Claims:WE CLAIM :

1. An improved arrangement of hydraulically operated counterweight lifting device for blast furnace main charging conveyor of the steel plant comprising of:

(a) A frame configured to take up counterweight and the lifting slings at two sides.

(b) A pair of blocks with bearing to mount hydraulic cylinders (actuators) at the side structure.

(c) A hydraulic valve stand with electrically (24V DC) operated DC valves and having further arrangement of pressure relief valve, isolation valve, accumulator, quick couplings and pipelines network configured for lifting and lowering the counterweight of the main charging conveyor and a valve desk for remote operation.

2. The arrangement of hydraulically operated counterweight lifting device as claimed in claim 1, wherein valve stand is installed in the conveyor drive house and very near to the actuator.

3. The arrangement of hydraulically operated counterweight lifting device as claimed in claim 1, wherein the material of pipelines is SS 304 and the pipelines network have been provided with all necessary fittings as per the maximum system pressure.

4. The arrangement of hydraulically operated counterweight lifting device as claimed in claim 1, wherein the said piping network arrangement along with pilot operated check valves and ball valves for isolation provides leak proof holding of the load and isolation.

5. The arrangement of hydraulically operated counterweight lifting device as claimed in claim 1, wherein the associated feature of relief valve gives additional safety against overload.

6. The arrangement of hydraulically operated counterweight lifting device as claimed in claim 1, wherein the valve desk is configured for operating the said valve with the power fail condition by initializing electrically operated two position DC valves for operation of cylinders for opening when power fails and closing when the power to the solenoid is ON.

7. The arrangement of hydraulically operated counterweight lifting device as claimed in claim 1, wherein the two hydraulic cylinders of configuration 125X70X1400 which have a maximum pressure capacity of 200 bars are used.

8. The arrangement of hydraulically operated counterweight lifting device as claimed in claim 1, wherein the hydraulic cylinders are trunnion mounted and are installed on the side of the guide support.

Dated: this day of March, 2017.

(N. K. Gupta)
Patent Agent
Of NICHE
For SAIL

To,
The Controller of Patents,
The Patent Office, Kolkata.
, Description:IMPROVED ARRANGEMENT OF COUNTERWEIGHT LIFTING IN MAIN CHARGING CONVEYOR OF A BLAST FURNACE

FIELD OF INVENTION:

The present invention relates to an improved arrangement for lifting up the counterweight (VGTU) of the main charging conveyor by using hydraulic force. More particularly the present invention relates to a hydraulic operated device to immediately lift or lower the counterweight as per requirement within a time span of 10-15 minutes only.

BACK GROUND OF THE INVENTION:

In the hostile environment of steel plants, there are areas where the safety of man and machine, at times get compromised due to potential hazards like hot metal handling, operating conveyor belts and other moving equipments in close vicinity.

In a huge furnace like BF #5, the furnace feeding is of utmost importance in order to tap out hot metal continuously from it. This requires a continuous feeding device like a charging conveyor belt, in place of skip cars, which is conventionally used in smaller furnaces. Due to this reason, in bigger furnaces, the main charging conveyor is considered as the most vital equipment.

In BF#5, the main charging conveyor is 1800 mm wide and approx. 1 km long with its counterweight weighing approximately 20 tons. Since the commissioning of this furnace, there had been many breakdowns in this conveyor, mainly due to the failure of different conveyor pulleys. Every time for replacing the pulley, this counter weight had to be lifted manually with the help of four nos. of 5 ton chain pulley blocks. This process required about 4 hours with 8 persons. It is worthwhile mentioning here that due to this activity of manual lifting of counter weight, the outage duration of such a large furnace was getting extended un-necessarily by 4 hours, causing substantial loss to the company. .

Thus the prevailing practice of manual lifting up the counterweight of the main charging conveyor had the following issues:
i) Extended shut down of the furnace.

ii) Complete job being manual labour dependant.

iii) Lower furnace availability and consequently higher down time with high

maintenance cost.

iv) Any breakdown in the belt in odd hours is a problem as the resources have to be mobilized on war footing basis and it often takes time.
v) The manual lifting devices have their own safety related issues.

The application of hydraulics is everywhere, simple and easy to use. The very thought of applying simple hydraulics for the lifting, load holding and lowering of the counterweight was thought of. In particular, there has been a need to develop a hydraulic system with power pack, field piping, cylinder and valve desk to lift the counterweight. This also calls for the requirement of structural engineering to hold the cylinder and the device to lift the load. The new system needed to be put in parallel with the old system to facilitate continuity of operation and provision of a standby system in case of need during operation and maintenance.

PRIOR ART:

The original process of lifting the counterweight is elaborated below.

1. Using 4 manual lifting devices (chain blocks) of appropriate capacity (minimum 5 ton) at four corners.
2. Holding the counterweight structures using suitable slings and “D” shackles.

