Metallurgical apparatus – Means for melting or vaporizing metal or treating liquefied... – By means introducing treating material
Patent
1998-10-13
2000-10-31
Kastler, Scott
Metallurgical apparatus
Means for melting or vaporizing metal or treating liquefied...
By means introducing treating material
C21C 532
Patent
active
06139792&
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with the structure and process of exchange of an oxygen lance for use in the conversion of iron to steel.
In the process for the conversion of pig iron to steel oxygen is blown onto or through the top surface of molten pig iron and scrap contained in a converter vessel. In this specification oxygen is to be taken to be any gas, including air, or mixtures of gases, which might be blown onto the pig iron/steel mixture unless otherwise stated.
A conventional oxygen lance assembly consists of a lance body coupled to a head. The lance body is comprised of at least an inner pipe, intermediate pipe and an outer pipe arranged concentrically. The inner pipe provides an oxygen passage to deliver oxygen from the normally upper head end to a lower tip end from which it is expelled. The annular spaces between the pipes provide a water passage whereby water coolant is pumped from the head to the tip and returned to the head. The head provides means to couple the lance body to oxygen and water supplies. The lance body has to be changed frequently because it deteriorates rapidly in the hostile working environment and for process reasons.
A conventional lance assembly is known from U.S. Pat. No. 3,170,977. U.S. Pat. No. 3,170,977 illustrates a lance assembly known as a plug and socket system. In this assembly the lance body has a head end in the form of a plug which plugs into a head in the form of a socket. In use the head is permanently supported on a gantry. Various pipes are connected to ports in the head whereby oxygen and coolant fluids can be delivered to and circulated in the lance. The head end of the innermost pipe projects from the head end of the intermediate pipe which in turn projects from the head end of the outer pipe. Thus cylindrical peripheral male mating surfaces are exposed on each pipe. Within the socket of the head, cylindrical female peripheral mating surfaces are provided which engage with the exposed male mating surfaces of each pipe. Thus, when the lance body is plugged into the head socket axially spaced annular chambers are formed which communicate with water delivery and return ports in the head and with the corresponding passages in the lance body. The inner pipe sockets directly into an inner pipe aperture communicating with the oxygen delivery port in the head. To prevent water leaks into the oxygen passage a pair of O-ring seals are retained in annular channels formed the female mating surface which receives the inner pipe mating surface.
The lance head is coupled to the lance body by means of hooks formed on one of the lance head and body which engage with pins formed on the other of the lance head and body. To exchange a lance body, the lance body is first engaged and suspended by means of a crane. The pins are released from the hooks and the old lance body displaced axially to withdraw the head end from the socket in the head and is then carried away. A replacement lance body is carried in by a crane. The head end of the replacement lance body must then be accurately aligned coaxially so that the sealing surfaces, which have sliding fit tolerances, can be slid into engagement by having the crane raise the lance body. The hooks are then engaged with the pins to retain the lance body in the head and the crane is withdrawn.
The lance body and head are heavy and the lance body has a large moment of inertia. The lance body is suspended from a crane via a hook and trunnion pin arrangement. The crane operator is also necessarily remote from the head and must be guided by an assistant on a gantry supporting the head, it is consequently difficult to accurately align the head and lance body.
The aforementioned problems experienced with aligning the conventional lance body and head must be obviated in order to automate the exchange of the lance body.
Because there is a close sliding fit tolerance between the mating surfaces, the mating surfaces are subject to wear from abrasion and this encourages corrosion so reducing the endurance of the lance body and the head
REFERENCES:
patent: 3170977 (1965-02-01), Obenchain
patent: 4732370 (1988-03-01), Berry et al.
patent: 5377960 (1995-01-01), Leczo et al.
patent: 5865876 (1999-02-01), Watkins et al.
Craig Ian Mervyn
Kibble Brian James
Kastler Scott
Kvaerner Davy Ltd.
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