Final Control Element

I don't want to admit how long I've know Emerson's Kurtis Jensen, but it does goes back to the pre-Emerson days at Fisher Controls. Kurtis is an instrument product manager for the Fisher Valve and Valve Automation businesses. He's penned a great article for Valve magazine, A Bright Future for Wireless Technology. He encapsulates his thoughts:

Industry has a watchdog that can save costs, provide reliability and allow more confidence that our valves are in good health and operating at peak capacity. The technology can also work toward a safer work environment and provide more information for improving processes.

The watchdog of course is wireless. Just as how it has become indispensible in our homes and given us the freedom to connect from anywhere, Kurtis describes its benefits to process manufacturers. It eliminates:

...the time and effort it takes for manual audits; the amount of occasions in which someone is sent into undesirable conditions; and product variances, which when reduced can improve product quality.

In most processes, manual valves can be found in many places. One example is their use in maintenance cleanout activities. Adding wireless valve position feedback can:

...improve process reliability: it protects product quality, it protects against scrap or rework, and it protects against clean-up actions. The end result is a more reliable process and greater confidence that all is well.

Without this valve position feedback, more operational resources are required to follow standard operating procedures to verify that the valves are in their correct open or closed position.

Kurtis reminds the reader why manual valves are automated:

First, moving the valve may require too much manual effort. Second, it may be desirable to eliminate having personnel in dangerous conditions such as precarious heights or hazardous environments. Third, it might be necessary to reduce complexity and time needed to coordinate valve adjustments during plant operations.

For the on-off variety of automated valves, many today are driven from the automation system by a solenoid. The command is issued but there is no feedback from the valve that it went from open to close or close to open. Traditionally, this feedback required two sets of wiring on the valve positioner side and two discrete input (DIN) channels on the automation system side. This may not be a big issue if spare pairs of wire are available and spare DIN channels are available. Usually though, if it's not a big issue and knowing its state is important, the valve position feedback is already present. Kurtis notes:

Knowing more about a valves' health enables better decisions and faster maintenance. It is just as simple and easy to achieve significant improvements on these old valves as with new projects. Facilities that implement wireless feedback have the competitive advantages of operating cost reductions, improved product quality, increased production volumes and increased levels of safety.

Beyond more feasible valve monitoring, Kurtis closes with a thought from the automation system control strategy perspective:

Designers of control strategies will take advantage of wireless valves to enable greater control as well as greater process and equipment health awareness, all of which results in greater confidence in operations and processes.

Kurtis summed up his thoughts on wireless even beyond valves to me in an email, "If it moves you can monitor it!" If you have manual valves or others without position feedback that has caused operational or safety-related issues, this might be an article worth your time to read.

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Last week, I shared how resonance can contribute to excessive machine vibration in the post, Spotting and Fixing Resonance in Plant Equipment. A colleague pointed me toward another true Emerson Expert, Dr. Allen Fagerlund. Al's expertise is on noise measurement and prediction. He also serves on the ISA75, Control Valve Standards and its subcommittee, ISA75.07, Control Valve Noise Measurement and Prediction.

I came across a paper that he and colleagues had written a few years ago, Identification and Prediction of Piping System Noise. It describes how various components in a plant's piping system can be sources of noise. The piping system forms a network through the facility, with sound waves radiating through this network. The authors describe this noise:

In an ideal sense, noise generated by any component or source will propagate in the fluid and cause the pipe wall to vibrate, with subsequent radiation from the outer surface to an observation point. In reality there also can be a direct structureborne path from the source to the pipe which adds to both the vibration level and to the radiated noise.

For flowing, incompressible liquids:

Generally liquid noise is not a problem unless cavitation [formation of vapor bubbles] occurs somewhere in a system. Since the noise from cavitation is an indicator of potential damage to piping and equipment, it has been more important to develop guidelines to prevent cavitation than to develop methods to predict the level of the noise.

I know from my days on offshore platforms that high-pressure natural gas piping was a large source of noise. Compressible fluid flows are potential sources of noise across a broad frequency range. The authors note that structural resonance is typically checked in the system design phase, but acoustic resonance may not be. The fix:

...is either to eliminate or change the frequency of the source tone or to decouple the resonance, whichever is most efficient and/or effective. Broadband noise can also excite system resonances which makes decoupling more difficult. Reducing the source noise levels are the main option.

Sources of noise include turbulent flow of compressible fluids, changes in pipe diameter, termination of piping at a manifold or vessel, and noise induced by equipment such as, "Compressors, valves, orifices, area expansions, spargers, etc..."

Some automation suppliers provide noise prediction for their equipment. Al is part of the Fisher Valve division, which has a noise prediction section in the Control Valve Handbook. Unfortunately, other piping components don't have methods to predict noise levels. The authors reference the work, VDI 3733:

...a compendium of information on the noise generated by piping systems. The influence of piping components as well as piping configurations are examined and presented in a quick calculation style without having to work through a detailed explanation of the phenomenon involved. Its broad subject coverage makes it a unique reference.

The problem with broadband sources of noise is that their frequency range can include resonant frequencies of the piping. Noise at these resonant frequencies can cause acoustic fatigue, which is structural fatigue of the pipe wall from high-amplitude vibration. The authors point out:

Acoustic fatigue is generally not a concern for external noise levels below 110dB for unlagged piping (acoustically insulating the pipe to reduce noise levels below 110dB will not reduce the fatigue risk since the pipe is still vibrating with the same amplitude).

Al is applying his expertise in the new Marshalltown flow lab, where the team has built an extensive noise-abatement testing lab to continue to advance the science of ways to reduce acoustical noise in plants.

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Update:I received an email that the link to the article was not working. It is working for me. Here's an alternative link to the article to a Google Docs version that worked for the person who emailed me. If you have troubles with the original link, let me know if this alternative link also does not work.

Handheld field communicators have been the tool of maintenance technicians to configure and calibrate their smart field devices since the 1980s. With technology advancements and by taking a fresh look at handheld usability with a lens on the problems maintenance techs were trying to solve--the Emerson team developed a new application.

I caught wind of this application, ValveLink Mobile, which is included in the 475 and 375 Field Communicators with the v3.2 software and the Easy Upgrade utility. I went the source, Emerson's Ken Hall, for a download of what maintenance technicians might find useful in their day-to-day work. Ken is a software product-marketing manager for the Fisher FIELDVUE team.

