US2515649A

US2515649A - Steam system

Info

Publication number: US2515649A
Application number: US78843A
Authority: US
Inventors: Orville A Hunt; Tiller Louin
Original assignee: Reconstruction Finance Corp
Current assignee: Reconstruction Finance Corp
Priority date: 1949-02-28
Filing date: 1949-02-28
Publication date: 1950-07-18
Anticipated expiration: 1967-07-18

Description

3 Sheets-Sheet 1 I STEAII SYSTEM o A. HUNT ETAL July 18, 195o Filed Feb. 28, 1949 AC]A o. A. HUNT ErAL sm SYSTEM July 1s, 195o :s sheets-sheet 2 Filed Feb. 28', 1949 afkrau". :5.8

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July 18, 1950 o. A. HUN-ri ErAL 2,515,649

STEAM sYs'ma I Filed Feb. 2a, 1949 :s sheets-sheet s Patented July 1 8, i950 STEAM SYSTEM Orville A. Hunt and Louin Tiller, Chicago, Ill.,

alsignors, by mesne assignments, to Reconstruction Finance Corporation, Chicago, Ill., a' corporation of the United States Application February 2s, 1949, semi No. 78,843

` 19 claims y(ci. 237-9) Our invention relates to steam systems with special reference to steam systems for drying operations and is directed to improvements on the type of steam system yset forth in the Harrison et al. Patent 2,366,332 issued January 2, 1945. 'l-he present application is a continuation-in-part `oi the Harrison et al. application 701,252 filed October 4, 1946, and the Tiller 8i Hunt application 762,628 led July 22, 1947, both of which are abandoned. These prior disclosures, as far as consistent herewith, are incorporated in the present disclosure by reference.

Other copending applications disclosing the subject matter related hereto are: S. N. 78,604, led February 26, 1949; S. N. 78,605, lecl February 26, 1949; S. N. 78.842, filed February 28, 1949; S. N. 80,802, filed February 28, 1949; and S. N. 777,894, filed October 4, 1947.

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

A steam system of the type here under consideration is characterized by the release of fluid from the return end of the system into a region of substantially lower pressure for the maintenance and regulation of flow velocity inthe system. The steam system is what may be termed a clear channel system with open communication from the end of the return line back through the steam-using equipment to the steam source (no traps) so that the velocity throughout the ment of the valve. Control by the make-up water is highly satisfactory because a specific minimum make-up water demand is inherent in every steam system and may therefore serve as a.

vreliable 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 rlow velocity of a steam system in this wayby 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 feedwater 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 substansystem will be responsive to the pressure drop at the end of the return line created by the release of fluid. In this method of operation a 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: first, to control the release of acceleration steam effectively, and second, to make the release oi' 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 the particular steam system and for maximum economy the B. t. u.s of the released steam must be reclaimed.

In the disclosureof 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 Vusing make-up water to cool the thermostat eletial quantity is taken from the system the makeup water demand may be relatively small. Ina, 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 makes it possible to set up and regulate highvelocity ilow 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 a limitingfactor in the number of B. t. u.s that can be transferred to 9. given quantity of water.

This limiting factor becomes important when the make-up Water demand is small while the revquired amount of acceleration steam to be reing action to achieve reliable velocity control combined with economical use of the released steam. The object is to supplement or replace entirely the make-up water for cooling action to create system-wide velocity.

In various practices of the present invention this object may be attained by recycling make-up 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 make-up 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 of acceleration steam upstream from the valve for the creation of ilow velocity in the system.

Further objects of the invention relate to ilexibility 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 different 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 diierent steam systems.

A further object of the invention is to provide means for promoting flow velocity in the steam system by fluid released from the return side of the system without incurring the flash 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 differential for creating ilow velocity and the advantage of a closed steam system being the maintenance of condensate under pressure to prevent flash losses.

