CA1097184A - Flow control system - Google Patents
Flow control systemInfo
- Publication number
- CA1097184A CA1097184A CA315,084A CA315084A CA1097184A CA 1097184 A CA1097184 A CA 1097184A CA 315084 A CA315084 A CA 315084A CA 1097184 A CA1097184 A CA 1097184A
- Authority
- CA
- Canada
- Prior art keywords
- fluid
- valve
- demand
- facility
- reagent
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D1/00—Pipe-line systems
- F17D1/08—Pipe-line systems for liquids or viscous products
Abstract
ABSTRACT OF THE DISCLOSURE
A fluid flow control system e.g. for an integrated continuous fluid reagent production facility and one or more reagent consumption facilities, involving an interconnected reagent storage facility, has fluid flow control valves connected together and sensing the demand and supply situa-tion to the consumption facilities, to provide continuous even flow of reagent either from production or from storage or both. A main valve ensures that, whenever possible, demand for reagent is satisfied directly from production. A storage withdrawal valve ensures that, in the event that the reagent flow through the main valve is insufficient to satisfy demand, the flow to the consumption facilities is supplemented by withdrawals of reagent from storage. The fluid flow valves are operated by signals deriving from the fluid flows and pressures at various locations in the system. The storage withdrawal valve is fed with a bias signal derived from the rate of production of reagent in the production facility, which maintains it at its threshold opening condition when demand is being satisfied completely by flow through the main valve. Then in the event that demand increases beyond that which can be satisfied by the flow through the main valve, the storage withdrawal valve opens immediately to satisfy the demand and maintain substantially continuous flows without deadbands or surges of reagent.
A fluid flow control system e.g. for an integrated continuous fluid reagent production facility and one or more reagent consumption facilities, involving an interconnected reagent storage facility, has fluid flow control valves connected together and sensing the demand and supply situa-tion to the consumption facilities, to provide continuous even flow of reagent either from production or from storage or both. A main valve ensures that, whenever possible, demand for reagent is satisfied directly from production. A storage withdrawal valve ensures that, in the event that the reagent flow through the main valve is insufficient to satisfy demand, the flow to the consumption facilities is supplemented by withdrawals of reagent from storage. The fluid flow valves are operated by signals deriving from the fluid flows and pressures at various locations in the system. The storage withdrawal valve is fed with a bias signal derived from the rate of production of reagent in the production facility, which maintains it at its threshold opening condition when demand is being satisfied completely by flow through the main valve. Then in the event that demand increases beyond that which can be satisfied by the flow through the main valve, the storage withdrawal valve opens immediately to satisfy the demand and maintain substantially continuous flows without deadbands or surges of reagent.
Description
~0~7~8~
This invention relates to fluid flow control systems, and more particularly to the control of fluid flows from a plurality of interconnected sources, such as one or more fluid chemical reagent producing and storage facilities, and one or more facilities of consumption of the reagent.
In integrated chemical facilities, it is common to have a reagent producing facility, involving the use of various chemical processes to produce a fluid chemical reagent, connected to one or more reactors where the reagent is used in chemical manufacture of other products. In such cases, the rate of production of the reagent is sub~ect to wide varia-tions, from 0 when the facility is closed down, to a very large number when the facil.ity is on full production, e.g.
200,000 pounds per hour. Similarly, the demand for the reagent may fluctuate widely, particularl~ where two or more consump-tion facilities, e.g. reactors, are fed from the same produc-tion facility. It is not desirable to have the production rate of the reagent tied in to fluctuate with the demand rate of the reactors, on economic grounds, since it may be necessary to close down one or more of the reactors due to conditions which have nothing to do with the ability to continue producing the reagent. An example is a crude oil cracker, producing ethylene, adapted to feed two or more reactors utilizing the ethylene, for example an ethyl benzene producing facility and a polyethylene producing facility.
-- 1 ~
`.i~
.. :: : , , : ,. ,:. - - , , :
. , ~, . . .
.. . .: ,: : . ...
~ . .:: . ~
: ': : ~ :
~L0~7~84 In such arrangements, thereEore, it is common to integrate storage facilities into the system, so that when the reagent is being produced faster than it is being consumed, the excess reagent is fed to storage. ~hen demand for the reagent exceeds supply, the demand is satisfied at least in part from the storage. A series of pressure responsive valves are included in the interconnecting ducts, to regulate the supply to and from the storage facility tcommonly one or more underground cabins).
The conventional way of controlling the fluid reagent supply is by the provision of valves operating in spli`t range service, in the supply lines from the reagent producing facility to the consumption facility, on the one hand, and from the storage facility to the consumption facility on the other.
The valve in the supply line, the main valve, opens so as to meet the demand whenever possible fully from the production facility. The valve in the storage supply line only opens when the demand exceeds the rate of reagent production, so as to supplement the supply from storage.
The use of such split range valve arrangements works well provided that the rate of production is in excess of the demand. When the demand exceeds the rate of production, however, problems arise. Fluctuations in the demand, when the demand exceeds the rate of production, lead to delays in satis-fying the demand ("deadbands") and surging of the reagent.
,:
: , .: . ~
~97~84 Such fluctuations can, in many cases, be of large magnitude.
For example, when three different sources of consumption are connected into the system, and only two of them are in operation, there will be a sudden and very significant increase in demand when the third consumer comes into operation. This can cause delays and uneven flows because of the split range valve operating arrangement, if the total demand increases be~ond the rate of production. Surging of the reagent to the reactors is most undesirable, since it may lead to the tripping of safety control devices to close down the reactors completely.
It is an object of the present invention to provide a new and improved fluid flow control system, for an integrated fluid production and consumption operation.
The present invention provides a process and apparatus whereby the fluid flow control valves are arranged to operate in conjunction with one another, with main supply valve opening to supply reagent to consumption from production whenever possible, and the storage withdrawal valve being arranged to track the main valve so that it is always on the threshold of moving to its open position. By the arrangement of the invention, in the event that demand increases beyond the rate of production, so that the demand cannot be satisfied by increased flow through the main valve, however much the main valve is opened, the storage withdrawal valve opens :-: - : :: ; :: . . : ., : . . : , , - , ~- , . :;- ,: ~ . . .
~9'7~
substantially instantaneously to meet increased demands from storage. This is achieved by supplying to the storage withdrawal valve a bias signal derived from a measurement of fluid flows upstream of the main valve, i.e. rate of production of reagent. The delays, "deadbands" and surging of reagent previously encountered with prior art arrangements when the valves are set in split range service are thus essentially eliminated.
Thus, according to the present invention, there is provided a process for continuous control of fluid flows from plural interconnected fluid supply facilities to a fluid consumption facility, in which first and second flow control valves are interposed in communication ducts between respective first and second fluid supply facilities and the consumption facility, which comprises:
continuously monitoring consumption demand to obtain signals~thereof, and continuously feeding the demand responsive signals to the first and second c:ontrol valves;
causing the demand responsive signals to act pre-ferentially to open the first valve to the required extent to meet the demand by fluid flow through the first valve, and to open the second valve only in the event that fluid flows through the first valve cannot meet the demand;
supplying a bias signal to the second valve, the bias . ;
:
.. : . ~ .