For those unfamiliar with AMS ValveLink software, it allows maintenance and operations folks to monitor control valve health and performance online and spot problems before they affect the process. Ken pointed out the news of more than one million FIELDVUE digital valve controllers sold, so that's quite a number of valves to check on. Many are not connected on-line to an asset management software package such as AMS Device Manager or to a control system such as the DeltaV system. The way to communicate with these digital valve controllers is through the handheld device.

What maintenance techs were missing from these handheld devices was the ability to perform advanced diagnostics tests to see if the valve was sticking, sluggish, leaking, etc. These problems can impact the performance of the process, cause variability in what's being produced, or even lead to unplanned shutdowns. These tests could be done with ruggedized PCs rated for the valve's location with the AMS ValveLink software, but this approach was not ideal from a usability perspective. This is especially the case if the maintenance tech were on a ladder, catwalk, or other difficult position.

The ValveLink and AMS technologists worked to bring a subset of this functionality to the 375 and 475 handhelds, and even to Windows Mobile-based smart phones connected to the DVC6200 and DVC6000 controllers with a Bluetooth HART modem. The ValveLink Mobile software had to be accessible by a finger or thumb on the touch screen.

For the DVC6000 controller installed with the higher-level diagnostics, this application can perform tests such as valve signatures, dynamic error bands, and valve stroking. In fact, Ken noted that the tech can see the diagnostic graph built in real-time to spot where the problem might be occurring. When combined with the visual and audio feedback from being near the valve, this can help get to the root cause more quickly.

Ken also noted that the diagnostic tests performed on the handheld or smart phone can be downloaded back to the AMS Device Manager using Bluetooth, IrDA, or SD memory. Initially this application supports the HART-based DVC6200 and DVC6000 controllers and future versions will support Foundation fieldbus, the DVC2000 and DVC6000 SIS.

Here's a 3 ½-minute "silent-movie" video, which shows the diagnostics running on the handheld device and Windows Mobile smart phone.

Given the control valve's importance in the performance of the process, bringing these diagnostics into the hands of the maintenance technicians can go a long way in reducing abnormal situations, excessive variability, and unplanned shutdowns.

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Being lousy at secrets, I thought I'd share some news in an email from ModelingAndControl.com's Greg McMillan. He's just completed a book, Essentials of Modern Measurements and Final Elements for the Process Industry: A Guide to Design, Configuration, Installation, and Maintenance. It's a collaborative effort with several of the Emerson measurement, final element, automation systems, and safety instrumented systems experts.

Here's a few that I featured on this blog with links to their posts including:

• Mike Boudreaux
• Jim Gray
• Mark Nixon
• Sarah Parker
• Bill Zhou

On the ISA book web site, Greg describes it:

Advances in sensor technology and in digital positioner and variable speed drive algorithms, combined with smart features, offer a step change in the performance of modern measurement instruments and final elements. The installed accuracy of many smart instruments has increased by an order of magnitude. There has been a correspondingly dramatic reduction in the drift of transmitters and a similar improvement in the resolution of control valves.

This comprehensive resource aims to increase awareness of the opportunities afforded by modern measurement instruments and final elements, and to show how to get maximum benefit from the revolution in smart technologies. It builds an understanding of the fundamental aspects of measurements, measurement instruments, and final elements for applications in the process industry. The terminology and ideas presented provide a firm foundation for subsequent chapters that focus on what is needed for lowest life-cycle cost and best automation system performance. The last chapter provides a comprehensive exploration of the technology that supports the rapidly expanding opportunities of WirelessHART instrumentation.

The book is written for students or those new to instrumentation and offers guidance and insights for the more experienced folks among us.

Greg notes that the book is done except for the final reviews of copyediting and layout. The ISA book site has it available for order now, but currently lists October 30 as the in-stock date.

If you're unfamiliar with Greg's past works, he has many of them freely available as eBooks.

Update and bump: I wanted to let everyone know that this book is now printed. I know this because I'm holding one in my hands. It's available for order in the ISA Bookstore but not yet stocked in Amazon.com.

Update 2: ControlGlobal.com's Sound Off! blog gives Greg and team's book 4.5 out of 5 stars.

Emerson's Riyaz Ali, whom you may recall from earlier posts, wrote an Inside Functional Safety article recently titled, Digital Technology: A remedy for sick shutdown valves in Safety Instrumented System (SIS) applications. The paper is available for purchase from Inside Functional Safety, so I can't upload or link to it, but I'll highlight a few points Riyaz makes. Here's a portion of the abstract:

In the event of a safety demand, the final control element of a safety instrumented function (SIF) loop is a key component to a process going to a safe state. Unlike the logic solver or sensors (analog transmitters), the final control element requires a total shutdown to check the mechanical integrity. With the invention of the digital valve controller, a final control element's mechanical movement can be tested online by moving a span of 10% or 15% without disrupting the process.

For those not familiar with two of the major international safety standards for process manufacturers, IEC 61508 and IEC 61511, Riyaz provides this contrast:

IEC61511 is an industry specific version, specifically dealing with process industries in the "Functional Safety: Safety Instrumented Systems for the Process Industry Sector." IEC61511 provides clarity to the use of IEC61508 in automation protection systems for the process industries by using industry specific vocabulary, specific examples, and tailored requirements.

As mentioned in the abstract, the final control element is a critical portion of the safety instrumented function or safety loop to take the process to a safe state. It could be an emergency shutdown valve, blow down valve, emergency isolation valve, emergency venting valve, or on/off valve. These valves may remain dormant for long periods, so they must be tested periodically to make sure they will operate properly upon a safety demand situation.

Riyaz notes that conventional testing requires either process shutdowns or bypasses, the latter which add complexity and risk to the process flow. Completely testing the final control element's performance requires "...an in-line test that strokes the valve for full travel."

Without bypasses, the loss of production means process manufacturers want to extend these full stroke tests as long as possible, until the plant is shutdown for turnaround maintenance.

Riyaz describes ways developed to extend the time intervals for the final control element testing by partially stroking the valves. He writes:

It was recognized that the most likely failure mode of a discrete shutoff valve is to remain stuck in its normal position. To test for this type of failure, it is not necessary to completely stroke the valve to test its functionality. A large percentage of covert valve failures can be detected if a limited form of testing can determine that the valve is not stuck and will begin to move. Furthermore, if this type of test could be performed online without shutting down the process, improvements in the PFDavg could possibly be obtained without the loss of production.

