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Emerson Process Management's Fisher® Design GX:
Development of a Reliable, Easy-to-Use Control Valve for Today’s Challenging Process Control Environment
Reduced manpower. Shortened outage turnaround times. Smaller engineering staffs. Reduced maintenance budgets. These are the types of pressures process managers face as they are asked to cut operating costs and maximize process availability.
Additionally, as maintenance and engineering staffs have been reduced, there is a growing need for critical process equipment such as control valves to be easier to select, install, and maintain. Once commissioned, it is vital that control valves perform as required, and most importantly, be reliable.
It is for this demanding environment that Emerson Process Management developed the new Fisher® Design GX control valve and FIELDVUE® DVC2000 digital valve controller.
In launching the Design GX development project, Emerson’s Fisher assembled a worldwide team and embarked on a mission to first listen and learn from their customers, and then develop a control valve that would meet the requirements of today’s tough process industry market.
Considerable resource was invested in the market research phase of the project. The project team conducted an extensive program of customer interviews in a wide range of countries. Just as important, insight was gained into the problems end-users encounter when valves are selected, sized, ordered, installed, and maintained.
Internet-based customer surveys, using choice-based conjoint analysis techniques, were used to identify what valve users value most when making a control valve selection. In parallel, "voice of the customer" phone surveys were conducted to gain further insights into customer / supplier relationships.
The primary requirement heard from users was that a control valve must be reliable, and perform as required. Ease of maintenance ranked very high, as well as reduced spare parts inventory. Other criteria includes ease of control valve and actuator sizing, selection, and ordering due to time and manpower constraints. Valve users indicated a strong desire for a singular, simplified valve platform, in which the design architecture is modular and parts are shared across sizes. Live-loaded, environmental packing was desired as standard.
Finally, valve customers indicated a desire for a reduced size and weight valve / actuator assembly, utilizing a compact multi-spring actuator. An integrated positioner mounting that eliminates the need for external tubing was ranked as highly desirable, as well as well as the flexibility to mount positioners via a NAMUR mounting.
Armed with the market requirements, brainstorming sessions were held around the world, and a large array of concepts was developed. Valve concept testing sessions were then held with valve users around the world, with an objective of determining whether the requirements had been understood and properly translated into designs. The final valve and actuator design was finally selected.
The design team, in concert with the research and development groups, set to work bringing the concepts to life in a rigorous test and evaluation program.
The engineering team made extensive use of computerized design evaluation and analysis tools. Finite element analysis (FEA) was used to optimize the structural parts in order to ensure strength, reliability, and compliance with ANSI and EN standards. In particular, high stress areas such as casings, flanges, bolted joints, welds and stems were analyzed and refined before actual parts were tested. (See Figure 1)
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Figure 1 – Finite element analysis of the actuator casing |
Modal analysis of the actuator was preformed to determine natural frequency, and to insure rigidity of the extended structure. (See Figure 2)
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Figure 2 – Modal analysis of the actuator for resonant frequencies |
The flow geometry through a valve body is critical for flow stability, capacity, and valve performance. CFD analysis (computational fluid dynamics), a design tool that permits "virtual flow testing," was employed to refine and optimize the valve flow geometry before actual parts were ever tested in a flow line. CFD techniques provided capacity and flow characteristic analysis, cavitation predictions, fluid force and flow field analysis. Later flow testing of prototype parts found agreement within 5% of the CFD predictions. (See Figure 3)
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| Figure 3 – CFD analysis of the valve body flow geometry |
As the design direction solidified, testing of prototypes commenced in the Fisher Test and Evaluation Facility in Marshalltown, Iowa (USA). The key objectives were to validate performance and modify the design if required, and insure that the new product line was robust, accurate, and most of all - reliable.
Valve body and trim prototype flow testing was conducted to verify capacities and "fine-tune" the flow characteristics. Once the flow geometries were finalized, flow capacity tests were conducted on production valves for every body size and trim set combination.
Extensive testing of the valve trim parts was conducted to insure shutoff and flow performance. Galling tests were performed on the contacting parts to insure material compatibility.
The actuator prototypes were subjected to an arduous testing process to insure the design would provide long service in a wide range of applications and environments. The rigidity of the various actuator sizes was verified through vibration resonant frequency testing. The actuator diaphragm material underwent accelerated aging tests in kilns at elevated temperatures up to 116°C (240°F) to simulate the aging effects of a high-temperature environment.
Rapid cycle testing was performed on the actuator prototypes, in which the actuator was fully opened and closed for a minimum of 300,000 cycles at full casing pressure (100,000 cycles each at -29°C / -20°F, ambient, and 82°C /180°F on one actuator). This was done to test the pressure integrity of the actuator casing and diaphragm, and verify the strength and operability of the actuator assembly.
After testing, the actuators were torn down, and all parts examined for wear and damage. Improvements were made to the design if required, and the testing repeated.