~: '' : ,: :
- :.-:
~[3197~4 signal being marginally insufficient to cause opening of the second valve and being additive to the demand responsive signal, so that a change in the demand responsive signal indicating an increase in demand will cause immediate opening of the second valve in the event that the signal change fails to cause increased fluid flows through the first valve.
In the preferred process according the invention, the consumption demand is monitored by measuring pressure in the fluid flows downstream of the first and second valves, these pressure measurements being converted to signals (preferably elect-rical, but optionally pneumatic) for feeding to the control valves so as to control the degree of opening thereof. The bias signal is preferably variable in relation to fluid flows upstream of the control valves, and is determined by means of a flow meter inter-posed in the main supply conduit upstream of the fluid flow control valves. Normally, the first fluid supply facility will be a production facility, for example a crucle oil cracker producing various separated fractions of fluid reagents such as ethylene,and the second fluid supply facility will be a storage facility, such as one or more underground stora~e caverns for the selected fluid reagent. For ease of description and convenience, the process will be described in more detail with reference to an ethylene production and supply facility, but it will be appreciated that the process is of wider application, and can be adapted for use with substantially any liquid or gaseous .
7~914 chemical reagent, fuel or the like which is produced at a production facility and consumed at a consumption facility, the production and consumption processes being desired to be conducted substantially independently of one another~ and including a storage means interconnected with the production and consumption facilities so as to ensure continuity and sufficiency of supply automatically, when the production and consumption rates are not in balance.
In the most preferred process according to the inven-tion, the fluid flow rates are continuously monitored up-stream of the control valves, and the bias signal for the second valve is derived from this flow rate, as an electrical signal `directly proportional to the upstream flow rate.
Normally, such measurements will be conducted with a flow meter, measuring the flow rate by means of pressure drop across an orifice plate, which will give a signal proportional to the square of the ~low rate. There is then provided a means for converting the signal into the required bias signal and supplying it to the second valve, the conversion means comprising a square root extractor and an analogue computer.
The input to the analogue computer is an electrical signal directly proportional to the measured flow rate upstream of the control valves, i.e. the rate of production, and from this the analogue computer produces a signal which it supplies to the second valve to m~intain it at its threshold opening condition, .
-~ ;
.
: -~L~31971~
ready to be opened substantially instantaneously upon supply thereto of additional, additive electrical signal from the pressure sensing means provided downstream of the main valve.
According to a further aspect of the present inven- , tion, there is provided an apparatus for controlling fluid flows between a plurality of fluid supply facilities and at least one fluid consumption facility, said apparatus com-prlslng:
first and second fluid conducting conduits adàpted to supply fluid respectively from the first supply facility and the second supply facility to the fluid consumption facility;
first and second fluid flow control valves interposed respectively in the first and second fluid conducting conduits r said valves being positionable in response to demand responsive signals in fully open, fully closed and a continuous range of intermediate positions;
pressure sensing means adapted to monitor pressures of fluid downstream of the fluid control valves and ~0 to feed demand responsive signals proportional to the monitored pressures back to the fluid flow control valves to adjust fluid flows therethrough;
the first and second fluid control valves being in split range service such that demand is satisfied prefer-entially by fluid flows through said first valve, and through .
.. , . . ~ .
I~
~97~E34 said second valve only when demand cannot be satisfied byfluid flows through said first valve;
flow measuring means adapted to measure flows upstream of the first fluid flow control valve in the first conduit and to produce a signal in response thereto;
signal conversion means connected to the flow measuring means and the second fluid flow control valve, adapted to convert the signal from the flow measuring means to a bias signal for the second valve proportional to the flow rate measured by the flow measuring means;
said bias signal maintaining the second valve in a threshold opening condition such that an increase in the demand responsive signal supplied to the second valve will cause substantially immediate opening thereof.
The nature of the process and apparatus according to the invention, its mode oE operation, and its differences from conventional, prior art split range valve arrangements, will be clear from the following specific description with reference to the accompanying drawings, showing an example
This invention relates to fluid flow control systems, and more particularly to the control of fluid flows from a plurality of interconnected sources, such as one or more fluid chemical reagent producing and storage facilities, and one or more facilities of consumption of the reagent.
In integrated chemical facilities, it is common to have a reagent producing facility, involving the use of various chemical processes to produce a fluid chemical reagent, connected to one or more reactors where the reagent is used in chemical manufacture of other products. In such cases, the rate of production of the reagent is sub~ect to wide varia-tions, from 0 when the facility is closed down, to a very large number when the facil.ity is on full production, e.g.
200,000 pounds per hour. Similarly, the demand for the reagent may fluctuate widely, particularl~ where two or more consump-tion facilities, e.g. reactors, are fed from the same produc-tion facility. It is not desirable to have the production rate of the reagent tied in to fluctuate with the demand rate of the reactors, on economic grounds, since it may be necessary to close down one or more of the reactors due to conditions which have nothing to do with the ability to continue producing the reagent. An example is a crude oil cracker, producing ethylene, adapted to feed two or more reactors utilizing the ethylene, for example an ethyl benzene producing facility and a polyethylene producing facility.
-- 1 ~
`.i~
.. :: : , , : ,. ,:. - - , , :
. , ~, . . .
.. . .: ,: : . ...
~ . .:: . ~
: ': : ~ :
~L0~7~84 In such arrangements, thereEore, it is common to integrate storage facilities into the system, so that when the reagent is being produced faster than it is being consumed, the excess reagent is fed to storage. ~hen demand for the reagent exceeds supply, the demand is satisfied at least in part from the storage. A series of pressure responsive valves are included in the interconnecting ducts, to regulate the supply to and from the storage facility tcommonly one or more underground cabins).
The conventional way of controlling the fluid reagent supply is by the provision of valves operating in spli`t range service, in the supply lines from the reagent producing facility to the consumption facility, on the one hand, and from the storage facility to the consumption facility on the other.
The valve in the supply line, the main valve, opens so as to meet the demand whenever possible fully from the production facility. The valve in the storage supply line only opens when the demand exceeds the rate of reagent production, so as to supplement the supply from storage.
The use of such split range valve arrangements works well provided that the rate of production is in excess of the demand. When the demand exceeds the rate of production, however, problems arise. Fluctuations in the demand, when the demand exceeds the rate of production, lead to delays in satis-fying the demand ("deadbands") and surging of the reagent.
,:
: , .: . ~
~97~84 Such fluctuations can, in many cases, be of large magnitude.
For example, when three different sources of consumption are connected into the system, and only two of them are in operation, there will be a sudden and very significant increase in demand when the third consumer comes into operation. This can cause delays and uneven flows because of the split range valve operating arrangement, if the total demand increases be~ond the rate of production. Surging of the reagent to the reactors is most undesirable, since it may lead to the tripping of safety control devices to close down the reactors completely.
It is an object of the present invention to provide a new and improved fluid flow control system, for an integrated fluid production and consumption operation.
