MAIN DIRECTIONS AND DEVELOPMENTAL PROSPECTS OF GATE VALVE DESIGNS G. I. Sevast'yanikhin, S. A. Makhmutov, and O. S. Basalaev

UDC 621.646.5:65.012.4

Production plans and improvement of gate valves were based on the results of multiple evaluations of their technical levels by existing methods of comparing the indexes of technical perfection of test and base samples, supported by results of control and comparative tests. The evaluation of technical levles includes identifying the range of required indexes; formulating the analog groups and establishing the values of their indexes; picking out the base specimens from the analog groups; comparing the test with the base specimen; and drawing the conclusions from the evaluation results. The range of indexes should ensure the comparability of specimens and be the same for all analogs and test specimens. The range of indexes was established using international and national standards, product supply specifications, and catalogs and prospects of companies producing gate valves. The technical level of 405 types and sizes of commonly-used gate valves classified into three main groups were evaluated: steel gate valves, 261 varieties; cast iron gate valves, 130 varieties; and gate valves made of nonferrous alloys, 14 varieties~ In turn, the steel valves were classified into eight subgroups based on nominal pressure, and cast iron ones into three subgroups based on design features (parallel, wedge, and sliding) with two subgroups of nominal diameter of the opening (Dn = 50 to 400 and 500 to 2000 mm). The foreign analogs selected were the best ones produced by the leading companies of capitalist countries: Theodor Jansen, FAG, KSB, Babcock, Eisenwerk Heinrich Schilling, Erhardt, Rheinhutte (FRG); Crane, Malbrank, and Serseg (France); Hopkinsons, Hattersiey Newman Hender, Robert Court (UK); Eisenwerk Schilling, Hubner Grey, Hubner Wamag (Austria); Itnart (Spain); Welwochs (USA); and Raymondi (Italy). The range of comparative indexes included nominal pressure, nominal diameter of opening, working medium temperature, material of main components, weight, reliability indexes (service life, reserve, and running period before failure), degree of hermetic sealing, and resistance coefficient. Based on the test results, gate valves were placed in one of two categories: conforming to world level (227 varieties) and inferior to it (178 varieties). An analysis of parameters in which the valves were inferior showed that 41 were inferior in weight, 40 in reliability, 26 in hermetic sealing level, and six in functioning. The following were the results of 65 cast iron and nonferrousalloy valves: five were inferior in weight, I0 in reliability, and 50 in functioning. Studies to improve the technical level of gate valves carried out at the Central Accessories Design Bureau (CADB) in collaboration with the producers ensured high-quality products but revealed the need to modify the policy in evaluating the technical level of gate valves by orienting it to attain competitiveness in the world markets. Such work is already being carried out at the Scientific Production Combine (SPC) Lenpromarmatura, Georgievsk Accessories Works, Namangansk Engineering Works, and others. This work is based, on a thorough analysis of the structural constituents and components of foreign gate valves, analysis of foreign standards prescribing output parameters, characteristics and the entire design-production-supply cycle, research on designing various con-

Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 4, pp. 3-6, April, 1992.

0009-2355/92/0304-0215512.50

9 1992 Plenum Publishing Corporation

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Fig. I. Flexible pipe gate valve (Pn = 0.6 MPa and D n = 50 to 300 mm).

stituents and components, perfecting the production technology using new materials, laser hardening, and plasma coating of sealing surfaces. The results were used to draw design specifications and implement product certification to ensure the competitiveness of gate valves in the world markets. High-strength cast iron as a structural material is widely used in engineering for producing loaded components and competes successfully with structural steels. When designing high-strength cast iron valves, one of the directions for product innovation is to perfect production and then enlarge its volume. High-strength cast iron with spheroidal graphite (HCSG) aroused the interest of engineers for its following advantages: reduced melting period (by 25% compared to steel melting); better casting properties than steel and hence greater yield of castings (up to 25%); and mechanical and plastic properties on par with or better than those of steel. The possibilities of using high-strength cast iron in accessories manufacture are extensive. Thus, in the early '70s, Grove (Italy) supplied ball cocks with HCSG balls for the 1400 mm diameter gasline being laid in the Far North. Rheinhutte (FRG) products HCSG valves, including for safety systems, for pressures up to i0 MPa and D n ~ 800 mm while the Japanese firm Asahi produces valves for pressures Pw = 2 MPa and temperatures up to 350~ (steam or oil media). Foreign experience and the local needs which could not be fully met by steel valves as also the experience of the Baku Petroleum Engineering Works in producing the first experimental and commercial batches of gate valves (Dn = 1 0 0 m m a t Pn = 2.5 MPa and temperature 300~ for water, steam, petroleum, and oils, as also the components of petroleum industry gate valves for oil well capping at Pn = 2 1 M P a served as the base for carrying out test and design studies for producing gate valves of high-strength cast iron. Kharkov Highway Institute, All-Union Institute for Transport Accessories, CADB, and Leningrad Polytechnical Institute took part in developing the casting technology and quality control of body components. Based on the experimental results trical center, the Rules for Designing lines were modified to provide for the cast iron (conforming to GOST 7293-85)

