US2130463A - Meter foe - Google Patents

Description

Sept 20, 1938.

I w. H. HOYT METER FOR STEAM BOILERS Filed May 26, 1956 2 Sheets-Sheet 1 s Y E N R O T T A Sept. 20, 1938. w. H; HOYT METER FOR STEAM BOILERS 2 Sheets-$heet 2 Filed May .25, 193s :5. mi I'm BY mjm%.

ATTORNEYS Patented Sept. 20, 1938 UNITED STATES PATENT oFFicE 1 Claim.

This invention relates to meters for steam boilers and has for an object to provide an air flow pen responsive to steam and draft pressure variations in the boiler and adapted to indicate and record the percent of air being used to support combustion.

In practice a boiler operator must manipulate the draft and fuel feed soas to maintain a required percentage of air to support combustion during all changes in steam output. Gas samples may be analyzed to determine the specific percentage of air that must be supplied to completely burn a unit of the fuel. Then, in order to maintain best operating conditions, this percentage of air must be maintained a constant throughout all changes of steam output from zero to maximum load. To eliminate guess work and haphazard manipulation of the dampers and coal feed the present invention provides a meter which records and indicates to the operator the steam flow and the exact percentage of air being used and he thereupon can maintain this percentage a constant by so manipulating his draft and coal feed as to prevent any movement of the air flow pen above or below this required constant, during all readings of steam output variations recorded by the steam flow pen of the meter.

With the above and other objects in view the invention consists of certain novel details of construction and combinations of parts hereinafter fully described and. claimed, it being understood that various modifications may be resorted to within the scope of the appended claim Without departing from the spirit or sacrificing any of the advantages of the invention.

In the accompanying drawings forming part of this specification,

Figure 1 is a diagrammatic View showing a meter and its operative connections with the steam line and draft passage of the boiler, constructed in accordance with the invention.

Figure 2 is a plan view of the pivotally mounted frame and the rotatable cam shaft and reciprocating follower forming the motion translating device for operatively connecting the air flow pen and the steam flow pen to be responsive to steam and air pressure variations in the boiler.

Figure 3 is a side elevation of the parts shown in Figure 2.

Figure 4 is a fragmentary view of the calibrated dial of the meter.

Referring to the drawings in which like characters of reference designate similar parts in the various views, In designates a substantially rectangular frame which is provided at the ends with gudgeons ll that pivotally mount the frame to rock on its longitudinal axis in bearings l2 disposed at the upper ends of bracket arms I3 which may be supported in any preferred manner upon the back plate I l of the meter.

A shaft I5 is mounted transversely of the frame to turn axially in bearings it carried by the sides of the frame. projects beyond one side of the frame and is equipped with a cross bar H which forms means for oscillating the shaft. A cam I8 is fixed to the shaft between the sides of the frame 1G by means of a collar l9 and screw 28 whereby the cam may be adjusted upon the shaft.

A follower disc 2| is disposed Within the em closure of the frame and is provided with a stem 22 which is slidably fitted in an axial opening formed in one of the gudgeons l l Pivotal movement of the frame will impart no sliding movement to the follower and hence no change in the position of the extreme end of the follower stem, while axial rotation of the shaft I5 in one direction will bring a high side of the cam against the follower disc 2i to slide the follower longitudinally of the frame and. change the position of the free end of the follower stem. A bell crank lever 23 is pivoted at its elbow, as shown at 24, on a bracket 25 carried by the back plate M of the meter and the long arm of the bell crank lever extends downwardly and is counterweighted, as shown at 26, to bear against the extreme end of the follower stem and cause the follower to recede as the low side of the cam is brought to bear upon the follower disc 2! during movement of the shaft l5 in a retrograde direction.

A link 21 is pivotally connected to one end of the cross bar I! and through this link variations in draft pressure in the boiler are translated to the cross bar. A link 28 is pivotally connected to the opposite end of the cross bar I! and through this link variations in steam pressure in the steam line of the boiler are translated to the cross bar, as will bepresently described. Thus it will be seen that when the movements of the links 21 and 28 are unequal the cam ill will be rotated on the bearings l6 and the follower will move the bell crank lever 23 to actuate the hereinafter described air flow pen. When the movements of the links 2? and 28 are identical the frame I5 will be rotated on the bearings l2 and the position of the cam l8 with respect to the follower 22 Will remain unchanged.