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:

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. l 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 of the unit includes an upright tank or receiver I 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 spa'ce for the numerous elements that make up the control combination. The casing may be of sheet metal construction with upper and lower sliding doors I2 that may be opened for access to the interior. The casing includes a panel board I3 on which 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 Ipipe I5 for supplying new water to the unit; a pipe I6 connected to the discharge side of the 'usual boiler feed pump; a pipe I1 which is the boiler feed line for supplying water to the boiler; the return line I8 of 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 parts of the new master control unit. The parts of the unit itself are shown inside a rectangle 22 indicated by a broken line ln Fig. 2. Everything inside this rectangle in Fig. 2 is inside the c/asing 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 21 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 26 to the steam supply so that lowering pressure in the return line I8 will cause flow velocity responses in each of the steam using devices.

The return line I8 is terminally connected to the side of a steam separator 3I which preferably, but not necessarily, also serves as a heat exchanger for using the returned condensate to heat new make-up water. The combined heat exchanger and separator 3| is shaped and dimensioned to permit the condensate to separate from the steam and, if desired, suitable bailles 32 may be added to facilitate such separation.

' 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 oiI from the pump if desired. When the valve 31 is closed all of the condensate and steam that reaches the heat exchanger 3I must flow from the heat exchanger through a pipe 38. The pipe 38 conducts uid from the return line I8 into the receiver tank I0.

The pipe 38 leads to a two-stage combined heater and mixer 40 which in turn communicates with a spray head 4I. Flow through the pipe 38 into the tank I0 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 an manual adjustment 45 on the thermostat 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 ln the twostage heater 40 and divides, one portion owing intoan upper jet 41 for the first stage heatingof new water, and the other portion flowing into a lower jet 48 for the second stage heating. The upper jet 41 is directed into a Venturi throat 50 and the lower jet 48 is directed into a corresponding Venturi throat 5 I each jet and throat forming a low pressure space for the introduction of fluid.`

New water for the steam system from the previously mentioned supply pipe I5 passes through a float-controlled valve 52 and through a vent condenser 53v to a pipe 55 that enters the two-stage heater 4I) in the low pressure space between the first 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 5I, where it is joined by the second portion of hot fluid from the pipe 38. From the twostage heater the heated water flows into the spray head 4I in heat-exchange relation with the thermostatic bulb 43. The water is not only heated but is also under considerable pressure in the spray head 4I and is discharged downwardly through the spray ports with considerable violence.

Preferably, the tank I is maintained slightly above atmospheric pressure, say, 3 or 4 pounds above atmospheric pressure. For this purpose the tank is of closedV construction and the vent 2l is provided with both a vent valve 58 and a relief valve 59. The vent valve B may be adjusted at a slightly open position to maintain the desired pressure in the tank or 3 or 4 pounds per square inch and the relief valve 59 may be adjusted to pop ofi at, say, 8 to l0 pounds per square inch.

It is contemplated that the spray capacity of the spray head 4I will be so limited relative to the input of fluid that the pressure in the spray head will rise above the pressure prevailing in the tank Il) when the thermostatic valve 42 is open. Under such conditions, the pressure in the spray head may go substantially above the tank pressure. It is further contemplated that the extent to which pressure will rise in the spray head 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 nely divided particles from the spray head 4I into the interior of the tank I0, the water particles are shattered by hashing action and the non-condensible gases are effectively 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 6Il= of the deaerated make-up Water supplied by the above-described spray action. When the level of this body drops, a suitable float 6I opens the previously mentioned valve 52 by suitable mechanical means including an upwardly extending operatingr 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 overflow pipe is provided witha float valve 64 that is normally closed but opens automatiunduly. When desired, the whole water content of the tank may be ilushed out by, opening a drain valve 66.' Preferably signal means is provided, as will be later described, to indicate when the float valve 52 is open. For this purpose, a mercury switch 16 is mounted on a rocker arm 11 of the float-controlled mechanism actuated by the float 6I. The mercury switch 16 closes whenever the float drops in response to deman for new'make-up water.

