US2515650A - Steam heating system - Google Patents

Description

July i8 1950 o. A. HUNT ETAL STEAM HEATING SYSTEM 3 Sheets-Sheet l Filed Feb. 26, 1949 /r/ .//Lfe f 1122575 July 18, 1950 o. A. HUNT ErAL STEAM HEATING SYSTEM Filed Feb. ze?, 1949 3 Sheets-Sheet 2 Muir-. Nl@

man wenn Patented July 18,l 1950 UNITED STATES PATENT `OFFICE STEAM HEATING SYSTEM Orville A. Hunt and Louin Tiller, Chicago, 1li.,

assignors, by mesne assignments, to Reconstruction Finance Corporation, Chicago, lll., a corporation of the United States Application February 26, 1949, Serial No. 78,604

subject matter related hereto are: S. N. 78,605,

filed February 26, 1949; S. N. 78,842, filed February 28, 1949; S. N. 78,843, iiled February 28, 1949; S. N. 80,802, illed February 28, 1949; and S. N. 777,894, iiled October 4, 1947.

The general object of our invention is to achieve greater efliciency in a steam system by heat conservation and better heat transfer and preferably to do so by means oi a compact automatic master control that may be manufactured as a self-contained packaged unit for incorporation in existing steam systems.

A feature of the above mentioned patented system is operation in a pulsating manner4 to provide pressure pulsations in the steam chests oi' the system and velocity surges in the return lines. Such pulsating operation is advantageous in many respects and is of special importance in reducing resistance to heat flow on the part of condensate iilms and films of non-condensible gas that are inevitably formed on the inside of the steam chests of heating equipment. One of the specific objects of the present invention is to provide improved pulsating action, an improved pattern of pulsation and positive control over the duration and frequency of the pulsations.

Other objects `of the invention relate to the problems of control and economy. in the operation of a steam system of the type set forth in the above mentioned patent. Such a steam system is characterized by the release of fluid from the return end oi.' the system into a region of substantially lower pressure for `the maintenance and regulation of flow velocity in the system. 'I'he steam system is what may be termed a clear channel system with open communication from the en'd of the return line back through the steam using equipment to the steam source (no traps) so that the velocity throughout the system will be responsive to the pressure' drop at the end oi' the return line created by the release oi' fluid. In this method of operation a 2 small fraction of the total steam survives to the end of the return line and is termed "acceleration steam because its release accelerates velocity throughout the system.

Two problems arise in this method of operating a steam system: rst, to control the release of acceleration steam eiectively, and second, to make the release of steam as economical as possible. The acceleration steam must be released in such amount and such manner as to maintain a particular velocity level or range of velocity best suited for lthe particular steam system and for maximum economy the B. t. u.s of.

the released steam must be reclaimed.

In the disclosure o1 the above mentioned Harrison patent these two problems of control and economy are met by using a. thermostatic valve to govern the release of acceleration steam and using make-up water to cool the thermostat elementfof the valve. Control by the make-up water is highly satisfactory because a specic minimum make-up water demand is inherent in every steam system and may therefore serve as a reliable base for velocity regulation. And it is economical to use make-up water to cool the thermostat because the steam released by the thermostatic valve preheats the make-up water. The make-up water carries the reclaimed heat units directly to the boiler to keep them in the steam system.

It is possible to control ,the ow velocity of a steam system in this way by the inherent demand for make-up water by the system, no matter how small that demand may be. It is easier to establish this kind of control, however, when the make-up water demand of the steam system is of substantial quantity. In a laundry, for example, the make-up Water demand is relatively high, say, on the order of 50% of the total boiler feed- `water when the wash water for laundry operation is heated by introducing steam and condensate from the system directly into the wash water in an open tank.

When no steam or condensate in any substantial quantity is taken from the system the makeup water demand may be relatively small. In a laundry, for example. if the wash water is heated by steam coils and the condensate from the steam coils is returned to the boiler the make-up water demand will be small in quantity. In such a situation care is taken to set up a triggering action whereby a small increment of water reaching a thermostat causes the release of a suitably larger quantity of steam. Such triggering action 6I makes it possible to set up and regulate high 3 I A velocity flow through a steam system by means of and on the basis of a relatively small demand for make-up water.

As for economy in reclaiming the heat units of the released steam by make-up water there is va limiting factor in the number of B. t. u.s that can be transferred to a given quantity of water.

'I'his limiting factor becomes important when the make-up water demand is small while the required amount of acceleration steam to be released is relatively large.

Itis apparent then that while the use of makeup water to cool the thermostat element of a thermostatic valve is practical. no matter how small the make-up water demand of a steam system, nevertheless it would be advantageous in certain situations to have available other means of controlling the release of acceleration steam and reclaiming the B. t. u.s of the released steam.

A purpose of the present invention is to provide other means than the cooling action of `make-up water on a thermostat element to achieve reliable velocity control combined with economical use of the released steam. The object is to supplement or replace entirely the cooling eiect of the make-up water for creating system-wide velocity.

