Which action is required before adjusting the relief valve in a hydraulic system with a pressure regulator?

To adjust the relief valve in a hydraulic system with a pressure regulator, it is essential to eliminate the action of the unloading valve. The unloading valve may interfere with the pressure readings and adjustments that need to be made. By disabling or eliminating its influence, you ensure that the pressure in the system reflects the actual operating conditions, allowing for precise calibration of the relief valve without any erroneous feedback from the unloading valve's operation.

Adjusting the relief valve involves setting the pressure at which it opens to allow fluid to escape and maintain system safety. If the unloading valve is active, it could disrupt the pressure levels that you are trying to set, leading to an inaccurate adjustment. Hence, taking this action ensures that the relief valve can be properly calibrated for safe and efficient operation within the specified parameters of the hydraulic system.