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 contro1 unit at the top. The pipe I6 is connected to the inlet end of a heat-exchange coil 68 shown diagrammati ically in the previously mentioned combined heat-exchanger and steam separator 3|. The outlet end of this coil 68 is joined to the previously mentioned boiler feed line I1 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 sep arator 3I. For this purpose, the pipe in the master control unit that connects with the pipe I6 from the boiler feed pump 61 is provided with a branch |03 leading to a spray head |04 inside the separator 3l and two manually adjustable valves |05 and IDB are provided as shown to permit variation in proportioning the ow 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 float 6I in the master control l tank IIJ 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 theheat load on the system, it is apparent that the master control unit is responsive to changes in the heat load on the system.

The previously mentioned pipe I4 is connected to the pipe 55 as shown in Fig. 2 for the purpose of introducing cooling water into the pipe 55 to supplement the make-up Water that is introduced by the float valve 52. The pipe I4 may be connected to various sources of cooling water in various practices of the invention.

In the present arrangement thev cooling water is condensate supplied by a piece of steam using equipment II2 that operates on low pressure steam. Fig. 2 shows a supply pipe IIS yfrom the steam header 25 to the piece of equipment II2, this supply pipe being provided with a suitable pressure-reducing valve II5. The return pipe II6 from the piece of equipment I I2 may be provided with a suitable restriction IIT, and is connected to the coil |I8 of a heat exchanger H9. The other end of the coil II8 is connected to the pipe I4.

The heat exchanger IIS has an inflow pipe |20 and an outflow pipe I2I to permit any suitable cooling fluid to be circulated for continuously cooling the condensate flowing through the cally whenever the water level in the tank rises 15 coil IIB.

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 I8 through the restrictions 28 because of the open communication through the system. In this arator 3 I.

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 100 lbs. per square inch gauge pressure 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 I is at 4 to 6 lbs. gauge pressure the temperature therein will be in the range 224230 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 uid 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 4I as long as the spray head interior is at the same pressure as the interior of the tank I0 the initial flow of or a slow-acting valve. If a slow-acting valve is rising 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 4I used, it will tend to stay open at an equilibrium position in the absence of water ow and will merely open wider in response to new water. In such instances, the pulsations in the system are governed primarily by the periods of water flow. Since every steam system has losses, however, which must be made up by new water, the new water demand can be relied upon to continually cause opening action of the valve 42 to create pulsations.

Since the master control responds to demand for new water at the boiler end of the system and 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 demand of the boiler for a pound of water to replace a pound of steam consumed in the system causes enough velocity to be created to sweep out the resulting condensate from the steam chests in the system.

When the load on the steam system is steady the master control unit functions as automatic means to keep the overall or average velocity of 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 in condensate returned and the demand for make-up v water would temporarilyincrease. Such increase in the demand for make-up water would, however, act on the thermostat bulb 42 to increase velocity. 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.

Since changes in the load on the steam system cause corresponding changes in the demand for new 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 ow from the equipment through the return line of the system. The pressure pulsations attack the noncondensible gas films in the steam chests by causing a flashing action because each time the pressure drops slightly, a. portion of every particle of water in the steam chests ilashes into steam. There are countless water particles in and near the gas films and at 100 lbs. pressure per square inch the condensate that flashes into steam increases in volume over 240 times. As a result, each particle of water becomes an explosive center of turbulence to disrupt the gas films and to promote heat transfer to the matel rial in process. The gases torn away from the gas films are quickly picked up by the velocity surges and swept into and through the return 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 is returned 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 effectively preheated. In a system using steam at 100 lbs. per square inch, the condensate passed through the pump,35 is maintained well above 300 F.

The new water is heated in four stages and then is intermixed with the high temperature condensate in the boiler feed line il. 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 t8 in thecombined heat exchanger and separator 3|. As a result, the temperature of the make-up water as it leaves the coils B8 is nearly 300.

The supplemental cooling water introduced through the pipe I4 flows into the pipe I5 in the same manner as make-up water and has the same valve-opening effect on the thermostatic valve 42. In a system having a relatively low demand for make-up water this additional cooling water not only simplifies the problem of causing the thermostatic valve to open for creating adequate ow velocity throughout the system claimed and makes it unnecessary for acceleration steam to be wasted.