Methods to perform this partial stroke testing include mechanical limiting devices and more recently logic solver-based testing:

...which sends fixed pulsations to the solenoid valve to monitor the subsequent movement of the valve. The pulse duration is set to allow slightly more than the required 10-15% movement. The feedback to valve movement is provided by an analog limit switch.

Whichever method is used, written safety procedures are important to make sure plant trips don't occur and proper documentation and maintenance is performed by properly trained personnel.

Riyaz shares how a digital valve controller is a good solution for these partial stroke tests because it:

...receives a control signal from the logic solver. It incorporates travel feedback of the valve position plus supply and actuator pneumatic pressures. This allows the smart positioner to diagnose not only itself, but also the health of the valve and actuator.

Since the process is not shutdown, the tests can be run more frequently and initiated by the logic solver, HART handheld communicator, panel, and/or PC. The tests are also automatically documented and can provide comparisons between tests. In the event of a safety demand, the digital valve controller can also provide a log to help understand the sequence of events for post-event analysis.

He clarifies that partial stroke tests, "...do not eliminate the need for full stroke test; however, it does extend the proof test interval." This extension is often long enough to reach the plant turnaround where all the final control elements can have full stroke testing performed.

If you are unfamiliar with some of these ways of partial stroke testing, you may want to purchase the paper or review some of the past blog posts in which I've featured Riyaz.

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I've featured quite a number of experts around Emerson over these past three years. Some categories, like Process Optimization, have more than 50 posts. There is quite a bit of wisdom mixed in all those posts.

A few months ago, I was asked by Plant Engineering magazine managing editor, Jack Smith, if I'd be willing to write a process optimization article highlighting some of the ideas offered in these posts. It was a thrill to be asked and I quickly agreed.

I wrote a draft and went back to some of the experts highlighted, such as Mark Coughran and Pete Sharpe, for their improvement suggestions. The resulting article, Downturn a good time to review, improve process optimization went live on PlantEngineering.com website last Friday and is printed in the March 2009 magazine edition.

I tried to stress things you could do as a plant engineer to improve your process without having to spend a lot of capital, which is an issue for many process manufacturers in this global economic slowdown. Finding ways to reduce process variability is a good first step. Sources of variability that our variability consultants have tabulated over the years include:

• Control valve performance - 30%
• Improper tuning - 30%
• Improper process and/or control scheme design - 20%
• Other - 20%. The 20% of other causes are not necessarily design- or control-scheme related, but more operational issues that occur over time.

I distilled down five ways to reduce this variability: size control valves properly, minimize loop dead time, measure process dynamics and compensate for them, tune the loops, and apply advanced process control. I won't spill all the secrets divulged in the article but instead highlight a couple of points.

My Fisher valve colleagues often remind me of the importance of the control valve since it directly touches the process.

Control valves, being variable in gain, must be correctly sized and characterized for the application's flow to be sufficiently linear to stay within specified gain limits over the operating range of the process.

Other parts of your control loops to check for:

...sources of dead time include inadequate signal conditioning on transmitters, incorrect transmitter range/resolution, poor physical location of transmitters and measurement lags from applied filters and dampeners.

Without the proper process dynamic measurement applications, many plant engineers have had to rely on rules of thumb and guesswork to loop tuning parameters. With the process dynamics understood, you can tune the loops with linear responses and try to reduce the non-linearities in the others in several ways including:

...changing any master loop configuration to prevent interaction with the slave loops. See if you can remove unnecessary interlocks that may disturb the control loop. If you uncover extremely high process gains, adding upstream control loops can help. Other advanced regulatory control strategies such as feedforward, cascade, override and split-range control can compensate for different process conditions.

With the basics addressed, you can look for areas to apply advanced process control, especially in big, energy-consuming units.

I hope some of the ideas excerpted from the article help you find ways to improve your process and help your business through these challenging times.

MP3 | iTunes

Update:I heard from Jack that this article is currently the most popular one on the PlantEngineering.com website. Thanks for stopping by to read it!

InTech magazine has a web exclusive on the importance of safety valves in a safety instrumented system. The article, Valve failure: Not an Option, describes methods of implementing partial stroke testing (PST) to reduce the probability of failure upon demand, average (PFD_avg).

For those not familiar with a partial stroke test, I found this definition:

This test checks for valve movement without fully stroking the valve. Many applications will allow 10% movements to verify valve response without upsetting the critical process line. Diagnostic data is collected and an alert is given if the valve is stuck.

The purpose of this test is to improve PFD_avg to possibly increase the safety integrity level (SIL) rating of the safety valve in a safety instrumented function (SIF), to extend the proof test interval, or a combination of both. Extending the proof test interval may allow process operators to avoid additional downtime by scheduling proof tests during turnarounds.

The author enumerates four methods of performing the PST: by the emergency shutdown system (ESD), by a positioner-based device, by a 2-out-of-2 (2oo2) or 2-out-of-3 (2oo3) redundant device, and by a 2-out-of-4-doubled diagnostic (2oo4D) redundant device.

The part of the article that jumped out for me, which I needed to ask Emerson's Riyaz Ali about was:

Using a positioner-based device is perhaps the worst option, as it is a complete misapplication of technology. Positioners should modulate control valves, whose movement is very small. ESD valves on the other hand are fully open or fully closed, and go from one state to the other as quickly as possible. Because positioners have a very small Flow Factor (Cv), they cannot vent a valve diaphragm quickly as required to satisfy the process safety time, and are suitable only for smaller valves. To compensate for this deficiency, an interposing SOV can vent the valve diaphragm. This SOV is not tested during the PST and remains in an open position for an extended period of time. As such, it may not be able to close (vent) upon demand and is itself a source of both dangerous failures and spurious trips.

In addition to the interposing SOV, positioners use a pneumatic valve-nozzle arrangement, which operates independently of the positioner electronics. Given the nozzle orifice plugs up (often by a tiny spec of dirt or water in the air supply), shutting off the electronics will not vent the valve diaphragm. This is a dangerous failure mode, as venting the diaphragm (closing the valve) is critical to achieving the safe state. Unfortunately, most positioner product safety evaluations do not address this dangerous failure mode.

Riyaz offers some counterpoints. Advanced positioners or digital valve controllers such as the Fisher DVC6000 SIS have been designed specifically to operate safety shutdown valves and has gone through the rigorous design, testing and certification process defined in the IEC 61508 international safety standard for use up to SIL 3 applications. This design, testing and certification process was developed to ensure the applicability of the technology for this process safety application.