In various practices of the present invention this object may be attained by recycling makeup water, by recycling condensate, by recycling a mixture of make-up Water and condensate, and by withdrawing condensate from some point in the system to supplement or replace the makeup water. Other means to the same end apart from cooling action on the thermostat element of the thermostatic valve may be action carried out upstream from the thermostatic valve. One such action may be the continual Withdrawal or pumping of condensate from the return line for the creation of velocity in the system. Another such action may be the condensing acceleration steam upstream from the valve for the creation of flow velocity in the system.

Further objects of the invention relate to flexibility or adaptability in a control unit of the character described. Flexibility is especially important because the unit must be adapted to the specific requirements of widely diiferent steam systems. In this regard another object of the invention is to provide an exceptionally extensive range of adjustability permitting the control unit to be tuned or adjusted precisely to the particular requirements 'of widely different steam systems.

A further object of the invention is to provide means for promoting ow velocity in the steam system by fluid released from the return side of the system without incurring the 'ilash losses that characterize a conventional open steam system. In this regard it is proposed, in effect, to combine the advantages of open and closed steam systems. the advantage of an open steam system being the availability of a ,large pressure diierential for creating flow velocity and the advantage of a closed steam system being the maintenance of condensate under pressure to prevent ash losses.

A further object of the preferred practice of the invention is not only to promote velocity in the system by pressure drop at the end of the return line, but also to deliver the make-up water to the boiler at a higher temperature than possible in any conventional steam system. This dual object is accomplished by transferring heat from the return line to the make-up water as the make-up water travels from the usual feed pump to the boiler. Thus the make-up water causes condensation in the return line to promote ilow velocity in the system and at the same time is' itself raised to a high temperature on the order of 300 F. It is possible to heat the make-up water to this high temperature and to do so without creating any pumping problem because the additional heating occurs on the discharge side of the feed pump where the water is under high pressure.

The above and other objects and advantages of the invention will be apparent in the following description taken with the accompanying drawings.

In the drawings. which are to be considered as merely illustrative: g

Fig. 1 is a front elevation of a typical embodiment of the invention as a self-contained master control unit;

Fig. 2 is a diagram of a representative steam system incorporating one form of the new control unit; and

Fig. 3 is a similar diagram illustrating other practices of the invention.

Fig. 1 illustrates how the invention may be embodied in a piece of apparatus that may be manufactured as a self-contained unit for installation in steam plants, usually in the boiler room. This form lof the unit includes an upright tank or receiver III and a housing or casing II associated therewith. The housing may completely enclose the tank or may, as in the present construction, extend forward from the tank to provide an enclosed space for the numerous elements that make up the control combination. The casing may be sheet metal construction with upper and lower sliding doors I2 that may be opened for access to the interior. The casing includes a panelboard I3 onwhich are various indicating devices that will be described later.

Fig. 1 shows six pipes'connected to the master control unit. These six pipes are: a pipe I4 for supplying supplemental cooling water to the unit; a pipe I5 for supplying new Water to the unit; a pipe I6 connected to the discharge side of the usual boiler feed pump; a pipe Il which is the boiler feed line for supplying water to the boiler; the return line I8 oi the steam system and, at a lower level, the pipe 20 to the intake side of the boiler feed pump. If desired, an additional vent pipe 2| may be connected to the vent opening of the tank I0.

Fig. 2 shows diagrammatically the principal elements of a steam system including the important lparts of the new master control unit. The parts of the unit itself are shown inside a rectangle 22 indicated .by a broken line in Fig. 2. Everything inside this rectangle in Fig. 2 is inside the casing II of the unit shown in Fig. l.

In the system shown in Fig. 2, steam from a boiler 23 is supplied through a header 25 to a plurality of equipment heat exchangers or steam using devices 26. Such devices may be, for example, the various machines in a laundry or the drying equipment used in paper manufacture. plastics, etc. Return pipes 2l from the various pieces of equipment connect with the previously mentioned return line I8.

Instead of traps, each of the return lines 21 is provided with a suitable restriction such as a nipple 28 of relatively small diameter. It will be noted that in such an arrangement there will be open communication from the return line I8 back through the various pieces of equipment.

The condensate that is separated from the steam gravitates through a pipe 33 to the intake side of a condensate pump 35 that is included in the working parts of the master control unit.

`The pump 35 discharges the condensate upward through a pipe 36. Preferably the pump 35 operates continuously.

A valve 31 is provided in the pipe 33 to cut the heat exchanger off from the pump 'if desired. When the valve 31 is closed all of the condensate and steam that reaches the heat exchanger 3| must flow from the heat exchanger through a pipe 38. The pipe 3B conducts uid from the return line I8 into the receiver tank l0.

The pipe 38 leads to 'a two-stage combined heater and mixer 40 which in turn communicates with a spray head 4|. Flow through the pipe 3B into the tank l0 is controlled by a thermostatic valve 42 having a thermostat bulb 43 extending into the spray head 4I. The thermostat control is such that the valve 42 opens in response to decrease in temperature of the thermostat bulb 43 and closes in response to increasing temperature of the bulb. The critical temperature at which the valve opens and closes may be varied by virtue of a manual adjustment 45 on the thermostatic valve 42.

