US3064631A - Arrangement for injecting water into a boiler operating under forced circulation conditions - Google Patents

Description

3,064,631 TING WATER INTO A BOILER OPERATING v UNDER FORCED CIRCULATION CONDITIONS E. SCHWANDER Filed Dec. 24, 1959 Nov. 20, 1962 ARRANGEMENT FOR INJEC RgeuLAToR- Patented Nov. 20, 1962 3,064,631 ARRANGENIENT FOR DIJECTING WATER INTO A BOILER OPERATING UNDER FORCED CIRCU- LATION CONDITIONS Erwin Schwander, Reichshoifen-Usines, France, assignor to Societe dEtude de Vehicules S.E.V., Reichsholfen- Usines, France Filed Dec. 24, 1959, Ser. No. 861,903 Claims priority, application France Dec. 31, 1958 2 Claims. (Cl. 122-451) The present invention relates to an arrangement for injecting water into a boiler operating under forced circulation conditions.

It is one object of the present invention to provide an arrangement for injecting water into a boiler operating under forced circulation conditions, with a view to adjust the input of water, of the type described, in particular, in the US. Patent No. 2,855,904. This patent applies to feed regulators, as described in the French Patent No. 795,764 and in the German Patent No. 671,- 961.

It is necessary, in order that the injection means may operate with a maximum efliciency and reliability, to satisfy the following conditions:

(1) the amount of injected water can be only a reduced fraction which is well defined With reference to the total amount of feed water; according to the power of the boiler, it should include 0.5 to 2% of the total amount of water;

(2) only pure water should be injected, so as to avoid any deposit of material on the feed regulator, the sensitivity of which would be otherwise jeopardized;

(3) the amount of injected Water should be always proportional to the amount of feed water introduced into the boiler during the injection period;

(4) the water introduced in small amounts should be injected pulsatorily, as far as possible.

It is therefore possible, at least in theory, to provide a small volumetric pump for the introduction of the injection water, said volumetric pump being driven by a control linkwork in unison with a piston pump forming the actual feed pump for the circuit.

The use of such a pump would lead however to the following drawbacks:

In the first place, it would be difiicult to control the suction through a valve for the very small volumes of liquid to be fed and, furthermore, the pump would feed throughout the compression stroke; in other words, it would not operate pulsatorily. Lastly, the unavoidable and variable losses of a piston pump would jeopardize the accurate measurement of the small amounts of water to be injected.

For the control of the feeding of once-through boilers, regulators are known, which respond to the steam condition, that means simultaneously to the pressure and the temperature of the steam. Such regulator is described in the French Patent No. 795,764. It consists of a small container which is partly filled with water, and which is disposed at a point of the boiler, in which the evaporation of the water is terminated. The pressure within the container is transmitted to one side of a membrane, while the pressure in the boiler at the point of disposal of the container is transmitted to the other membrane side. It is now clear that as long as the steam in the boiler is wet at that point or even dry saturated, the pressures in the boiler and in the container will be equal, and that the membrane remains in its balanced position.

If, however, the temperature of the steam rises beyond the saturated steam temperature corresponding to the prevailing pressure, the pressure in the container will be gerater than the pressure in the boiler, and the membrane will bend through by yielding to the increased pressure on one side thereof. This bending through is applied for the start of the feeding of the water, which feeding remains in operation until the membrane returns to its balanced position.

This method has the drawback that the boiler Will be overfed towards the end of the feeding period, since it does not have any return-feed. This remedy is provided in the French Patent No. 1,029,535 and the corresponding US. Patent No. 2,855,904. It resides in an arrangement according to which, upon starting the feeding of water, a very small quantity of water, which is exactly proportional to the quantity of water fed into the boiler, is injected pulsatory towards the described regulator, whereby this latter is cooled and the feeding is stopped. The long feeding period of the regulator, known before without return-feed, is divided thereby and a plurality of short feeding periods is created. The duration of the non-feeding periods and the duration of the feeding periods depend now upon the value of the over-temperature of the steam beyond the saturated steam temperature. An over-feeding of the boiler is, thereby, avoided.

It is, therefore, another object of the present invention to provide an arrangement for injecting water into a boiler operating under forced circulation conditions, which includes a diaphragm pump inserted in the boiler circuit and satisfies simply and fully the above conditions. The pump may be used in all cases where the feed pump comprises a piston pump equipped with one or more cylinders. I

With these and other objects in view which will become aparent in the following detailed description, the present invention will be clearly understood in connection with the accompanying drawing, in which the only FIGURE is a schematic showing of the water-feeding circuit of a boiler.

