Control valves are valves that checks the flow or pressure of a fluid, within the production channel. These valves usually respond to signals that are independently triggered by devices such as flow meters and temperature gauges. For the purposes of efficiency, these valves need to work as designed to ensure smooth flow of operations within organization. However, this is not often the case as the valves may grow faulty.
It is always recommended that periodic examination of the control valve conditions be done to check the quality of the sealing, tightness of closed valves, their failures or leakage. This is to try and avert any possible loss that can result from the valves. There are two methods of control valve repair that can be used by any oil producing company. The first one being, on-site repair, which is meant for valves that are welded into pipelines, it is generally the most cost effective method. There are various tools and equipment that are used for onsite repairs depending on the type of the control valve and the extent of the damage. For instance, in globe valves with small and medium damage, and a normal diameter of DN 8 , VALVE S1 machine is used. The machine is electrically driven, or a compressed air motor and guided by hand. Onsite control valve repairs are cheap because it does not involve movement of valves from the site and no cutting tools are used as these valves are welded on the pipeline. Onsite repair can also be done on severely damaged gate valve housings. A local build up welding using the means via WIG process after which the sealing surface is grounded using a high speed grinding machine. The old damaged sealing is then removed and replaced with a new one after the necessary repairs have been made.
On the other hand, workshop control valve repair, which involves either partial or total repairs, are costly as compared to the onsite control valve repair. The machines used in the above process can also be used in the workshop. Here the valves are first sorted, then dismantling, marking, and then the inspection is done to locate the defects. Hydraulic or pneumatic screw drivers are very vital at this stage and so are the nut splitters. Then follows the cleaning process, which basically involves the either one or more of the below procedures:
- Sand or shot blasting either by using steel balls or glass pearls
- High pressure cleaning by steam or water
- Chemical solution washing in distict automatic machines
- Machine cleaning
The valves are again classified in two groups; one with valves that do not require turning or welding and the other, valves that require those operations. The repairs are then done according to the damage.