The present invention provides a process and apparatus whereby the fluid flow control valves are arranged to operate in conjunction with one another, with main supply valve opening to supply reagent to consumption from production whenever possible, and the storage withdrawal valve being arranged to track the main valve so that it is always on the threshold of moving to its open position. By the arrangement of the invention, in the event that demand increases beyond the rate of production, so that the demand cannot be satisfied by increased flow through the main valve, however much the main valve is opened, the storage withdrawal valve opens :-: - : :: ; :: . . : ., : . . : , , - , ~- , . :;- ,: ~ . . .
~9'7~
substantially instantaneously to meet increased demands from storage. This is achieved by supplying to the storage withdrawal valve a bias signal derived from a measurement of fluid flows upstream of the main valve, i.e. rate of production of reagent. The delays, "deadbands" and surging of reagent previously encountered with prior art arrangements when the valves are set in split range service are thus essentially eliminated.
Thus, according to the present invention, there is provided a process for continuous control of fluid flows from plural interconnected fluid supply facilities to a fluid consumption facility, in which first and second flow control valves are interposed in communication ducts between respective first and second fluid supply facilities and the consumption facility, which comprises:
continuously monitoring consumption demand to obtain signals~thereof, and continuously feeding the demand responsive signals to the first and second c:ontrol valves;
causing the demand responsive signals to act pre-ferentially to open the first valve to the required extent to meet the demand by fluid flow through the first valve, and to open the second valve only in the event that fluid flows through the first valve cannot meet the demand;
supplying a bias signal to the second valve, the bias . ;
:
.. : . ~ .
~: '' : ,: :
- :.-:
~[3197~4 signal being marginally insufficient to cause opening of the second valve and being additive to the demand responsive signal, so that a change in the demand responsive signal indicating an increase in demand will cause immediate opening of the second valve in the event that the signal change fails to cause increased fluid flows through the first valve.
In the preferred process according the invention, the consumption demand is monitored by measuring pressure in the fluid flows downstream of the first and second valves, these pressure measurements being converted to signals (preferably elect-rical, but optionally pneumatic) for feeding to the control valves so as to control the degree of opening thereof. The bias signal is preferably variable in relation to fluid flows upstream of the control valves, and is determined by means of a flow meter inter-posed in the main supply conduit upstream of the fluid flow control valves. Normally, the first fluid supply facility will be a production facility, for example a crucle oil cracker producing various separated fractions of fluid reagents such as ethylene,and the second fluid supply facility will be a storage facility, such as one or more underground stora~e caverns for the selected fluid reagent. For ease of description and convenience, the process will be described in more detail with reference to an ethylene production and supply facility, but it will be appreciated that the process is of wider application, and can be adapted for use with substantially any liquid or gaseous .
7~914 chemical reagent, fuel or the like which is produced at a production facility and consumed at a consumption facility, the production and consumption processes being desired to be conducted substantially independently of one another~ and including a storage means interconnected with the production and consumption facilities so as to ensure continuity and sufficiency of supply automatically, when the production and consumption rates are not in balance.
In the most preferred process according to the inven-tion, the fluid flow rates are continuously monitored up-stream of the control valves, and the bias signal for the second valve is derived from this flow rate, as an electrical signal `directly proportional to the upstream flow rate.
Normally, such measurements will be conducted with a flow meter, measuring the flow rate by means of pressure drop across an orifice plate, which will give a signal proportional to the square of the ~low rate. There is then provided a means for converting the signal into the required bias signal and supplying it to the second valve, the conversion means comprising a square root extractor and an analogue computer.
The input to the analogue computer is an electrical signal directly proportional to the measured flow rate upstream of the control valves, i.e. the rate of production, and from this the analogue computer produces a signal which it supplies to the second valve to m~intain it at its threshold opening condition, .
-~ ;
.
: -~L~31971~
ready to be opened substantially instantaneously upon supply thereto of additional, additive electrical signal from the pressure sensing means provided downstream of the main valve.
According to a further aspect of the present inven- , tion, there is provided an apparatus for controlling fluid flows between a plurality of fluid supply facilities and at least one fluid consumption facility, said apparatus com-prlslng:
first and second fluid conducting conduits adàpted to supply fluid respectively from the first supply facility and the second supply facility to the fluid consumption facility;
first and second fluid flow control valves interposed respectively in the first and second fluid conducting conduits r said valves being positionable in response to demand responsive signals in fully open, fully closed and a continuous range of intermediate positions;
pressure sensing means adapted to monitor pressures of fluid downstream of the fluid control valves and ~0 to feed demand responsive signals proportional to the monitored pressures back to the fluid flow control valves to adjust fluid flows therethrough;
the first and second fluid control valves being in split range service such that demand is satisfied prefer-entially by fluid flows through said first valve, and through .
.. , . . ~ .
I~
~97~E34 said second valve only when demand cannot be satisfied byfluid flows through said first valve;
flow measuring means adapted to measure flows upstream of the first fluid flow control valve in the first conduit and to produce a signal in response thereto;
signal conversion means connected to the flow measuring means and the second fluid flow control valve, adapted to convert the signal from the flow measuring means to a bias signal for the second valve proportional to the flow rate measured by the flow measuring means;
said bias signal maintaining the second valve in a threshold opening condition such that an increase in the demand responsive signal supplied to the second valve will cause substantially immediate opening thereof.
The nature of the process and apparatus according to the invention, its mode oE operation, and its differences from conventional, prior art split range valve arrangements, will be clear from the following specific description with reference to the accompanying drawings, showing an example
2~ of the invention and the prior art, and in which:
1 ~ ~; ' ', ~1~97~34 FIGURE 1 is a diagrammatic process flow sheet of the process according to the prior art;
FIGURE 2 is a diagrammatic process flow sheet generally corresponding to that cf FIG. 1, but including an embodiment of the invention.
With reference to FIG. 1, there is diagrammatically shown therein a portion of a process flow sheet in which the ethylene output from an ethylene production facility 10, such as a crude oil cracker, is supplied to an ethylene consuming reactor facility 12, via a main supply line 14, namely a flow control pipe line. The demand at facility 12 may vary between wide limits, from ~ero whenthe facility 12 is shut down, to a very large value, e.g. 200,000 pounds/h~ur of ethylene when the ethylene reactor is in full production. The ethylene output from production facility 10 may also vary between similar wide limits depending upon conditions within the ethylene produc-tion facility 10. The main supply line 14 is therefore coupled to a stora~e facility 16, namely one or more under-ground caverns, in such a way that, when output from produc-tion facility 10 exceeds demand at facility 12, the excessethylene production is fed to storage facility 16, and con-versely, when demand at facility 12 exceeds output from production facility 10, the ethylene from production facility 10 is supplemented by supply from storage facility 16 to satisfy the demand.
_ 9 _ r , ~, '; - :
' ~, , -.
'. ' , . : .
.
