Patent GB-814729-A (GB)
Title: Improvements in or relating to systems for heating by circulation of liquids
Inventor: SAUNDERS JACK NORMAN
IPC: G05D16/18
Filed: 1955-08-19
Abstract: 814,729. Heating by circulation of fluids. WARMAC Ltd. Aug. 16, 1956 [Aug. 19, 1955], No. 23905/55. Class 64(2) [Also in Group XXIX] In a heating system in which liquid is circulated by a pump 14 through an automatically-stoked boiler 12 and radiators 13, the liquid is under pressure so that its temperature is above its boiling point at atmospheric pressure, e.g. water is circulated at 120 p.s.i. and 300-320‹F. Two interconnected vessels 15, 16 are used to maintain the pressure constant, pumps 25, for passing liquid from vessel 16 to vessel 15 through a pipe 20, being started automatically by a pressure-responsive switch 24 when the pressure falls in a pipe 19 connecting the top and bottom of the higherpressure vessel 15. The connection is through a valve 23 operated by a supply of pressure liquid controlled by the pressure in the vessel 15. Pipe 20 also includes, incidentally, an inlet 31 through which the system is charged. When the boiler 12 is started and the liquid in vessel 15 expands and the pressure rises, the valve 23 is opened automatically to allow liquid to pass to the expansion vessel 16 to the lower-pressure vessel 16. Raising of the liquid level in the vessel 15 operates a float valve in an external chamber, communicating with the vessel above and below the liquid level, so that nitrogen from bottles 18 passes into the chamber and thence to the vessel to restore pressure therein. Nitrogen replaces the initial air charge which passes into solution. Bottles 26 charge the lower-pressure vessel 16 with nitrogen to atmospheric or slightly higher pressure and a float, Fig. 5 (not shown), in a chamber 30 rises, when the liquid level of the vessel 16 rises, to open a valve (see Group XXIX) at the end of a pipe 37a at the top of the vessel to release nitrogen and prevent the pressure rising. Thus a constant pressure is maintained in the vessel 16. Any liquid lost from the system is replaced from a tank 27 by way of a float-controlled valve 29. If water under pressure, e.g. from a static head tank, is not available for use in operating the valve 23, it may be operated, Fig. 4 (not shown) with the aid of a flow of liquid bled off from the pipe 22 connecting the pipe 19 to the bottom of the vessel 15. This flow is cooled and passed, through a reducing valve, to a diaphragm of the valve 23 and then to a relay in which it is controlled by the pressure in the vessel 15, i.e. the valve 23 is responsive indirectly to the pressure in the gas space in the vessel. The flow drains, finally, to the float chamber 30 of the lower-pressure vessel 16. A rise in the pressure, in the vessel 15 above working pressure, arrests the bleed-flow from pipe 22 and opens the valve 23 until the pressure returns to normal. There are protection devices such as a pressure-relief valve 47 in the pipe 19 and an alarm circuit, Fig. 6 (not shown), closed for operation if a large leak should cause the pressure but not the temperature in the vessel 15 to drop or if the liquid level therein should fall due to failure of the nitrogen feed control and including a hand-reset solenoid switch, for controlling the firing of the boiler. The circuit has two switches in series and responsive respectively to the temperature and pressure in the vessel 15, the latter switch closing only when the pressure drops, and these switches are in parallel with a switch closed by a magnetic float valve 22a, in the pipe 22, when the liquid level falls. The Provisional Specification describes also a system in which pumps-maintaining pressure in the higher-pressure vessel are operated by a pressure-operated switch controlled by a thermostat and in which the nitrogen supply to the lower-pressure vessel is controlled by a pressure-responsive switch.