Ball Valve Repair: Should You Repair or Replace?
by Kelly Songer, Director of Valve Services, Precision Spray & Coatings
When deciding whether to repair or replace a valve, there are a few key factors to think about, like cost, maintenance schedules, and any issues with corrosion or erosion.
Start by defining your goals and what success looks like in terms of the valve’s technical needs. Repairing a valve can take time, so you want to be sure it’s the right choice—and it should only be considered if it's a cost-effective option. Before jumping into repairs, it’s worth considering if there are other valve types that could work better. Is the current valve the best fit for its location? Is it dealing with a tough service application? These are important questions to ask before moving forward.
Valve repairs can also play a role in planning for plant maintenance and shutdowns, and they support preventative maintenance efforts. In many cases, repairs can be completed in 2 to 6 weeks.
The Repair Process: Evaluation
Repairing a metal-seated ball valve involves multiple steps. In this article, we'll focus on evaluating components that are scrapped, replaced, or still repairable, and then dive into the processes of parts manufacturing and repair, including thermal spray coating, grinding, and lapping.
Scrapped Components:
Commonly scrapped components include one-time-use items like packing, body gaskets, thrust washers, seat gaskets, and any severely damaged parts or seats. Whether a component can be reused or not largely depends on the design of your valve.
Repairable Components:
These typically include the ball, stem, body, end piece, and metallic parts with minor damage. Such damage can often be fixed through welding, machining, or undercutting/coating to restore the components to their original size.
In many severe service design concepts, a straight-through flow port is used. Typically, the body and end piece do not experience significant damage unless there is a high-velocity leakage. However, leakage around the outside diameter (OD) of the seat can lead to additional erosive effects. If leakage occurs, assess the extent of the damage and determine if it can be repaired through welding. Extensive welding can result in distortion, and for deep welds, it's essential to adhere to relevant valve standards and pressure vessel codes.