One end of the shaft The link 28 is pivotally connected to one end of a steam flow pen 29 which is pivoted intermediate its ends on a suitable bracket 30 on the back plate 14 and bears with its free end upon a dial, 3|, best shown in Figure 4. The dial may be calibrated as illustrated to indicate the daylight and the night hours by radial division lines 32 and to indicate steam flow in thousands of pounds per hour, and air percent, by concentric circles 33. Alternate ones of the radial division lines are calibrated respectively, at the circles, to read rate of steam flow from 10 to 100 thousands of pounds per hour, and to read percentage of air from 20 to 200 percent. The steam flow pen 29 will as usual draw anannular wavy line upon the dial which latter is of course turned by a conventional clock work mechanism, not shown, and will record upon the dial the changes in steam output as various appliances are cut in or cut out, from 10 to 100,000 pounds per hour.

However, as will later appear, the operator will control the air flow pen to draw its line constantly upon a predetermined one of the concentric circles, say for example, the circle marked 100%, during all of the various readings of the steam flow pen.

As' shown in Figure 1', the bell crank lever 23 is connected by a link 34 to one end of an air flow pen 35 which is pivoted intermediate its ends on a suitable bracket 36 on the back plate l4 and bears with its free end' upon the dial 3l' con tiguous to the free end of the steam flow pen, as best shown in Figure 1. Movement of the bell crank lever 23 will move the air flow pen upwardly or downwardly upon the dial according to the direction of rotation of the cam 1'8. By observing the recording of the air flow pen the operator may learn whether too much or too little air is being supplied for complete fuel combustion and may regulate the coal feed and drafts to confine the air flow pen to movement upon the predetermined air percentage circle to maintain best fire conditions.

Movement of the link 28 at one end of the cross bar I! is controlled by a difference in pressure on opposite sides of a tapered nozzle 31 in a steam line 38 connected to the steam drum 39' of the boiler 40. Apparatus suitable for this purpose is a valve controlled pipe 4| connected to the steam line on the high pressure side or large end of the nozzle and conducted into an inverted can 42' which is sealed in a mercury bath 43 disposed in the vertical leg of a tank 44 mounted on the back plate M. A valve controlled pipe 45 is also connected to the steam line on the low pressure side or small end of the nozzle and opens through the top of the horizontal leg 45 of the tank 44, said leg containing'a; water bath in which the top of the can 42' is submerged". Variations in pressure on opposite sides of the nozzle will thus cause the can to rise or fall.

An arm 48' is rigidly secured to the can and is secured at the free end to a stand rod 49 by a shaft which is rotatably mounted and provided with a gland 50 in the top of the horizontal leg of the tank. A link 5| is connected at one end of the top of the rod and at the opposite end to one leg of a bell crank lever 52' which is pivotally mounted at its elbow on a bracket 53 secured to the back plate I4, and which has its other leg secured to the link 28. Movement of the can is thus imparted to the link 28 to apply a movement upon one end of the cross bar it and to simultaneously actuate the steam flow pen.

Movement of the link 21 at the opposite end of the cross bar I! is controlled by a difference in pressure at two points in the draft line of the boiler. Apparatus suitable for this purpose is a pipe 54 which may be connected at a point of high negative pressure in the draft line of the boiler and conducted into an inverted can 55 which is sealed in a water bath 56 in a tank 51 mounted on the back plate l4. A pipe 58 is connected to the boiler at a point of low negative pressure in the draft line, or path of the: draft through the boiler, and is conducted into an inverted can 59 which is sealed in the water bath 56 of the tank. Stand rods 60 and 6| rise from the tops of the cans and are pivotally secured to the opposite ends of a walking beam 62 which is pivoted, as shown at 63, on a bracket 64 carried by the back plate l4. A crank arm 65 is formed integral with the walking beam at its pivot and is connected by a link 66 to one leg of a bell crank lever 61 which is pivoted at its elbow on a bracket 68 carried by the back plate and which has its opposite end pivotally connected to the link 2!.

Variations in pressure in the draft line of the boiler at the points of entrance of the pipes 54 and 58 will cause one of the cans to sink and the other can to rise which movement will be imparted to the walking beam and exert a force on the cross bar I! through the link 21'.

