If a formal valve specification is not available, obtaining most of the following information can get the discussion started. You can also use this email worksheet to have one of our technical support specialists guide you through the selection process. The same criteria is also beneficial with a formal valve specification but the selection process becomes simpler.

• Identify if valve is a 2-way valve for flow, pressure or temperature control or a 3-way mixing, bypass or diverting application
• Type of operator – Pneumatic or Electric
• Control Signal (type and value) and any required accessories
• Modulating Service or ON/OFF Service
• Valve size, connections & materials of construction if important
• Flowing Medium (water, steam, air, etc.)
• Flow Rate required (gpm, lb./hr., scfh, etc.)
• Pressure at the valve inlet (psig - Normal & Maximum)
• Pressure drop available fully open (psid)
• Temperature at the valve inlet (deg. F - Normal & Maximum)

Much of the criteria listed above is also used is sizing a valve for occasions where an engineering specification was not created. This process them becomes known as Sizing & Selecting. Much verification is involved to ensure safe and proper performance of the complete control valve assembly. This is best accomplished through the use of the Warren Sizing & Selection program or by working directly with one of our sales engineers.

Globe valves have earned their distinction as the preferred control valve style. The flow path through a globe valve spreads a pressure drop through the entire device, while other valve styles tend to concentrate the pressure drop at the vena contracta. The vena contracta is the place in the final control element where flowing velocity is at its maximum, and pressure is at its minimum. It is the place where phenomena such as "flashing", "choking" and "cavitation" originate. Because it slows pressure drop and recovery rates within its body, the globe valve is more resistant than ball, plug and butterfly valves to those counter-productive, sometimes destructive events. This inherent stabilizing characteristic of the globe valve enhances its ability to control a fluid stream. Additionally, ball valves have inherently higher dB levels of audible noise compared to globe valves, contributing to potential OSHA violations, regardless of the now common characterized trims.