` y In various practices oi the invention with the described apparatus, various parts may be taken out of operation if desired. Thus, as already noted, the condensate pump 35 may be cut oir so that all the uid 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 3l 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 directly 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 circulating pump i130 may be kept out of operation in those instances in which the cooling effect of the make-up water alone on the thermostat 43 is sufficient to keep the system operating at high efficiency.

The instrument panel In the preferred form of the invention, the panel board I3 is provided with the following instrumentalities. A dial 31 indicates the deaeration temperature, and a dial 88 indicates the deaeration pressure, both values being taken near the thermostatic bulb 43 where the iluid under pressure flows into the spray head 4I. A dialil shows the return line pressure near the point at which the return line I8 connects with the combined heat exchanger and separator 3i. A dial 90 shows the temperature of the ieedwater delivered to the boiler through the feed line I1,

' and a dial 9| shows the pressure of the make-up but also solves the problem of reclaiming the heat units of the released acceleration steam. The fact that the pressure in the steam using equipment II2 is relatively low by virtue of the pressure reducing valve II would ordinarily insure suilciently low temperature in the return line I I6 for the desired cooling action on the thermostat bulb 43. So in many instances the heat exchanger 'II9 is not necessary to insure sufficiently cool Water supply through the pipe I4.

It is apparent that the arrangement shown in Fig. 2 supplements the velocity-creating effect of the make-up water in several ways. 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 I0 is under pressure, the cooling eiect of the vent condenser 53 reduces the pressure 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 from the lower end of the separator 3i creates iiow in the'return line I8. In the fourth place, the condensing of steam in the separator 3I by the cooling eiect of the water coil 68 and/or the cooling effect of water introduced by the spray head I04 serve to promote. ilow by contraction of the iiuid mixture at the end of the return line.

All of these factors working together create and maintain whatever ilow velocity is desired in any 55 In the iirst water supply taken near the connection of the water supply pipe I5 with the unit. A dial 92 indicates the pressure prevailing inside the master control tank I0.

the periods in which the system is taking in new water, and a second signal lamp 96 responds to energizatlon of the solenoid valve 'I0 to indicate the occurrence of Water pulses into the two-stage heater 40.

Tuning the unit to suit a particular steam system- A feature oi the invention is that it incorporates a number of elements that may be changed or adjusted to cause the master control unit to match precisely the requirements o f any steam 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.

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

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

2. The'rate of supply of the new water may be I varied to change the cooling el'ect of the new A signal lamp isk Yresponsive to the mercury switch 'I6 to indicate 3. The closing action oi' the thermostatic valve 42 as weil as the opening action may be limited to any degree desired.

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

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

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

7. The cooling action of the heat exchanger lill on the condensate in the pipe |4 may be varied.

Description of Fig. 3

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

The pipe |4` in the master control unit is shown connected to the coil H8 of the heat exchanger ||9 as heretofore described. In this instance, however, the coil receives condensate from a trap |22 of a steam coll |23 that heats water in a closed pressure tank |24. This tank, for example, may be the tank for heating wash water in a laundry. Steam is supplied to the steam coil |23 by a pipe |25 from the steam header 25 and the flow of steam into the coil is governed by a thermostatic valve |26 in a wellknown manner.

Fig. 3 shows a water pipe |21 for supplying the tank |26 and shows how the proportion of the new water that is by-passed through the heat exchanger l I9 may be varied to vary the cooling effect on the condensate in the coil H3. The by-passed water is preheated by the condensate in the coil ||8 and on the other hand, the condensate is cooled down suiciently to activate the' thermostatic valve 42 of the master control unit when the condensate reaches the thermostat 43. The proportion of water by-passed through the heat exchanger ||9 is varied by manipulating two valves |28 and |23.

Fig. 3 also includes means for recycling the deaerated make-up water or more accurately stated, the mixture of deaerated make-up water and condensate stored in the tank |0. This water is recirculated into contact with the thermostat 43 to supplement the valve-operating function of the new make-up water.

