Looking Beyond PID Tuning Parameters for Control Performance Issues

Emerson's Mark Coughran

When a variability problem emerges in a production process, the first suspect is often to look at the tuning of PID [proportional-integral-derivative] loops. While adjustments can be easily made in most automation systems, this is often not the source of the problem.

ISA Intech: Know when to look outside the PID tuningIn an ISA Intech article, Know when to look outside the PID tuning, Emerson’s Mark Coughran provides 10 actual examples from his and his fellow Control Performance Consultants' experiences where the problems were outside the loop tuning parameters.

Mark opens noting that PID loop tuning skills are important and a good starting spot:

However, a proper loop tuning exercise—including measuring the process dynamics—should be the first step when approaching most loop performance problems. Many loop problems can be solved readily by tuning, and testing for the process response often reveals loop behavior that can help locate problems outside the controller.

The ten real-world examples Mark cites include: control valve response, valve positioner assembly, transmitter failure, signal communication, extra filter in logic, low cutoff in logic, master loop parameters for cascade, lessons learned.

I’ll share one example and invite you to read the article for the others. Continue Reading

Best Practices for Solving Crude and Fuel Blending Challenges Webinar

It used to be that refineries had a fairly constant and predictable supply of crude with similar properties coming in. Blending on the front end with the crudes and on the back end with the fuels produced were optimized for the crude oil properties.

As new supplies from shale oil production have come along with their attractive pricing, the properties of the crude are more variable. This variability poses challenges in both crude oil blending and fuel blending operations. And stricter clean fuel regulations add to the challenges refiners face.

Emerson's Julie Valentine

Emerson's Arnie Josefson

Emerson’s Julie Valentine and Arnie Josefson will be conducting a live webinar, Best Practices for Solving Crude and Fuel Blending Challenges, on September 19 at 1pm EDT.

They will share how certain blending methods and technologies are now no longer optimal for blending these new opportunity crudes or meeting these tighter fuel product specifications. Julie and Arnie will highlight best practices for minimizing these new blending challenges and optimizing performance at both ends of the refinery.

Beyond varying feedstocks, refiners face new product specifications for the grades they blend, seek to reduce giveaway and improve tank utilization, and work to mitigate the possibility of corrosion and fouling caused by asphaltene precipitation and higher total acid number (TAN) from the blended crudes. Continue Reading

Selecting the Right DP Level Device for the Temperature Conditions

With the season in change from summer to autumn here in the northern hemisphere, let’s look at differential pressure (DP) level measurement performance at various temperature ranges and particularly at cold weather performance.

This quick 2:35 YouTube video, DP Level Solutions Optimized for Cold Climates: Improved Response Time, highlights the importance of selecting the right technology and fill fluids depending on the temperature range of the application.

Traditionally for cold climate DP level applications, heat tracing has been required on the capillaries running from the process to the DP transmitter. Not only does this add expense, it adds complexity and expense to install and maintain. Without this heat tracing, the measurement response time can slow considerably or stops completely. Continue Reading

Gaining Experience in the Refining and Petrochemical Industries

The work is ongoing along the Texas & Louisiana gulf coast to come back from the massive flooding from Hurricane Harvey. A MarketWatch article notes that more that 20% of the total U.S. refining capacity was shut down and only slowly now coming back online. And an RBN Energy post highlights the impact on the natural gas liquids (NGL) and petrochemical manufacturers in this region.

As a key supplier to these industries, Emerson and its local business partners in the affected areas have taken significant steps to help in the recovery efforts.

One of the many challenges is that it has been many years since a hurricane has hit the Texas and Louisiana coast. Many of the experienced engineers, operators and maintenance technicians have retired with less experienced personnel now in place to restart these large, complex facilities.

The picture in this tweet from the American Fuel & Petrochemical Manufacturers captures the time and complexity in bringing a refinery back online:

Emerson's Doug White

While large teams come together to do the intensive work to restart these facilities, experience will be gained to help these facilities to operate more efficiently and to better perform restarts in the event of another planned or unplanned shutdown.

I also wanted to mention some training modules available for those new to automation and control in these industries. Emerson’s Doug White shares his vast refining experience in these recorded, on demand educational modules.

You can watch the first module, An Introduction to Refining, for no charge. Continue Reading

Monitoring Pressure Relief Devices

Effectively managing pressure in hydrocarbon-based production processes is critical from a safety, environmental and efficiency standpoint. Pressure relief devices (PRDs) are found throughout the production processing equipment.

Emerson's Marcio Donnangelo

Emerson's Marcos Peluso

At last spring’s 115th American Fuel & Petrochemical Manufacturers (AFPM) Annual Meeting in San Antonio, Texas, Emerson’s Marcio Donnangelo and Marcos Peluso wrote an article, Comply with environmental regulations and detect PRD malfunctions, for the AFPM Conference Daily.

AFPM Conference DailyThey opened noting the increasingly stringent emissions regulations that refiners and petrochemical manufacturers face and the requirements to monitor for fugitive emissions. They define PRDs as including:

…pressure relief valves, pressure safety valves or rupture disks. They activate when pressure approaches the maximum allowable working pressure of the vessel or process component.

While in many cases the gas or liquid is released to a recovery system:

…some PRDs release process fluid directly into the environment, potentially creating explosive and toxic emergencies.

Pressure releases indicate an abnormal process situation, so: Continue Reading