including those from abroad; provide favorable credit terms for such funds when earmarked for small businesses engaged in the above-noted priority areas of activity; - provide small businesses created on the basis of structural subdivisions of existing plants with material-technical resources, including resources made available by placing limits on their centralized distribution in accordance with procedures established by the founding documents and charter of the SB; - ensue that Gossnab SSSR and its system, the Ministry of Trade of the USSR, the Councils of Ministers of the union and autonomous republics, and existing factories and organizations arrange for the sale of materials and equipment to SB's from excess inventory, with the sale taking place through a network of commercial centers and small wholesale outlets; in addition, the above-mentioned agencies should assist SB's in selling their finished products through the trade network on a contractual basis and help start companies that will specialize in the leasing of machines and equipment to SB's; - have Gosstroi SSSR (State Committee for Construction) organize the development, on a competitive basis, of standard designs of buildings and installations for SB's; these designs should rely heavily on the use of prefabricated building modules and modern building techniques; - measures should be developed and implemented by government ministries and departments to increase the production of prefabricated components along with the equipment required to build facilities for small businesses; - ensure that the Ministry of Foreign Trade of the USSR, working with the Councils of Ministers of the constituent republics, the Trade and Industry Center of the USSR, the International Center for the Development of Small Business, the Committee on International Collaboration Between Small and Medium-Sized Businesses, the Union of Scientific and Engineering Societies of the USSR, and other interested organizations develop and sanction by December 1, 1990 measures on rendering assistance to small businesses in the development of foreign trade, including providing them access on a contractual basis to a common system of foreign-trade information.

NEW DESIGN OF H O T - B L A S T VALVE

A. F Marchenko

a n d V . K. T e r t i t s a

Designers at the Planning-Design and Engineering Institute for Metallurgical Equipment have come up with a new design of hot-blast valves (Fig. 1). The body of the valve is welded from cast flanges and forged parts. Locking rings 1 are composed of U-shaped sections with closed ends made by hot forging. The profile of the sections is machined and the U - s h a p e d piece is welded into the flanges on the valve body. This prevents hot air from leaking out between the rings and the body. The welds are outside the zone that is washed by the flow of hot blast. The inside part of the rings, in the path of the blast, is covered with high-refractory concrete 2. This reduces heat flow and, accordingly, thermal stresses in the rings. T h e branch pipes that supply the coolant 3 are welded into the rings, which eliminates the need for bellows and prevents the leakage of air into these components. The coolant is removed from the top part of the rings directly into the neck of the body. The number of sites at which coolant enters and exits the valve body and rings was reduced by a factor of 2.8 from the previous design. The neck of the body was made longer and the height of the cover was reduced accordingly. This allowed designers to remove the joint between the body and the cover from the high-temperature zone and improve the service conditions for this component. An access hole 4 for the removal of worn lining is provided in the lower part of the body. The valve cover is a welded component composed of parts of rolled shapes. The inside surface of the cover is insulated with high-refractory concrete 5. Since the presence of the concrete and a reduction in area of the cover

Translated from Metallurg, No. 2, pp. 34-35, February, 1991. 0026-0894/91/0102-0027512.50 9

Plenum Publishing Corporation

27

Outlet from disk I

Inlet to ~ disk f5 i

I Inlet to and Outlet from 9 , cover Outlet from body

,

U

~

2 Inlet to body I

W//f

X///I_tVl

o

J

!

to rings

Fig. 1. Design of hot-blast valve.

This modification of the previous design permitted a 10=fold reduction in the n u m b e r of coolant inlets and outlets. exposed directly to the heat flow significantly reduces the thermal loads on this component of the valve, designers provided only for cooling of the lower region (the flanged joint with the body). The valve disk is welded and consists of an edge-machined forging and a piece of sheet metal. The side of the exterior of the disk is protected by a layer of high-refractory concrete 6, ensuring a reduction in the thermal loads and reducing heat losses when the disk is in the closed position. Designers decreased the cross section of the cooling cavities in the main thermally loaded components, the locking rings and disk. This change increased cooling rate and efficiency by eliminating local boiling of the coolant water and the deposition of suspended matter inside the cavities. The new valve has fewer parts than the old valve, and previously unreliable joints have been eliminated. At the same time, the new valve contains less metal than the old design and is thus cheaper to service. The amount of heat lost from the hot blast passing through the valve depends on the stove operating regime and the location of the heat-absorbing elements of the valve relative to the flow of hot blast. The valve is closed when the stove is "on gas." In this position, most of the thermal load is received by the lateral surfaces of the disk and the inside surfaces of the locking rings from convection of slow-moving air, as well as from the radiation of the hot blast and the walls of the hot-blast line. The other surfaces of the valve are subjected to significantly smaller thermal loads, since they participate only in heat exchange with slow-moving air through natural convection. When the valve is open (when the stove is "on blast"), the disk is located in the neck of the valve and, analogously to the inside surfaces of the valve, it participates only in convective heat exchange witth slow-moving air. Most of the load in this regime is taken up by the locking rings, which are washed by the high-velocity flow of hot blast. In the new valve, the internal surfaces of the locking rings are protected by a layer of high-refractory concrete.

28

As was shown by heat-engineering calculations and measurement of the thermal loads on the valve under service conditions, the latter are 1390 kW for unlined valves and 625 kW for lined valves in the "on-blast" regime. Theanalogous loads in the "on-gas" regime are 670 and 240 kW, respectively. In tests of a prototype 1300-mm-diameter hot-blast valve conducted at the Nizhniy Tagil Metallurgical Combine, the Interdepartmental Certification Commission gave a positive assessment of the unit and recommended it for serial production. According to the findings of the G K N T of the USSR, the new hot-blast valve conforms to the highest international standards.

MODERNIZATION OF T H E E L E C T R O D E - H O L D E R SYSTEM ON AN E L E C T R I C FURNACE

V. K. Tarasov, O. L. Reznikov, A. Ya. Zhuk, and V. N. Kanyuk

In the course of normal operation of ultrahigh-power arc steelmaking furnaces, electrodynamic forces induce low-frequency horizontal vibrations of the electrodes. The amplitude of these vibrations reaches 10-15 mm on the DSP25 N2 furnace at the "Krasnyi Oktyabr'" plant, which has adversely affected the service life of the load-bearing components of the mast of the electrode-positioning mechanism and led to breakages of electrodes from extreme bending stresses. The stresses develop near the electrode-fastening head and at the joints between electrodes due to spontaneous unscrewing of the nipples.

/J

Fig. 1

Fig. 2

Fig. 1. Sketch of the load-bearing component and mast arm of the old electrode-holder system: 1) mast arm; 2) longitudinal ribs; 3) box beams; 4) longitudinal rollers; 5) transverse rollers. Fig. 2. Sketch of the load-bearing component and mast arm of the new_electrode-holder system, regulator, and good vibration-damping by the load-bearing component. Zaporozh'e Industrial Institute. Translated from Metallurg, No. 2, pp. 35-36, February, 1991.

0026-0894/91/0102-0029512.50 9

Plenum Publishing Corporation

29