As previously stated, when the movements applied by the links 21 and 28 on the opposite ends of the cross bar are identical, the position of the cam with respect to the follower will remain unchanged and no movement will be imparted to the air flow pen. However, should, for example, a greater demand be made upon the boiler due to a sudden cutting in of more appliances, it will be apparent that the air percentage will become inadequate and a drop in air percentage will be immediately indicated by the air flow pen moving below the predetermined air percentage circle on the dial due to a change in position of the cam with respect to the follower. The operator may now open his draft to increase the air supply to the required amount to bring the air flow pen back again upon its predetermined air percentage circle on the dial. Should appliances be suddenly cut off, for example, and more air supplied than is needed, the air flow pen will rise above the predetermined air percentage circle on the dial whereupon the operator may again regulate his drafts to cause a reverse movement of the cam with respect to the follower and again bring the air flow pen back to the predetermined air percentage circle on the dial. Thus guess work and haphazard operation of the boiler will be eliminated and the operator will be enabled by glancing at the air flow pen to read the exact percentage of air being supplied and regulate his drafts and fuel feed to maintain a predetermined constant percentage of air which will insure .complete fuel combustion at all times.

The device is supposed to indicate and record the percent of total air per pound of fuel at all values of steam flow, and for the period of operation of the boiler.

Considering the steam flow meter, the drop in pressure across the orifice 31 exerted at the can 42 by means of the pipes 4| and 45 causes can 42 to rise and move elements 48 and 49 counterclockwise about the shaft to which they are rigidly attached to its ends. This will cause element 49 to rotate bell crank 52 counterclockwise and cause link 28' to move down.

This drop in pressure across the orifice 31 varies as the square of the flow of steam through the orifice. Doubling the flow of steam will therefore produce four times the pressure drop across orifice 31 and can 42, and link 28 will now move a distance four times as great as when the flow of steam through the orifice 31 had a value only one half as great. This motion of link 28 varies as the pressure drop across orifice 31 and may be said to be a measure of the flow through it. Considering the air flow mechanism, the loss in draft, or difference in negative pressure between the end of pipe 58 located in the sidewall near the furnace and the end of pipe 55 located in the sidewall near the boiler outlet, when exerted by means of pipes 58 and 54 beneath cans 59 and 55, cause the can 55 to sink and the can 59 to rise, since 55 is at the higher value of draft. Walking beam 62 will turn counterclockwise and link 2'! will be moved down.

The draft drop between 58 and 54 varies as the square of the flow of flue gas through the boiler. Doubling the flow of flue gas will therefore produce four times the draft drop between the ends of pipes 58 and 54 and beneath the cans 59 and 55. Link 21 will now move a distance four times as great as when the flow of flue gas through the boiler was only one half as great. This motion of link 27 varies as the draft drop between pipes 58 and 54 and may be said to be a measure of the flow of flue gas, but since the products of combustion in the flue gas are a measure of the air supplied for combustion, the motion of link 2'! may be said to be a measure of the flow of air supplied for combustion.

Samples of flue gas may be drawn from the boiler outlet just before the damper and analyzed volumetrically with the Orsat apparatus to determine the percent of total air. This analysis may be made for any value of steam flow.

If it is assumed that the evaporation per pound of fuel is a constant, which assumption is within the limits of accuracy of the Orsat measurements, then doubling the steam flow will necessitate doubling the amount of fuel supplied to the furnace. By proper manipulation of the back damper it is possible to supply twice the amount of air to burn this increase in fuel. Orsat analysis at each value of steam flow will show the same value of percent of total air, since by proper manipulation of the damper the air supply has been increased in exact proportion to the fuel supplied and the percent of total air ratio is therefore a constant.

By making arm 65 of the walking beam 62 the proper length and proportioning the cross sectional area of the cans 55 and 59 correctly for a given boiler, with the doubling of the steam flow mentioned in the above paragraph, links 21 and 28 will move equal distances and apply equal movements at each end of the cross bar ll.

Since the movements applied by links 27 and 28 attached to the ends of crossbar l! are equal they balance each other, and there can be no rotation of cam l8 to cause sliding motion of follower 22, and pen arm 35 will remain fixed in its position on the chart. If the cam I8 is in the correct position on the shaft l5 the pen arm 35 will indicate the per cent of total air corresponding to the Orsat determinations, and the cam assembly will be forced to rotate about bearings I2 an amount dependent on the equal down ward motion of links 21 and 28.

