The Protectoseal Series No. 500 Flash Arrester Fill Units are particularly suited for installation in storage tank openings where tanks are filled by direct connection from trucks or railroad tank
cars. These fittings include a perforated metal flash arrester to protect tank contents against fire and explosion from external sources of ignition when the fill hose is not connected.
Installation is made by simply threading the fitting directly onto the tank fill pipe. The hose from the supply source can then be connected to the external NPT threads on the head assembly. Liquid
flows through the perforated metal flash arrester into the tank. When the hose is removed, this flash arrester prohibits ignition of the vapors inside the tank if some external ignition source is
present. When the fill line is not in use, the opening should be covered by the cast threaded cap that is provided. This cap may be padlocked for added security. It is recommended that the storage
tank be fitted with a Protectoseal flash arrester/venting device, such as the Series Nos. 830, 860 or 670. When properly sized and applied, these supplemental vents will prevent excessive pressure
or vacuum accumulations within the tank during filling and emptying