proposed this loop, we were concerned. Based on the different mathematical input/output (transforms) relationships (Figs. 2 and 3) between the two-level processes, there could be loop instability in trying to calculate a reasonable setpoint for the bypass flow loop. While the surge tank's large volume capacity added to stability of the loop, the small heated vessel had a small capacity and high throughput. Theoretical Laplace trans

Log in to view this article.

Not Yet A Subscriber? Here are Your Options.

1) Start a FREE TRIAL SUBSCRIPTION and gain access to all articles in the current issue of Hydrocarbon Processing magazine.

2) SUBSCRIBE to Hydrocarbon Processing magazine in print or digital format and gain ACCESS to the current issue as well as to 3 articles from the HP archives per month. $409 for an annual subscription*.

3) Start a FULL ACCESS PLAN SUBSCRIPTION and regain ACCESS to this article, the current issue, all past issues in the HP Archive, the HP Process Handbooks, HP Market Data, and more. $1,995 for an annual subscription.  For information about group rates or multi-year terms, contact J'Nette Davis-Nichols at or +1 713.520.4426*.

*Access will be granted the next business day.

Related Articles

From the Archive



{{ error }}
{{ comment.comment.Name }} • {{ comment.timeAgo }}
{{ comment.comment.Text }}