Abstract: The manually actuable electric switch has a fusible element which melts on subjection to a predetermined temperature to discontinue the flow of electric current through the switch. The structure is incapable of operation on melting of the fusible element without replacement of the element, thereby preventing accidental reactivation of the switch prior to termination of the unusual thermal conditions causative of the melting of the element. A manually operable plunger normally used to open and close the switch is mechanically connected to the stem of the switch through the fusible element. Melting of the element severs the mechanical connection between the plunger and the switch.

Abstract: A shutoff valve installed on the discharge side of a pump to automatically shutoff hazardous liquid flow in the event of a rupture on the downstream side of the shutoff valve. The shutoff valve operates in response to a predetermined pressure drop across a valve and may also function to stop the driver of the pump and close the shutoff valve in response to excessive temperature conditions. Various installational arrangements may be provided in order to associate the shutoff valve with the hazardous fluid flow line.