TECHNICAL FIELD OF THE INVENTION

This invention relates generally to a system of improved hydraulic circuit for strip guide control and more particularly to an independent hydraulic system for strip guide control of pay-off reel.

BACKGROUND AND THE PRIOR ART

In earlier designed rolling mills, the strip guides of pay-off reel are operated through mill’s centralized hydraulic system. The mill’s centralized hydraulic system caters both the conventional hydraulic equipment and servo hydraulic equipment, such as strip guide control of the mill. The mill’s centralized hydraulic system of 15000 liters capacity caters the requirement of hydraulic oil of both conventional hydraulic operated equipments and servo hydraulic operated equipments of the mill through different branches of pipelines from a common hydraulic accumulator. The centralized system maintains the hydraulic oil flow rate at 460 lpm @ 70 bar pressure to operate the hydraulic cylinders of the strip guide system to control their lateral movements of the pay-off reel mandrel. The hydraulic cylinders are operated at 150mm/sec (max) speed.

Although readily available, due to the centralized hydraulic arrangement maintaining high degree cleanliness, pressure & flow requirement of hydraulic oil for servo hydraulic equipment could not be achieved. This affects the performance of the strip guide control equipment of the pay-off reel, in the form of slow & erratic operation. The poor performance of strip guide control equipment leads to the undesirable winding formation (telescopicity) of coils at recoiler. The coils with bad profile gets damaged while handling process and ultimately rejected as a seconds & scraps. However due to various operational deficiencies of the centralized system, the hydraulic oil’s flow rate, pressure, cleanliness level etc., of the strip guide equipment could not be maintained accurately. As this servo based hydraulic system depends on these parameters, the performance of the strip guide system gets heavily affected which leads to loss of production of the mill. It in turn affects the productivity and profitability of the mill.

Thus there is a need to modify the existing centralized hydraulic system and design, develop and install an independent hydraulic circuit for the strip guide control system. The performance of the strip guide control equipment can be improved significantly, if the equipment can be self sufficient to cater its input hydraulic oil requirement instead of depending on the centralized system.

OBJECTS OF THE INVENTION

A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.

Another object of the present invention is to modify the mill’s centralized hydraulic system in order to isolate the servo hydraulic operated strip guide control system, without affecting the performance of various upstream and downstream conventional hydraulic equipments of the centralized system.

Another object of the present invention is to design and develop an independent and energy efficient hydraulic system / power unit for efficient operation of the strip guide control system of payoff-reel.

Another object of the present invention is to integrate the dedicated controls of strip guide control system of pay-off reel with the mill’s centralized control & monitoring system for efficient control & monitoring from the centralized location.

Another object of the present invention is total elimination of breakdowns of ‘strip guide control system of pay-off reel’ from the earlier level of 20 nos per annum.

Another object of the present invention is to improve mill availability by 200 hrs per annum due to elimination of breakdowns of the strip guide control system.

Another object of the present invention is to reduce the generation of bad profiled coils i.e., formation of telescopicity in finished coils by 50%.

Another object of the present invention is to improve coils’ profile formation wherein the amount of telescopicity in finished coils is well within the acceptable range of +/- 0.5 mm.

Another object of the present invention is to improve the performance of strip guide control equipment of pay-off reel.

Another object of the present invention is to increase the efficiency of its input hydraulic control system.

Another object of the present invention is to increase the productivity of the mill.

Yet another object of the present invention is installation and commissioning of a dedicated hydraulic power unit for the strip guide control system of pay-off reel of a Cold Rolling Mill.

These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION

There is provided a system of an independent hydraulic system for strip guide control of pay-off reel.

According to one embodiment of the present invention, there is provided the mill’s centralized hydraulic system in order to isolate the servo hydraulic operated strip guide control system, without affecting the performance of various upstream and downstream conventional hydraulic equipments of the centralized system.

