Diagnostic Tools for Control Valves

Dr. Jörg Kiesbauer
SAMSON AG,Frankfurt/Main
Digital positioners offer interesting features regarding improved process plant reliability and maintenance or servicing. This could provide the basis for using software tools for early fault diagnosis and performance visualization of control valves with extended functions. These tools can completely preserve the control valve 's condition when new. It can be subjected to trend analyses as well as to preventative maintenance and servicing while in operation.This article describes these possibilities based on an example of such a new diagnostic tool.
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Intrinsic safety and flameproof enclosure -
an impossible team in explosion
protection?

Dipl.-Ing Guido König and Prof. Dr.-Ing. Heinfried Hoffmann
SAMSON AG, Frankfurt/Main
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Valve sizing from Samson Controls

General information

Demo version

Update to current version

Other Links
Valve Sizing and Selection - Sizing flow valves is a science with many rules of thumb that few people agree on.  This article covers  a more standard procedure for sizing a valve as well as helping to select the appropriate type of valve. From Cheresources.com

Samson Controls - Technical Information 

Samson Controls - Technical Information - Some great information from our valued sponsor Samson Controls
Cavitation in Control Valves
Introduction to Self-operated Regulators
Plant design and control valve selection under increasing cost and time pressure, Part 1 and Part 2 - thanks to Samson Controls, Conval and Valve World 
Control valve design aspects for critical applications in petrochemical plants - Part 1, Part 2 and Part 3 - thanks to Samson Controls, Conval and Valve World . This is an excellent paper in three parts which covers Control Valve Design and Sizing.
Temperature Regulators - The characteristic feature of self-operated temperature regulators is their compact design, including a sensor, a valve and a capillary tube. Their simple operating principle is based on fundamental mechanical, physical and thermodynamic laws.
Enhanced reliability for final elements thanks to SA Instrumentation and Control

Noise Calculation and Prediction

Valve Noise Prediction verses Velocity Head Limitations in Gas Applications-Joseph Shahda - Principal Engineer Masoneilan -from our valued sponsors Austral Powerflo Solutions and Masoneilan
In recent years, the control valve industry has seen an important debate about the validity of limiting the valve trim exit velocity head to a maximum of 480 kPa in gas and steam applications. This velocity limitation is assumed to provide an acceptable noise level and avoid problems that arise in control valve gas and steam applications. However, in a very large number of applications, adopting a velocity limiting approach may require the use of expensive multi-stage or multi-turn trim designs.

This article demonstrates that low noise levels can be achieved without following this overly conservative and expensive trim exit velocity head limitation. It also highlights that having a trim exit velocity head lower than 480 kPa will still generate a very high valve noise level if the valve outlet Mach number is high.

Masoneilan Noise Control Manual-from our valued sponsors Austral Powerflo Solutions and Masoneilan

This 24 page manual provides comprehensive informative material regarding noise in general and control valve noise in particular. 

It covers Control Valve Noise, Aerodynamic Noise Prediction, Aerodynamic Control Valve Noise Reduction, Atmospheric Vent Systems, Hydrodynamic Noise and Installation Considerations.

Selection and Application

Avoid control valve application problems with physics-based models -Kinetic energy criteria have many limitations- from our valued sponsors Austral Powerflo Solutions and Masoneilan -This article explores the rationale for KE limitations and demonstrates that KE criteria often provide very rough approximations of the actual physical phenomena that cause valve problems

Implementing MPC to Reduce Variability by Optimizing Control Valve Response- Ever had a problem with split range valves, this paper may just help! Thanks to www.controlglobal.com and our sponsor Emerson Process Management 

Maintenance

8.09 How to achieve optimal Control Valve Performance - Shawn Anderson and Neal Rinehart. - Leaders in the process industries realise that good process control performance is an essential element in achieving world-class reliability as well as optimizing overall process efficiency. Since control valves are the only devices in the process loop that actually “move” to adjust the process, their performance is critical. The best way to achieve excellent performance is to initially select the most appropriate final control valve for the application and then to maintain its performance over time -from our valued sponsor Emerson Process Management

1.10 Other Links  to Articles on Control Valves

The Plant Maintenance Resource Center has some very useful links on Control Valves including;

• Control Valve Actuator Operating Modes - Details on fail safe conditions, fail closed and fail open.