Riyaz notes that it is true that a very few applications do require shorter process safety times. He points out that it is not necessary to use a solenoid valve (SOV) to improve the stroking speed. Positioners can use pneumatic devices to achieve faster stroking time. I discussed a quick-exhaust example in an earlier post. For process manufacturers who still would like to use an SOV in the SIF loop, these SOVs have different capacities to meet the stroking speed requirements. Also, some of the more modern positioners like the DVC6000 SIS can also monitor the health of the SOV when it's used with a single-acting actuator. It performs checks for the dangerous failures of SOVs on-line without affecting the process.

Some digital valve controllers, like the DVC6000 SIS, are suitable for use in a SIL3 SIF in standalone mode. When used in standalone mode or in pneumatic series with SOV or other pneumatic accessories, it continuously checks the pneumatic integrity (functioning of I/P and pneumatic relay) to ensure that these components are working and ready to drive the valves upon a safety demand (see figure 13). If, during normal operation, any abnormality is noted, an alert is sent to the HOST system.

Riyaz also provides clarification that air quality requirements are always specified in each product bulletin for pneumatically operated valves and specifically, the safety manual of a field device always recommends to follow the ISA S7.0.01 air quality standard, which specifies the air be clean, dry, without oil, water or any particulate contaminates.

For your IEC 61511 process safety risk mitigation efforts, partial stroke testing performed by digital valve controllers can help you reduce the PFD_avg on your safety shutdown valves.

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Update: Welcome, Plant Engineering Live blog readers! Jack, I appreciate the great recap of this post!

Update 2: Thanks to Dr. Beckman for pointing out my error on 2004D in the comment section of this post. It is "diagnostic" and not "double" as I'd originally written. I've also shown Dr. Beckman's comments to Riyaz and asked if he'd like to add a comment... stay tuned!

I'm lucky enough to receive a copy of Andrew Bond's Industrial Automation Insider newsletter each month through an Emerson subscription agreement. Andrew covers the happenings among the automation suppliers and standards bodies. You can also find some of Andrew's writings on the ControlGlobal.com site.

In the November 2008 newsletter, one item that caught some attention around here was this nugget:

...first TÜV-approved SIL3 Foundation fieldbus safety valve controller to appear on the market. The device delivers status changes automatically via Foundation fieldbus and incorporates real time alarm management eliminating the need for external wiring or I/O cards.

I have the privilege of working in the vicinity of two very knowledgeable people with respect to process safety, Riyaz Ali and Mike Boudreaux.

Riyaz notes that the Foundation SIF specifications are still under development. In a recent Fieldbus Foundation release, it quotes ARC's Larry O'Brien:

It is very clear that end users want this technology and are striving to include FF-SIF systems in their project specifications. Many major end users will probably be specifying FF-SIF systems for their new projects starting in 2011.

A September 2008 ARC whitepaper, Foundation Fieldbus Safety Instrumented Functions Forge the Future of Process Safety, provides background on the Foundation SIF standard advancement and its current draft status. Mike and Riyaz were present at the successful May 2008 Foundation SIF end user demonstration project in Amsterdam, and Mike shared his experiences with me. Riyaz also shared that one of the function blocks, the SIF_DO block, will not be available from the Fieldbus Foundation until the first half of 2009.

Many automation suppliers are developing products based on the current Foundation SIF draft, including Emerson. I asked Riyaz about the current solution Emerson provides until the standard is ratified. Riyaz responded:

The current solution for use in a Foundation fieldbus SIS application is to use the DVC6000f PD instrument. Several hundred units have been supplied worldwide to process manufacturers where partial stroke test scripts are run from host systems, such as the DeltaV system and AMS Device Manager.

In this application, process manufacturers use a solenoid valve operated by a hardwired digital output from the SIS logic solver.

Riyaz expects that until process manufacturers have sufficient experience, they will continue to use an independent solenoid valve to take the SIS valve to the fail state, while at the same time using a DVC6000f PD for partial stroke diagnostics using Foundation fieldbus through the basic process control system (BPCS).

Mike notes that both the DeltaV and DeltaV SIS systems are capable of performing these safety instrumented function predictive diagnostics. The DeltaV system is being used to perform partial stroke testing with the DVC6000f PD using Foundation fieldbus communications. The DeltaV SIS system is being used to automate partial stroke testing with the DVC6000 SIS safety valve controller using HART communications. This additional diagnostic coverage assists process manufacturers with their IEC 61511 safety lifecycle efforts.

Using diagnostics enabled by Foundation fieldbus and HART communications, the DeltaV and DeltaV SIS systems with DVC6000 digital valve controllers can provide many of the benefits today that are promised by Foundation SIF in the future.

MP3 | iTunes

Update: Next week is the Thanksgiving holidays in the U.S. and I'll not be posting. We'll be upgrading our version of Movable Type software. Wish us luck!

Last week I mentioned uploading two of ModelingAndControl.com blog's Greg McMillan's recent presentations. Like I did with his first presentation, here's a short recap of the second one, Control Loop Foundation for Batch and Continuous Control:

What are great about Greg's presentations are the specific application examples. Visit the slides 19-21 to see ways of improving neutralizer control using Feed forward control, signal characterization and proper piping to provide proper spacing for measurement devices. Similarly, slides 22-24 show ways to improve distillation column control using Feed forward control and signal characterization. You mostly don't realize the benefits of improved control until you reduce variability and move the setpoint closer to the operating limit.

Greg is really good at boiling things down. Here are his words summing up basic opportunities in process control (from slides 27 and 28):

