How To: The Top 10 things to consider when selecting ...

You've been assigned the critical task of selecting industrial valves for a project or maintenance work, and you've been given a list detailing the specific valves, sizes, and specifications required. That's an excellent starting point!

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However, it's essential to consider how much thought has been put into determining if the specifications are accurate, whether the selected valves are appropriate, and if they will effectively fulfill the intended purpose.

Many assumptions often accompany the valve selection process, including:

• 'This is what we used previously' 'for a completely different process

• 'Contractor X specified we should use this' 'but based on what evidence?

• 'The site's standard is X' 'but what if that valve type is unsuitable for this application?

• 'We've always used this valve' 'yet have been dealing with persistent downtimes and frequent failures

Getting your valve selection right from the outset is crucial. In this article, I will guide you through a straightforward 10-step process to ensure your valve selection is informed and based on facts rather than assumptions.

Introduction:

I recognize that numerous checklists for valve selection are already available in the market. Some of them are fairly simple but unfortunately also incomplete, while others may be so complicated that those who are not experts struggle to grasp the key concepts.

Over the years, having worked in various valve application fields such as Oil & Gas, Power Generation, and Waterworks, I have developed my own checklist. This checklist encompasses all the crucial points to consider when selecting on-off valves. I aimed to share personal insights, tips, and external links that could help mitigate common errors during the valve selection process.

This might not be groundbreaking information for seasoned valve specialists, but it could be a genuine aid for any newcomers venturing into the valve selection domain.

THE 10 POINT VALVE SELECTION CHECKLIST (by Michel F. Bolle)

1) Applicable Main Standard – DIN (EN)/ASME or Others?

Often overlooked, clarifying applicable standards is one of the most critical aspects of valve selection. Two primary standards dominate the valve market: EN (European) and ASME (American).

Depending on where the facility operates, one standard may be preferred over the other. This information is typically stated in the project's technical specifications.

Other applicable standards may include GOST (Russian) or AWWA (American Water Works Association), among others. In the EU, for instance, most valves are subject to PED standard requirements. Therefore, it would be impossible to install a large, high-pressure gate valve made in the USA within the EU without CE marking and the requisite PED approval.

TIPS:

Under EN standards, pressure class is indicated in PN while size is specified in DN; conversely, American standards refer to pressure class as #(lbs) and size in (inches). Don't take this as an absolute rule on new or replacement projects. A valve labeled as DN 400 with PN100 may not necessarily comply with EN standards, leading to widespread confusion as many mix up EN & ASME standards, and hybrid (mixed standards) valves flood the market. Always double-check!

2) Type of Valve?

The required valve type is typically determined by the process and its primary function. Will the valve serve solely for isolation (on-off) purposes, or do we need it to control a specific flow? Is it meant to prevent back-flow or function as a safety valve? Should the valve be suited for steam (most likely a gate valve) or water (often a butterfly valve)?

Additionally, it is crucial to establish whether the valve needs to seal in both directions (e.g., a soft-seated centric butterfly valve) or only in one direction (e.g., a double eccentric butterfly valve).

For replacement projects, the decision is relatively straightforward, as existing valves are usually swapped out for the same type.

TIPS:

A valuable source of information regarding different valve types and their applications is the catalogs from valve manufacturers, which typically detail the main applications for each valve category. For example: 'Gate / Globe Valves: optimal for steam.'

3) Size of Valve?

Valves are generally installed in piping systems where the pipe size is pre-defined. As such, selecting a valve that matches the pipe size is often straightforward. Nevertheless, several factors may affect valve size selection, including:

- Maximum Allowable Pressure Drop (if any)

- Maximum Flow Rate (if applicable)

It is essential to consider these factors when defining the valve size. Occasionally, the valve size may be larger or smaller than the pipe size, which could be a significant cost-saving consideration.

TIPS:

For numerous valve types, such as globe or ball valves, two size options are generally available in the market: Full Bore or Regular Bore (Reduced bore). Knowing if there's any requirement for maximum allowable pressure drop is vital when making this choice.

For example, if a valve is located at the bottom of a pipe meant solely for water drainage, the pressure drop may not be overly significant, allowing for the use of a reduced bore valve. Conversely, if required for a steam system directing steam to a turbine, pressure drop considerations may be vital to the turbine's performance.

4) Pressure Class?

In many situations, the pressure class for a valve is determined by the piping system's defined pressure class.

If not provided, the pressure class is influenced by the pressure, temperature, and the materials used for the body and bonnet of the valve.

TIPS:

To accurately determine the pressure class, it is crucial to be aware of the design pressure and temperature for the piping system. If one specifies a pressure class based on operating conditions, the chosen valve may not withstand the worst-case scenario.

5) Body/Bonnet Material?