The steam or steam mixed with condensate that flows through the pipe 38 and the valve 42 enters a central upright passage 46 in the twostage heater 40 and divides, one .portion iiowing into an upper jet 41 for the first stage heating of new water, and the other portion iiowing into a lower jet 48 for the second stage heating. The upper jet 41 is directed into a Venturi throat 56 and the lowerjet 48 is directed into a corresponding Venturi throat 5|, each jet and throat forming a low pressure space for the introduction of fluid. 1

New water for the steam system from the previously mentioned supply pipe l5 passes through a float-controlled valve 52 and through a vent condenser 53 to a pipe 55 that enters the twostage heater 46 in the low pressure space between the rst jet 41 and Venturi throat 50. The resulting mixture flows through a lateral connecting .passage 56 into the low pressure space between the second jet 48 and second Venturi throat 5|, where it is joined by the second portion of hot iiuid from the pipe 38. From the twostage heater the heated water flows into the spray head 4I in heat exchange relation with the thermostat bulb 43. The water is not only heated but is also under considerable pressure in the spray head 4| and is discharged downwardly through the spray ports with considerable violence.

Preferably the tank l0 is maintained slightly above atmospheric pressure, say, 3 or 4 lbs. above atmospheric pressure. For this purpose the tank is of closed construction and the vent 2| is provided with both a vent valve 58 and a relief valve 59. The vent valve 58 may be adjusted at a slightly open position to maintain the desired `the spray header 4| will be so limited relative to the input of fluid that the pressure in the spray header will rise above the pressure prevailing in the tank ||l whenthe thermostatic kvalve 42 is open. Under such conditions the pressure in the spray header may go substantially above the tank pressure. It is further contemplated that the extent to which .pressure will rise in the spray header under given conditions may be varied either by varying the number of spray openings or changing the size of the spray openings.

When the heated water is released in finely divided particles from the spray header 4| into the interior of the tank i6. the water particles are shattered by flashing action and the noncondensible gases are eiectively released from the water to escape upwardly through the vent opening 2|. The vent condenser 53 not only reclaims heat from the escaping gases but also condenses any vapors that tend to escape with the gases, the recovered condensate dripping to the bottom of the tank.

The tank I0 contains in its lower portion a reserve body 60 of the deaerated make-up water supplied by the above described spray action. When the level of this body drops, a suitable iioat 6| opens the previously mentioned valve 52 by suitable mechanical means including an upwardly extending operating rod 62. If the level of the water body 60 rises too high, it overflows through an overflow pipe 63. To prevent the release of pressure through the overflow pipe 63 the overiiow pipe is'provided with a float valve 64 that is normally closed but opens automatically whenever the waterlevel in the tank rises unduly. When desired, the whole water content of the tank may be iiushed out by opening a draink valve 66.

In the preferred practice of our invention the master control unit is provided with means for introducing and controlling pulsations in the steam system. An example of such an expedient is the use of an intermittently operated water valve 10 shown in Fig. 2.

The water valve 10. which is in series with the previously described iioat valve 52 to control the water ow into the vent condenser 53, is of the solenoid type controlled by an electric circuit, the valve being open when the circuit is energized and being closed when the circuit is deenergized.

A pair of wires 1| supply current to a timer 12 and wires 13, 14 and 15 complete the circuit with the solenoid valve 10 in series with a mercury switch 16. The mercury switch 16 is on a rocker arm 11 of the iioat control mechanism actuated by the float 6| and closes whenever the float drops in response to demand for new make-up water;

Thus, the valve 10 is intermittently operated during any period inwhich the float control valve 52 is open. It is apparent that the i'loat control valve 52 may be omitted entirely if desired. The timer 12 is of a well known type that is'manually adjustable to divide a fifteen-second time period into two parts in any desired proportion. For example, the timer may, in repeated cycles, cause the solenoid of the valve 10 to be energized for five seconds and de-energized for ten seconds.

The deaerated make-up water, usually at above 212 F. by virtue of the pressure existing in the tank I0, is taken from the tank through the previously mentioned pipe 20 to the intake side of the usual boiler feed pump 61 and is discharged by the pump into the previously mentioned pipe I6 that is connected to the control unit at'the top. 'I'he pipe I6 is connected to the inlet end of a heat exchange coil 68 in the previously mentioned combined heat exchanger and steam separator'3l. The outlet end of this coil 68 is joined to the previously mentioned pipe 36 from the condensate pump 35 to supply the previously mentioned boiler feed line as indicated in Fig. 2.

Inside the master control unit means may be provided to divert at least some of the discharge from the boiler feed pump 61 directly into the shell of the combined heat exchanger and separator 3|. For this purpose the pipe in the master control unit that connects with the pipe I6 from the boiler feed pump 6l is provided with a branch |03 leading to a spray head |04 inside the separator 3| and two manually adjustable valves |05 and |08 are provided as shown to permit variation in proportioning the flow between the coil 68 and the spray head |04.