~L~97~4 For this purpose, there is provided a valved supply line 18 and a valved withdrawal line 20 connecting between the main supply line 14 and the storage facility 16. The storage supply line 18 communicates with the main supply line 14 upstream of the communication thereof with the valved withdrawal line 20. Between these points of communication the main supply line 14 is provided with a main valve 22. The storage supply line 18 is provided with a storage supply valve 24. The withdrawal line 20 is provided with a storage with-drawal valve 26. All of the valves 22, 24, 26 are fluid flow control valves, settable at open, closed and at a continu-ous range of partially open positions, in responsè to electri-cal signals derived from pressure sensors arranged to sense the pressures at various locations in the main supply line 14.
Thus, storage supply valve 24 i.s connected to receive signals from and hence be controlled by upstream pressure sensor 28, which senses the pressure Pl in the main supply line 14 up-stream of main valve 22. Storage withdrawal valve 26 and main valve 22 are both connected to receive signals from and hence be controlled by downstream pressure sensor 30, which senses the pressure P2 in the main supply line 14 downstream of the main valve 22. The valves 22 and 26 operate in split range service, so that valve 22 opens to permit ethylene flow therethrough in response to signals from downstream pressure sensor 30 over a first range corresponding to high pressure , ..: . .
-:. . . :- ,.: , , i. ~ .: ::
7~ 4 ranges. When the lower limit of the higher pressure range sensed by sensor 30 is reached, main valve 22 is fully open, and then any further decrease in pressure sensed by pressure 30 starts the opening of storage withdrawal valve 26, whilst maintaining main valve 22 fully open.
It will be appreciated that a decrease in pressure P2 is caused by an increase in demand of reactor facility 12.
Provided that the demand of ethylene by reactor facility 12 does not exceed the production of ethylene by facility 10, storage withdrawal valve 26 can remain closed and the ethylene can all be supplied directly from production via main valve 22, opened to the sufficient degree in response to pressure P2 to permit the necessary rate of flow of ethylene to satisfy the demand. If the supply from production facility 10 exceeds the demand from reactor facility 12, the pressure Pl sensed by pressure sensor 28 rises, to cause opening of storage supply valve 24 to the re~uired degree to bring the pressure Pl back to its preset value and feed the excess ethylene to storage facility 16. It will also be appreciated that main supply valve 22 and the storage withdrawal valve 26 must be sized so that, when fully open, they can pass a flow rate of ethy- ;
lene to meet the maximum demand of reactor facility 12.
Similarly, storage supply valve 24 must be large enough so that it can pass the maximum production rate of ethylene from production facility 10 to storage 16 when reactor 12 is shut down.
. .
.
. , . ~ .
7~
The system thus far described is in essence a split range control valve system commonly encountered in continuous svstems of production, storage and consumption of ~lui~. Provided that either the production rate or the consumption rate remains substantially constant, such a system works well to keep the demand supplied without undue fluctuation in flow rates to the reactor facility 12. Problems arise, however, when the supply or demand fluctuates, and when the demand for consumption exceeds the rate of production.
For example, in the situation where the production facility 10 is operating at 60% of its maximum rate to produce a flow rate of ethylene of 6~ units per hour, the system operates satisfactorily whilst the reactor facility 12 demands 60 units of ethylene per hour or less. The entire supply to reactor facility 12 is through main valve 22, which opens to the extent of 60% so as to prevent oversupply or unde~supply to the reactor 12. This open degree of main valve 22 is determined by the pressure P2 sensed by the downstream pressure sensor 30. Under such circumstances, storage withdrawal valve 26 remains closed. If, however, the demand now rises to 90 units per hour, i.e. hi~her than the rate of production from production facility 10, pressure P2 downstream of main valve 22 will drop. This will cause main valve 22 to open further, but this will not of itself cause P2 to rise back to the pre-set level. Main valve 22 cannot pass more than 60 units per ~, :
' :
, ~
,' .
:
971~4 hour of ethylene even when fully open, since no more than 60 units is being supplied to its upstream side. The 90 unit per hour demand is not satisfied until main valve 22 has moved from its 60~ open to its fully opened position, and then storage withdrawal valve is opened sufficiently to meet this excess demand. There is consequently a time delay between the-increase in demand and the satisfaction of this demand, in which the supply rate does not increase (i.e. a "deadband") whilst main valve 22 opens to its full extent and then while storage withdrawal valve 26 opens to the desired ex*ent. The delay period is promptly followed by a surge of ethylene from - -storage facility 16, which is undesirable and may upset the operation of reactor facility 12.
Such a problem is encountered with any continuous supply system with valves in split range service, where the `~`
main valve has only a limited supp].y of fluid product ~thereto, and where either production rate or demand may fluctuate.
Overlapping of the operating ranges of the main valve 22 and the storage withdrawal valve 26, so that storage withdrawal valve 26 starts to open before the main valve 22 is fully open, does not eliminate the problem. Even when the valve ranges overlap, there will be ranges at which increases in demand will not be satisfied promptly, until the pressure P2 has dropped sufficiently to bring the storage withdrawal valve to its opening range. Then the ethylene will surge.
Figure 2 of the accompanying drawings illustrates - ~.' ' . `: ```: ' ' ' ; `' ' :, . . . .
`' :` '. ' ~ .
~L097~
diagrammatically a process according to the invention. As in the case of the process of FIG. 1, the variable output ethy-- lene production facility 10 communicates with the variable demand consuming reactor facility 12 via a main supply line 14 having a main valve 22 therein. A supply line 18 with a storage supply valve 24 communicates with storage facility 16 and main supply line 14 upstream of main valve 22. A
withdrawal line 20 with a storage withd-awal valve 26 communi-cates with the storage facility 16 and the main supply line 14 downstream of main valve 22. An upstream pressure sensor 28 senses a pressure Pl in the main supply line 14 upstream of main valve 22 and controls the opening and closing of storage supply valve 24 as before. A downstream pressure sensor 30 senses pressure P2 in main supply line 14 downstream of main valve 22, and transmits electrical signals corres-ponding to deviations of P2 from a preset value, to control main valve 22 and storage withdrawal valve 26.
In addition, however, the embodiment shown in FIG. 2 includes a flow meter 32 in the main line 14 upstream of main valve 22, the flow meter 32 being of the type which records flow as a result of measurement of the pressure difference across an orifice plate. The flow meter 32 is coupled to a flow transmitter 34 to transmit the electrical signal from the flow meter 32, the signal being proportional to the s~uare of the flow rates, due to the method of flow rate measurement.
.; ~
,. .
::
.:
:: .: ~
... .. .. ..
