US2200471A - Measuring and control system - Google Patents

Description

y 14, 1940- P. s. DICKEY 2.200.471

MEASURING AND CONTROL SYSTEM Filed Aug. 25, 1936 2 Sheets-Sheet 1 wil- INVENTOR PAUL S. D/C/(EY BY WTW May 1 1940- P. s. DICKEY MEASURING AND CONTROL SYSTEM 2 Sheets-Shet 2 Filed Aug. 25, 1936 Mm m 3% 2 mm 4 w 06 //l 1.1/4 m on J Mm v. /P v v 1.7 AW 6 a M rm E mm M 5 MEECUE y A9555 UEE 1 fMEEGfA/CY Fun WA l/E INVENTOR Patented May 14, 1940 UNITED STATES MEASURING AND CONTROL SYSTEM Paul S. Dickey, Cleveland, Ohio, assignor to Bailey Meter Company, a corporation of Delaware Application August 25, 1936, Serial No. 97,813

5 Claims.

This invention relates to measuring apparatus applicable to heat exchangers, and in particular to vapor generating systems and apparatus. I provide in connection therewith improved apparatus for controlling the operation thereof.

In binary-vapor generating systems it is known to vaporize a liquid such as mercury, condense the mercury vapor, and utilize the condenser as a steam boiler. The mercury vapor may be passed through a mercury vapor turbine prior to I entering the condenser. The steam produced in the mercury condenser may go to any desired point of usage.

In the present system, the mercury liquid is heated to nearly its vaporization temperature by the heat produced by the combustion of fuel and air. The heated liquid is then flashed in an unheated vaporizer-separator from which the vapor is passed through a turbine and to a condenser. The unvaporized liquid which collects in the separator, and make-up liquid from the condenser hot well, is then forced into the liquid heater. It is to the control of combustion for the liquid heater that my invention particularly relates.

In the drawings:

Fig. 1 illustrates, in vertical semi-section, the mercury heater and vaporizer-separator to which the control is applied and which is illustrated in somewhat diagrammatic manner.

Fig. 2 is a wiring diagram of an interlocking protective system in connection with the arrangement of Fig. 1.

Fig. 3 is a sectional elevation of a differential relay.

Fig. 4 is a sectional elevation of a pilot valve.

Referring now to Fig. 1, I indicate at I a mercury heater having a combustion chamber 2 supplied with fuel and air for combustion. The heater is of the forced circulation type having a liquid mercury circulating pump 3' supplying the wall tubes 4 and the encircling tube section 5. The combustion space 2 is substantially completely encased by the wall tubes 4 which fan out at their lower portion in a manner to allow the products of combustion to pass therethrough and then to move upwardly at the rear of the wall tube bank, passing successively through the mercury liquid tube section 5, the mercury heater section 6, and the steam superheating bank I.

The liquid mercury entering through the conduit 8 passes through the tubes 4, 5 to an upper encircling header 9 from which an outflow conduit Ill leads to a vaporizer-separator ll external of the heater.

It is desired that no mercury be vaporized in any part of the heater unit or conduit l0 prior to its entrance through the pressure reducing nozzles I2 into the flash chamber I3. This means that while the temperature is to be raised as high as possible, it is not to be raised to the temperature corresponding to the pressure.

Mercury entering the flash chamber l3 through the nozzles I2 is given a whirling motion and liquid mercury which remains unvaporized passes through flow straightening baffles M to the collector or standpipe l5. Level in the standpipe I5 is maintained by a mercury level device 5, so that a constant head will be available for the circulating pump 3 at all times.

Products of combustion from the chamber 2 pass between the wall tubes 4 at or near the bottom and upwardly behind the wall tubes through the other tube sections to the upper end of one leg of a U shaped air heater passage. Leaving the air heater they pass out through a stack connection l1.

A motor l8 driving a fuel oil pump l9 and an air blower 20 will normally operate at a uniform speed, although the motor may be provided with speed varying means for test purposes or to basically establish desired rate of output.

Air to support combustion enters the blower 20 through a Venturi tube 2| used for measuring the air, and leaves the blower to pass through the air heater 22 to the duct 23surrounding the oil burner 24. The latter is supplied by a conduit 25, the rate of flow therethrough being regulated by the valve .26 and measured through the agency of an orifice 21.