• Decrease stick-slip and improve the sensitivity of the final element (Standard Deviation is the product of stick-slip, valve gain, and process gain)
  • Use properly tuned smart positioners, short shafts with tight connections, and low friction packing and seating surfaces to decrease valve slip-stick and dead band (do not use isolation valves for throttling valves)
  • If high friction packing must be used, aggressively tune the smart positioner
  • Improve valve type and sizing and add signal characterization to increase valve sensitivity
  • Use variable speed drives where appropriate for the best sensitivity
• Improve the short and long term reproducibility and reduce the interference and noise in the measurement (Standard Deviation is proportional to reproducibility and noise)
  • Use magnetic and Coriolis mass flow meters to eliminate sensing lines, improve rangeability, and reduce effect of Reynolds Number and piping
  • Use smart transmitters to reduce process and ambient effects
  • Use RTDs and digital transmitters to decrease temperature noise and drift
• Reduce loop dead time (Minimum Integrated Error is proportional to the dead time squared)
  • Decrease valve dead time (stick and dead band)
  • Decrease transport (plug flow volume) and mixing delay (turnover time)
  • Decrease measurement lags (sensor lag, dampening, and filter time)
  • Decrease discrete device delays (scan or update time)
  • Decrease analyzer sample transport and cycle time
• Tune the controllers (Integrated Error is inversely proportional to the controller gain and directly proportional to the controller integral time)
• Add cascade control (Standard Deviation is proportional to the ratio of the period of the secondary to the process time constant of the primary loop)
• Add feed forward control (Standard Deviation is proportional to the root mean square of the measurement, feed forward gain, and timing errors)
• Eliminate or slow down disturbances (track down source and speed)
• Add inline analyzers (probes) and at-line analyzers with automated sampling since ultimately what you want to control is a composition
• Optimize set points (based on process knowledge and variability)
• To realize the benefit of reduced variability, often need to change a set point

He sums up the presentation with these key points:

• Tune the loops
• Use digital positioners and throttle valves to get resolution better than 0.5%
• Use Coriolis and Magmeters to get accuracy better than 0.5% of rate
• Add cascade and feed forward control for disturbances
• Model the process to dispel myths and build on process knowledge
• Improve the set points
• Add composition control
• Reduce the size and speed of disturbances
• Transfer variability from most important process outputs
• Add online data analytics (multivariate statistical process control)
• Add online metrics to spur competition, and to adjust, verify, and justify controls

View or download the presentation if you think some of this guidance might benefit you.

MP3 | iTunes

Emerson's Fisher division recently announced a new three-way, temperature-control valve and actuator system. The release highlighted its potential use by process manufacturers:

The new GX 3-way has the ability to accurately control the temperature of water, oils, steam, and other industrial fluids. Applications include heat exchangers and lubricating skids.

For those not well versed with three-way valves, you'll find use for them in both flow mixing (converging) and flow splitting (diverging) applications.

I caught up with Brad Smith, the global GX control valve product manager, about some potential applications for this valve. Brad began by sharing the development objectives for this valve. Typically, when a process manufacturer cannot achieve the required control, they must reassess process-piping arrangements, often going to a 2-valve arrangement. This GX 3-Way valve provides the level of control to avoid re-piping and 2-valve arrangements.

Brad shared with me that the biggest application focus for this 3-way valve is in temperature control around heat exchangers. It was designed for high-capacity applications and precise linear characteristics required for accurate temperature control. Brad cited a specific heat exchanger application in beer brewing where the wort temperature is maintained with a glycol coolant.

Another common application for this 3-way valve is pH control on feedwater to a boiler. When the pH of the feedwater rises beyond a predetermined level, a three-way valve adds fresh make up water to reduce the pH back to target levels.

A third application Brad discussed was for test separator manifolds. Test separators are mainly used in oil & gas production facilities to measure the amounts of oil, gas, and water from the well. The manifold contains three-way valves coming from each wellhead that uses the test separator. Some installations use the three-way valves while others prefer globe valves.

A final application Brad shared was in the steel industry. Rod mills require good temperature water box control.

Most process manufacturers have temperature control applications requiring mixing flow streams or splitting flow streams. This three-way valve might have the flow characteristics and properties your application requires.

MP3 | iTunes

I received an email last week with some questions to an earlier post, Checking Your Safety Solenoid Valves. While protecting the emailer's anonymity, I thought I'd share the questions and answers provided by Emerson's Riyaz Ali with you.

The first question was about the assertion, "What the technology team found through extensive research and development is that the solenoid valve can be pulsed for a split second by smart SIS logic solvers like the DeltaV SIS system." The question was:

The apparent assumption here is that the DVC6000 SIS is added to the solenoid valve installation but does not replace it. This raises the question of what benefit the DVC6000 SIS has over other versions.

Riyaz responded:

The digital valve controller (DVC) is used as a diagnostics device to initiate partial stroke tests (PST) and to continuously monitor the health of valve, even if there is no change in input signal to the DVC. The DVC6000 SIS is certified for use in Safety Instrumented Function loop without solenoid-operated valves (SOV). Applications which require faster stroking speed and where a process manufacturer is more concerned about "safety availability" and would like to have either or device pneumatically in series to take the final element to a safe state, will employ DVC and SOV.

It is true that physically the DVC6000 and DVC6000 SIS have the same components (except sticker on cover and different firmware in microprocessor) but unlike the general DVC used for process control, the DVC6000 SIS for safety has built in:

• safe guard against spurious trip during PST
• PST on line in service without change of input signal
• configurable stroking speed to ramp (rather than step) slowly of fast during partial stroke test
• capture the PST test results and store in the non volatile memory of device
• using associated software allows the analyzed test results of health of the final Element
• audit documentation (comparisons and storage)
• returns the valve to its normal state after completion of test
• manual reset feature
• automate PST without any other user interface

A second question arose about what value there is if the DVC6000 goes to zero mA and loses power and thus losing its diagnostic:

Again, it doesn't appear that the SIS version is bringing anything to the party. If configured in the 0-20mA or 0-24 volt DC scheme and used as part of the safety trip, communications are lost during the trip and the feature described does not apply. If it is not used to trip the valve, why use the SIS derivative?

Riyaz answered:

When DVC is used with 0-20mA or 0-24VDC, it only loses its capability to trigger the event in the case of "Safety Demand". It otherwise has all other capabilities of a DVC6000 SIS operated by 4mA. When used with 0ma or 0VDC, DVC does take an active part in "Safety Shutdown" and makes "Final Element" to attain "Safe State". The DVC6000 SIS, when operated with 4-20mA, can capture and store the results in the nonvolatile memory for study and understanding of event which could provide vital clues of the event and also could provide learning lessons for the future. This provides the opportunity for safety reliability engineers to access and evaluate the "Demand Condition". Also, the details obtained can be used with regulatory bodies who would like to have audit of device in the case of demand.

The whole purpose of migrating from discrete on-off switch contacts to analog input (sensors) / output (final element) for logic solvers have evolved use of microprocessor-based field devices in safety instrumented systems. If one uses microprocessor-based devices then why should they not use 4-20mA instead of 0-20mA? I am still in the opinion that the analog signal for field device provides continuous monitoring by logic solver for its input and output. If one decides to use microprocessor-based devices, it makes sense to use 4-20mA rather than 0-20mA for the DVC, which does not offer any advantages. On top of it, the DVC6000 SIS when used with 4-20mA is certified for its compliance to IEC 61508.