Other embodiment of the present invention provides an independent and energy efficient hydraulic system / power unit for efficient operation of the strip guide control system of payoff-reel.

Other embodiment of the present invention provides for integration of the dedicated controls of strip guide control system of pay-off reel with the mill’s centralized control & monitoring system for efficient control & monitoring from the centralized location.

Other embodiment of the present invention provides for total elimination of breakdowns of ‘strip guide control system of pay-off reel’ from the earlier level of 20 nos per annum.

Other embodiment of the present invention provides for improvement of mill availability by 200 hrs per annum due to elimination of breakdowns of the strip guide control system.

Other embodiment of the present invention provides for reducing the generation of bad profiled coils i.e., formation of telescopicity in finished coils by 50%.

Other embodiment of the present invention provides for improvement of coils’ profile formation wherein the amount of telescopicity in finished coils is well within the acceptable range of +/-0.5 mm.

Other embodiment of the present invention provides for improving the performance of strip guide control equipment of pay-off reel.

Other embodiment of the present invention provides for increasing the efficiency of its input hydraulic control system.

Other embodiment of the present invention provides for increasing the productivity of the mill.

Yet other embodiment of the present invention provides for installation and commissioning of a dedicated hydraulic power unit for the strip guide control system of pay-off reel of a Cold Rolling Mill.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Fig 1 illustrates the design of dedicated hydraulic circuit diagram.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.

Reference is first invited to Fig 1 where the design of dedicated hydraulic circuit diagram is shown which mainly consists of a 2000 litre capacity storage tank (1.01) with all its necessary safety and operational accessories, 3 nos. of pressure compensated variable displacement axial piston pumps (1.27.1, 1.27.2, 1.27.3) with their independent drive motors assembly (1.26.1, 1.26.2, 1.26.3) and couplings (1.10, 1.28), strainers, pre-filters, pressure relieve valves (1.14, 1.34), pressure reducing valves, check valves (1.17, 1.36, 1.37.3), isolation valves, duplex type pressure line filters, 2 nos. of diaphragm type accumulator with its accessories (1.40, 1.38, 1.52), return line filters (1.20, 1.41) with check valve, indicators / gauges, off-line plate type heat exchanger (1.18), piping, flexible hoses etc.

The invented system is thus an independent hydraulic system for strip guide control of pay-off reel.

DETAILED DESCRIPTION OF THE INVENTION

Accordingly in the present invention the strip guide control system along with its hydraulic valve station was detached to isolate it from the mill’s centralized hydraulic circuit through suitable modifications in the existing hydraulic circuit, without disturbing the hydraulic circuit of the remaining upstream and downstream conventional hydraulic operated equipments of the centralized system.

A dedicated servo hydraulic system was designed and developed for strip guide control system of capacity at 460 lpm @ 100 bar to efficiently operate the hydraulic cylinders at 150 mm/sec. The actuation speed of the hydraulic cylinders is very critical parameter for quick and accurate correction of lateral movement of the un-coiler’s mandrel. The correcting velocity of the cylinders is calculated considering the mill’s speed of operation. The oil flow velocity is maintained at 4.4 m/s in the pipelines. The dedicated hydraulic power system of strip guide control system mainly consists of a 2000 litre capacity storage tank with all its necessary safety and operational accessories, 3 nos. of pressure compensated variable displacement axial piston pumps with their independent drive motors assembly and couplings, strainers, pre-filters, pressure relieve valves, pressure reducing valves, check valves, isolation valves, duplex type pressure line filters, 2 nos. of diaphragm type accumulator with its accessories, return line filters with check valve, indicators / gauges, off-line plate type heat exchanger, piping, flexible hoses etc.

