Muffled 'pop' safety valve, c 1875. Section

Muffled 'pop' safety valve, c 1875. Sectioned. Locomotive safety valve of the type patented by Mr G H Crosby between 1875 and 1905. The name of this valve is due to the popping sound made by the sudden release of steam. It is designed to open suddenly to its full extent when the boiler presure exceeds the working presure. The valve is fitted with a muffler to quieten the discharge, which it does without causing any back presure.