A pressure relief valve includes a valve body having an inner wall defining a cylindrical bore. The inner wall includes a threaded region having a plurality of threads. The valve includes a pressure control calibration spring including a calibration portion and a force application portion. The calibration portion is threaded into the threads of the threaded region. The valve body includes an aperture in fluid communication with the cylindrical bore. An inner perimeter of the aperture defines a valve seat. A valve member is receivable on the valve seat. The force application portion urges the valve member into engagement with the valve seat and has a pitch that is greater than a pitch of the calibration portion. Rotation of the calibration portion in the threads of the threaded region of the valve body adjusts the spring force applied to the valve member by the force application portion.

A pressure regulator manages fluid pressure along a pathway between an inlet port and an outlet port. A poppet opens and closes the pathway within the regulator. In certain regulators, a biasing member biases the poppet in common direction with the inlet port. In certain regulators, the poppet defines a through passage to route the fluid past the biasing member. In certain regulators, an adjustment interface arrangement enables a user to set what fluid pressure level closes the pathway by changing a pre-load applied to the poppet.