US3828737A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Control system for once-through boilers
Assignee: Mitsubishi Heavy Industries Ltd
•
Filing: 1973-08-02
•
Granted: 1974-08-13
•
Expires: 1993-08-02
Abstract
Abstract The control system controls the fuel flow rate, during starting of a once-through boiler, and includes detectors measuring the feed water temperature at the outlet of a water-cooled furnace wall and the gas temperature at the outlet of the furnace. The system includes further detectors detecting abnormal conditions with respect to the feed water temperature and the gas temperature, and setting means for setting the final desired temperature of the feed water during starting and the temperature of the feed water during full operation. The control is effected by pulses from a pulse generating circuit operable to generate a starting pulse, control pulses having a predetermined duration and predetermined intervals, and holding pulses having a phase and timing equal to those of the control pulses. A setting point generating circuit is selectively switched into a follow-up mode in which there is no starting pulse and a setting point equal to the actual temperature of the feed water at the outlet of the water-cooled furnace wall is generated, a temperature rise mode in which the start pulse is generated and the holding pulses are generated, and the setting temperature is varied during predetermined time intervals in accordance with a generated temperature change rate, and a holding mode in which the setting temperature is held at a constant level.
Inventors
- 👤 M Fujii
- 👤 S Oyagi
- 👤 T Kamei
- 👤 I Mori
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 07:04
CPC Classifications
F; F22; F22B; F22B35/00; F22B35/06; F22B35/10; F22B35/18
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
227 words
A control system for the starting phase of a once-through boiler comprising, in combination, a pulse generating circuit generating a start pulse, control pulses having a predetermined duration and predetermined intervals, and holding pulses having a phase and timing equal to those of said control pulses; first detector means measuring the actual water temperature at the outlet of a water-cooled wall of the furnace of said boiler; a rate change generating circuit connected to said first detector means and generating a desired temperature rise rate automatically in response to a controlled variable; a setting point generating circuit connected to said rate change generating circuit and to said pulse generating circuit and operable to set a setting water temperature at the outlet of said water-cooled wall responsive to temperature rise rate signals from said rate change generating circuit; and a controller circuit connected to said setting point generating circuit and to said pulse generating circuit and operable responsive to start and control pulses, and to deviation of said actual water temperature from said setting water temperature to provide a fuel flow rate correction signal in a direction to reduce such deviation; said control system increasing the water temperature at the outlet of said water-cooled furnace wall stepwise responsive to a start pulse and to said control pulses at a rate change controlled by said rate change generating circuit.
Claim 2
Dependent Claim
227 words
A control system for the starting phase of a once-through boiler comprising, in combination, a pulse generating circuit generating a start pulse, control pulses having a predetermined duration and predetermined intervals, and holding pulses having a phase and timing equal to those of said control pulses; first detector means measuring the actual water temperature at the outlet of a water-cooled wall of the furnace of said boiler; a rate change generating circuit connected to said first detector means and generating a desired temperature rise rate automatically in response to a controlled variable; a setting point generating circuit connected to said rate change generating circuit and to said pulse generating circuit and operable to set a setting water temperature at the outlet of said water-cooled wall responsive to temperature rise rate signals from said rate change generating circuit; and a controller circuit connected to said setting point generating circuit and to said pulse generating circuit and operable responsive to start and control pulses, and to deviation of said actual water temperature from said setting water temperature to provide a fuel flow rate correction signal in a direction to reduce such deviation; said control system increasing the water temperature at the outlet of said water-cooled furnace wall stepwise responsive to a start pulse and to said control pulses at a rate change controlled by said rate change generating circuit.
Claim 3
Dependent Claim
77 words
A control system, as claimed in claim 1, further including second detector means measuring the gas temperature at the outlet of said furnace; and a gas temperature control circuit connected to said second detector means, to said pulse generating circuit and to said controller circuit and operable to reduce the fuel flow rate correction and to interrupt said control pulses when the gas temperature at the outlet of the furnace is in excess of a predetermined level.
Claim 4
Dependent Claim
91 words
A control system, as claimed in claim 2, including first abnormal condition detector means connected to said pulse generating circuit and to said controller circuit and operable to interrupt said control pulses when said actual water temperature is abnormal or in excess of a prdetermined level; and second abnormal condition detector means connected to said gas temperature control circuit and to said pulse generating circuit and operable to interrupt said control pulses when the gas temperature at the outlet of said furnace is abnormal or in excess of a predetermined level.
Claim 5
Dependent Claim
44 words
A control system, as claimed in claim 1, in which said setting point generating circuit is operable, in the absence of a start pulse, to generate a setting water temperature equal to said actual water temperature at the outlet of said water-cooled furnace wall.
Claim 6
Dependent Claim
39 words
A control system, as claimed in claim 4, in which said setting point generating circuit is operable, responsive to a start pulse but in the absence of holding pulses to maintain said setting water temperature at a constant level.
Claim 7
Dependent Claim
48 words
A control system, as claimed in claim 5, in which said setting point generating circuit is operable responsive to start and holding pulses to vary said setting water temperature during consecutive predetermined time intervals responsive to a desired temperature rise rate signal from said rate change generating circuit.
Claim 8
Dependent Claim
31 words
A control system, as claimed in claim 6, including manually operable means selectively operable to condition said setting point generating circuit to maintain said setting water temperature at a constant level.
Claim 9
Dependent Claim
69 words
A control system, as claimed in claim 2, including a first setting point setter operable to set a setting water temperature during the starting phase of said boiler and a second setting point setter operable to set a setting water temperature during normal operation of said boiler; and switch means selectively operable to connect either of said first and second setting point setters to said setting point generating circuit.
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) | 1977-08-12 | 1978-02-11 | 1978-08-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-08-12 | 1982-02-11 | 1982-08-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-08-12 | 1986-02-11 | 1986-08-13 | $7700.00 | Window Closed / Lapsed |