Valves for relieving pressure from high-pressure fluid systems have a valve fitting and a valve actuator. The pressure relief valve is normally shut and is adapted to open at a relief fluid pressure. It comprises a valve fitting and an actuator. The actuator has a valve stem, a spring, and an electromagnet. The stem is coupled to a valve body and mounted for linear reciprocation. The spring applies a mechanical force that biases the stem to place the valve in a normally shut state, but allows the valve to open at a first fluid pressure below the relief pressure. The electromagnet applies a magnetic force that, together with the mechanical force, holds the valve in an operationally shut state at a second fluid pressure above the relief pressure. The valve may be opened at fluid pressures above the first fluid pressure by de-energizing the electromagnet at the relief pressure.

A ceramic balancing check valve has a valve housing, a controller, a balancing valve unit, and a check valve unit. The valve housing has a main body having two side drainage holes, a control rod. The controller has an upper ceramic plate, a lower ceramic plate, and a base, the lower ceramic plate secured on the base, the upper ceramic plate capable of rotating relative to the lower ceramic plate. The control rod is capable of rotating and driving the upper ceramic plate. The upper ceramic plate has a side outlet aligned with the side drainage hole and a bottom outlet. The lower ceramic plate has two first hot intake holes and two first cold intake holes and further has a first hot and cold outlet. The base has a second hot intake hole, a second cold intake hole, and a second hot and cold outlet.