As a further design verification step, field trial units were shipped to control valve users around the world for "real life" in-line testing in a variety of applications. Feedback from the installation sites is that the valve and actuators are performing well, and that users are pleased with the product features.
The culmination of the development project has been the introduction of the Fisher Design GX control valve. This capable and reliable globe-style control valve is available in sizes 1 – 4 inch for ANSI Classes 150 and 300, and in sizes DN25 to DN100 for body ratings of PN 10-40. (See Figure 4)
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The Design GX is available in a wide range of materials (carbon steel, stainless steel, alloys), and comes with live-loaded PTFE environmental packing as standard. Graphite packing, extension bonnets, and bellows extensions are available.
The Design GX has been optimized so that no actuator sizing is required. Once the valve body size and flow capacity has been selected, the actuator choice is easy and automatic – there is only one actuator for each body size / port size combination. No spring selection is required, and bench set considerations have been eliminated.
The valve and actuator design architecture has been optimized so that a number of parts can be used across valve sizes. As a result, product complexity and inventory costs are reduced. The packing sets and plug/stem assemblies are common across several valve sizes. The actuator power modules (casing, springs, and diaphragm) are modular and are used across the valve size range, and the stem connector is common to all sizes. |
| Figure 4 – Fisher Design GX Control Valve and DVC2000 Digital Valve Controller |
The new Fisher DVC2000 Digital Valve Controller was developed in parallel with the Design GX control valve. The DVC2000 incorporates the powerful diagnostics of FIELDVUE into an easy to use package that has automatic calibration and tuning capabilities. The information that it provides, via PlantWeb digital plant architecture, can be used to simplify the maintenance of the control valve.
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The push button configuration and multi-language LCD local interface make the DVC2000 simple to commission and operate. When fitted to the GX valve, the DVC2000 mounts directly to an interface pad on the actuator yoke leg, eliminating the need for mounting brackets. Internal passageways in the actuator route the pneumatic output to the actuator casing, eliminating the need for external air supply tubing in most constructions. The GX will also accommodate other valve positioners, via the NAMUR mounting standard.
The DVC2000 features linkage-less position feedback when mounted to the GX control valve. There are no touching parts between the controller and the valve stem, which simplifies controller installation. If maintenance is required, the DVC2000 can be easily removed from the valve. (See Figure 5)
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Figure 5 – Integrated positioner with linkage-less feedback |
The Design GX assembly line was designed with product reliability and quick delivery in mind. The assembly line incorporates stations for testing friction, travel, and seat leakage while the valve is being assembled. Pass/ fail alerts tell the technicians whether the valve assembly is performing to the product specifications. (See Figure 6)
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In summary, the Design GX was designed with valve end-user requirements as the driving force. Reliability and robustness have been designed into the GX control valve platform to maximize process uptime. The optimized design architecture, incorporating modular components, drives down inventory costs and maintenance training requirements. Valve selection is simplified, as no actuator sizing is required, reducing engineering costs.
When mounted with a DVC2000 digital valve controller, the Design GX offers increased installation and maintenance simplicity. Tubing is eliminated in most cases, and the controller can be calibrated at the push of a button.
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| Figure 6 – Valve assembly line, with station for testing travel, seat leak, and friction. |
In closing, Emerson Process Management is pleased to announce that the very first Design GX sold went to a pulp and paper mill in the United Kingdom. The GX is serving as the speed control valve to the main grinder, which grinds the incoming logs. Reports are that the Design GX is performing well.
Author:
Paul Gassman is the Sliding Stem Valve Product Manager for the Fisher Valve Division of Emerson Process Management.
For additional information, contact a local Emerson/Fisher sales office.
About Emerson Process Management
Emerson Process Management (www.emersonprocess.com), an Emerson business, is a leader in helping businesses automate their production, processing and distribution in the chemical, oil and gas, refining, pulp and paper, power, food and beverage, pharmaceutical and other industries. A division of Emerson, Fisher Controls International LLC (www.emersonprocess.com/fisher) is a global leader in the design, manufacture and application of final control systems. Fisher’s technology and innovation in process control play a key role in Emerson’s combining of superior products and technology with industry-specific engineering, consulting, project management and maintenance services. Emerson brands include: PlantWeb®; Fisher®; Micro Motion®; Rosemount®; DeltaVTM; Ovation®; and AMS
About Emerson
St. Louis-based Emerson (www.gotoemerson.com) is a global leader in bringing technology and engineering together to provide innovative solutions to customers in process control; electronics and telecommunications; industrial automation; heating, ventilating and air conditioning; and appliance and tools. Sales in fiscal 2002 were $13.8 billion.
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Fisher, PlantWeb, Rosemount, Micro Motion and DeltaV are marks of one of the Emerson Process Management family of companies. Other marks are the property of their respective owners. |