of using a batch of gate valves at a thermal-elecand Operational Safety of Steam and Hot Water Pipeproduction of body components using high-strength for Pn up to 4 MPa and temperature up to 350~

The CADB has at present revised the All-Union Standard OST 26-07-793-73 "Castings of Gray, Malleable, and High-strength Cast Iron for Pipeline Accessories and Drive Systems for them:" specifications for cast body components of HCSG pipeline accessories were modified and the lower operational temperature limit reduced to -60~ This helps not only substitute carbon steel by HCSG valves but also enlarges their application field. Production of high-strength cast iron gate valves has commenced at several plants. The Nikopol'ski Casting-Engineering Works Bol'shevik is developing gate valve prototypes for D n = I00 and 150 mm and Pn = 2.5 MPa (to substitute steel valves) and values for D n =

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Fig, 2

Fig, 3

Fig. 2.

Slide valve with elastic rings in the slide,

Fig. 3.

Slide valve (Pw = I0 MPa and D n = 250 mm).

i00 and 150 mm and Pn = 1.6 MPa (to substitute gray cast iron 30ch6br valves). Under an agreement with the Georgiev Accessories Plant, the CADB designed several gate valves for Pn = 1.6, 2.5, and 4 MPa. These were approved by the All-Union Oil Refining and Petrochemical Industry Research and Design Institute, the main buyer of these accessories. The Kashirsk Works and Tsentrolit and Temirtau Casting-Engineering Works have commenced work on producing high-strength cast iron gate valves for D n = 50, 80, and i00 mm and Pn = 1.6 MPa. HCSG gate valve specifications can be divided into two groups: resultant technological) and organizational-technical.

structural (and the

Using HCSG does not call for any special design specification for the valves, i.e~ the steel valve designs can be successfully adopted. The main problem, however, is to develop the surface hardening technology of sealing surfaces and welding of components (welding of seat in the body or stem to the lid). The E. O. Paton Electrowelding Institute is developing the technology of plasma fusion of hard-facing material in a separate ring followed by its welding to the body and direct hard-facing on the disk. Automatic hardfacing directly in the body is proposed. The high-strength cast iron engineering center of the SPC AzlNmash has developed valve sealing surfaces with adequate corrosion resistance without the need for hard-facing. Another prohlem is the identification of specifications for steel and HCSG valves for similar parameters, e.g. main parameters, structural lengths, and sizes of flange joints should be standardized. An urgent task is to include HCSG accessories in the system of Rules for Operational Safety of Systems and Accessories in Different Industries, It would be interesting to assess the prospects of developing gate valve designs for pulp media since hydraulic transport systems.of pulp media and reliable pipeline accessories are engineering problems all over the world. Pipeline systems handling hydraulic mixtures are characterized by several factors acting on the pipeline accessories. These are hydraulic abrasive wear of the flow parts, working parameters of the hydraulic mixture, and operational regime of the equipment. General purpose gate valve designs with extremely short service lives cannot meet the operational conditions of hydraulic transport systems. Special designs are needed. 217

