While reviewing multiple technical specifications from customers just this past year, areas were often discovered where products and technology would be excluded for reasons that may have been true years ago, but no longer apply. Using the word “shall” in a spec dictates no deviation from what is written, often forcing vendors to provide more expensive solutions.
Some unnecessary specifications include:
Provide throttling ball valve for pulp mill applications.
Provide globe valves for hot gas recycle applications.
Cage-guided valves should not be used with high-viscosity fluids, fluids that contain solids or in slurries.
Rotary valves shall have splined shafts to limit lost motion.
Stellite is not acceptable in boiler feedwater due to attack of water-treating chemicals.
Such requirements often deny a plant the chance to use new or different proven technologies. For example, a high-performance butterfly valve works just as well as a ball valve in most pulp mill applications. Angle valves can handle hot gas recycle applications just as well as globe valves in many instances, saving weight and often cost and lead time.
Often multiple solutions for the same application, such as outgassing, exist. In these instances, service conditions, sizing methods particular to the application (such as bracket sizing), and end user experience should help determine what valve is the best fit for a particular application. In outgassing applications, there are some cases where a more cost-effective rotary solution can be used, and others where a highly engineered severe-service solution must be used to withstand harsh operating conditions.
The requirement that cage-guided valves should not be used with high-viscosity fluids, fluids that contain solids or in slurries does not allow a plant to use new trim designs even when they would be perfectly acceptable and even a lower cost option in many cases.
The requirement that control valves with special trim for noise reduction should have globe bodies and cage trims eliminates the use of angle bodies or an even more cost-effective solution – a rotary valve with a noise attenuator. Depending on the application, an angle valve might be a better option than a globe valve, or a rotary valve with an attenuator could reduce noise levels and save money (see Figure 1).
The requirement that rotary valves shall have splined shafts to limit lost motion excludes large sizes of rotary valves and scotch yoke pneumatic actuators, often to the detriment of project costs and lead times.
As for the stellite requirement, in 2005 Emerson concluded an investigation revealing that feedwater treatment technologies and methods have changed significantly over the past 25 years, allowing Alloy 6 stellite to be an acceptable solution. And in many cases, 440C stainless steel is more cost-efficient and provides similar erosion resistance.