Fig. 3 shows a small circulating pump |30 having its intake |3| connected to the tank I0 to draw water therefrom. The output from the pump is delievered 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 backflow. Preferably a by-pass |34 having a by-pass valve |35 is provided from the discharge side of the pump back to the tank I0. This valve |35 and a, second valve |36 in the pipe |32 may be manipulated to vary the amount of recirculated fluid 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, 3 shows the discharge from the circulating pump |30 as passing through the coil |31 of a heat exchanger |33. The heat excorresponding return line I3 for the purpose of claiming the invention.

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 in 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.

changer |33 is provided with an intake pipe |33 i We claim as our invention: l. In a steam system having a boiler, at least one steam-using device, and a return line, said device and return line forming a clear channel from said boiler for flow-promoting pressure communication through the system, the combination therewith of: a valve to release iiuid from said return line to promote ilow 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, and means to cool said thermostat with uid to favor opening of the valve for promoting iiow, said cooling fluid being, at least in part, condensate returned from the system.

2. In a steam system having a boiler, at least one steam-using device connected to the boiler, and a return line connecting the steam-using device to the boiler and closed to the outer atmosphere, said device and return line forming a clear channel from said boiler for flow-promoting pressure communication through the system, the combination therewith of: a valve to release fluid from said return line to promote flow in said device, boiler feed means having its intake connected directly with said return line to further promote flow through 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, and means to cool said thermostat with fluid to favor opening of the valve for promoting iiow.

3. In a steam system having a boiler, atleast one steam-using device, and a return line, said device and return line forming a clear channel from said boiler for now-promoting pressure communication through the system, the combination therewith of: a valve to release iluid from said return line to promote iiow 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, and

means to cool said thermostat with condensate returned from the system to favor opening of said valve for promoting flow.

4. In a steam system having a boiler, at least one steam-using device, and a return line, said device and return line forming a clear channel from said boiler for now-promoting pressure communication through the system, the combination therewith of: 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 iluid discharge of the valve, means to direct make-up water into cooling relation with said thermostat for opening action of said valve in response to the demand of the system for water, and means to cool said thermostat additionally with condensate from the system.

5. In a steam system having a boiler, at least one steam-using device, and a return line, said device and return line forming a clear channel from said boiler for flow-promoting pressure communication through the system, the combination therewith of: a valve to release fluid from said return line into a region of substantially lower pressure, means confining and retarding the dischargefrom said valve to cause pressure rise therein when the valve is open, a thermostat for causingopening 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 in said confining means to be heated by the fluid discharge of the valve, means to introduce make-up water into said confining means for cooling of said thermo' stat in response to the make-up water demand of the system, and means to introduce additional said return line into a region of substantially lower pressure, a thermostat for causingropening 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 temperatureJsaid thermostat being positioned to be heated by the fluid discharged from the valve, means to convey condensate from one of said steam-using devices into heat-exchange relation with said thermostat for cooling` the water from the system into said confining means Y ation 'of the valve in response to temperature' above said given temperature, said thermostat being positioned to be heated by the fluiddischarge of the valve, and means to recycle said fluid discharge at lower temperature into heatexchange relation with said thermostat for cooling of the thermostat to cause opening action of said valve.

7. In a steam system having a boiler, at least one steam-using device, and a, return line, said device and return line forming a clear channel from said boiler for flow-promoting pressure communication through the system, the combination therewith of: 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 oper- 4 ation of the valve inI response to temperature above said Agiven temperature, said thermostat being positioned to be heated' by the fluid disthermostat, and a heat exchanger to cool said condensate before the condensate reaches said thermostat.

9. In a steam system having a boiler, at least one steam-using device, and a return line, said device and return line forming a clear channel from said boiler for flow-promoting pressure communication through the system, the combination therewith of: a valve to release fluid from said return line into a region of substantially lower pressure for promoting flow in the steam system, means to bring cooling Huid into heatexchange 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 iluid discharged from the valve, and means-to cool said thermostatwith water to increase the opening action of said valve.

