A: When a building’s service pressure exceeds an appliances’ inlet pressure capability, a line regulator is added to manageably reduce the pressure. But if that line regulator were to fail, it could expose downstream equipment to the incoming service pressure. Accordingly, both the line regulator and appliance’s valve train need to be engineered with this possibility taken into account.
Unfortunately, failures like this are not uncommon. Equipment is often selected without consideration of the failure modes. Safety devices should be chosen with consideration of the maximum potential inlet pressure in the event of an emergency.
Alternately, OEM’s may not be aware of building service pressures when they specify and select components, instead opting for the cheapest solution. As a result, it is not uncommon to find a low-cost, low-pressure valve train improperly applied in a potentially high-pressure environment. In such situations the valve train may not provide the necessary protection and could fail in a variety of modes, the results of which may be catastrophic to the facility and employees.