The Mark 63 is designed to maintain a constant differential between the pressure on the discharged side of the regulator and the signal pressure loaded on the diaphragm. The Mark 64 provides the same flow capacity as the Mark 63, but with less offset in controlled pressure due to a larger diaphragm.
The Mark 63CDF features a flow-through spring housing that is designed to permit “in-oil-line” installation. This is especially desirable where air or steam is used for fuel oil atomization.
The fuel oil flow through the spring housing reduces the possibility of the oil asphalting on top of the diaphragm, which would cause a loss of differential pressure control and operating sensitivity. For added protection in this service, the Mark 63CDF includes a separated double diaphragm that prevents the fluids from mixing in the event the diaphragm were to rupture.