The final question came up when I wrote, "One final point Riyaz emphasized is the DVC6000 SIS spurious trip protection which provides maximum output pressure to the solenoid at minimum input signal in a case where the 4-20mA signal between the smart logic solver and digital valve controller is lost or severed." The question was:

Here the SIS is driven by a 4-20 mA signal but, amazingly, it is configured to fail to danger on loss of the control signal. I still don't see the benefit of the DVC6000SIS over its siblings.

Riyaz responded:

This is typically ETT (Energize to Trip) scenario, where during normal operation customer will use 4mA (because plant availability is highest) and upon Safety Demand customer would like to provide 20mA to DVC so that DVC can trip the valve.

In fact, one of the major oil and gas producers has already used this same scenario in their plant. They are using SOV to trip the valve and DVC for diagnostics, partial stroke test and SOV health test and uses DVC with reverse relay. Even if someone cuts the power to input signal of DVC, it still supplies full pressure to avoid any spurious trips.

I thought sharing this email exchange might provide answers for your IEC 61511 compliance efforts if you had similar questions when reading the earlier post.

My colleague, Deb Franke, pointed me to a great article in her RSS feeds. The ChemicalProcessing.com article, Innovative Fixes for Saving Energy in Plants, describes some ideas to help reduce plant energy costs. Although energy costs have come down in recent weeks, they are still one of the largest controllable costs as I have mentioned in an earlier post.

The article points out innovative solutions including dual drive pumps, variable speed motors, water/glycol systems, automated blowdown systems, low BTU sweep gas and wireless sonic leak detectors. Give the article a read if you think some of these might apply in your plant processes.

I forwarded the article to Emerson's Lou Heavner, whom you may recall from earlier advanced process control application posts. I asked what new and innovative, energy saving ideas he might have to share.

Lou had a couple of ideas. But, being the modest sort, he added a caveat that they may not qualify as new or innovative. To me, if you're looking for ways to reduce your energy costs and you didn't consider one of these, it's definitely new.

Lou's first thought was on distillation processes. He writes:

In distillation, relative volatility and hence difficulty of separation tends to improve at lower pressure. When cooling water and/or air are used to condense the overheads, the pressure is often tightly controlled for stability in the face of changing ambient conditions and the extra cooling capacity available during nights or colder weather is not fully utilized. If pressure is allowed to "float" and as much condensing occurs as is possible, pressure will fall in the column and separation will normally improve. This means less heat is needed in the reboiler and hence energy savings when using steam or some other "costly" utility stream to provide reboil.

His second thought was around combustion processes burning fuel gases with changing compositions. Lou notes:

In heaters or boilers where the gaseous fuel consists of a hydrocarbon mixture of varying composition (like refinery fuel gas), a change in fuel can have an effect on the heat generated by combustion and on the excess air level in the flue gas for a given fuel flow rate. Sometimes, if variability of the flue gas justifies, companies will install fuel quality analyzers that measure composition or heating value. In many cases, the same thing can be achieved and better flow control at the same time, by using a Coriolis mass flow meter. It turns out that the mass flow of a hydrocarbon and the "btu" flow are directly related since both are related directly to MW.

You can't do this with PT compensated flow, because it knows nothing of MW. But Coriolis measures mass directly and can be used to reduce variability of "btu" feed to the burner. This can be dramatic where the fuel gas varies significantly. It is not a good solution if the "btu" content changes due to the presence of inerts (like N₂ or CO₂) or non-hydrocarbons (like H₂ or CO), since they do not exhibit a linear relationship between mass flow and "btu" flow. But if they are present in small quantities and don't vary much, the concept can still work.

On processes that degrade the "quality" of energy, Lou shares:

Saving energy can be as simple as minimizing thermodynamically irreversible operations. Mixing, heat transfer, and throttling of process flows are common examples of irreversible processes. In general, industry should avoid over-purifying/heating/cooling followed by mixing or blending to achieve the target composition/temperature. Process design should attempt to get as much work as possible out of utilities and recover as much heat as possible. Pinch technology is one approach to heat integration design used by process engineers. Of course, there are practical limitations like capital cost considerations, dynamic response and controllability, and availability/reliability of utilities, especially ambient cooling.

Also, control valves should be selected to minimize throttling losses and allocation and valve position should be used to minimize overall pressure drop in systems like utilities where resources are shared by different units or equipment. For example, if multiple reactors are cooled with a shared refrigeration unit, the coolant temperature setpoint can be raised (reducing the refrigeration required) until one of the user's demand exceeds the capability of its corresponding control valve to deliver.

Let's hope that something between the ChemicalProcessing.com article and Lou's thoughts provides you at least one idea that can help reduce your plant's energy bills.

Two very knowledgeable people in safety instrumented systems (SIS), Mike Boudreaux and Riyaz Ali, shared with me the story behind the recent news about the DVC6000 SIS digital valve controller (operated by 4-20mA) being certified to be compliant with IEC 61508 for use up to SIL 3 safety instrumented functions (SIF).

With this certification, DeltaV SIS logic solver's HART two-state, 4-20mA output and the Fisher DVC6000 SIS without any additional solenoids or other auxiliary devices can be used for SIL 3 applications. This configuration provides capturing trip events during safety demand, which provides crucial data for reliability and analysis by safety engineers of event. It's also helpful information for regulatory audits.

Now, I used my trusty friend Google to learn more about the HART two-state channel and found this page in DeltaV Books On-Line on the function block in the logic solver that helps make this happen. Basically:

...DeltaV SIS Logic Solver Digital Valve Controller (LSDVC) function block provides an interface to the DVC6000 SIS for safety shutdown and for partial stroke testing. The HART Two-state Output Channel provides the control signal and the HART communications path to the digital valve controller. You can configure the output channel to have an OFF_CURRENT of 0 mA or 4 mA. The control signal can command the valve controller to the tripped state regardless of the configured OFF_CURRENT value. Using an OFF_CURRENT value of 4 mA allows HART communication between the Logic Solver and the valve controller whether the valve controller is in the normal or the trip state. When the OFF_CURRENT is 0 mA, the power is removed entirely when the LSDVC function block drives the channel Off.

