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US3981444A
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Method for starting a steam-heated heat exchanger by regulating the pressure of the heating-steam
Assignee: BBC Brown Boveri AG Switzerland
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Filing: 1975-05-29
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Granted: 1976-09-21
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Expires: 1995-05-29
Abstract
Abstract The invention involves a closed loop control method and apparatus for starting up a steam-heated heat exchanger by controlling the heating-steam pressure. According to the invention a correcting variable is established by a controller from an actual pressure value, measured by an actual value transmitter, and from a reference value, generated by a reference value generating device, the heating-steam pressure being modified by at least one control valve on the basis of said correcting variable. The pressure reference value S is selected from three pressure set values, S T , S P1 and S P2 , the lesser value of S T and S P1 being established as an intermediate pressure set value S' (that is, S' = Min (S T , S P1 )), and the pressure reference value S is selected as being the greater value of S' and S P2 (that is, S = Max (S', S P2 )), where S T represents that permissible maximum desired pressure value which is a function of the momentary metal temperature T h of an endangered component of the heat exchanger, S P1 represents that permissible maximum pressure set value which is a function of the momentary existing quantity of working medium and thus of the momentary existing power, and S P2 represents the permissible minimum pressure set value as a function of the same momentary factor.
Inventors
- 👤 Gerhard Weiss
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 09:42
CPC Classifications
F; F01; F01K; F01K3/00; F01K3/18; F01K3/26; F01K3/262; F22; F22B; F22B35/00
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
222 words
Closed loop control method for starting a steam-heated heat exchanger by controlling the heating-steam pressure, where a correcting variable is established by a controller from an actual pressure value, measured by an actual pressure transmitter, and from a reference value generated by a reference value generating device and where the heating-steam pressure is modified by at least one control valve on the basis of said correcting variable, the characteristics being that the pressure reference value S is selected from three pressure set values S T ,S P1 and S P2 , that the lesser value of S T and S P1 is established as an intermediate pressure set value S', that is S' = Min (S T ,S P1 ), and the pressure reference value S is selected as being the greater value of S' and S P2 , that is S = Max (S', S P2 ), where S T represents that permissible maximum pressure set value which is a function of the momentary metal temperature T h of the endangered component (14) where S P1 represents that permissible maximum pressure set value which is a function of the momentary existing quantity of working medium and thus of the momentary existing power, and where S P2 represents the permissible minimum pressure set value as a function of the same momentary factor.
Claim 2
Dependent Claim
222 words
Closed loop control method for starting a steam-heated heat exchanger by controlling the heating-steam pressure, where a correcting variable is established by a controller from an actual pressure value, measured by an actual pressure transmitter, and from a reference value generated by a reference value generating device and where the heating-steam pressure is modified by at least one control valve on the basis of said correcting variable, the characteristics being that the pressure reference value S is selected from three pressure set values S T ,S P1 and S P2 , that the lesser value of S T and S P1 is established as an intermediate pressure set value S', that is S' = Min (S T ,S P1 ), and the pressure reference value S is selected as being the greater value of S' and S P2 , that is S = Max (S', S P2 ), where S T represents that permissible maximum pressure set value which is a function of the momentary metal temperature T h of the endangered component (14) where S P1 represents that permissible maximum pressure set value which is a function of the momentary existing quantity of working medium and thus of the momentary existing power, and where S P2 represents the permissible minimum pressure set value as a function of the same momentary factor.
Claim 3
Dependent Claim
44 words
Method according to claim 1, in which the pressure set values S P1 and S P2 and generated from generating function which furnish the maximum permissible pressure set value as a function of the working medium quantity and thus the power P (FIGS. 2,3,4).
Claim 4
Dependent Claim
77 words
Method according to claim 1, which comprises measuring the temperature T h at the hot point, and the temperature T k at the cold point of the endangered component, computing the difference Δ T = T h - T k and comparing said difference with a permissible temperature difference Δ T zul , based on the permissible temperature stresses, and generating a pressure set value S T , based on the result of this comparison (FIG. 2).
Claim 5
Dependent Claim
103 words
Method according to claim 3, according to which if the difference Δ T is smaller than the permissible Δ T zul , a pressure set value S T of constant, maximum value is produced, but if the difference Δ T is greater than the permissible difference Δ T zul , the pressure set value S T is reduced in proportion to the deviation of the difference Δ T from the permissible difference Δ T zul and the heating-steam pressure is decreased in accordance with the reduced desired pressure value S T until Δ T again becomes equal to Δ T zul (FIG. 2).
Claim 6
Dependent Claim
55 words
Method according to claim 4, according to which if the reduced pressure set value S T becomes smaller than S P2 , the load gradient of the working medium quantity is reduced in accordance with the set value S A , formed on the basis of the difference S T - S P2 (FIG. 2).
