Boiler mounting refers to the fittings and devices necessary for the safe operation of a boiler. These include two safety valves, a steam stop valve, a feed check valve, a fusible plug, and a blow off cock. The blow off cock is used to discharge water from the boiler periodically to remove mud and scale. It consists of a plug, body, shank, and wheel. The safety valve opens automatically when steam pressure inside the boiler exceeds safe limits to prevent overpressurization. The spring loaded safety valve commonly used has a valve, springs, standards, and lever to lift the valve off its seat when pressure rises above the threshold.