Mike noted that continuous diagnostics is possible because the valve closes when delivered a 4 mA signal. The DVC6000 SIS records the results of a demand event by logging all the results of travel and pressure data points in the microprocessor memory. This event log is critical for plant personnel, reliability engineers, and auditing authority to understand the final element status before and after the trip or demand event. Before the new certification was obtained, diagnostics would be lost on shutdown because the signal to the DVC would be 0 mA.

These on-line diagnostics coupled with partial stroke testing can be automatically initiated from the DeltaV SIS logic solver. This means that the final control element is periodically checked to help protect against spurious trips and to test for demand availability. The operator can also manually initiate these partial stroke tests from operator faceplates. The DVC6000 provides pass/fail status back via HART digital communications for alarming and historical event recording.

Riyaz pointed out that Type B devices (generally microprocessor-based) the IEC 61508 international safety standard (part 2, table 3) mandates redundancy in SIL 3 applications. This means the DVC6000 SIS connected to the DeltaV SIS HART two-state channel is suitable for SIL 1 and SIL 2 applications without redundancy, but for SIL 3 SIFs, IEC61508 mandates a full redundancy or hardware fault tolerance of one.

Achieving this certification helps reduce the components in these SIFs and increase the diagnostic coverage and capture of historical SIS information on demand.

I've seen a number of stories about applications for wireless transmitters, but not for wireless valve monitoring. That all changed earlier this week when I received a Twitter direct message "tweet" from a colleague. For those not yet on Twitter, it's an option to send direct communications, unseen by others, when you have a reciprocal follow relationship with one another. It's like instant messaging but comes with the stream of others' short notes in your follow list. I have it set up where these direct messages come as text messages to my phone as well. I mention all this because it's another way communications are rapidly evolving from the world of email in which we've lived over the past many years.

The Valve magazine article, The Reliability and Security of Wireless Valve Monitors, is written by Emerson's Kurtis Jensen, an instruments product manager for Fisher and Valve Automation products.

One of Kurtis' closing paragraphs provides the primary reasons process manufacturers may consider wireless monitoring on some of their valves:

Most operations have a large number of "blind valves" that are either manual or semi-automatic but provide no valve position feedback, normally because of cost or location. As such valves age, their performance can degrade to sluggish, slow operation. The true position of the valve may be questionable, and operators have to start visiting certain trouble-prone valves to verify their position. Where valve position monitoring does not currently exist, wireless monitoring is a great way to start using this technology with minimum risk."

If you've ever come across the ModelingandControl.com blog, you'll know that sluggish valve performance is a contributor of deadtime that impacts overall control performance and plant efficiency.

As with any newly introduced technology, its ease of use is critical in its adoption. Kurtis notes that an upcoming release of a wireless position monitor product is non-contact and does linkage-less position sensing. After attaching and calibrating the device, it sends valve position information wirelessly across the self-organizing network to the automation system or asset management software.

He discusses some of the reliability and security aspects that I've described in earlier posts. The reliability aspects are largely to do with the self-organizing nature of the WirelessHART field networks. Alternative communications paths are taken from the devices to the wireless gateway when permanent or temporary obstacles happen.

Security is addressed in the WirelessHART standard and described by Kurtis through its changing encryption, message authentication, data verification and frequency hopping.

An important point made is that, "...wireless should not be viewed as a direct replacement for wired instrumentation." It's well suited for:

...hard-to-reach locations, in areas hazardous to plant personnel, where power does not exist and where running wires is not allowed or prohibitively expensive, to name a few.

This certainly opens up opportunities in many facilities to reduce the number of blind spots the operations staff face that must be covered by periodic manual inspection. The opportunities for wireless monitoring may be with the valves were early notification of performance degradation can help avoid overall poor control performance.

Recently, Emerson's Fisher Control Valve and Regulators division announced that several lines of control valves received SIL 3 certification for on/off operation per the IEC 61508 international safety standard. Safety valves with digital valve controllers have been certified for many years, but these are the first control valves to achieve this independent third-party certification. Up to this point, the prior use methodology has been required to demonstrate the control valves are "proven in use" for safety applications.

I caught up with Andy Evans, a product manager in Fisher's European operations. Andy shared with me the motives behind pursuing this certification:

...the architectural constraints in IEC 61508 state that a final element needs a Safe Failure Fraction of greater than 60% to be used in a SIL 2 loop as a single device. The generic data, which was being used prior to having specific FMEDA (Failure Modes, Effects, and Diagnostic Analysis), was less than 60%.

Andy also noted that process manufacturers were increasingly requesting the certification given the efforts required with the "prior use" approach. The team decided to pursue certification for the Fisher GX, Vee-ball, easy-e and HP valve families.

The valve technology organization worked with the third-party safety professionals, Exida. They followed the basic process outlined in the IEC 61508 standard. The team went through an initial documentation plan including verification and validation (V&V) followed by the detailed writing of the safety requirement specifications (SRS). These activities completed the analysis phase of the safety lifecycle.

They went through the FMEDA for the mechanical portions of the actuators and valve bodies based on their physical properties and field experience. This analysis looks at the effect of each component in the valve failing in its worst possible way and then categorizing that failure.

Exida has a database of frequency of failure for each type of component. These failures are categorized into safe & dangerous (dangerous meaning stopping the valve moving to its safe state) and detected & undetected.

After the FMEDA analysis was performed, functional tests (integral), conceptual design, and detailed design assessments were done.

The final steps on the path to certification were a thorough evaluation of the engineering development process and documentation assessment for design modifications, change request processes and impact analyses.

Having these control valves certified for up to SIL 3 safety instrumented functions provide process manufacturers great flexibility in the selection of final control elements for their IEC 61511 safety compliance efforts.

I read Siemens' Charles Fialkowski's latest post, Introducing a non-redundant, redundant SIL 3 solution? about their SIL 3 HART I/O card. He discusses how technology has changed where newer SIL-3 rated safety instrumented systems (SIS):

...don't require redundancy to achieve high levels of safety. In the past, safety systems required dual, triple or even quadruple redundancy just to achieve high levels of safety.

He points out that advances in technology have allowed diagnostic coverage not possible in earlier SIS designs. He closes his post:

Another common misunderstanding is how these systems address field redundancy (sensors and final control elements). While I can't speak for the Emerson or Yokogawa system, I do know for a fact that the new Siemens HART analog input module handles redundant field devices just like any dual, triple or quadruple redundant system would.