Referring now to the drawing, the feed water is sucked in by the piston pump 1 out of a suction pipe 2 provided with a suction valve 3. At each compression stroke of the pump system, the water is delivered upon opening of a delivery valve 4 into a delivery pipe 5, in which a nonreturn valve 6 is inserted. The water-feeding or delivery pipe 5 passe then through a cooler 7 and enters at 8 into the boiler 9; the part played by the cooler 7 will be defined hereinafter.

The steam obtained passes at the output point 10 out of the boiler 9 through a steam pipe 11 which is connected with the boiler. Inside the pipe 11, there is fitted ahead of the boiler valve 12, a regulator 13 and an injec tion nozzle 14. The latter is fed by a pipe 15 provided with a stop cock 16 and connected with the delivery end of a diaphragm pump 17 forming the characteristic and essential means of the improved arrangement.

Furthermore, the diaphragm pump 17 is connected, through a pipe 18 opening into its suction end, with the cooler 7 and, through another pipe 19, its diaphragmclosed chamber is permanently connected with the cylinder of the piston pump 1. The pump 17 comprises a diaphragm 20, a delivery valve 21 and a suction valve 22.

The cooler 7 includes a closed container connected through a shunt pipe 23 with the steam pipe 11, while the water-feeding delivery pipe 5 extends inside the cooler 7, as already mentioned.

Due to this arrangement, the steam entering the cooler 7 is condensed therein and the condensate is delivered into the diaphragm pump 17 under the action of the pressure prevailing at the output point 10 and inside the boiler 9. It should be remarked that, during the delivery stroke of the pump 1, the water pressure prevailing inside the pump 1 and the pipe 19 rises beyond the steam pressure inside the pipe 11, by an amount equal to the sum of the losses in the head to which the water and the steam are subjected along their path between the feed pump 1 and the output of the steam at 10.

The operation of the arrangement thus described is as follows: During the suction stroke of the pump 1, the condensate obtained in the cooler 7 fills, through the pipe 18 and the suction valve 22, the diaphragm pump 17 under the steam pressure prevailing inside the steam pipe 11. I At the beginning of the delivery stroke of the pump 1, the diaphragm 20 of the pump 17 bends and urges the Condensate contained in the pump 17 though the valve 21, the cock 16 and the pipe 15 towards the injection noz- Zle 14-, since the water pressure inside the cylinder of the pump 1, which pressure is necessary for the opening of the delivery valve 4, is substantially higher than the pressure of thesteam at 11.

In the drawing, the pump 1 includes only one cylinder, but, obviously, it is possible to use a multicylinder pump. The present invention has the following advantages:

The amount of water injected is measured accurately and this accuracy is higher than that obtained with a piston pump, the leaks in which, in the case of such small throughputs, would have a highly objectionable action.

T he injection is performed pulsatorily during a'fraction of the time required for the delivery stroke of the suction pump. V V

The valves of the diaphragm pump operate under -high ly satisfactory conditions in spite of their small size. When filling the pump with the water to be injected, the full pressure of the boiler is operative and the suction valve may be loaded with a considerable closing pressure.

The injection water consists of a pure condensate.

The condensation heat of the injection water is recovered by the feed water.

While I have disclosed one embodiment of the present invention, 'it is to be understood that this embodiment is given by example only and not in a limiting sense, the scope of the present invention being determined by the objects and the claims.

I-claim:

1. In combination with a boiler,

a piston pump,

a first pipe means feeding water from the delivery end of said piston pump into said boiler,

of said first pipe disposed within said heat ex-- changer,

a steam pipe emerging from said boiler,

a shunt pipe connecting said steam pipe with said heat exchanger and feeding a fraction of steam from said boiler into said heat exchanger in heat exchangerelation with said portions of said first pipe, whereby said steam is transformed into condensate,

a diaphragm pump including a diaphragm,

a second pipe means feeding said condensate to the suction side of said diaphragm pump,

a third pipe means connecting the delivery end of said piston pump with the pressure side of said diaphragm .pump and subjecting said diaphragm to pressure in pulses in response to the increased pressure cycles of said piston pump,

a regulator means disposed in said steam pipe downstream from said. shunt pipe and controlling the water feed into said boiler, V v

a fourth pipe means connecting the delivery end of said diaphragm pump with said steam pipe at a point adjacent said regulator andfeeding pulsatorily said condensate in exactly measured quantities into said steam pipe and impinging on said regulator means.

2. The combination, as set forth in claim 1, wherein said diaphragm pump includes a compression chamber,

and the volume of said compression chamber corresponding exactly, to the amount of injection water required for each stroke of saidpiston pump.

References Cited in the file of this patent UNITED STATES PATENTS 2,800,117 AIaIll July"23, 1957 2,855,904 Schwander Oct. 14, 1958 2,921,564 Mattox Jan. 19, 1960 FOREIGN PATENTS 801,777 Germany Jan. '22, -1

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