válvula de alívio de pressão

A pressure-relief valve has a housing having an annular flange defining a pressure-vent hole centered on an axis and having an axially directed end face and a radially outwardly directed outer surface. A cap can fit axially over the flange in a closed position and has a skirt radially juxtaposed with the outer surface in the closed position. A spring braced axially between the cap and the housing urges the cap into the closed position. A first annularly continuous seal secured to the end face axially bears on and hermetically engages the cap in the closed position. A second annular seal secured to the outer surface has an outer edge elastically engaging the skirt in the closed position and formed with a notch through which fluid trapped between the first and second seals in the closed position can drain.