The feed water pump 61 may be controlled in a well-known manner by means responsive to changes in the water level in the boiler 23 or in some practices of the invention may be manually adjusted to run continuously at approximately the rate required to keep the boiler level constant. In either event, the oat 6| in the master control tank |0 will drop periodically to cause new water to be supplied to the system in accord with the boiler demand. Since the boiler demand for make-up water varies with the heatload on the system, it is apparent that the master control unit is responsive to changes in the heat load on the system.

A second expedient .that may be used to create and control pulsations in the system instead of the solenoid valve 10 or in addition to the solenoid valve is the use of intermittently flowing water from any suitable source entirely independent of the water demand by the boiler.

In the particular arrangement shown in Fig. 2, s. small circulating pump, has its intake |3| connected to the tank |0 to draw water therefrom. 'I'he output from the pump is delivered through a, pipe |32 to the previously mentioned pipe 55 so that it may reach the thermostat 43 to cause opening action of the thermostatic valve 42. A check valve |33 prevents back flow. Preferably, a by-pass |34 having a by-pass valve |35 y valve |36 in the pipe |32 may be manipulated to vary the amount of recirculated fluidy that reaches the pipe 55.

. In some instances it is desirable to cool the discharge from the circulating pump |30 for greater cooling effect on the thermostat 43. For this purpose, Fig. 2 shows the discharge from the circulating pump |30 as passing through the coil |31 of a heat exchanger |38. The heat exchanger |38 is provided with an intake pipe |39 and an outflow pipe |40 so that any suitable fluid medium may be circulated therethrough.

Preferably, the circulating pump |30 is operated intermittently to cause pulsating ow through the pipe |32 and preferably the pulsations of this flow are synchronized with the pulsations of ilow through the pipe when the unit -along with non-condensible gases.

a cable |4| that is connected in parallel with the solenoid valve 10 to be operated simultaneously therewith by the timer 13.

Operation The manner in which the steam system operates and is controlled by the described unit may be understood from the foregoing description.

Steam condenses in each one of the steam chests in the pieces of equipment 26 to give up heat to the material in process, but a portion of the steam flows continuously into the return line |8 through the restrictions 28 because of the open communication through the system. In this method of operation, the flow velocity is substantially higher than the overall or average velocity in a conventional trap system and the small proportion of steam that is continuously passing through the restrictions 28 effectively carries the condensate out of the steam chests The drop in pressure at the restrictions 28 causes some of the condensate to flash into steam thereby slightly increasing the steam content of the fluid mixture that reaches the combined heat exchanger and separator 3|.

The adjustment 45 of the thermostatic valve 42 is high enough to make the valve open in an intermittent manner thereby to cause pulsating flow throughout the system. In a steam system having approximately lbs. per square inch gauge Ypressure in the steam header 25 the setting of the thermostatic valve may be, for example, somewhat above 230 F. In any event the temperature setting of the thermostatic valve will be above the normal temperature prevailing inside the tank I0. If the tank I0 is at 4 to 6 Ibsgauge lpressure the temperature therein will be-in the range 224-230 F.

Since the temperature in the master control tank is below the temperature setting of the thermostatic valve the environment of the spray header 4| tends to cool the thermostat bulb below the temperature setting thereby to cause the thermostatic valve 42 to open. When the valve 42 opens, however, the thermostat bulb is again heated above its critical temperature by the fluid released from the separator 3| thereby causing the thermostatic valve to close.

Since a temperature above 230 F. cannot be attained in the spray head 4| aslong as the spray head interior is at the same pressure as the interior of the tank l0 the initial flow of steam from the thermostatic valve'or the initial flash of steam by flash action from condensate released through the valve does not have a temperature above 230 F. Since the restrictive action of the spray openings is effective to cause risingv back pressure in the spray header, however, the temperature rises correspondingly and soon climbs above the temperature setting of the thermostatic valve. It is apparent then that the flow passage from the thermostatic valve 42 to the discharge openings of the spray header 4| functions as a pressure accumulation space to make possible the relatively high temperature required for the purpose of valve control as well as for the purpose of deaerating the make-up water.

By virtue of the described cycle of alternate heating and cooling, the valve 42 opens inter-. mittently in an automatic manner to maintain a desired minimum average'ow velocity in the system during periods when no new make-up water is flowing. Whenever new make-up water is required the float Il lowers to open the water valve 52 and at the same time the mercury switch l tilts to close a circuit through the solenoid valve l0 and timer 12. As long as the iloat 6l is lowered the solenoid valve 'In opens intermittently to release pulses of make-up water for ilow through the vent condenser 53 and pipe 5S into the two-stage heater-mixer 40. Each pulse of water causes the thermostat 43 to be cooled thereby to open the thermostatic valve 42 for the release of steam from the system. The steam mixes with the new water and the new water released by the spray header 4l under pressure and at a temperature higher than 212 F. is eil'ectively deaerated. The deaerated water drops to the bottom of the tank III while the released non-condensible gases ilow upward to the vent 2|. The vent condenser 53 not only condenses any vapors that may tend to escape butvalso reclaims heat from the separated gases.