~g7~84 The signal is fed to a square root extractor 36 to produce a new signal directly proportional to the flow rate measured by flow meter 32. Thence the directly proportional signal is fed to an analogue computer 38. The computer 38 puts out a bias electric signal, the magnitude of which is determined by the input from the flow meter 32, i.e. the rate of production at any given time, via diode 40 to storage withdrawal valve 26. As in the previous case illustrated in FIG. 1, downstream ~.
pressure sensor 30 sends electrical signals, the magnitude of 10 which.. are directly proportional to deviations in pressure P2 ;~
from a preset value, to both the main valve 22 and the storage withdrawal valve 26. The electrical communication between sensor 30 and storage withdrawal valve 26 is via a diode 42, so as to prevent feed of bias signal to main valve 22. In the arrangement according to the invention, however, storage withdrawal valve 26 receives two additive signals, namely the bias signal from the computer 38 and the direct signal from the downstream pressure sensor 30. The bias signal from computer 38 keeps the storage withdrawal valve at the thresh-hold of opening, no matter what magnitude of signal it recives from downstream pressure sensor 30. The bias signal magnitude is arranged in relationship to the flow rate in the main supply line 14 upstream of the main valve 22 and varies accordingly, adjusted by computer 38. Effectively, the storage withdrawal valve 26 "tracks" the main valve 22 by this ~ 15 -~L~97~
arrangement. Even when the pressure P2 is only sufficient to send a signal to main valve 22 to open it to 50~ of its fully opened position, the bias signal to the storage with-drawal valve 26 is sufficient to put the storage withdrawal valve 26 on the threshold of opening. When pressure P2 drops due to increased demand, the increased main signal from down-stream pressure sensor 30 to storage withdrawal valve 26 immediately causes valve 26 to start opening to supply the demand, in the event that the fu-ther opening of main valve 22 due to this increase signal does not immediately increase the ethylene supply to restore the previous value of P2, e.g.
because production rate is less than the demand rate. It is as if the storage withdrawal valve 26 has anticipated the problem, being supplied with a bias signal computed in accordance with the rate of production as determined by ~he flow meter 32, so as to be ready to open the instant the demand rate exceeds the production rate. In this way, even supply of products to the reactor facility 12 is ensured, without deadbands or surging, despite fluctuatlng production and fluctuating demands.
As a specific example, let it be assumed that the valves 22 and 26 are in split range service, the electrical output from downstream sensor being from 4-20 mil~amps, inversely proportional to the pressure sensed. In the high pressure range P2, giving signals of 4-12 m;ll;amps, valve 22 . . , . . :: :; ,, :
.. . . .
. .
~097~.~4 opens gradually, i.eO to be fully closed at 4 milliamp signals and below, and fully open at 12 miI~amp signals and above, whilst valve 26 remains fully closed. In the low pressure range of P2, giving signals of 12-20 mil]iamps, valve 22 remains fully open and valve 26 starts to open, until it too is fully opened at 20 miL~amps. The crossover point is thus 12 mi~iamps. When the flow rate measured by flow meter 32 is zero, i.e. production is shut down, a bias signal of 8 milliamps is transmitted by computer 38 to storage withdrawal valve 26, which adds to the 4 mi~iamps minimum signal from pressure sensor 30 to give a total signal of 12 m~iamps to valve 26, and put it on the threshold of opening. Now, if consumption starts at reactor 12 thereby causing pressure P2 to drop, the increased signal from sensor 30 immediately causes valve 26 to open, to supply the demand, despite the fact that the signal from sensor 30 may still be in the 4-12 m~liamp range, causing only partial opening of main valve 22. The delay in meeting the demand, whilst the pressure P2 drops sufficiently first to open main valve 22 fully and tllen to open valve 26, and subsequent surging, is avoided.
If production were at 50~ of maximum capacity of facility 10, with consumption at 12 in balance therewith, main valve 22 would be 50% open, since it sized to accommodate full production. The signal being received from downstream ~ . .
.
.
:~0~7~4 pressure sensor 30 is therefore 8 milliamps, to maintain this 50% open condition and keep P2 steady. To maintain the storage withdrawal valve 26 at its thresl~old, therefore, a bias signal of 4 milliamps is supplied. Now the valve 26 opens as soon as signal from pressure sensor 30 exceeds 8 milliamps.
The computer 38 thus arranges the magnitude of the bias signal in accordance with the measured flow rate of production rate.
When production is at 100% of capacity, the bias signal is zero. The magnitude of the bias signal bears a direct linear relationship to the production rate.
It will be appreciated that the various components making up the apparatus and used in the process of the present invention are conventional in form, and ~are commer-cially available. Those skilled in the art will readily choose suitable components to meet the process to be controlled, ollowing the ~eneral teachings of this disclosure. For example, in an ethylene production facility of the type described in detail herein, with variable production and flow rates between 0 and 200,000 pounds/hour, a suitable flow meter for use as item 32 described herein is Canadian Meter Co. orifice plate.
A suitable flow transmitter for use as item 34 is a Taylor Model No. 1301 T.
A suitable square root extractor for use as item 36 is Taylor Model No. 1336 N.
A suitable analogue computer is Taylor Model No. 1023 T
(millivolt to current transmitter calibrated for this application).
i .
. ~ . , . ~ .
- , ,. , .. . : . : . ~ : , .,, . , ~ ,. ;: : :-; . . . :
~97184 . . . ~
All of these various items are readily available ;
commercially, and do not require detailled description herein. ~;
The process flow sheet drawings included herein and referred to above are, of course, diagrammatic only, for purposes of -~
illustration of the invention and the prior art. In practice, other components are included according to standard procedures, such as heat exchangers to maintain the fluid in either the gaseous or the liquid state as required for the processes. The production facility 10 may be provided with level controlling devices and the like, and additional flow meters may be inserted at various places for observation of the flow rates and process, all according to standard procedures according to the prior art. The pressure sensors indicated by reference numerals 28 and 30 in the accompanying drawings are also standard items, conventionally used according to the prior art in similar flow control systems where pressure in a flowing ~luid is to be monitored and converted to electrical signals.
Suitable such pressure sensors available commercially are available frcm Taylor, and listed by them, in a range of appropriate sizes.
It will be appreciated that the process and apparatus described in detail herein with reference to the accompanying drawings are exemplary and illustrative only, and are not to be construed as limiting upon the scope of the invention.
Various changes and modifications can be made, without depart-ing from the spirit of the invention. The scope of the 1~97~8~
invention is defined and limited only by the scope of the appended claims,
1 ~ ~; ' ', ~1~97~34 FIGURE 1 is a diagrammatic process flow sheet of the process according to the prior art;
FIGURE 2 is a diagrammatic process flow sheet generally corresponding to that cf FIG. 1, but including an embodiment of the invention.
With reference to FIG. 1, there is diagrammatically shown therein a portion of a process flow sheet in which the ethylene output from an ethylene production facility 10, such as a crude oil cracker, is supplied to an ethylene consuming reactor facility 12, via a main supply line 14, namely a flow control pipe line. The demand at facility 12 may vary between wide limits, from ~ero whenthe facility 12 is shut down, to a very large value, e.g. 200,000 pounds/h~ur of ethylene when the ethylene reactor is in full production. The ethylene output from production facility 10 may also vary between similar wide limits depending upon conditions within the ethylene produc-tion facility 10. The main supply line 14 is therefore coupled to a stora~e facility 16, namely one or more under-ground caverns, in such a way that, when output from produc-tion facility 10 exceeds demand at facility 12, the excessethylene production is fed to storage facility 16, and con-versely, when demand at facility 12 exceeds output from production facility 10, the ethylene from production facility 10 is supplemented by supply from storage facility 16 to satisfy the demand.
_ 9 _ r , ~, '; - :
' ~, , -.
