A safety valve is usually a mechanical valve controlled by a preset spring pressure. The safety valve consists of a steel spring in the centre, a cone, a seat, an outlet and an inlet, and a lighter. The safety valve spring holds the valve closed. If the system pressure increases, the system pressure overcomes the force of the safety valve spring, resulting in compression of the safety valve spring. Now the safety valve will open and blow off the excess pressure that has built up in the system. Once the safety valve has opened and blown off the overpressure to normal operating conditions, the spring in the valve will overcome the force in the system, causing the valve to close again.
The spring force is important for a safety valve, as an incorrectly adjusted valve could in the worst case lead to an explosion. However, if the spring is broken, the valve will not be able to withstand the system pressure, which leads to it blowing off continuously and creates an economic loss as expensive media is blown off via the safety valve.