Fig. 4

Fig. 5

Fig. 4. Parallel gate valve with onesided seal and flat fixed slide (Pn = 1 M P a , D n = 200, 250, and 300 mm). Fig. 5. Parallel gate valve with onesided seal in the valve (Pn = 1MPa, D n = i00, 150, 200, 250, 300, 350, and 4 0 0 m m). Let us examine the gate valves made of nonmetallic materials; e.g., flexible pipe gate valves (Fig. i). In this equipment, the section is shut off by contraction of an elastic flexible pipe which is resistant by hydraulic abrasive wear, withstands well the loads at points of fixing the flexible pipe to the body, and possesses flexibility while ensuring hermetic sealing when closed. As the flow section has no dead zones, flexible pipe gate valves have the highest transmissive capacity at fairly low coefficients of hydraulic resistance. Their range of application is, however, restricted (with respect to pressure, temperature, and flow rate) due to limitations of chemical resistance and ability of rubbers to maintain elastic properties and also because the inner surface of the elastic flexible pipe is exposed to hydraulic abrasion caused by the working medium (the angle between the particle flow direction and the inner surface ~ = 0 ~ in the open position and slanting flow (~ = 18 to 60 ~ ) in the opening and closing periods when the resistance of the elastic material, especially against streams containing solid particles with sharp faces, is minimal. As a result, flexible pipe gate valves are mainly designed for D n ~ 200 mm and Pn up to 0.6 MPa and temperatures not above II0~ Slide valves with linings of elastic superhard nonmetallic materials are the result of rationalizing and modernizing the design of flexible pipe gate valves. Linings of elastic materials can be made, e.g., in the form of two separate pipe joints hermetically passed together against the end surfaces in the open position (type of Clarkson (USA) gate valves), in the form of inserted components outside the flow of the working medium, relatively complex form (gate valve L-160 of SPC Lenpromarmatura) or in the form of ring sections [Adamson Chronister Valves (UK) gate valves, Fig. 2]. The design of gate valves with elastic inserts is the result of economic considerations while selecting the main structural material for the flow section, technological possibilities of producing the components of elastic materials, and their suitability for repairs. The tendency to develop modified gate valves with inserts of simple geometric form is perceptible. 218

From the view point of the action of flow, slide valves with elastic inserts, like flexible pipe gate valves, can provide full flow without dead zones in the open position. The difference from flexible pipe gate valves is that the flow is shut off using a sliding strip and not by constricting a flexible pipe. The peripheral section of the slide is profiled in many designs to facilitate flow shut off. As elastic inserts in the open position or than flexible pipe gate to 150 to 200~ and in meters.

are subjected to the action of the flowing hydraulic mixture only are placed outside the flow, these designs are more wear resistant valves and can be used in wide-ranging media and temperatures (up a practically unrestricted pressure range and nominal flow dia-

When using materials, their resilience compensates for the relative wear of contact surfaces. Inserts of superhard materials provide the required hermetic sealing due to their high resistance to hydraulic wear (type 3S valves produced by UkrNIIugleobogashchenie). Among the main drawbacks of slide valves is the presence of dead zones in many designs requiring periodic cleaning as the working medium enters them during the valve opening and closing. Technological difficulties of producing wear-resistance slide valves, especially in large sizes, the need for compulsorily cleaning the dead zones, and providing for their signification wear called for more rational designs, i.e., parallel double-sided valves and metal to metal packing. VNIIgidrougol' designed typical parallel double-sided valves for hydraulic mixtures for D n = 125 mm and Pw = 12 MPa (type ZPR-5A). The complex wedge in the valve, in general, adversely affects working with hydraulic mixtures and the presence under it of dead zones that cannot be cleaned sharply restricts the application range and reduces the reliability of these valves. To eliminate these drawbacks, the SPC Penztyazhpromarmatura designed slide valves PT19034 (Fig. 3) with the slide in the form of a plate with a shaped peripheral section. Valves produced by Hiruta Valve (Japan) are of such design. However, these too have a dead zone in the flow section requiring cleaning. The drawbacks of parallel double-sided and slide valves can largely be overcome in Darallel one-sided valves. These primarily L19031 (Fig. 4) for alumina plants and L19021 and L19025 for coal slurries and slimes designed by the CADB and recommended for manufacture. These valves have a flat slide pressed to the seat using firm supports (wedges) in the body. Improved versions of parallel one-sided gate valves have a profiled flow section type AZGM (designed by the Lugansk Engineering Institute), KZ19036 (designed by the CADB and Kurgansk Accessories Plant, KAP), L16009, LI6010, and LI6011 (Fig. 5, designed by the CADB). Their production is being developed by the SPC Lenpromarmatura and KAP. Further improvement of one-sided gate valves could proceed toward the search for wearresistant material, nonconventional methods of protecting the sealing surfaces from wear, and design optimization. Moreover, the scientific and technical principles of their design should be further developed. These pertain especially to the development of the theory of pressure effects between the drive and the hydraulic mixture to ensure strength reliability of the valve by optimizing the main components: scientific rationalization of the application range of formulae for calculating contact pressures ensuring hermetic sealing with respect to pressure, medium composition, and width of sealing surfaces; improving the method of strength calculations of original components; studying the wear resistance of new and promising structural materials; and working out scientific recommendations for using the accessories for flow control of two-component media includingthose tending to form solid deposits.

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