Reducing vapour pressure giveaway

Challenge: A major petroleum company in North America needed to blend gasoline, gasoline components, and additives without exceeding vapour pressure limits set regionally by the US Environmental Protection Agency (EPA).

Grabner Instruments

Viewed : 1985

Article Summary

Non-compliance can lead to heavy financial penalties, so the ability to receive precise, accurate, and reliable vapour pressure results, just downstream of the blend header, is essential. Operators also must consider the ‘giveaway’ – the ‘delta’ between the vapour pressure of the finished product and the set vapour pressure limit. Just a couple of tenths of psi can equate to added costs of millions of dollars annually since producers could expand their product volume by blending less expensive components such as butane to increase the vapour pressure closer to the limit.

The refinery used non-Ametek analysers, which had reached their end of life and were no longer supported by the supplier. Moreover, the method used for certifying gasoline took approximately 15 minutes to complete.

Obtaining faster results closer to real-time would enable operators to adjust process controls in response to vapour pressure results, allowing ‘tighter’ blending. The refinery operators were looking for a robust, online vapour pressure analysis solution with the precision and accuracy demanded by the mandated vapour pressure methods but with faster results. Additionally, the new analyser had to be easy to maintain, with a rapid return on investment (ROI), low cost of ownership, and near-zero downtime.

Refinery operators considered several factors in developing a solution, preferably from a supplier that has provided vapour pressure analysers for decades. So, brand recognition became crucial because of the need to deliver precise, reliable results certified by a benchtop laboratory analyser. For this application, Grabner Instruments developed a ‘double’ version of its Vapour Pressure System Online (VPSOD), with two measuring cabinets fitted on a single frame (see Figure 1).

The measurements within each cabinet are triggered 50% out of phase with the other, which reduces the resulting interval from seven minutes to approximately 3.5 minutes. This analyser possesses best-in-class precision and a quick-change measuring cell that practically eliminates downtime (less than five minutes) in the event of failure.

The first installation was carried out at a plant in California. Eight VPSOD systems have since been installed across several midstream locations, with some having two units. Retrofit projects are ongoing, with additional plans to implement this successful vapour pressure monitoring solution at further critical sites.

With installation complete, all refineries with the new equipment are running successfully, resulting in more profitable and reliable gasoline-blending operations. The VPSOD system has led to operators being able to capture faster ROI, sometimes within just a couple of tank blends, and millions of dollars in annual revenue across their sites.

The double-cabinet design not only lowers the measuring interval but allows the customer to run different methods on up to six measurement channels for seasonal specifications (such as vapour lock in the summer), so they can satisfy more than one volatility specification with a single unit. In addition, the quick-change measuring cell has practically eliminated downtime, while the redundancy of having two measuring cabinets ensures continued uptime in case of a cabinet failure that cannot be resolved promptly.

A senior engineer with responsibility for several refineries said, “We are delighted with the results, which fully met our expectations. The Grabner Instruments team was friendly, knowledgeable, and professional and provided us with timely communication and support throughout the installation process.”

This short case study originally appeared in PTQ's Technology In Action Feature - Q2 2023 Issue.

For more information: Angel.Schell@ametek.com

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