10. In a steam system having a boiler, at least one steam-using device, and a return line, said 'device and return line forming a clear channel from said boiler for flow-promotingA pressure communication through the system, the combination Y therewith of: a valve to release uid from said return line in to 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 one steam-using device, and a return line, said device and return line forming a clear channel from said boiler for now-promoting pressure communication through the system, the combination therewith of: 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 oi the valve in response to temperature 11. In a steam system having a boiler, at leastV above said given temperature, said thermostat being positioned to be heated by the fluid 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 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 'flow-promoting condensation in said return line.

12. In a steam system having a boiler, at least one steam-using device, and a return line, said device and return line forming a clear channel from said boiler for flow-promoting pressure communication through the system, the combination therewith of 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, and means to cause make-up Water to flow first through said condenser then into heat-exchange relation with said thermostat and then through said passage for flow-promoting condensing action in said return line.

13. In a steam system, a combination as set forth in claim 12, which includes means to cool said thermostat with condensate from the system.

14. In a steam system -having a boiler, at least one steam-using device, and a return line. said device and return line forming a clear channel from said boiler for flow-promoting pressure communication through the system, the combination therewith of: a separator included in said return line, a receiver tank maintained above atmospheric pressure but substantially below the pressure in said return line, a valve to release uid from said return line into said receiver, al 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 direct make-up water first through said condenser and then in heat-exchange relation with said thermostat for coolingr of the thermostat and then to cool the interior of said separator for flow-promoting condensation from said separator.

15. In a steam system having a boiler, at least one steam-using device, and a return line, said device and return line forming a clear channel from said boiler for How-promoting pressure communication through the system, the combination therewith of: means to bring cooling uid into heat-exchange relation with the contents of said return line for causing condensation of steam therein to set up a pressure differential across the system for promotion of flow in the system, a condensate pump for returning condensate to said boiler, said condensate pump having its intake port in a communication with-said return line to remove condensate therefrom for further promotion oi ow in the system, a valve to release fluid from said return line into a region oi substantially lower pressure than the return line to set up a still further pressure differential across the system for still further promotion of ow in the steam system, a thermostat controlling said valve, said thermostat being positioned for rise in temperature by heat supplied by said return line, and 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.

16. In a steam system having a boiler. at least one steam-using device and a return line, said device and return line forming a clear` channel from said boiler for flow-promoting pressure communication through the system, the combination therewith of: means to release steam from said return line thereby to promote ow through the system, means to provide condensate from the system apart from said return line at a temperature substantially lower than the temperature in said return line, means to bring said released steam into heat-exchange relation with said condensate, thereby to condense at least a part of said steam and at the same time to raise the temperature of the condensate, and means to return said heated condensate to said boiler under sustained pressure.

17. In a steam system, a combination as set forth in claim 16, in which said means for bringing steam into heat-exchange relation with condensate intermixes the steam and condensate.

18. In a steam system having a boiler, at least one steam-using device and a return line, said device and return line forming a clear channel from said boiler for flow-promoting pressure communication through the system, the combination therewith of: means to provide condensate from the system apart from said return line, means to cool said condensate substantially below the temperature prevailing in said return line, means to release steam from said return line into heatexchange relation with said condensate, thereby to raise the temperature of the condensate and at the same time to condense at least a part of said released steam.

19. In a steam system having a boiler, at least one steam-using device and a return line, said device and return line forming a clear channel from said boiler for dow-promoting pressure communication through the system, the combination therewith of: means to provide condensate from the system apart from said return line, means to cool said condensate substantially below the temperature prevailing in said return line, and means to bring said condensate into heat-exchange relation with steam that reaches v the end of the system through said return line, thereby heating the condensate and at the same time condensing said steam.

ORVILLE A. HUNT.

LOUIN TELLER.

REFERENCES CITED UNITED STATES PATENTS Name Date Harrison et al Jan. 2, 1945 Number