Claim 7
Dependent Claim
75 words
Method according to claim 1, in which the pressure set value S T is derived on the basis of a minimum pressure set value S To , calculated for the time t = 0 and which can likewise equal zero, and on the basis of at least one permissible pressure gradient Δp/Δt selected in such a way, that a permissible temperature gradient ΔT/Δt dependent on the permissible temperature stress shall not be exceeded (FIG. 3).
Claim 8
Dependent Claim
78 words
Method according to claim 1, according to which there is generated a temperature set value T S , based on an initial, minimum temperature set value T So , valid for the time t = 0, and a permissible temperature gradient ΔT/Δt as a function of the permissible temperature stress, that is T S = T So + ΔT/Δt t, and the temperature set value T S is reconverted to a pressure set value S T (FIG. 4).
Claim 9
Dependent Claim
110 words
Method according to claim 1, wherein a difference ΔS = + S P1 - S T is formed and tested as to its sign, and the results of this test produce the effect that if ΔS >0, the time t, which advances in formation of the pressure set value S T will continue to run and the pressure set value S T will continue to increase correspondingly, but if ΔS = 0, the time t is stopped and the pressure set value S T is maintained constant, and if ΔS<0, the pressure set value S T will take on the value of the pressure set value S P1 (FIGS. 3,4).
Claim 10
Dependent Claim
106 words
Apparatus for carrying out the method set forth in claim 1, which comprises: a S P1 generator (9) generating the pressure set value S P1 ; a S P2 generator (10) generating the pressure set S P2 ; a S T generating device (11) generating the pressure set value S T ; a smallest value selector (12) connected between the S P1 -generator (9) and the S T -generating device (11), providing an intermediate pressure set value S'; and a largest value selector (13) connected between the smallest value selector (12) and the S P2 generator (10) and generating a pressure reference value S (FIGS. 2,3,4).
Claim 11
Dependent Claim
67 words
Apparatus according to claim 9, further comprising a measuring device (15) to measure the temperature T h at the hot point of the endangered component (14), a measuring device (16) to measure the temperature T k at the cold point of the endangered component (14), and a differencing element (17), following the temperature-measuring devices (15,16) deriving the difference ΔT = T h - T k (FIG. 2).
Claim 12
Dependent Claim
109 words
Apparatus according to claim 10, further comprising a S T limiter (19), connected between the differencing element (17) and the smallest value selector (12), and a ΔT zul -generator (18), connected to the S T -limiter (19), the ΔT zul -generator (18) being used to derive and transmit to the S T limiter (19) a permissible temperature difference ΔT zul based on the permissible temperature stress, the S T limiter (19) being provided to compare the difference ΔT = T h - T k with the permissible temperature difference ΔT zul and to generate a pressure set value S T based on the result of this comparison (FIG. 2).
Claim 13
Dependent Claim
34 words
Apparatus according to claim 11, which comprises a B T limiter (26), following the S T limiter (19), for effecting any necessary reduction in the load gradient of the working medium quantity (FIG. 2).
Claim 14
Dependent Claim
72 words
Apparatus according to claim 9, wherein the S T -generating device (11) connected to a smallest value selector (12) is used to derive the pressure set value S T as a function of the time t, based on a pressure set value S To , valid for the time t = 0, and on at least one permissible pressure gradient Δp/Δt, selected in consideration of a permissible temperature gradient ΔT/Δt (FIG. 3).
Claim 15
Dependent Claim
97 words
Apparatus according to claim 9, which further comprises a summing element (20), connected between the S P1 generator (9) and the S T -generating device (11) and being used for computing the algebraic sum ΔS = + S P1 - S, furthermore a limit value indicator (21) connected between the summing element (20) and the S T -generating device (11) and being used for testing the algebraic sum ΔS = + S P1 - S T as to its sign and establishing a pressure set value S T based on the result of said test (FIG. 3).
Claim 16
Dependent Claim
86 words
Apparatus according to claim 9, further comprising a T o generator (22) generating an initial minimum temperature set value T So , valid for the time t = 0, an integrator (23) computing a permissible temperature increase ΔT t = t k . ΔT/Δt, valid for the time t, and summing element (24), connected between the T o generator (22) and the integrator (23), and calculating the sum T S = T o +ΔT t , the desired temperature value for the time t (FIG. 4).
Claim 17
Dependent Claim
41 words
Apparatus according to claim 15, in which a S T function generator (25) is connected to the summing element, and reconverts the temperature set value T S representing a saturated steam temperature, to a pressure set value S T (FIG. 4).
Claim 18
Dependent Claim
92 words
Apparatus according to claim 9, in which a summing element (20) is connected between the S P1 generator (9) and the S T function generator (25) and computes the algebraic sum ΔS = S P1 - S T , and in which a limit value indicator (21) is connected between the summing element (20) and the integrator (23) and tests the algebraic sum ΔS = + S P1 - S T as to its sign to establish a pressure set value S T based on the result of this test (FIG. 4).
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-09-21 | 1980-03-22 | 1980-09-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-09-21 | 1984-03-22 | 1984-09-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-09-21 | 1988-03-22 | 1988-09-21 | $7700.00 | Window Closed / Lapsed |