'. ' , . : .
.
~L~97~4 For this purpose, there is provided a valved supply line 18 and a valved withdrawal line 20 connecting between the main supply line 14 and the storage facility 16. The storage supply line 18 communicates with the main supply line 14 upstream of the communication thereof with the valved withdrawal line 20. Between these points of communication the main supply line 14 is provided with a main valve 22. The storage supply line 18 is provided with a storage supply valve 24. The withdrawal line 20 is provided with a storage with-drawal valve 26. All of the valves 22, 24, 26 are fluid flow control valves, settable at open, closed and at a continu-ous range of partially open positions, in responsè to electri-cal signals derived from pressure sensors arranged to sense the pressures at various locations in the main supply line 14.
Thus, storage supply valve 24 i.s connected to receive signals from and hence be controlled by upstream pressure sensor 28, which senses the pressure Pl in the main supply line 14 up-stream of main valve 22. Storage withdrawal valve 26 and main valve 22 are both connected to receive signals from and hence be controlled by downstream pressure sensor 30, which senses the pressure P2 in the main supply line 14 downstream of the main valve 22. The valves 22 and 26 operate in split range service, so that valve 22 opens to permit ethylene flow therethrough in response to signals from downstream pressure sensor 30 over a first range corresponding to high pressure , ..: . .
-:. . . :- ,.: , , i. ~ .: ::
7~ 4 ranges. When the lower limit of the higher pressure range sensed by sensor 30 is reached, main valve 22 is fully open, and then any further decrease in pressure sensed by pressure 30 starts the opening of storage withdrawal valve 26, whilst maintaining main valve 22 fully open.
It will be appreciated that a decrease in pressure P2 is caused by an increase in demand of reactor facility 12.
Provided that the demand of ethylene by reactor facility 12 does not exceed the production of ethylene by facility 10, storage withdrawal valve 26 can remain closed and the ethylene can all be supplied directly from production via main valve 22, opened to the sufficient degree in response to pressure P2 to permit the necessary rate of flow of ethylene to satisfy the demand. If the supply from production facility 10 exceeds the demand from reactor facility 12, the pressure Pl sensed by pressure sensor 28 rises, to cause opening of storage supply valve 24 to the re~uired degree to bring the pressure Pl back to its preset value and feed the excess ethylene to storage facility 16. It will also be appreciated that main supply valve 22 and the storage withdrawal valve 26 must be sized so that, when fully open, they can pass a flow rate of ethy- ;
lene to meet the maximum demand of reactor facility 12.
Similarly, storage supply valve 24 must be large enough so that it can pass the maximum production rate of ethylene from production facility 10 to storage 16 when reactor 12 is shut down.
. .
.
. , . ~ .
7~
The system thus far described is in essence a split range control valve system commonly encountered in continuous svstems of production, storage and consumption of ~lui~. Provided that either the production rate or the consumption rate remains substantially constant, such a system works well to keep the demand supplied without undue fluctuation in flow rates to the reactor facility 12. Problems arise, however, when the supply or demand fluctuates, and when the demand for consumption exceeds the rate of production.
For example, in the situation where the production facility 10 is operating at 60% of its maximum rate to produce a flow rate of ethylene of 6~ units per hour, the system operates satisfactorily whilst the reactor facility 12 demands 60 units of ethylene per hour or less. The entire supply to reactor facility 12 is through main valve 22, which opens to the extent of 60% so as to prevent oversupply or unde~supply to the reactor 12. This open degree of main valve 22 is determined by the pressure P2 sensed by the downstream pressure sensor 30. Under such circumstances, storage withdrawal valve 26 remains closed. If, however, the demand now rises to 90 units per hour, i.e. hi~her than the rate of production from production facility 10, pressure P2 downstream of main valve 22 will drop. This will cause main valve 22 to open further, but this will not of itself cause P2 to rise back to the pre-set level. Main valve 22 cannot pass more than 60 units per ~, :
' :
, ~
,' .
:
971~4 hour of ethylene even when fully open, since no more than 60 units is being supplied to its upstream side. The 90 unit per hour demand is not satisfied until main valve 22 has moved from its 60~ open to its fully opened position, and then storage withdrawal valve is opened sufficiently to meet this excess demand. There is consequently a time delay between the-increase in demand and the satisfaction of this demand, in which the supply rate does not increase (i.e. a "deadband") whilst main valve 22 opens to its full extent and then while storage withdrawal valve 26 opens to the desired ex*ent. The delay period is promptly followed by a surge of ethylene from - -storage facility 16, which is undesirable and may upset the operation of reactor facility 12.
Such a problem is encountered with any continuous supply system with valves in split range service, where the `~`
main valve has only a limited supp].y of fluid product ~thereto, and where either production rate or demand may fluctuate.
Overlapping of the operating ranges of the main valve 22 and the storage withdrawal valve 26, so that storage withdrawal valve 26 starts to open before the main valve 22 is fully open, does not eliminate the problem. Even when the valve ranges overlap, there will be ranges at which increases in demand will not be satisfied promptly, until the pressure P2 has dropped sufficiently to bring the storage withdrawal valve to its opening range. Then the ethylene will surge.
Figure 2 of the accompanying drawings illustrates - ~.' ' . `: ```: ' ' ' ; `' ' :, . . . .
`' :` '. ' ~ .
~L097~
diagrammatically a process according to the invention. As in the case of the process of FIG. 1, the variable output ethy-- lene production facility 10 communicates with the variable demand consuming reactor facility 12 via a main supply line 14 having a main valve 22 therein. A supply line 18 with a storage supply valve 24 communicates with storage facility 16 and main supply line 14 upstream of main valve 22. A
withdrawal line 20 with a storage withd-awal valve 26 communi-cates with the storage facility 16 and the main supply line 14 downstream of main valve 22. An upstream pressure sensor 28 senses a pressure Pl in the main supply line 14 upstream of main valve 22 and controls the opening and closing of storage supply valve 24 as before. A downstream pressure sensor 30 senses pressure P2 in main supply line 14 downstream of main valve 22, and transmits electrical signals corres-ponding to deviations of P2 from a preset value, to control main valve 22 and storage withdrawal valve 26.
In addition, however, the embodiment shown in FIG. 2 includes a flow meter 32 in the main line 14 upstream of main valve 22, the flow meter 32 being of the type which records flow as a result of measurement of the pressure difference across an orifice plate. The flow meter 32 is coupled to a flow transmitter 34 to transmit the electrical signal from the flow meter 32, the signal being proportional to the s~uare of the flow rates, due to the method of flow rate measurement.
.; ~
,. .
::
.:
:: .: ~
... .. .. ..