The dedicated hydraulic power unit of the strip guide control system is installed near the pay-off reel in the same working level for quick and accurate response of hydraulic cylinders’ operation. A dedicated control panel with various control features to operate the equipments of the system is installed inside the existing control room of Automatic Gauge Control system. The hydraulic pumps are grouped in to three categories, such as AB, BC, AC for regular operations, so that one pump out of the three pumps kept as stand-by. An independent control desk with various control features and indication lamps is provided near the hydraulic power unit for control & monitoring of the system. The control system of the strip guide control is also connected with the mill’s centralized control system through suitable hardware and software linkages for centralized monitoring and control from the mill’s main control room.

The following data were taken into consideration in designing an improved hydraulic system for the strip guide control system:
• Width of strip/coil processed: 820 – 1250 mm
• Weight of the coil processed: 15 - 18 tons.
• Thickness of the strip: 0.15 mm to 0.80mm
• Maximum mill speed: 30 m/s
• Type of hydraulic oil used: HLP 46 / Mineral oil-150SSU
• System Pressure: 100 Kg/cm2
• Nos. of hydraulic cylinders: Two
• Size of each cylinder:
 Bore: 10”
 Stroke: 1050 mm
 Rod dia: 4.5”
 Velocity: 150 mm/sec
• Flow rate of oil in pressure line: 460 lpm
• Flow velocity in pipelines: 4.4 m/s
• Type of servo valve existing: Electro-hydraulic Controller
• Dyna-guide (GPE make)
SPECIFICATION OF DIFFERENT EQUIPMENT

Storage tank:
The 2000 L capacity, mild steel made rectangular shaped storage tank is provided with all necessary safety & operational features as per IS standards / International standard. The features such as breather gap and oil filter, sampling valve, drain plug & valve, thermometer and sight glass, strainer for fresh oil inlet, magnetic suction screen, return line filter, strainer for air filtration, level indicators with inter locking limit switches, pressure gauge with snubbers and gauge shut off valves, relief valve, isolation valves, inspection covers & cleanout doors, oil filling line with a strainer etc., are provided. The tank is designed to reduce the possibility of vortex effects and improves heat dissipation. The suction and return line shall be suitably separated by a baffle plate inside the tank to assist in cooling, settling and de-aerating return oil prior to recirculation. The baffle plate is extend to 75% of the maximum oil level and have the bottom corners cut diagonally, giving sufficient opening to allow the oil level to equalize on both sides of the baffle. The tank has enough volume to let returning fluid slow down from a high entrance velocity and lets heavier contaminants settle and entrained air space.

Pump:
Three nos. of variable delivery, pressure compensated, axial piston pumps of each 230 LPM flow capacity at 100 bar delivery pressure are provided in the dedicated hydraulic power unit. Two pumps are clubbed as AB, BC, CA categories, in order to keep one pump as stand-by operation. The combination of two pumps is capable of supplying the hydraulic oil at 460 lpm flow rate as required in system. The pumps are assembled with necessary relief / unloading valves, pressure gauges, manifold block, shut off valves, suction flange, mounting bracket etc.

Drive motor:
Three nos. of electric drive motors (one of each pump) of each 45 KW, 4P, foot mounted, TEFC, 415VAC, 50Hz, 1500 rpm, 225M are installed to drive the pumps of the dedicated hydraulic system.

Pressure Line Filters:
One no. duplex type pressure filter of 10 microns filtration capacity with no-bypass arrangement was provided in the pressure line of the dedicated system. The pressure line filter is provided with DT switch and DP setting facility for better control performance in the system.

Hydro-pneumatic Accumulator:
Two nos. of diaphragm type accumulators of 20 L capacity each are installed in the system for leakage compensation in the system. The accumulators are provided with skirt type support for vertical installation, pre-charged with nitrogen at designed pressure, ASME welded steel construction, with mating flanges for top and bottom nozzles, with all necessary operational and safety features, safety block, logic cartridge valve-insert & cover, direction valve, pilot operated accumulator shut-off valve, manifold, coupling, stand etc. for better control and performance.

