Selecting a Butterfly Valve Instead of a Globe Valve for Fluid Control in a Utility Service in the Offshore Industry (Based on an Industrial Experience)

Karan Sotoodeh

doi:10.12691/ajme-6-1-4

Abstract

Straight pattern globe valves are widely used in the oil and gas industry to regulate and control the flow of fluids. During operation, these valves are exposed to problems such as cavitation. Cavitation happens when the pressure in a liquid suddenly drops, leaving behind a bubble of gas. There are some strategies that can be used to mitigate the risk of cavitation, such as designing the valves as per API 623 standard, selecting a different valve type such as Y-Type or axial valves, or hard facing the valve internals. These solutions increase the cost of valve selection and are more suitable for the valves in process services, such as valves containing hydrocarbon. The main question this research seeks to answer is whether a butterfly valve (e.g., wafer type) is a good replacement for a straight pattern globe valve in utility services such as water. It is noticeable that wafer type butterfly valves are much cheaper than globe valves, especially when it comes to exotic materials. 12 control valves in water services in titanium and duplex in an offshore unit were selected for research. The manual valves on the bypass of the control valves were evaluated for globe or butterfly valve selection. The data analysis included two methods of cavitation analysis and pressure drop analysis. The risk of cavitation for both butterfly and globe valves is almost the same. The analysis shows that butterfly valves are slightly more prone to cavitation risk. When it comes to pressure drop calculation analysis, none of the globe valves were suitable. On the other hand, 6 butterfly valves were suitable for the fluid control after pressure drop and cavitation analysis. In conclusion, butterfly valves are recommended for fluid control in utility services such as water.

Highlights

Valves are mechanical devices in a piping system that are used to direct, stop, start, mix, and regulate the flow, pressure, or temperature of the process fluid. [1] Straight pattern globe valves, widely used in the oil and gas industry, allow the flow to be regulated or controlled
Straight pattern globe valves that are used in the oil and gas industry are at high risk of cavitation during fluid control operations
For this reason a relatively new standard, American Petroleum Institute (API) 623, was created to design a more robust straight pattern globe valve by hard facing the valve internals, creating a stronger connection between stem and disk, and other solutions. More expensive valves such as Y-type globe and axial valves can be used for fluid control in process services such as hydrocarbon

Summary

Introduction

Valves are mechanical devices in a piping system that are used to direct, stop, start, mix, and regulate the flow, pressure, or temperature of the process fluid. [1] Straight pattern globe valves, widely used in the oil and gas industry, allow the flow to be regulated or controlled. In many globe valves in liquid services, the pressure at the narrow area below the plug can drop below the vapour pressure of the liquid When this happens, “flashing” can happen when the bubbles of the gas are vaporized from the liquid. The bursting bubbles that cause cavitation can produce excessive noise and vibration and create localized stresses (loads) on the valve bodies in addition to pitting, corrosion, and erosion. These problems reduce the efficiency of the globe valve

New Standard

Conclusions & Recommendations