Mercury vapor leaves the flash chamber l3 through a conduit 28 and throttle valve 29 to a mercury vapor turbine 30. From the turbine the vapor enters the steam generating condensers 3| wherein the mercury is condensed to a liquid and After the liquid mercury has been heated in the tube section 6 it leaves by way of the conduit 36 to enter the standpipe l5. It will be observed that the arrangement is suchthat should the flash chamber l3 supply very little liquid mercury to the standpipe l5, thus causing the level to which the indicator I6 is responsive to become lower, this decrease in level will result in positioning of the regulating valve 35 in an opening direction, thus allowing a greater flow of liquid mercury from the hot well through the heater section 6 to the standpipe l5 to restore the liquid level therein for maintaining a constant head available for the circulating pump 3.

A mercury level indicator I6 comprises a casing enclosing an expansible metallic bellows hav ing its lower end fastened to the casing and its movable uppermost end adapted to position a pressure packed rod for axially positioning a pilot stem 31 in a pilot casing 38-. A static head of liquid mercury is effective on the outside of the metallic bellows at all times while the static head effective upon the interior of the bellows depends upon the liquid mercury level within the standpipe |5. The result is that the pilot stem 31 is continually positioned directly responsive to variations in liquid mercury level within the standpipe l5 and is adapted to produce a loading pressure, effective upon the diaphragm regulating valve 35, for positioning the same in direct response to variations in liquid mercury level.

In general I desirably control oil fiow and air flow in accordance with the load on the mercury turbine and additionally responsive to mercury vapor pressure ahead of the turbine throttling valve. Variations in load cause a sudden change in the fuel and air supply and the mercury pressure controller acts as a modulator or readjusting control.

To that end a load indicator 39 is provided which is adapted to establish an air loading pressure proportional to turbine load. Such pressure is developed by the positioning of an air pilot valve similar to 38 and the loading pressure is then transmitted through a capillary, or small pipe 40, to be effective within the chamber 4| (Fig. 3) of the averaging relay 42. Actually the device 39 indicates the position of the mercury control vapor throttle valve and gives a rapid change of the .air loading pressure with changes in load.

A Bourdon tube 43 is sensitive to mercury vapor pressure within the conduit 28 ahead of the turbine throttle valve 29 and is adapted to position the pilot stem 44 of a pilot valve 45, making efiective an air loading pressure varying in step with the mercury vapor pressure through the pipe 46- upon chamber 41 of the relay 42.

An air loading pressure pipe 48 leads from the relay 42 to position the fuel oil control valve 26, and by way of the relay 49 and pipe 50 is effective to position a damper operator 5| for moving the damper 52 to control air supplied to the Lmit.

Referring now to Fig. 3, which illustrates in sectional elevation the construction of the relay 42, it will be noted that a diaphragm 53 separates the chambers 4|, 41. A member 54 is attached to and moved with the diaphragm 53. The member 54 is attached to one end of a tension spring 55 and to a second diaphragm 56 which separates the chambers 51, 58. The chamber 58 is open to the atmosphere while the chamber 51 is in com munication with the pipe 48.

The arrangement is such that the assembly comprising the member 54 and diaphragms 53, 56 is loaded by the tension spring 55. The air loading pressure representative of load, applied through the pipe 40 to the chamber 4|, is effective on one side of the diaphragm 53, while the air loading pressure representative of mercury vapor pressure, effective through the pipe 46,

acts upon the upper side of the diaphragm 53. The resultant of forces acting upon the diaphragm 53 and the force of the spring 55, causes a movement or positioning of the member 54, which at its lowermost end is adapted to position a valve actuating beam 59 so arranged that if the member 54 moves upwardly there will be an exhaust of air from the chamber 51 to the atmosphere, while if the member 54 moves down wardly there will be an admission of pressure fluid from a supply source to the chamber 51.

The pressure available within the chamber 51 is effective through the pipe 48 upon the diaphragm of the valve 26. The valve 26 will then be adjusted responsive to both mercury turbine load and mercury vapor pressure. Inasmuch as an increase in turbine load will call for an increase in fuel oil while an increase in mercury vapor pressure will call for a decrease in fuel oil, the two variable factors are applied in opposition to the diaphragm 53 so that the resultant positioning of the'valve 25 will satisfy both variables.

Referring now to Fig. 4 I illustrate in sectional elevation the construction of a pilot valve such as 45 having a stem 44 adapted for axial positioning therein relative to ports 6|. Lands 60 are spaced along the stem 44 in relation to the spacing of the ports 6|. A source of air under pressure is available between the lands and continuously bleeds to the atmosphere around both lands, thus lubricating them in axial positioning and eliminating end thrust or friction through movement. If the stem 44 is positioned upwardly, a pressure gradient is created at the upper lefthand exit of the casing 45, such gradient of pressure varying with axial movement of the pilot stem.