In the usual method of operation the ilow of new water is adequate to keep the thermostatic valve 4`2 open in opposition to the heating ef' fect released by the thermostaic valve, so that the thermostatlc valve stays open as long as the ilow of new water continues. As soon as waterilows into the two-stage heater-mixer ceases, the thermostatic valve immediately closes in response to the high temperature iluld from the return line. Thus the thermostatic valve will open and close in response to each pulse of water released by the solenoid valve 1B.

This continual interruption of the water flow by the solenoid valve has important effects. It increases the amplitude and abruptness of the pulsations throughout the steam system. It increases the frequency of the pulsations by increasing the frequency of the water cooling effects on the thermostatic bulb 43. It also stretches out the periods of time in which the demand for new water by the boiler is effective to create pulsations in the system.

Although opening the thermostatic valve 42 to createvelocity may tend to lower' the pressure of the condensate delivered to the condensate pump 35, the valve opens only intermittently so that such tendency to drop pressure can occur only intermittently.

A special advantage of this adjustable arrangement for breaking the make-up water ilow into pulses is that the rate at which new water is supplied and deaerated may be more or less independent of the action of the boiler feed pump 61. For example, the boiler feed pump 61 may, in a given installation, operate for five minutes and then remain idle for twenty minutes. During the ve minutes of pump operation the water level ofthe reserve body of make-up water 60 in the tank Ill will drop several inches. During the following twenty minutes in which the pump is *idle the solenoid valve 10 will release pulses of water into the receiver to restore the water level.

The timer 12 may, if desired, be so adjusted that the time taken for the water level to be restored is approximately twenty minutes. Thus the new water is sent through the deaeration process gradually, notwithstanding the periodic abrupt drops in the water level inside the tank I0.

The valve 42 may compeltely close or only nearly close in response to rising temperature,

and the valve may be either a quick-acting valve or a slow-acting valve. If a slow-acting valve is used, it will tend to stay Open at an equilibrium in doing so speeds up velocity at the return end of the system, the unit may be said to tie the two ends of the system together functionally. The result is a closed chain of causes in which the demandv of the boiler for a pound of water to replace a, pound of steam consumed in the system' vcauses enough velocity to be created to sweep out the resulting condensate from the steam chests in the system. v

When the load on the steam system is steady the master control unit functions as automatic means to keep the overall or average velocity ot the pulsating flow at a substantially constant level. Under constant operating conditions, with the average velocity level of the pulsating flow substantially constant, the boiler demand for new water will be met by a substantially constant ratio of new water to condensate. Under such circumstances if velocity were to tend to lag, there would be an immediate decit to condensate returned and the demand for make-up water would temporarily increase. Such increase in the demand for make-up water would, however. act on the thermostat bulb 42 to increase velocity.l Thus. any tendency for velocity to drop would be automatically corrected. In like manner any tendency for velocity to speed up excessively, would be automatically corrected by reducing the demand for make-up water and thereby reducing the quantity of uid released by the valve 42.

Such changes in the load on the steam system cause corresponding changes in the demand for Anew water by the boiler with corresponding changes in the quantity of make-up water required in a. unit of time. it is apparent that the average or overall velocity of the system also shifts up and down automatically with changes in the load on the system.

Each ,time the valve 42 opens. it causes two things to happen. It causes a pressure pulsation or slight pressure drop in every steam chest in the system,and it causes velocity in the whole system to speed up. In other words, each opening movement of the valve 42 causes a pressure pulsation in each piece of equipment and at the same time causes a strong surge of flow from the equipment through the return line of the system. The pressure pulsations attack the non-condensible gas films in the steamchests by causing a ilashing action because each timev the pressure drops slightly, a portion of every particle of water in the steam chests ashes into steam.V

There are countless water particles in and near the gas iilm and at lbs pressure per square inch the condensate that ilashes into steam increases in volume over 240 times. As a result, each particle of water becomesan explosive center of turbulence to disrupt the gas films and to promote heat transfer to the material in4 process. 'I'he gases torn away from the gas fllms are quickly picked up by the velocity surges and swept into and through the returnl line of the system. The velocity surges also sweep condensate out of the steam chests continuously and keep the condensate films exceedingly thin.

Only high temperature water reaches the boiler 23 because the condensate that isreturned directly to the boiler through the pump 35 is not permitted to drop to atmospheric pressure and because all new water added to the system is eil'ectively preheated. In a system using steamV at 100 lbs. per square inch, the condensate-passed through the pump 35 is maintained well above The new water is heated in four stages and then is intermixed with the high temperature con- 'densate in the boiler feed line I1. The first stage of heating the new water is in the vent condenser 53; the next two stages are in the two-.stage heater 40; and the fourth stage is accomplished by the coils 68 in the combined heat exchanger and separator 3l.v As a result, the temperature of the make-up water as it leaves the coils 68 is nearly 300.