The material selection for constructing the main valve components (body/bonnet) is largely influenced by the medium it will be exposed to. It falls upon the valve specifying engineer to first ensure material compatibility with the medium (gas, steam, fluid, etc.). Additionally, the piping system's design conditions must be taken into account (e.g., cast-iron WCB has a temperature threshold of 425°C).

If the piping system's material is already established, consider yourself fortunate; you can choose the valve with matching material properties.

TIPS:

Don't forget that external conditions can significantly affect material choice. For instance, while A105 carbon steel is ideal for a globe valve in Central Europe, in Russia's cold winters, using LF2 material rather than A105 may be necessary. Very corrosive environments might also necessitate Aluminium Bronze over Stainless Steel for valve body material.

6) TRIM Materials?

Choosing the trim (stem/seat/disc or ball) materials typically aligns with the selected body/bonnet materials and is also contingent on the medium, design conditions, and the desired leakage rate.

While discussing trim, encompassing all sealing materials directly interacting with the trim (e.g., gaskets, packings) is paramount.

For more information on gate valve manufacturers in the USA, please contact us; we are happy to provide professional advice.

Additional factors that could influence material selection are how frequently the valve will be used and its expected lifespan. Based on this, higher-grade trim materials may be necessary.

TIPS:

If your operation might generate vacuum conditions while the valve is in service, you may need to modify the trim materials & design (e.g., lantern rings on gate valve packings).

A widely used reference for this is the API Trim chart. Here’s a useful link:

https://blog.projectmaterials.com/valves/api-trim-chart/

7) Leakage Rate (Valve Testing)?

Often associated with trim considerations, the maximum allowable leakage rate is a critical factor that is sometimes overlooked. Some applications may not prioritize this aspect; however, once leakage requirements are addressed, it becomes essential to determine the applicable valve testing standard.

Here’s an excellent overview and explanation of the different standards:

http://globalsupplyline.com.au/wp-content/uploads//10/Valve_Leakage_Rates_Test_Std.pdf

TIPS:

Defining '0' leakage on its own is misleading and often confused with 'bubble-tight'. Always verify which standard governs the maximum allowable leakage rate.

8) Connections?

The most common connection types for valves are screwed (ex: NPT or Gaz), welded (SW or BW), or flanged.

Usually, the connection type is defined by the integration of the entire piping system. Consider safety dimensions, emission aspects, and maintenance requirements while making connections.

Ensure that the valve connection precisely matches the pipe connection.

TIPS:

Experience suggests certain trends in connection usage:

- Power Plant Steam Systems: Welded (up to 2” SW, larger BW)

- Refineries: Flanged

- Gas Systems: Welded

- Residential Heating Systems: Screwed

- Water Distribution/Wastewater: Flanged

9) Actuation

Once we have determined the valve type, we need to decide how to operate it. Common actuation methods include:

- Hand-operated (lever/hand wheel)

- Electric actuator

- Pneumatic actuator

- Hydraulic actuator

- Self-actuated (by the medium)

TIPS:

Note that electric actuator voltage requirements can vary depending on installation location. This must be confirmed when selecting an actuator. The size of hydraulic and pneumatic actuators depends on the available minimum air or oil pressure.

10) Painting

Over the course of my past 20 years' experience, I've observed that one in every two Non-Conformance Reports (NCRs) related to valves has stemmed from painting issues.

Various projects may involve specific painting specifications or color codes. The decision on painting can be influenced by factors such as temperature resistance (both ambient and medium), location, color codes, and required painting thickness, making it a crucial aspect often neglected during valve selection.

TIPS:

Typically, stainless steel or aluminium bronze valves are supplied unpainted; however, in some instances, piping color codes necessitate painting for these valves. Always check twice.

Other Considerations for Valve Selection:

• Accessories (limit switches, solenoid valves, lantern rings)
• Noise
• Emission
• Weight
• Dimensions
• Installation (e.g., horizontal or vertical)

Despite the complexities involved, valve selection need not be overwhelming. By following a straightforward checklist that assures all critical factors are considered during the selection process, you can make informed decisions.

If you find yourself lacking knowledge in specific areas, such as material resistance, don't hesitate to consult with your trusted valve partner. Valve manufacturers are typically eager to offer guidance.

Last but not least, the time invested in a careful valve selection is a wise investment! Many valve-related issues at production sites arise from poor initial selection.

Feel free to share and comment on this article; feedback is always welcome.

Michel F. Bolle - Industrial Valve Expert - 20.6.

Contact us to discuss your needs for a Ductile Iron Ball Check Valve. Our experienced sales team is here to assist in identifying the best options suited to your specific requirements.

"Dedicated to the passion for industrial valves" - Michel F. Bolle

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