~g7~84 The signal is fed to a square root extractor 36 to produce a new signal directly proportional to the flow rate measured by flow meter 32. Thence the directly proportional signal is fed to an analogue computer 38. The computer 38 puts out a bias electric signal, the magnitude of which is determined by the input from the flow meter 32, i.e. the rate of production at any given time, via diode 40 to storage withdrawal valve 26. As in the previous case illustrated in FIG. 1, downstream ~.
pressure sensor 30 sends electrical signals, the magnitude of 10 which.. are directly proportional to deviations in pressure P2 ;~
from a preset value, to both the main valve 22 and the storage withdrawal valve 26. The electrical communication between sensor 30 and storage withdrawal valve 26 is via a diode 42, so as to prevent feed of bias signal to main valve 22. In the arrangement according to the invention, however, storage withdrawal valve 26 receives two additive signals, namely the bias signal from the computer 38 and the direct signal from the downstream pressure sensor 30. The bias signal from computer 38 keeps the storage withdrawal valve at the thresh-hold of opening, no matter what magnitude of signal it recives from downstream pressure sensor 30. The bias signal magnitude is arranged in relationship to the flow rate in the main supply line 14 upstream of the main valve 22 and varies accordingly, adjusted by computer 38. Effectively, the storage withdrawal valve 26 "tracks" the main valve 22 by this ~ 15 -~L~97~
arrangement. Even when the pressure P2 is only sufficient to send a signal to main valve 22 to open it to 50~ of its fully opened position, the bias signal to the storage with-drawal valve 26 is sufficient to put the storage withdrawal valve 26 on the threshold of opening. When pressure P2 drops due to increased demand, the increased main signal from down-stream pressure sensor 30 to storage withdrawal valve 26 immediately causes valve 26 to start opening to supply the demand, in the event that the fu-ther opening of main valve 22 due to this increase signal does not immediately increase the ethylene supply to restore the previous value of P2, e.g.
because production rate is less than the demand rate. It is as if the storage withdrawal valve 26 has anticipated the problem, being supplied with a bias signal computed in accordance with the rate of production as determined by ~he flow meter 32, so as to be ready to open the instant the demand rate exceeds the production rate. In this way, even supply of products to the reactor facility 12 is ensured, without deadbands or surging, despite fluctuatlng production and fluctuating demands.
As a specific example, let it be assumed that the valves 22 and 26 are in split range service, the electrical output from downstream sensor being from 4-20 mil~amps, inversely proportional to the pressure sensed. In the high pressure range P2, giving signals of 4-12 m;ll;amps, valve 22 . . , . . :: :; ,, :
.. . . .
. .
~097~.~4 opens gradually, i.eO to be fully closed at 4 milliamp signals and below, and fully open at 12 miI~amp signals and above, whilst valve 26 remains fully closed. In the low pressure range of P2, giving signals of 12-20 mil]iamps, valve 22 remains fully open and valve 26 starts to open, until it too is fully opened at 20 miL~amps. The crossover point is thus 12 mi~iamps. When the flow rate measured by flow meter 32 is zero, i.e. production is shut down, a bias signal of 8 milliamps is transmitted by computer 38 to storage withdrawal valve 26, which adds to the 4 mi~iamps minimum signal from pressure sensor 30 to give a total signal of 12 m~iamps to valve 26, and put it on the threshold of opening. Now, if consumption starts at reactor 12 thereby causing pressure P2 to drop, the increased signal from sensor 30 immediately causes valve 26 to open, to supply the demand, despite the fact that the signal from sensor 30 may still be in the 4-12 m~liamp range, causing only partial opening of main valve 22. The delay in meeting the demand, whilst the pressure P2 drops sufficiently first to open main valve 22 fully and tllen to open valve 26, and subsequent surging, is avoided.
If production were at 50~ of maximum capacity of facility 10, with consumption at 12 in balance therewith, main valve 22 would be 50% open, since it sized to accommodate full production. The signal being received from downstream ~ . .
.
.
:~0~7~4 pressure sensor 30 is therefore 8 milliamps, to maintain this 50% open condition and keep P2 steady. To maintain the storage withdrawal valve 26 at its thresl~old, therefore, a bias signal of 4 milliamps is supplied. Now the valve 26 opens as soon as signal from pressure sensor 30 exceeds 8 milliamps.
The computer 38 thus arranges the magnitude of the bias signal in accordance with the measured flow rate of production rate.
When production is at 100% of capacity, the bias signal is zero. The magnitude of the bias signal bears a direct linear relationship to the production rate.
It will be appreciated that the various components making up the apparatus and used in the process of the present invention are conventional in form, and ~are commer-cially available. Those skilled in the art will readily choose suitable components to meet the process to be controlled, ollowing the ~eneral teachings of this disclosure. For example, in an ethylene production facility of the type described in detail herein, with variable production and flow rates between 0 and 200,000 pounds/hour, a suitable flow meter for use as item 32 described herein is Canadian Meter Co. orifice plate.
A suitable flow transmitter for use as item 34 is a Taylor Model No. 1301 T.
A suitable square root extractor for use as item 36 is Taylor Model No. 1336 N.
A suitable analogue computer is Taylor Model No. 1023 T
(millivolt to current transmitter calibrated for this application).
i .
. ~ . , . ~ .
- , ,. , .. . : . : . ~ : , .,, . , ~ ,. ;: : :-; . . . :
~97184 . . . ~
All of these various items are readily available ;
commercially, and do not require detailled description herein. ~;
The process flow sheet drawings included herein and referred to above are, of course, diagrammatic only, for purposes of -~
illustration of the invention and the prior art. In practice, other components are included according to standard procedures, such as heat exchangers to maintain the fluid in either the gaseous or the liquid state as required for the processes. The production facility 10 may be provided with level controlling devices and the like, and additional flow meters may be inserted at various places for observation of the flow rates and process, all according to standard procedures according to the prior art. The pressure sensors indicated by reference numerals 28 and 30 in the accompanying drawings are also standard items, conventionally used according to the prior art in similar flow control systems where pressure in a flowing ~luid is to be monitored and converted to electrical signals.
Suitable such pressure sensors available commercially are available frcm Taylor, and listed by them, in a range of appropriate sizes.
It will be appreciated that the process and apparatus described in detail herein with reference to the accompanying drawings are exemplary and illustrative only, and are not to be construed as limiting upon the scope of the invention.
Various changes and modifications can be made, without depart-ing from the spirit of the invention. The scope of the 1~97~8~
invention is defined and limited only by the scope of the appended claims,
Claims (10)
1. A process for continuous control of fluid flows from plural interconnected fluid supply facilities to a fluid consumption facility, in which first and second flow control valves are interposed in communication ducts between respective first and second fluid supply facilities and the consumption facility, which comprises:
continuously monitoring consumption demand to obtain signals thereof, and continuously feeding the demand respon-sive signals to the first and second control valves;
causing the demand responsive signals to act pre-ferentially to open the first valve to the required extent to meet the demand by fluid flow through the first valve, and to open the second valve only in the event that fluid flows through the first valve cannot meet the demand;
supplying a bias signal to the second valve, the bias signal being marginally insufficient to cause opening of the second valve and being additive to the demand responsive signal, so that a change in the demand responsive signal indicating an increase in demand will cause immediate opening of the second valve in the event that the signal change fails to cause increased fluid flows through the first valve.
continuously monitoring consumption demand to obtain signals thereof, and continuously feeding the demand respon-sive signals to the first and second control valves;
causing the demand responsive signals to act pre-ferentially to open the first valve to the required extent to meet the demand by fluid flow through the first valve, and to open the second valve only in the event that fluid flows through the first valve cannot meet the demand;
supplying a bias signal to the second valve, the bias signal being marginally insufficient to cause opening of the second valve and being additive to the demand responsive signal, so that a change in the demand responsive signal indicating an increase in demand will cause immediate opening of the second valve in the event that the signal change fails to cause increased fluid flows through the first valve.