It is apparent that the arrangement shown in Fig. 2 supplements the velocity-creating effect of the make-up water in several ways. In the nrst place, the relatively cool water or condensate supplied through the pipe I4 supplements the cooling effect of the make-up water on the thermostat 43. In the second place, because the tank I is under pressurethe cooling effect of the vent condenser 53 reduces the Vpressure and temperature inside the tank with consequent cooling action on the thermostat 43. In the third place, the continuous removal of condensate by the pump 35 from the lower end of the separator 3| creates ow in the return line I8. In the fourth place, the condensing of steam in the separator 3| by the cooling effect of the water coil |58V and/or the cooling effect of water introduced by the spray head |04 serve to promote flow by contraction of the fluid mixture at the end of the return line.

All of these factors working together create and maintain whatever flow velocity. is desired in any particular steam system independently of the make-up water demand of the system and regardless of how small the make-up water demand may be. This arrangement, moreover, causes all heat units of the acceleration steam to be reclaimed and make it unnecessary for acceleration steam to be wasted. j

In variouspractices of the invention with the described apparatus, various parts may be taken ont of operation if desired. Thus, as already noted, the condensate pump 35 may be cut oiI so that all the iluid from the return line I8 passes through the thermostatic valve 42 into the tank I0. To change over to this mode of operation it is necessary merely .to close the valve 31 to cut off the condensate pump 35 and to raise the temperature settings of the thermostatic valve 42. When the master control unit is operated in this manner it does not return condensate direct- 1y to the boiler under pressure but it does recirculate all of the condensate through the deaeration process to eliminate any air that may be picked up by the condensate.

It is obvious also that the circulatingl pump |30 may be kept out of operation in those instances in\which the cooling effect of the makeup water alone on the thermostat 43 is sumcient to keep the system operating at high eiciency.

The instrument panel In the preferred form of the invention the panel board I3 is provided with the following 1nstrumentalities. A dial 81 indicates the deaera- .tion temperature and a dial 83 indicates the deaeration pressure, both values being taken near .the thermostat bulb 43 where the lfluid under pressure flows into the spray head 4|. A dial 88 shows the return line pressure near the point at which the return line I8 connects with the combined heat exchanger and separator 3|. A dial 90 shows the temperature of the feedwater delivered to the boiler throughv the feed line I1 and a dial 9| shows the pressure of the make-up water supply taken near the connection of the water supply pipe I with the unit. A dial 92' indicates the pressure prevailing inside the master control tank I0. Asignal lamp 95 is-responsive to the mercury switch 'I6 to indicate the periods in n which the system is taking in new water, and a second signal lamp 96 responds to energization of the solenoid valve 10 to indicate the occurrence of water pulses into the two-stage heater 40.

Tuning the unit to suit a particular steam system V system Within a very wide range. As a result, the

control unit is extremely flexible and is not only readily adaptable to the requirements of any particular system but is also adaptable to changes in a steam system such as the addition of new heating equipment.

Any of the following adjustments may be made to vary the operation and control characteristics of the unit: l

1. The temperature adjustment 45 of the thermostatic valve 42 may be varied.

2. The rate of supply of the new water may be I varied to change the cooling eiect of the new water on the bulb 43. For example, the float valve 52 may be restricted or limited in its opening action to any degree desired.

3. The closing action of the thermostatic valve 42 as well as the opening action may be limited to any degree desired.

4. 'Ihe discharge capacity of thespray head 4| may be varied to vary the manner and degree oi pressure rise in the spray head.

5. The prevailing pressure in the master control tank |0 may be raised or lowered.

6. The proportion of make-up water diverted to the spray head |04 in the separator 3| may be varied by manipulation of the valves |05 and |06.

7. The duration of the water pulses controlled by the solenoid valve 10, as well as the water pulses generated by the circulating pump |30, may be varied by adjustment of the timer 13.

8. The proportion of the water recirculated past the thermostat 43 by the pump I 30 may be varied by adjustment of the two valves |34 and |35.

9. The temperature of the water recirculated by the pump |30 may be varied by varying either the temperature or rate of flow of the cooling medium employed in the heat exchanger |31.

f Description' of Fig. 3

The arrangement illustrated in Fig. 3 is largely similar to the previously described arrangement in Fig. 2 as indicated by the use of corresponding numerals to indicate corresponding parts.

One respect in which Fig. 3 differs from Fig.l 2 is in the omission of the circulating pump |30,

but it is to be understood that the circulating Y 13 pump may be added, if desired, In any particular installation.

The purpose of Fig. 3 is to illustrate how cooling water from somewhere in the steam system apart from the master control unit may be introduced into'the master control unit to supplement the cooling effect ofthe make-up water on the thermostat 43. For this purpose Fig. 3 shows pipe I4 connected to the pipe 55. The pipe I4 may bringr cooling fluid to the unit from various sources of cooling water in various practices of the invention. In the present arrangement the cooling water is condensate supplied by a piece of steam using equipment II2 that operates on low-pressure steam. Fig. 3 shows a supply pipe II3 from the steam header 25 to the piece of equipment II2, this supply pipe being provided with a suitable pressure reducing valve I I5. Thereturn pipe IIB from the piece of equipment II2 may be provided with a suitable restriction III and is connected to the coil yIIB of a heat exchanger I I9. The other end of thecoil IIB is connected to the pipe I4.

The heat exchanger IIS has an inflow pipe |20 and an outflow pipe'IZI to permit any suitable virtue of this arrangement cooling water flowsV to the master control unit through the pipe I4 to supplement the cooling eiect of the make-up water on the thermostat 43 and the pulses of water from both sources occur more or less simultaneously.

Our description in detail of preferred practices of the invention for the purposes of disclosure and to illustrate the principles involved will suggest to those skilled lin the art various changes and substitutions under our basic concepts. We reserve the right to all such departures from our disclosure that fall within the scope of our appended claims.

We claim as our invention:

3. In a steam system, a combination as set forth in claim l, which includes a valve for controlling 1. In a steam system of the character described having a steam source, at least one steam-using device and a return line, the combination therewith of means to promote flow velocity through the system, said dow-promoting means including: a valve to release fluid from said return line into a region of substantially lower pressure, a thermostat for causing opening operation of said valve in response to temperature below a given temperature and closing operation of the valve in response to temperature above said given tem-- perature, said thermostat being positioned to oe heated by the fluid discharge of the valve, means to flow relatively cool condensate from the system into heat-exchange relation with said thermostat for opening action of said valve, and automatic means to break said flow into short flow periods for intermittent operation of the valve to create pulsations in the steam system.

2. In a steam system, a combination as set forth in claim l, in which the iiow of said condensate is controlled by a valve and an automatic lcontrol continually opens and closes said valve to break up the flow of the condensate.

the flow of said condensate and an automatic timer controlling the operation of said condensate valve, said timer operating said condensate valve periodically and being adjustable with respect to such periodic action.

4. In a steam system of the character described having a steam source, at least one steam using device and a return line, the combination therewith of means to promote flow velocity through the system, said flow-promoting means including: a valve to release fluid from said return line into a region of substantially lower pressure, a thermostat for causing opening operation of said valve in response to temperature below'a given temperature and closing operation of the valve in response to temperature above said given temperature, said thermostat being positioned to be heated by the fluid discharge of the valve, a first means effective to provide a stream of make-up .Water `to cool said thermostat inresponse to demand for\makeup water by the system, and a second means to automatically reduce the oW of said stream intermittently when said rst means is effective.

5. In a steam system, a combination as set forth in claim l which includes a heat exchanger to reduce the temperature of said condensate before the condensate reaches said thermostat.

6. In a steam system, at least one steam-using device, a steam source connected therewith, a.

receiver, a return line conducting condensate from said device to said receiver, a valve controlling flow through said return line, a thermostat controlling said valve, means to direct the fluid released by the valve into heat-exchange relation with said thermostat to transfer heat thereto from the released fluid thereby to cause closing action by the valve, means to recycle the condensate from said receiver into heat-exchange relation with said thermostat thereby to cool the thermostat when said fluid is not being released by the valve and to modify the heating effect of the released fluid on the thermostat when the valve is open, and automatic means to continually vary the rate of flow of the recycled condensate.

7. In a steam system, at least one steam-using device, r. steam supply connected with said device, a return line in open communication with said supply through said device, a valve to release fluid from said return line to promote flow in said device, 'boiler feed means to convey condensate under pressure direct from said return line, a thermostat operatively connected with said valve for closing action of the valve in response to temperature above its setting and opening action of the valve in response to temperature below its setting, said thermostat being positioned to be heated by the discharge from said valve, means to cool said thermostat with a stream of new water flowing in response to the demand of the system for make-up water, means to cool said thermostat additionally with a stream of cooling fluid independent of the demand of the system for make-up water, and automatic means to break up at least one of said streams of cooling uid into short flow periods to create pulsations in the steam system.

8. In a steam system of the character described having a steam source, at least one steam-using device and a return line, thecombination therewith of means to promote flow velocity through the system, said flow-promoting means includ- 15 ing: a valve to release fluid from said return line into a region of substantially lower pressure, a thermostat for causing opening operation of said valve in response to temperature below a given temperature and closing operation of the valve in response to temperature above said given temperature, said thermostat being positioned to be heated by the uid discharge of the valve, a means to direct make-up water into heat-exchange relation with said thermostat to cause opening action of said valve, a heat exchanger included in said return line, said heat exchanger having a passage for.heating water, and means to direct make-up water in a pulsating manner into heat-exchange relation with said bulb for cooling action on the bulb and subsequently to direct the make-up water through said passage for How-promoting condensation in said return line.

