GB2099352A - A device for the extraction of waste gases during the scarfing of blooms or the like in a flame-scarfing machine - Google Patents

Abstract

A device for the extraction of waste gases during the scarfing of blooms (1) or the like in a flame-scarfing machine (2) comprises a suction hood (3) with a hood closure (4) disposed at the entrance to the flame-scarfing machine (2), the hood closure (4) being in the form of a lifting shield which can be initially lowered and set on the incoming bloom (1) and then lowered further, when the trailing end (5) of the bloom has entered the suction hood (3), to close the entrance completely, whereby virtually complete entrapment of the waste gases in the suction hood (3) is attained. <IMAGE>

Description

SPECIFICATION A device for the extraction of waste gases during the scarfing of blooms or the like in a flame-scarfing machine This invention relates to a device for the extraction of waste gases during the scarfing of blooms or the like in a flame-scarfing machine, and consisting of a suction hood and a hood closure disposed at the entrance to the flame-scarfing machine.

The processing of steel involves a series of working processes which give rise to heavy dust and dirt formation. One such working process is the flame scarfing of blooms or the like. The waste gases evolved during flame scarfing are usually caught up into a suction hood, extracted and cleaned in wet electrostatic precipitators. Although wet electrostatic precipitators guarantee the desired degree of air cleaning, the major problem is the satisfactory entrapment of the waste gases in the suction hood.

In the area where waste gases from flame scarfing are evolved, the suction hood is usually poorly sealed and consequently does not completely entrap the waste gases. When scarfing the ends of the blooms in particular, showers of sparks and clouds of waste gases quite frequently escape through the entrace to the flame-scarfing machine. This occasionally results in unacceptable air pollution and must be prevented in view of the legal requirements now in force, especially now that strict limits have been placed on the maximum permissible pollution indices to ensure clean air conditions.

A wide variety of hood closures is known, but none satisfies the requirements to prevent air pollution. In general they consist of curtains made from chains or hinged plate segments, and they are frequently torn away by the incoming blooms or the like. Torn curtains are defective as hood closures until they have been repaired again. The repairs are costly in time and money.

The object of the invention is to provide a device for the extraction of waste gases during the scarfing of blooms or the like in a flame-scarfing machine, the hood closure on which is outstandingly simple yet functionally reliable in construction, has a long useful life and ensures almost complete entrapment by the suction hood of the waste gases evolved during flame scarfing operations.

According to the present invention, an extraction device of the type in question has the hood closure adapted as a lifting shield which can be initially lowered and set on the incoming bloom and then lowered further, when the trailing end of the bloom has entered the suction hood, to close the entrance completely.

The invention arises primarily from the realization that, in contrast to the curtains hitherto in common use, the hood closure should never protrude into the path of the incoming bloom if damage is to be avoided. On the contrary, the hood closure should leave the path free for the incoming bloom at first and close up subsequently. At the start of the scarfing sequence, adequate closure is attained by setting the lifting shield down on the incoming bloom, since only the top face and possibly one sideface will be scarfed. Hence a lifting shield resting on the bloom ensures almost complete entrapment by the suction hood of the waste gases evolved during the scarfing process. The invention arises from the further realization that showers of sparks and clouds of waste gases are particularly formed and tend to escape from the entrance when the end of the bloom is undergoing scarfing.However, this phenomenon is prevented with certainty by the teaching of the invention, because the lifting shield completely closes the entrance as soon as the end of the bloom undergoing scarfing has entered the suction hood, i.e., before the end of the bloom concerned has reached the flame-scarfing machine and is actually undergoing scarfing. According to the invention, the entrance is closed in stages corresponding to the various rates of waste gas evolution, the means adopted being similar two a steel curtain.

Further and preferred features of the invention will now be described. Thus, the lifting shield may be actuated by an overhead lifting gear having driving means controlled by a tracking attachment for the bloom. In this respect, therefore, the hood closure operates virtually automatically. Thus, the tracking attachment is switched on by the travelling bloom and thereafter measures the distance travelled by the bloom. In this respect, therefore, the hood closure operates virtually automatically. Thus, the tracking attachment is switched on by the travelling bloom and thereafter measures the distance travelled by the bloom. As soon as the forward end of the bloom reaches the hood closure, the tracking attachment emits a starting signal for the overhead lifting gear, which then lowers the lifting shield and sets it on the bloom.Another signal is emitted in like manner by the tracking attachment when the trailing end of the bloom has passed the hood closure, so that the lifting shield can be lowered further until the entrance is completely closed. The overhead lifting gear preferably has a driving shaft rotatable by a driving motor and is mounted on the suction hood and a lever mechanism for the lifting shield is actuated by the driving shaft. This provides a readily accessible and compact arrangement of the overhead lifting gear. The lifting shield preferably takes the form of a steel plate slidable vertically in guide tracks in front of the suction hood and having supporting rollers mounted in the region of the bottom edge.The lifting shield rests on the bloom on these supporting rollers, so that only a slight air gap is left as the bloom advances freely into the suction hood underneath the lifting shield until it has completely entered the flame-scarfing machine.