If the steam flow is now held constant and the damper manipulated so as to double the air supply, the per cent of total air will be doubled,

since with the same amount of fuel being burned, twice the amount of air is being supplied to burn it. Link 28 will not move, but as previously explained link 21 will move a distance four times as great as when the flow was only one half as great, and cause cross bar I? to move down at the end to which link 2'! is attached rotating the cam I8 clockwise causing follower 22 to move bell crank 23 clockwise and cause pen arm 35 to rise on the chart. With the proper cam design the per cent of total air indicated on the chart will be twice what it was before the air supply was doubled.

In a similar manner if the damper is so manipulated that the air supply is held constant and the steam flow is doubled, then the per cent of total air will be halved, since with a constant air supply twice the amount of fuel is being burned. Link 21 will not move, but as previously" explained link 28 will move down a distance four times as great as when the flow of steam was only half as great. Cross bar l'l will be forced down at the end to which 28 is attached rotating the cam l8 counterclockwise causing bell crank 23 to move counterclockwise and cause pen arm 35 to fall on the chart. The per cent of total air indicated will be one halfwhat it was before the steam flow was doubled.

Angular rotation of the cam 68 and sliding motion of the follower 22 is therefore dependent upon the relative motions of links 27 and 28 and since it has been shown that this relative motion of 27 and 28 is a measure of the percent of total air ratio, the angular motion of the cam i8 is a measure of this ratio and by means of the follower 22 and the pen arm 35 will record variations of this ratio for all values of steam flow.

The exhaust. gases of a boiler are removed by means of a chimney or by a combination of chimney and induced draft fan. This draft is a negative or suction pressure, and the gas passages and combustion chamber are also subjected to this negative pressure.

The direction of gas flow through the boiler is from the fuel bed towards the back damper. With the damper closed and no flow of gas through the boiler the pipes 58 and 54 connected to the furnace and boiler outlet will be subjected to the same value of negative pressure or draft. This is because with no flow of gas there can be no frictional resistance and therefore no loss of draft between the pipes 58 and 54. Cans 59 and 55 connected to the pipes 58 and 54 will also be subjected to the same draft, and there will be no motion of the walking beam 62 since the forces at the two cans are equal.

However with an increase from a no flow condition to one of flow the brickwork and tube surfaces of the boiler will offer frictional resistance to the flow, and cause a loss of draft between the pipes 58 and 54. Pipe 55 being nearest to the source of draft will be subjected to the highest value of draft or negative pressure, pipe 58 will be subjected to the lowest value of draft, being lower than that of pipe 54 by the amount of the draft loss mentioned above.

Can 55 connected to pipe 54 will be at a higher value of draft than can 59 connected to pipe 58. Atmospheric pressure pushes down equally on the outside of the two cans, but since the greatest draft is between the can 55, the net force at the can 55 is greater than the net force at the can 59, and can 55 will sink and can 59 will rise and cause walking beam 62 to turn counterclockwise and move link 21 down causing cam I8 to be 4- rotated clockwise and by mean's :of follower 22 being rforced to theileft against the bell crank 23 will cause the pen arm 35 to :rise on the chart andindicatean increase in per cent of total air. Therefore the cam 13 is properly shown.

The term per cent of air used throughout the descriptionrrneans .per cent of total air.

For every pound of a given fuel burned in a boiler there is theoretically a definite quantity of airrequired to be supplied to just completely burnthe fuel and have no excess of air left that has not takenlpart in the combustion of the fuel.

In practice it is found necessary to supply an excess 'of air over that required theoreticallyior complete combustion.

The :ratio of the actual air supplied for combustion 'of the given 'fuel to that theoretically required for complete combustion is the per cent of total air and is what is meant by the term used in the description.

From the above description it is thought that the construction and operation of the invention will befully understood without further explanation.

'What is claimed is:

A meter for steam boilers includinga dial,-an airflow pen thereon, means responsive to steam flow, air flow responsive means responsive to draft pressure variations in the boiler, a. .pivoted frame, a follower slidably mounted thereon, -'a cam shaft carried by the frame, a cam on the shaft, a cross bar fixed to the shaft and having the ends respectively connected to the first two named means whereby balanced movement of the steam and air flow responsive means tilts the frame, movement of either the steam flow means or the air flow responsive means changing the position of the cam and means operatively connecting the follower to the air flow pen for actuating the air flow pen when the follower is moved.

WILLIAM H. HOYT.

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