Abstract: When plate heat exchangers are used with hazardous fluids the gasketing at the periphery may be replaced by welding the plates in pairs, with elastomeric gaskets between adjacent packs of plates. However, it is still necessary to have a gasket around the through holes (6) for the hazardous medium to seal them from the other medium. In accordance with the present invention, these gaskets are of duplex form (8, 9) with a sealed space (11) between the gasketing. In order to detect leakage into the sealed space a diluent fluid may be circulated through the sealed spaces and a detector, refer to FIG. 2.

Abstract: An electromagnetic fuel injector with a differential pressure actuated injector valve therein to control fuel injection is supplied with fuel at a predetermined supply pressure, the injector having incorporated therein a hydraulic fluid (fuel) powered booster pump means operable to increase the pressure of fuel from the original supply pressure to a higher injection pressure for effecting operation of the injector valve, the flow of hydraulic fluid (fuel) to effect operation of the booster pump means being controlled by a solenoid actuated valve means controlling inlet and discharge of fuel to a fluid control chamber in communication with the power piston of the booster pump through a control or metering orifice of predetermined size, whereby the rate of pressure intensification of fuel to the injector valve is controlled.