Thus, the bottom plate edge does not rest directly on the bloom and consequently remains unstressed, so that no damage need be feared from this aspect. It is within the scope of the invention to make the lifting shield like a curved screen or to wrap its edges round the entrance, in order to ensure maximum hood sealing.

The advantages accruing from the invention are to be seen substantially in that it provides a device for the extraction of waste gases during the scarfing of blooms or the like in a flame-scarfing machine, in which the hood closure is constructed in a relatively simple and functionally reliable manner which ensures a long useful life. The construction is functionally reliable because the lifting shield almost completely prevents the escape of showers of sparks and clouds of waste gases, i.e., waste gases in general, through the entrance, so that the unacceptable air pollution otherwise associated with flame scarfing is suppressed. It is in fact easy to meet the legal requirements with the device of the invention, even taking into account the strict limits now placed on maximum permissible pollution indices.Moreover, since the lifting shield is kept out of contact with the travelling bloom by the interposition of supporting rollers, leaving only a slight gap, there is no risk of damaging the lifting shield and incurring costly repair bills.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a part-sectional diagrammatic side elevation of an extraction device in accordance with the invention; Figure 2 shows part of Figure 1 on a larger scale, and Figure 3 is a plan view of part of the extraction device of Figure 1.

The device shown in the drawings for the extraction of waste gases during the scarfing of blooms 1 or the like in a flame-scarfing machine 2, consists basically of a suction hood 3 with a closure 4 disposed at the entrance to the flame-scarfing machine 2. The closure 4 is mounted in front of the suction hood 3 and is adapted as a lifting shield which can be initially lowered and set on the incoming bloom 1 and then lowered further, when the trailing end 5 of the bloom has entered the suction hood 3, to close the entrance completely.

The lifting shield 4 is actuated by an overhead lifting gear 6 having driving means controlled by a tracking attachment, not shown, for the bloom 1 passing through. The overhead lifting gear 6 has a driving shaft 7 and a driving motor 8 mounted on the suction hood 3 and a lever mechanism 9 for the lifting shield 4 actuated by the driving shaft 7. It is possible in principle to provide different lifting gear, for exam ple cylinder and piston units powered by compressed air or hydraulic fluid, chain mechanisms or the like. The lifting shield 4 takes the form of a steel plate slidable vertically in guide tracks (not shown) in front of the suction hood 3 and has supporting rollers 10 mounted in the region of the bottom edge.

The operating sequence is as follows: The incoming bloom 1 is passed along a roller table 11 towards the flame-scarfing machine 2. The lifting shield 4, the flame-scarfing machine 2 and the driving units 12 in front of and behind the flamescarfing machine 2 are in the "open" setting. When the bloom 1 has actuated a switching element 13 (optical, limit or proximity switch or the like), the tracking attachment - for example a tracking roller with a pulse counter - is set up to monitor the bloom 1. When a second switching element 14 is passed, the tracking attachment becomes "hot" and counts by means of pulses the distance traversed by the bloom 1 until it reaches the lifting shield 4, the flame-scarfing machine 2 and the first driving unit 12.When a prescribed count is reached (distance from the "hot" switching element to the hood closure), the lifting shield 4 is lowered and set with its supporting rollers 10 resting on the bloom 1. The lifting shield 4 remains in this setting during the flame scarfing of the bloom 1. When the end 5 of the bloom enters the suction hood 3, the lifting shield 4 is lowered further to close the entrance to the suction hood 3 completely for the remainder of the scarfing period. This prevents drawing in excess air, so that even when the "stop scarfing" signal is given the suction fans on the usual wet electrostatic precipitators (not shown) extract the entire output of waste gases and escape of waste gas through the entrance can no longer occur. When the bloom 1 has passed beyond the second driving unit 12, the entire equipment reverts to the starting positions, ready to accept the next bloom 1, i.e., the lifting shield 4 is raised into its starting ("open") position.

Claims (5)

1. A device for the extraction of waste gases during the scarfing of blooms or the like in a flame-scarfing machine, comprises a suction hood and a hood closure disposed at the entrance to the flame-scarfing machine, the hood closure being adapted as a lifting shield which can be initially lowered and set on the incoming bloom and then lowered further, when the trailing end of the bloom has entered the suction hood, to close the entrance completely.

2. A device as in Claim 1, wherein the lifting shield is actuated by an overhead lifting gear having driving means controlled by a tracking attachment for the bloom.

3. A device as in Claim 1 or Claim 2, wherein the overhead lifting gear has a driving shaft rotatable by a driving motor and is mounted on the suction hood, and a lever mechanism for the lifting shield is actuated by the driving shaft.

4. A device as in any one of Claims 1 to 3, wherein the lifting shield takes the form of a steel plate slidable vertically in front of the suction hood and has supporting rollers mounted in the region of the bottom edge.

5. A device for the extraction of waste gases during the scarfing of blooms or the like in a flame-scarfing machine substantially as hereinbefore described with reference to the accompanying drawings.