I thought I'd give the Emerson perspective so I caught up with DeltaV SIS product manager Mike Boudreaux. He first pointed out that DeltaV SIS has HART I/O and the DeltaV SIS logic solvers are SIL3 certified in simplex (non-redundant) mode and have been since DeltaV SIS began shipping in 2005. Other safety instrumented systems also accept HART I/O, but only to pass-through the HART data to asset management systems. DeltaV SIS makes this HART status information available in the logic solver.

Mike noted that only the analog, 4-20mA process variable (PV) is used for the safety instrumented function (SIF). The digital HART PV's are not accessible for use in SIFs, but the device status provided by the HART digital communications protocol is passed along with an analog input in DeltaV SIS. If a HART transmitter detects a problem, the status for an analog input will become "Bad." Conditions for a Bad status include earth leakage detection, loss of HART communications, device malfunction and device fixed-loop current to name a few.

This Bad status can be used in the logic solver. For example, in a multi-transmitter SIF, a voter block can be configured to ignore an input value if it is Bad. In accordance with the international safety standard IEC 61511, this capability can be used to provide continued safe operation of the process while the faulty part is repaired. DeltaV SIS will alert operations of this problem so that the device can be maintained in the specified mean time to repair (MTTR). Alternatively, the voter block can be configured to treat a detected failure as a vote to trip, which provides increased safety.

When a HART device detects a problem, an alert is displayed on the DeltaV operator station. SIS faceplates and detail displays for HART devices help operators view and manage HART device alarms.

DeltaV SIS also uses the HART communications protocol to enhance partial stroke testing. It validates the operation of the final control element--the most critical and most likely to fail in a safety instrumented function. The logic solver can generate HART commands to initiate a partial stroke test in a digital valve controller. The operators can initiate partial stroke tests manually from their operator workstations or they can be scheduled to occur automatically based on the specified test interval. The results from these tests are captured and integrated with the system event history. An alarm can be generated if a partial stroke test fails, alerting maintenance that there is a potential problem with a valve.

This diagnostic coverage and information feedback to operations provide process manufacturers better tools for compliance with the IEC 61511 safety lifecycle compliance efforts.

Update: Welcome readers of Gary Mintchell's Feed Forward blog. Thanks for the shout out, Gary!

In several parts of the world including North America, Emerson Process Management sells some of its products and services through local business partners. I came across a great Pulp & Paper magazine article, Control Valve Management Can Pay Off Big, written by Jeff Klatt. Jeff is with one of these local business partners, R.E. Mason.

Jeff recounted his experiences as a large paper mill's asset manager. What struck me about the article were not the technologies they ultimately applied, but rather his systematic approach to process improvement. I'll highlight some of the steps he recounts in the article to see if they might spur some ideas for improvement in your operations.

Jeff cited a study conducted by Emerson's Fisher Valve business that found that 80% of the control valves used by process manufacturers were not operating within their optimum parameters. Getting process improvements by addressing these was a large part of last week's post, Start with the Basics to Reduce Process Variability.

He described his initial step:

It seemed logical to first get acquainted with the valves in the mill and understand their roles in the papermaking process. One-by-one, I visited valves throughout the three main sections of the mill -utilities, fibers and product (papermaking) - documenting every one and building a personal database. Identifying, locating, and visually inspecting nearly 1,600 control valves in the mill turned out to be a monumental task that took months to complete.

Through this tedious process, he also engaged operations, which:

...explained which control loops had the greatest effect on product quality, productivity, and safety/environmental considerations. This knowledge was essential in establishing the most important valves, and in the end about 25% of all the valves were prioritized as critical to the mill's mission. These became the valves on which the majority of maintenance attention was focused.

As is often the case, this tedious work lays the foundation for future savings. He also had all the storerooms spare parts identified, tagged and catalogued. This effort allowed greater use of existing stock and fewer purchases of new parts, which improved the mill's working capital. In one year alone, 20 good control valves taken out of service and put into one of the storerooms were returned into service saving $55,000 (USD) in cost.

The prioritization of the critical control valves also provided focus on where to apply the technologies to improve the performance of the process. Jeff and team used the Flowscanner tool to find out more about the condition of the highest priority valves to direct the maintenance efforts. Also, digital valve controllers were added to these critical control valves over time to provide real-time diagnostics with the AMS software to begin a program of predictive maintenance. A valve's signature can be compared with its baseline performance to identify problems. These can be addressed before actual failures or variability-creating conditions occur. Jeff's team documented $50,000 a year in maintenance cost savings.

Jeff highlighted other savings such as a valve variability problem on a CIO2 flow valve being identified and addressed resulting in an annual savings of a $140,000. Another was documenting the useful lifecycle extension of 162 tested valves by an average of two years. Calculated cost savings were $86,000.

While the savings are impressive because they reoccur over time, the approach is what I found instructional. It started with a commitment to focus time and energy on these control valves because of their critical role in the process. Next was the discipline to analyze the current state and work with operations to identify the most critical control valves. This process laid the groundwork for the application of some of the technologies described to achieve lower costs and greater efficiency. From Jeff's quantified results, it appears this focus paid dividends.

I received an email with a great question to an earlier post, Improving Local Control around Safety Shutdown Valves. The question was:

Can you provide more information on your Local Control panel with Safety Shutdown Valve that haves a quick exhaust systems; can the partial stoke test not close the valve do to differential pressure on the quick exhaust system. Also if a shutdown signal is given during a test will it close the valve?

I spoke to Riyaz Ali, who shared his expertise in the earlier post. Here's his great answer in its entirety with picture and hyperlink added by me:

It is true that use of quick exhaust valve (QEV) on large valve with DVC6000 SIS for partial stroke test may dump large air during test. Generally, QEV operates on water column pressure differential and are sensitive. However, we recommend using volume booster on those applications where stroking speed is concern. One may argue that Volume Booster is for "Fill" time and not for "Exhaust". However, we have done test in the lab and established that volume booster will be much better pneumatic accessories, specifically when used with DVC6000 SIS for partial stroke test without causing instability in the operation during partial stroke test and as well meeting stroking speed requirements.

The picture illustrates a schematic of a large spring-return piston actuator with a DVC6000 and a volume booster to achieve a stroking speed requirement of less than two seconds.

During PST test, if demand arises DVC6000 SIS will take valve to safe state.

Here is more information about the LCP100 (Local Control Panel) for your perusal.

I hope that pulling this process safety-related question out of the realm of email into the open might help someone else with similar questions.

Update: I'd like to thank commenter JM for pointing out my LCP100 hyperlink going to the wrong spot. I've fixed. Thanks, JM!