• Control Valve Concepts - Control Valves Do What They Are Told!
• Control Valve Flow Characteristics - Trim design will affect how the valve capacity changes as the valve moves through its complete travel. Because of the variation in trim design, many valves are not linear in nature. THE RELATIONSHIP BETWEEN VALVE CAPACITY AND VALVE TRAVEL IS KNOWN AS THE FLOW CHARACTERISTIC OF THE VALVE. Valve trims are specially designed, or characterized, in order to meet the large variety of control application needs. This is necessary because most control loops have some inherent nonlinearities, which you can compensate for when selecting control valve trim.
• Control Valve Packing - Packing is a sealing system which normally consists of a deformable material such as TFE, graphite, asbestos, Kalrez, etc. Usually the material is in the form of solid or split rings contained in a packing box. Packing material is compressed to provide an effective pressure seal between the fluid in the valve body and the outside atmosphere.
• Control Valve Seat Leakage Classifications - There are actually six different seat leakage classifications as defined by ANSI/FCI 70-2-1976. But for the most part you will be concerned with just two of them: CLASS IV and CLASS VI. CLASS IV is also known as METAL TO METAL. It is the kind of leakage rate you can expect from a valve with a metal plug and metal seat. CLASS VI is known as a SOFT SEAT classification. SOFT SEAT VALVES are those where either the plug or seat or both are made from some kind of composition material such as Teflon.
• Control Valve Terminology - A comprehensive terminology list.
• Control Valve Tips & Tricks - An excellent list of useful tips and tricks for the control valve user.
• Control Valves - Flow Recovery Coefficient
• Control Valves - Pressure Recovery Factor
• Improving Valve Life and Operating Efficiency The Easy Way -  John C. Robertson - Eight often-overlooked valve maintenance basics.
• Use of Ultrasonic Analysis in the Testing of Isolating Valves - Offshore installations use a series of isolation valves to divert the flows from the various pumps. One of the main reasons a pump test can "fail", is if the isolating valves are passing. This article describes testing the isolating valves using ultrasonic analysis. Overhaul of an isolating valve costs significantly less than undertaking an unnecessary pump major overhaul.
• Valve Positioners - Some general but useful information on valve positioners.

1.10 Your Best Bet in Control Valves - Hans Bauman - Control valves may be the most important, but sometimes the most neglected, part of a control loop. The reason is usually the instrument engineer’s unfamiliarity with the facets, terminologies, and areas of engineering disciplines, such as fluid mechanics, metallurgy, noise control, and piping and vessel design that can be involved depending on the severity of service conditions - From ISA and InTech.

1.10 Determine the Characteristic Curve of an Installed Control Valve - Jeff Sines - The performance of a control valve is defined by its inherent and installed characteristic curves. The inherent characteristic curve is a plot of the percent of valve opening vs. the percent of maximum flow coefficient (CV). The inherent characteristic curve is determined by measuring the flow rate at various positions of valve travel with a fixed differential pressure across the valve (typically 1 psid) and calculating the CV at each position using a form of the generalized Control Valve CV equation - From Engineered Software.

Other Applications 

  Composite Valves 

Looking for a valve without corrosion problems? These valves made from plastics and potentially using Nanotechnology techniques may just solve them.

  Specialist Power Plant Valves

These valves are specific to those power plant issues such as de-superheaters, steam service etc.

Selection and Application of Positioners, Limit Switches, Solenoid Valves and Other Accessories- Information from our valued sponsor Samson Controls

Doing Business Differently-Digital Positioners-from our valued sponsors Austal Powerflo Solutions and Masoneilan

The Next Generation of Smarter Valves part 1 and part 2 - By Béla Lipták, thanks to ControlGlobal.com

Smart technologies sustain plant reliability, help control costs - Todd Gordon - This article highlights the benefits of DVC technologies in a power plant - from Emerson Process Management.

1.10 Positioner and Actuator Operating Modes - The terms "direct" and "reverse" are frequently used when discussing control valves, positioners, and controllers. While the definitions of direct and reverse seem pretty straightforward, they cause quite a bit of confusion - especially when split-ranging is done. From The Plant Maintenance Resource Center.
6.10 The Wireless Option - Harcros Chemicals Rethinks Its Position on Valve Positioning - Kurtis Jensen, Kevin Root & Lloyd Hale - From the outside, a chemical plant may look like a series of pipes, tanks, and railcars. However, within these plants, there are many valves that are employed to move liquids throughout the chemical production process. Some of these valves may be operated manually, which, generally speaking, increases the chance that they may be left in a position that is unwanted. In such a scenario, it would be advantageous to have some automated valve monitoring capability to ensure the appropriate positioning of valves in real-time. However, the complexity of hard wiring such valves is cost-prohibitive. Hence, the evolution of industrial wireless systems has opened up new opportunities for valve positioning applications in the chemical processing industry - from www.flowcontrolnetwork.com 

  Valve Actuators

This is ICEweb's Technical Information on Control and Quarter Turn Valve Actuators