Heat Exchanger:
One plate type heat exchanger (Liquid – Liquid) of 13 KW capacity is installed in the system for off line cooling of the hydraulic oil of the storage tank. The heat exchanger is designed to use the normal industrial water as a cooling medium to cool the oil in order to maintain the temperature of the oil within the acceptable limit. Suitable temperature gauges are provided in the storage tank to indicate the hydraulic oil’s temperature.

Audio & visual alarms are provided in the system to actuate at reaching high level of oil temperature.

One gear type pump of 54 LPM @ 10 bar capacity is provided for circulation of oil.
Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. However, all such modifications are deemed to be within the scope of the claims.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.

WE CLAIM

1. A hydraulic system for strip guide control of pay-off reel where the equipment can be self sufficient to cater its input hydraulic oil requirement instead of depending on the centralized system comprising:
a dedicated servo hydraulic system to efficiently operate the hydraulic cylinders;
a storage tank having almost all necessary and/or desired safety and operational accessories;
a dedicated control panel having various control features to operate the equipments of the system installed inside the existing control room of automatic gauge control system;
a pressure filter with no bypass arrangement provided in the pressure line of the dedicated system;
a duality of diaphragm type accumulators wherein each are installed in the system for leakage compensation;
a plate type heat exchanger installed in the system for off-line cooling of the hydraulic oil of the storage tank.
2. System as claimed in claim 1 further comprising plurality of hydraulic cylinders.
3. System as claimed in claim 2 wherein said hydraulic cylinders having hydraulic speed so as to provide quick and accurate correction of lateral movement of the un-coiler’s mandrel.
4. System as claimed in claim 1 wherein said servo hydraulic system having oil flow velocity of about 4.4 m/s.

5. System as claimed in claim 1 further comprising dedicated hydraulic power unit of the strip guide control system installed near the pay-off reel in the same working level for quick and accurate response of hydraulic cylinders’ operation.
6. System as claimed in claim 1 further comprising plural hydraulic pump means.
7. System as claimed in claim 6 wherein said pumps being driven by electric drive motors.
8. System as claimed in claim 1 wherein said storage tank is adapted to reduce the possibility of vortex effect and improve heat dissipation.
9. System as claimed in claim 1 wherein said storage tank comprising suction and return lines suitably separated by means of a baffle plate inside the tank thereby assisting in cooling, settling and de-aerating return oil prior to re-circulation.
10. System as claimed in claim 1 wherein said pressure filter is duplex type pressure filter having DT switch and DP setting facility for better control performance in the system.
11. System as claimed in claim 1 wherein said accumulators comprising skirt type support for vertical installation, pre-charged with nitrogen at designed pressure, ASME welded steel construction, with mating flanges for top and bottom nozzles.
12. System as claimed in claim 1 wherein said plate type heat exchanger comprising using normal industrial water as cooling medium to cool the oil in order to maintain the temperature of the oil within the acceptable limit.
13. System as claimed in claim 1 further comprising suitable temperature gauges to indicate the hydraulic oil’s temperature.

14. System as claimed in claim 1 further comprising one gear type pump for circulation of oil.
15. System as claimed in any of the preceding claims adapted for use in the strip guide control system of pay-off reel of a Cold Rolling Mill.
16. A hydraulic system for strip guide control of pay-off reel where the equipment can be self sufficient to cater its input hydraulic oil requirement instead of depending on the centralized system as herein substantially described and illustrated with reference to the accompanying drawings.

ABSTRACT

This invention relates generally to a system and method of improved hydraulic circuit for strip guide control and more particularly to an independent hydraulic system for strip guide control of pay-off reel where the equipment can be self sufficient to cater its input hydraulic oil requirement instead of depending on the centralized system. Due to various operational deficiencies of the centralized system, the hydraulic oil’s flow rate, pressure, cleanliness level etc., of the strip guide equipment could not be maintained accurately. The performance of the strip guide control equipment can be improved significantly, if the equipment can be self sufficient to cater its input hydraulic oil requirement.