Why are pumps usually kept running when picking up to check for flow?

When pumps are kept running while picking up to check for flow, the primary reason is to ensure maximum pressure on the bottom of the hole. Maintaining this pressure is crucial during the process of checking for flow because it helps to prevent any potential influx of formation fluids into the wellbore, which could lead to a well control issue.

When the pumps are operating, they create a hydraulic pressure that counteracts the pressure from the formations surrounding the well. This is vital in preventing a kick or an uncontrolled flow of hydrocarbons from the wellbore into the drilling environment. By keeping the pumps running, the wellbore remains pressurized adequately, thus providing the necessary barrier against any influx while obtaining reliable data regarding the well's flow conditions.

It's important to link this procedure with well control principles, as the state of pressure management is at the heart of maintaining well integrity and safety during drilling operations.