Thus a loading pressure may be established through the positioning of a pilot stem by a factor, such as load or mercury vapor pressure, and the pressure gradient will vary in definite relation thereto.

The air loading pressure available in the pipe 48, as a resultant of the indications of load and of mercury vapor pressure, is also effective in positioning the damper 52 for readjusting the rate of supply of air to support combustion. However, this effect upon the rate of air supply is modified or readjusted in accordance with the interrelation or ratio between actual rate of fuel oil flow and actual rate of air flow. The former is measured through the agency of an orifice 21 located in the conduit 25 and adapted to produce a pressure differential bearing a known and definite relation to the rate of flow through the orifice. Such pressure differential is applied to a rate of fiow meter 62 adapted to position an indicator 63 relative'to an index 64 and simultaneously to vertically position a pivotally connected link 65, to the lower end of which is pivotally connected one end of a floating member 68. Reading relative to the index 64 and a relative position of the right-hand end of the member 66 will be in accordance with actual rate of fuel oil flow to the burner 24.

A rate of flow meter 61 is responsive to the differential pressure created by the Venturi tube 2| and positions an indicator 68 relative to an index 69 to visually advise the rate of supply of air to the heater. Suspended from the indicator 68 I show a link 10 adapted to position the lefthand end of the floating member 66. Intermediate the ends of the member 66 is pivotally connected a pilot stem 1| adapted to be moved axially within the pilot casing 12 to establish an air loading pressure within the pipe 13 representative of relation between actual fuel oil flow and actual air flow. Such loading pressure is effective within the averaging relay 49, as is the pressure within the pipe 48. The resultant is effective through the pipe 50 upon the damper operator 5| for positioning the damper 52.

It will be observed that in general both fuel and'air are regulated conjointly in accordance with load and mercury vapor pressure. That the air supply is then additionally under the control of the existing relation between fuel and air supply to assure that they be maintained in desirable relation for most efficient combustion.

The fuel flow-air fiow readjustment of air or modulation of the primary control is necessary due to the different flow characteristics of the two fluids and the flow characteristics of the valve 26 and of damper 52.

Certain precautionary measures in the operation of such a unit are necessary and in that respect I provide a number of safety trips effective to shut off the supply of fuel oil to the combustion chamber in case predetermined conditions in the operation of the system are exceeded.

A solenoid actuated shutoff valve 14 is located in the fuel supply pipe 25. This valve is under the control of a mercury temperature-pressure switch 15, a mercury vapor pressure switch I6, a mercury turbine emergency trip 11, a steam turbine emergency trip 18, and a load responsive device 19.

In Fig. 2 the devices mentioned are shown in their relative wired relation. It will be observed that the solenoid 14 is connected in series with the mercury turbine emergency trip 11, the mercury temperature-pressure switch 15, the mercury pressure switch 16, and the steam turbine emergency trip 18. Furthermore, that the low load by-pass switch actuated from the indication of load 19 shunts the mercury temperature-pressure switch '15 for a purpose to be brought out hereinafter. Should the factor to which any of the devices l5, l6, H or 18 is responsive exceed a predetermined condition or position, the series circuit through the solenoid 14 will be opened. The solenoid is normally energized to hold the valve 14 open, while the devices 15, 16, I1 and I8 are normally close-circuited for this purpose. The low load device 19 is normally open circuited. Under emergency conditions, such as excessive mercury temperature, the switch '15 would open circuit the solenoid l4 and close the fuel supply line. Similarly should the emergency mercury vapor turbine trip open the device TI the fuel emergency valve would be closed. In similar manner an excessive mercury vapor pressure would actuate the device 16 and should the steamturbine which drives the circulating pump 3 trip off, then the device 18 would effect a closing of the emergency fuel valve 14.

In all cases of emergency closing of the fuel oil valve the blower will continue to operate to effect a cooling of the furnace and prohibit the possibility of an accumulation of explosive mixture of fuel vapor and air in the combustion chamber.

If desirable, the fuel shutoff valve 14 may be arranged to have a stop so that it will close only to a predetermined minimum and thus reduce the flame to nearly pilot proportions but not be completely extinguished, going to a minimum value until the mercury temperature falls to a safe value, or the other condition be restored to normal.

To prevent vaporization of liquid mercuiw prior to the flash chamber I3, an arrangement is provided such that the actual mercury liquid temperature in the outflow pipe I0 is maintained normally about 12 below saturation temperature. When the actual. temperature rises to nearly the saturation temperature for the existing pressure, or when the actual pressure drops to nearly the saturation pressure for the existing temperature, the circuit through the switch 15 will be opened, which will shut the emergency fuel oil valve or close it to a minimum open position.