3. Lifting the counterweight by working on all the four chain blocks simultaneously.

4. Putting additional slings of suitable capacity at four positions as safety measures.

OBJECTIVE OF THE INVENTION:

1. The basic objective of the invention was to provide an improved arrangement of hydraulic operated device to immediately lift or lower the counterweight as per requirement in shortest possible time.
2. The approximately 20 ton of counter weight is required to be lifted every time the belt requires any major maintenance such as replacement of pulleys or any belt replacement, piece insertion or shortening jobs etc.
3. To provide a system, which requires minimum manpower to operate

4. System to have a safe in-built load holding mechanism.

5. Enhanced safety of operating personnel.

6. To make the maintenance activity of the main charging conveyor easy, simple, quick, minimizing the down time of the furnace and improving the equipment availability with less manpower.

SUMMARY OF THE INVENTION:

In this invention the impetus is on the provision of a simplified system for the lifting of an approximately 20 ton of counterweight of a vital equipment in a modern and large blast furnace, where the shutdown costs approximately Rs. 23.33 Lacs / hr (contribution loss for the loss of one hour of production). This invention also focuses on the in-house uses of the resources to facilitate the above said purposes and the designing of the scheme entirely by the team itself. This system uses two hydraulic cylinders of suitable size and safe hydraulic pressure. Structurally, in this system the bottom of the counterweight box has been modified and has been provided with an extended girder to facilitate the fixing of a ‘D” shackle with sling which has to be connected to the eye of the cylinder. The cylinder is a trunnion mounted cylinder which can work up to a pressure of approx. 200 bars. The power pack used is of mobile type and comprises of the pump-motor, relief valve, direction control valve, load holding valve, gauges and hoses etc. The pipeline has been laid such that the two cylinders can act in tandem and the lines are branched into two and connected at the similar ports.

BRIEF DESCRIPTION OF THE ACCOMPANYING FEATURES:

Fig. 1 illustrates the system for lifting/holding/lowering the counterweight by using simple hydraulic system in accordance with the present invention.

DETAILED DESCRIPTION:

The said invention of improved arrangement of counterweight lifting system in the blast furnace comprises of the following

Mechanical arrangement — The counterweight or the vertical gravity take up has been fitted with a specially designed frame on which the lifting slings can be fitted at two sides. Two special plumber blocks with bearing have been designed and fabricated to mount the cylinders at the side structure as shown in Fig 1.

Hydraulic power pack along with pump motor and Valve Stand – The improved system uses a redundant power pack which comprises of a pump and motor. The pump is of Rexroth make and is a gear pump with a flow rating of approximately 30 litres / min and go up to a pressure of 315 bars. The motor is a 7.5 KW. The tank is of approximately 30 litres capacity and uses servo system 46 grade of mineral oil. The valve desk for this system has specially been designed with an operating philosophy

of manual / automated remote operation as per requirement to hold the load of approximately 20 ton for hours without any creep. Valve stand system comprises of manifold, manually / electrically operated DC valves for operation of cylinders for lifting/lowering operations, Hydraulic check valve for holding the load continuously, Pressure relief valve for hydraulic safety, Ball valves for isolation, gauges and hoses and other hydraulic components as per circuit for lifting and lowering the counterweight of the main charging conveyor

Actuators — Two hydraulic cylinders of configuration 125X70X1400 which have a maximum pressure capacity of 200 bars have been used. The cylinders are trunnion mounted and have been installed on the side of the guide support.

Pipelines, Isolation Valves, Fittings etc. – The said valve stand is installed on the tank itself in a pipeline network as shown in Fig. Material of pipelines is SS 304. Pipelines have been provided with all necessary fittings etc. Pipelines are of appropriate schedule as per the maximum system pressure. Isolation valves have been provided to make the system work in a working and standby configuration having leak-proof isolation with the help of the manual isolation valves.

Electrics - The electrical system is provided with suitable starter, isolation with switch off and safety against overload.

The improved hydraulic operated system is designed for lifting/holding/lowering the counterweight of main charging conveyor. This scheme is a replacement to the manual system by a better mechanized hydraulic system. In this system extra beams and holding system has been designed to accomplish the fitment of two hydraulic cylinders at two sides of the belt. The cylinder operates at maximum 150 bar of pressure and has been provided with a manual operated DC valve to operate the cylinder. The new valve desk has been designed with provision of load holding with pilot operated check valve, pressure relief valve, isolation valves, gauges and hoses.

The improved hydraulic lifting mechanism is a replacement to the old existing manually operated lifting method. The system has been designed to smoothly and simply operate the device and hold the load.

The valve desk along with the power pack has been installed at a safe location where

there is no hazard of proximity to the running belt. Therefore the maintenance of the valve stand, and valves and piping network for isolation of the old and new valve stands is very simple

The main inventive feature of improved arrangement is an improved yet simple hydraulic device with in-house designed system to lift and lower the counterweight.

Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration by way of examples and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. It will be apparent to those having ordinary skill in the art that a number of changes, modifications, variations, or alterations to the invention as described herein may be made, none of which depart from the spirit or scope of the present invention. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.