US2023593A - Method and apparatus for blowing down boilers - Google Patents

Description

Dean MB, 1935. w. J. HUGHES METHOD AND APPARATUS FOR BLOWING DOWN BOILERS Filed July 31, 1931 2 Sheets-Sheet l Des, M1), 1935. w. J. HUGHES 2,023,593

METHOD AND APPARATUS FOR BLOWING DOWN BOILERS Filed July 51, 1931 2 Sheets-Sheet 2 Patented Dec. 10, 1935 UNITED STATES PATENT OFFICE METHOD AND APPARATUS FOR BLOWING DOWN BOILERS Illinois Application July 31, 1931, Serial No. 554,181

4 Claims.

This invention relates to the operation of steam boilers or other apparatus working under pressure and has for its purpose an improved method and apparatus whereby the condition of the water or other liquid in the boiler may be regulated by withdrawal of a portion thereof.

In the operation of steam boilers there is ordinarily a continuous generation and removal of steam and a corresponding continuous feed of. water to compensate for the loss, so as to maintain the water level and volume in the boiler substantially constant. Since the feed water always carries a certain amount of impurity of nonvolatile nature there follows a concentration of such impurities within the boiler. If such concentration were allowed toproceed indefinitely the boiler would become clogged with solid matter but long before such a stage is reached trouble of one kind or another arises. To avoid such difficulties as arise from the presence of these impurities it has been the practice to withdraw water from the boiler, replacing it with fresh water, the concentration within the boiler being correspondingly reduced. The amount of water necessary to be so withdrawn and replaced varies greatly, being dependent chiefly upon the character of the feed water and the rate of boiler operation although other factors enter also.

For many years it was customary to make such withdrawal, or blowdown as it is usually called, periodically, say once per day or once per shift. The operation was manual, by the opening of a valve, the amount of water blown out each time being a matter of judgment of the operator. A very large proportion, probably a majority of boilers are still so operated.

This is far from a satisfactory method, since there is necessarily a considerable variation in the concentration and also because, to be on the safe side, the operator nearly always discharges more water than is necessary.

With increasing severity of operating conditions involving among other things much higher steaming rates, such blowing down at comparatively long intervals became increasingly unsat isfactory or even impossible in some cases and various methods of so-called continuous blowdown have been proposed. In some cases the outflow of concentrated boiler water is really continuous while in others it is intermittent but with discharge of a small volume at such frequent intervals as to be the same in effect as a continuousdischarge so far as the boiler operation is concerned. Each of these two methods as heretofore carried out is subject t9 G Frtain diflicuh ties which it is in part the purpose of the present invention to overcome.

Since the amount of concentrated water to be discharged is always a low percentage of the boiler feed and when expressed in units of volume or weight per minute represents a very small flow, difiiculties arise in the control of a continuous flow of this order. In large part these difiiculties are caused by the great difference between boiler pressure and atmospheric which necessitates very 10 small orifices. The 'high velocities generated cause cutting or erosion since the water always carries suspended matter, necessitating the use of special and expensive valves. Regulation and especially automatic regulation of such small orifices or valves is difiicult or impossible. Various means have been proposed to dissipate part of this pressure such as using a long pipe of small diameter to cause friction and with some advantages resulting but no method heretofore proposed is adequate.

The alternate method of periodic discharge of relatively small volumes avoidssome of these difficulties but is more complicated since it requires some kind of timing and actuating device. Of the two methods the former is preferable but the latter more practical.

My invention has for an object to provide a method and means whereby the discharge from the boiler may be continuous and under small difference in pressure between the two sides of the orifice or aperture, which may in consequence be relatively large and so readily adjustable and free from cutting or erosion.

Another object is to provide means whereby the flow through the orifice may be proportioned in relation to the feed water requirements of the boiler, or the condition of the water in the boiler.

Other objects and advantages will be apparent from the following description and pointed out in the claims.

While my invention is contemplated to be chiefly useful in connection with the operation of steam boilers and for purposes of illustration will be so described, it will be apparent that it is adapted to other purposes also.

In the accompanying drawings Fig. 1 shows my invention in very simple form, the control being entirely manual.

Fig. 2 shows an apparatus similar to Fig. l but with the addition of a device for automatically maintaining constant discharge.

Fig. 3 is similar to Fig. 2 but with the addition Charge from the boiler feed.

setting. For this there is provided the balanced f Fig. 4 illustrates auxiliary equipment useful in conjunction with blowoff by any of the previously illustrated devices.

In the various figures the same number is used to designate the same or like parts.

Referring now to Fig. 1 the numeral I designates aboiler ,or the drum of a boiler, 2 the steam outlet. 3 the normal water level, 4 the blowofi outlet, and 5 a shutofi valve-in the blowofi line I3, which leads to trap I6 having the discharge line I5. The regulating valve? in line 6 is provided with pointer handle 8, and scalefS.