A Bourdon tube 80 sensitive to the pressure of the mercury at the exit of the heater and just prior to the flash chamber is provided. Another Bourdon tube 8| sensitive to temperature of the mercury at that point is used, and in this temperature system I use mercury, so that a pressure (effective through a capillary or small pipe) will be created within the temperature system corresponding to the saturation tempera ture which is being measured. This pressure should always be lower than the actual pressure of the mercury as measured by the first Bourdon tube so long as the temperature of the mercury in conduit 10 is below the saturation or vaporization temperature. Should the temperature in conduit I0 approach the temperature corresponding to pressure, or pass it, then mercury would be vaporized at this point and this is not desired, so that sucha rise in temperature would trip out the fuel supply valve or take it to a predetermined minimum supply rate.

To prevent vaporization in the boiler tubes, when temperature in the mercury header becomes nearly equal to the saturation temperature corresponding to the then existing pressure, the circuit through the device 15 will be opened, which will shut the emergency fuel oil valve .14. The arrangement of the Bourdon tubes 80, 8| and the linkage actuating the electrical switch 15 is such that as long as below the saturation temperature corresponding to the pressure of the mercury the circuit is closed. If the pressure remains constant and temperature increases, then the circuit is opened, whereas if the temperature decreases the circuit remains closed. If temperature remains constant and pressure increases, then the circuit remains closed, while if the pressure decreasesthe circuit is opened.

The Bourdon tube 80 is provided with an indicator I02 movable relative to a fixed scale 503, while the Bourdon tube 8| is provided with 'an indicator I00 movable relative to a fixed scale NH. The differential depending link which positions the switch 15 carries an index I04 relative to a fixed scale I05.

The by-pass or shunting circuit through the device 19 is provided so that at light loads the device 15 is ineffective, as it may be necessary due to lack of sufiicient circulating pump power,

to allow the mercury to boil in the boiler tubes. In other words, when the load on the system decreases to a predetermined low load value the device 19 closes a circuit shunting the device 15 and thereafter any opening of the circuit at 15, due to excessive temperature above the vaporization point will not be effective in closing the fuel supply valve 14.

While I have illustrated and described certain preferred embodiments of my invention, it is to be understood that I am not to be limited thereby.

What I claim as new, and desire to secure by Letters Patent of the United States, is:

1. In combination, a conduit containing a liquid, a Bourdon tube whose movement is responsive to pressure of the liquid; a temperature system including a second Bourdon tube, a bulb, and a capillary connecting the tube and bulb; the temperature system containing liquid of the kind in the conduit, said bulb located in said conduit sensitive to temperature of the liquid therein, means positioned by said second Bourdon tube indicative of the saturation pressure corresponding to the actual temperature of the liquid, and means interconnecting said Bourdon tubes indicating the difference between said pressures.

2. A control system for controlling the processing of a fluid, comprising in combination, a pressure sensitive means whose movement is responsive to pressure of the fluid; a temperature sensitive system including means containing fluid of the kind being processed and whose movement is responsive to temperature of the fluid being processed and constructed to move in respect to saturation pressure corresponding to the actual temperature of the fluid, and control means conjointly positioned by said means.

3. A condition indicator for a fluid, comprising in combination, pressure sensitive means whose movement is responsive to pressure of the fluid; a temperature sensitive system including means containing fluid of the kind first mentioned and whose movement is responsive to temperature of the fluid and constructed to move in respect to saturation pressure corresponding to the actual temperature of the fluid, and means conjointly positioned by said means indicating relation between actual pressure and temperature equivalent pressure.

4. In combination, a conduit through which a fluid flows, an expansible-contractible means whose movement is responsive to pressure of the fluid; a temperature system including an expansible-contractible means, a bulb, and a capillary interconnecting the temperature system; the temperature system containing fluid of the kind in said conduit; said bulb located in said conduit sensitive to temperature of the flowing fluid, means positioned by said second expansiblecontractible means indicative of the saturation pressure corresponding to the actual temperature of the fluid, and means interconnecting said expansible-contractible means indicating the difference between said pressures.

5. Apparatus for indicating saturation pressure corresponding to actual temperature of a fluid, comprising in combination, a temperature system including a Bourdon tube, a bulb, and a capillary connecting the tube and bulb; the temperature system containing fluid of the kind first mentioned, said bulb located sensitive to temperature of the said first fluid, and means positioned by said Bourdon tube constructed to read in terms of saturation pressure of said fluid.

PAUL S. DICKEY.

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