The sub is designed to allow diversion of mud flow into annulus whenever required and combat common drilling problems, such as lost circulation and limited circulating rates. Sub operation control does not require dedicated trips.
It is always recommended to include the circulation sub into BHA in following cases:
Acid, chemical and bridging agent treatments, which can be dangerous for below located BHA components;
Reaming during loss of circulation, full loss of circulation;
Wellbore cleanout required for acceleration of the flow in annular space by increase of mud flow.
The sub has several configurations, which differ by number of operation cycles and activation/deactivation pressures without need of pulling out of hole.
There no need for presence of specific operational engineer at the rig.