Trap I may be of any of the well known types of steam traps which automatically discharge entering water while preventing the escape of steam, although preferably it. is of the kind to'allow a continuous discharge of water therefrom. Intermediate valve I and trap I0 the pipe 6 is shown connected at fitting I I by equalizing pipe I2, provided with valve I9, to the steam space II of the boiler I. In some cases, depending on the construction of the trap used, pipe I2 may lead directly to the trap instead of being connected to line 6.. Thus where the trap is of the common type where the water to bedischarged collects in the lower portion and there is a steam space over the water, the pipe I2 may be led to this steam space. At I3 is indicated a supply line for the boiler feed water, containing valve I 4. r 7

Assuming valves and I6 open and valve 1' closed it is apparentthat there will be transmitted to the lower side of valve! the pressure existing in steamspace I! while on the upper side will be applied this same pressure plus a head due to the diiference in level between the valve and the 'water level in the boiler, trap I 0 being effective to prevent escape of steam. If now valve I be opened the same condition will obtainand a flow 'will take place through the valve that is independent of the boiler pressure and determined by the water head referred to and the amount of valve opening. e

The above assumes the pipe 6 is of such size, as it may be, that with the maximum flow through I the pipe 6 is not completely filled with water between I I and I, so that steam can get bacl; from I2 to the underside of I. g If pipe 6 is smaller. or is so placed that it runs full of water,'the effective head will not be that between the levels of 3 and I but between that of 3 andsome other point drawings valve I will be positioned in some place in line 6 convenient of access and sufficiently below the water level in I tov provide headfor the maximum discharge of water required, with the valve wide open. Trap II] is preferablylocated at a lower level than valve 'I, since if the trap is set at a level above that of valve l the head effective on the latter is correspondingly diminished.

In the form shown in Fig. 2 the flow regulating valve I is replaced by the orifice I 8 and means are provided whereby the head efiective on the orifice to produce fiow therethrough maybe adjusted as desired and maintained constant at any given valve I 9 to the stem 22 of which there is connected the graduated lever carrying the weight 2f, the

moment of the weight tending to open thevalve.

tank 31.

. Stem 22 extends into diaphragm chamber 23 and is there attached to diaphragm 24.

The side of chamber 23 below the diaphragm is connected by pipe to the boiler or upstream side of orifice I 8. The downstream side of orifice I8 is open to the side of chamber 23 above the diaphragm.

With this arrangement the differential pressure across I8 is available on diaphregm 24 to oppose the moment of weight 2I and with valves 5 and I6.open a flow will be created'and maintained of such amount aswill establish a state of equilib- "-rium. Of the total head available to cause flow a portion. will be dissipated at orifice I8 and the balance by valve I9. Thus by the setting of weight 2 I any desired flow may be maintained.

In Fig. 3 is shown a modification wherein the discharge fiow instead of being manually set or maintained constant as in Figs. 1 and 2 is proportioned to the feed water supply to the boiler. To accomplish this the stem 22 of valve I9 is extended beyond diaphragm 24 into a second diaphragm chamber 25 and therein attached to diaphragm 21. With this construction weight 28 serves to counterbalance the weight of the moving parts and not for flow adjustment.

The upper side of diaphragm chamber 26 is connected by pipe 28, which may lead through a settling chamber, with the inlet side of an orifice 29 located in the feed water line l3. The lower side of chamber 26 is similarly connected by pipe 39 with the discharge side of orifice 29.

With this construction a flow of feed water through pipe I3 creates a corresponding differential on diaphragm 21 tending to pull down rcd 22 and so open valve I9. When valve I9 opens a flow takes place through pipe 6 and orifice I8 creating a diiferential on diaphragm 24 that tends to close-valve I 9. Obviously a state of equilibrium is reached when the flow through I8 is such that the thrust of diaphragm 24 equals that of diaphragm 21 and valve I9 will be held at such a degree of opening as to maintain this balance. Variations in the flow through I I3 to correspond with boiler requirements will upset the equibrium andvalve I9 will be moved until the flow through 6 again corresponds. In this way the discharge from the boiler is maintained at a constant ratio to the feed and so the concentration inthe boiler kept uniform. If it is desired to change the ratio of discharge to feed this may be done in various ways as by inserting a different orifice at either I8 or 29 or one of these may be made adjustable. v f V The water discharged as above described is at boiler temperature and so carries an amount of heat which it is many times desirable to conserve.

- type. The hot water from the bottom of 3I flows through pipe 35 to heat interchanger 36 and discharges thencerto waste through pipe 3 1. 7 coldfeed-water enters interchanger 36 through pipe38'and after absorbing heat from the blowofi water flows through pipe 39 to heater 34 and from thence through pipe 40 to boiler. feed pump II Instead of separating the steam and water as in flash tank 3! the pipe I5 maybe lead directly tointerchanger 36. 7

From the above description and accompanying drawings the principle of myinvention and the 'mode. of application will be readily understood "andvariousmodifications in the manner of ap The plication and in the uses to which it may be put will occur to those skilled in the art. All such modifications and applications are contemplated by me and the scope of my invention is not to be limited as to those matters otherwise than as the prior art and the appended claims may require.

What I claim is: i

1. The method of controlling boiler blowdown which comprises continuously flowing water from the boiler by gravity through an orifice while neutralizing the effect of the boiler steam pressure to cause flow therethrough, accumulating under boiler steam pressure the water delivered through the orifice and discharging the water by steam pressure to a zone of lower pressure at substantially the rate of accumulation.

2. The method of blowing down a boiler which comprises continuously transferring water from the boiler to a level below that of the water in the boiler by a gravity flow while neutralizing the efiect of the steam pressure in the boiler on said flow, and then discharging the water from the lower level under the influence of the steam pressure in the boiler.

3. The method of blowing down a boiler which comprises maintaining a gravity head on a measuring orifice, equalizing the steam pressure on the two sides of said orifice so that the flow therethrough will be independent of the steam pres sure, and subsequently discharging the measured 10 flow by boiler pressure.

4. The method of blowing down a boiler which comprises utilizing the head due to difierences in water level within the system to secure a flow through a measuring orifice and neutralizing the efieot of the boiler pressure on said flow so that said flow is independent of the steam pressure in the boiler and subsequently utilizing the boiler pressure to effect discharge from the system.

WALTER J. HUGHES.

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