The area above the flowtube in a sub-surface safety valve (DHSV) tends to scale up easily, preventing the valve from closing. This is due to the geometry of this area, and the fact that the sliding motion of the flow tube is sensitive to scale. This will cause production loss due to frequent remedial cycling for cleaning of this surface. In the worst-case scenario, intervention is needed to mechanically clean this area.
Read more in our Field Case (pdf).