9. In a steam system of the character described having a steam source, at least one steam-using device and a return line, the combination therewith of means to promote flow velocity through the system, said flow-promoting means including: a heat exchanger included in said return line, said heat exchanger having a passage for heating water, a receiver tank maintained above atmospheric pressure but substantially below the pressure in said return line, a valve to release fluid from said return line into said receiver, a thermostat for causing opening operation of said valve in response to temperature below a' given temperature and closing operation of the valve in response to temperature above said given temperature, said thermostat being positioned to be heated by the fluid discharge from said valve, a condenser in said tank, means to cause make-up water to flow in a pulsating manner first through said condenser and'then into heat-exchange relation with said thermostat, and means to cause the make-up Water to flow subsequently through said passage for now-promoting condensing action in said return line. y

10. In a steam system, at least one steam-using device, a steam supply connected with said device,

a return line in open communication with said.

supply through said device, a receiver connected with said return line, said receiver containing a supply of make-up water for the system, a valve torelease fluid from said return line into said receiver to promote flow in the return line, a thermostat operatively connected with said valve for closing action of thevalve in response to temperature above its setting and opening action of the valve in response to temperature below its setting, said thermostat being positioned to be heated by the discharge from said valve, means to supply make-up water to said receiver in a stream to cool said thermostat thereby to cause said valve to open, a valve controlling said stream, and means response to the liquid level in said receiver to repeatedly open and close said last mentioned valve during each time period in which the liquid is below a predetermined level.

11. In a steam system of the character described having a steam source, at least one steamusing device and a return line, the combination therewith of means to promote ilow velocity through the system, said now-promoting means including: a valve to release fluid from said return line to promote flow in said device, boiler feed means to convey condensate u nder pressure direct from said return line thereby to further promote ow in said device, a thermostat operatively connected with said valve for closing action of the valve in response to temperature above its setting and opening action of the valve in response to temperature below its setting, said thermostat being positioned to be heated by the discharge from said valve, means to cool said thermostat with uid to favor opening of the valve for promoting flow, and automatic means to break up the flow of said cooling fluid into periodic flow intervals.

12. In a steam system of the character described having a steam source, at least one steamusing device and a return line, the combination therewith of means to promote flow velocity through the system, said flow-promoting means including: a valve to release fluid from said return line into the region of substantially lower pressure for promoting flow in the steam system, means to bring cooling fluid into heat-exchange relation with the contents of said return line for causing condensation of steam therein for further promotion of flow in the steam system, a thermostat for causing opening operation of the valve in response to temperature below a given temperature and closing operation of the valve in response to temperature above said given temperature, said thermostat being positioned to be heated by the fluid discharged from the valve, means to cool said thermostat with water independently of the make-up water demand of the system to increase the opening action of said valve, and means to break up the ow of said cooling fluid into periodic flow intervals.

13. In a steam system of the character described having a steam source, at least one steamusing device and a. return line, the combination therewith of means to promote flow velocity through the system, said How-promoting means including: means to bring cooling fluid into heatexchange relation with the contents of said return line for causing condensation of steam therein to set up a pressure dierential across the system for promotion of flow in the system, a condensate pump for returning condensate vto said boiler, said condensate pump having its intake port in a communication with said return line to remove condensate therefrom for further promotion of flow in the system, a valve to release fluid from said return line into a region of substantially lower pressure than the return line to set up a still further pressure differential across the system for still further promotion of flow in the steam system, a thermostat controlling said valve, said thermostat being positioned for rise in temperature by heat supplied by said return line. means to cool said thermostat with fluid to modify the operation of said valve, said fluid being, at least in part, condensate from the system, and means to break up the flow of said cooling fluid into periodic flow intervals.

14. Ina clear channel steam system of the character described, in which steam is continually released from 'the return line of the system to create flow velocity in the system, the 'combination therewith of: means to employ the released steam for preheating make-up water, means to cause make-up water to flow into said preheating means, and means during periods in which the steam system demands new water to break up said flow of make-up water into periodic increments thereby to spread the make-up water demand over the major portion of the operating time of the system.

15. In a clear channel steam system, a combination as set forth in claim 14, which includes 17 means to vary said increments for different magnitudes of make-up Water demand.

16. In a clear channel steam system, a combination as set forth in claim 15, in which said varying means includes a timer continually repeating a given cycle, said timer being adjustable with respect to the quantity of make-up Water flowing in each cycle.

17. In a method of operating a clear channel steam system of the character described, in which steam is continually releasedlfrom the return end of the system to create flow velocity in the system and is used to preheat make-up water for the system, the improvement that comprises break-- ing up the Supply of make-up Water into periodic increments when the system demands make-up Water, thereby spreading the make-up Water de- 18 mand over the major portion of the operating time of the system, and releasing the steam in a corresponding series of increments to preheat the water increments.

ORVILLE A. HUNT. LOUIN TILLER.

REFERENCES CITED The following references arevof record in the 10 file of this patent:

UNITED STATES PATENTS

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