2. A process according to claim 1 wherein the consumption demand is monitored by measuring pressures in the fluid flows downstream of the first and second valves, said pressure measurements being converted to signals for feeding to the control valves.
3. Process according to claim 1 or claim 2 wherein the bias signal is variable in relation to fluid flows upstream of the control valves.
4. Process according to claim 2 wherein the first fluid supply facility is a production facility and the second fluid supply facility is a storage facility.
5. Process according to claim 4 including the steps of continuously monitoring fluid flow rates upstream of the control valves, and deriving the bias signal from said flow rate monitoring, as an electrical signal directly proportional to the upstream flow rate, the demand responsive signals derived from pressure measurements also being electrical signals.
6. Process according to claim 2, claim 4 or claim 5 wherein the fluid is gaseous ethylene.
7. Apparatus for controlling fluid flows between a plurality of fluid supply facilities and at least one fluid consumption facility, said apparatus comprising:
first and second fluid conducting conduits adapted to supply fluid respectively from the first supply facility and the second supply facility to the fluid consumption facility;
first and second fluid flow control valves inter-posed respectively in the first and second fluid conducting conduits, said valves being positionable in response to demand responsive signals in fully open, fully closed and a continuous range of intermediate positions;
pressure sensing means adapted to monitor pressures of fluid downstream of the fluid flow control valves and to feed demand responsive signals proportional to the monitored pressures back to the fluid flow control valves to adjust fluid flows therethrough;
the first and second fluid control valves being in split range service such that demand is satisfied prefer-entially by fluid flows through said first valve, and through said second valve only when demand cannot be satisfied by fluid flows through said first valve;
flow measuring means adapted to measure flows up-stream of the first fluid flow control valve in the first conduit and to produce a signal in response thereto;
signal conversion means connected to the flow measuring means and the second fluid flow control valve, adapted to convert the signal from the flow measuring means to a bias signal for the second valve proportional to the flow rate measured by the flow measuring means;
said bias signal maintaining the second valve in a threshold opening condition such that an increase in the demand responsive signal supplied to the second valve will cause substantially immediate opening thereof.
first and second fluid conducting conduits adapted to supply fluid respectively from the first supply facility and the second supply facility to the fluid consumption facility;
first and second fluid flow control valves inter-posed respectively in the first and second fluid conducting conduits, said valves being positionable in response to demand responsive signals in fully open, fully closed and a continuous range of intermediate positions;
pressure sensing means adapted to monitor pressures of fluid downstream of the fluid flow control valves and to feed demand responsive signals proportional to the monitored pressures back to the fluid flow control valves to adjust fluid flows therethrough;
the first and second fluid control valves being in split range service such that demand is satisfied prefer-entially by fluid flows through said first valve, and through said second valve only when demand cannot be satisfied by fluid flows through said first valve;
flow measuring means adapted to measure flows up-stream of the first fluid flow control valve in the first conduit and to produce a signal in response thereto;
signal conversion means connected to the flow measuring means and the second fluid flow control valve, adapted to convert the signal from the flow measuring means to a bias signal for the second valve proportional to the flow rate measured by the flow measuring means;
said bias signal maintaining the second valve in a threshold opening condition such that an increase in the demand responsive signal supplied to the second valve will cause substantially immediate opening thereof.
8. Apparatus of claim 7 wherein the first fluid supply facility is a fluid reagent production facility and the second fluid supply facility is a fluid reagent storage facility.
9. Apparatus of claim 8 wherein the signals are electrical signals and the signal conversion means comprises a square root extractor and an analogue computer, connected in series between the flow meter and the second fluid flow control valve.
10. The apparatus of claim 9 further including a third fluid conducting conduit adapted to supply fluid from the first conduit to the storage means, a third fluid flow control valve in said third conduit positionable in fully open, fully closed and a range of intermediate positions, second pressure sensing means adapted to sense pressure in the first conduit upstream of the first fluid flow control valve, means connecting the second pressure sensing means to the third fluid control valve so as to position said valve in accordance with pressure in the first conduit upstream of the first fluid flow control valve.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA315,084A CA1097184A (en) | 1978-10-31 | 1978-10-31 | Flow control system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA315,084A CA1097184A (en) | 1978-10-31 | 1978-10-31 | Flow control system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1097184A true CA1097184A (en) | 1981-03-10 |
Family
ID=4112793
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA315,084A Expired CA1097184A (en) | 1978-10-31 | 1978-10-31 | Flow control system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1097184A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5143257A (en) * | 1990-12-04 | 1992-09-01 | Kelrus Corp. | System for proportioned liquid dispensing |
-
1978
- 1978-10-31 CA CA315,084A patent/CA1097184A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5143257A (en) * | 1990-12-04 | 1992-09-01 | Kelrus Corp. | System for proportioned liquid dispensing |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5325884A (en) | Compressed air control system | |
| US5813801A (en) | Dense phase particulate conveying system and method with continuous air leakage management | |
| US3068796A (en) | Power level controller | |
| DE60029326T2 (en) | CONTROL DIAGNOSTIC DEVICE AND METHOD | |
| RU2475803C2 (en) | Method of controlling gas flow between plurality of gas streams | |
| EP0350658B1 (en) | Process for metering and controlling the mass flow of fuels in the partial oxidation of finely divided to powdery fuels | |
| HU193520B (en) | Process for regulating material-stream | |
| CN111928119B (en) | Mine gas safe blending system and gas blending ratio control method | |
| US4662798A (en) | Method and a device for measuring and/or regulating the mass flow of solid particles | |
| US3474815A (en) | Fluid proportioning and blending system | |
| CN103676647A (en) | Sewage aeration control device | |
| CN113107810A (en) | Compressed air use compensation device, tobacco production system and control method thereof | |
| CN101449224B (en) | Pressure setting method for gas pipeline | |
| CN103306701A (en) | Automatic control pressure-equalizing fire preventing and extinguishing system in large area | |
| CA1097184A (en) | Flow control system | |
| CN106369283A (en) | Pipeline flow control system and method | |
| US4482814A (en) | Load-frequency control system | |
| CN217928285U (en) | Remote pressure and flow regulating control device for natural gas pressure regulating station | |
| GB2231669A (en) | Flowmeters | |
| US3092127A (en) | Proportioning stream flows | |
| US4271673A (en) | Steam turbine plant | |
| JPS57134654A (en) | Hot water supply equipment | |
| CN217304035U (en) | Main feed water flow measuring device of steam generator under low load of nuclear power generation unit | |
| EP0087766B1 (en) | Process to control a gas network, especially under high pressure | |
| US3478767A (en) | Gated oscillator digital controller |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |