Preliminary survey of the master's work

Ageev Aleksey
Theme of master's work:
Increasing of reliability and safety of conveyor gallerries on by-product coke plant
Leader of work: Professor Alexandr Parfenjuk

INTRODUCTION

      The conveyor gallery represents an engineering construction of bridge type in weight of hundreds tons, located on significant height (up to 40 m and more). Galleries consist of superstructures and pillars. Conveyors for transportation of bulk solids are placed inside of superstructures and also various technological communications go there. On by-product coke plants the construction iron of conveyor galleries work in conditions of an average degree of aggression of corrosive environment, the basic wear mode is corrosion.
      Functioning of conveyor galleries provides continuous transportation of coal, charge and coke. The long stop of the conveyor at any stage of manufacture can cause the disorder of coke ovens that is defined by a continuity of a production cycle. Bunkers of coal storage provide a stock for 3 days, and bunkers of oven-coal bin provide a stock for 1 day [1].
      Crash of galleries causes ecological damage and constitutes a menace for a life and health of workers. At emergency states danger to the attendants and assemblers grows. The found out defects should be quickly liquidated, and it is very difficult to provide the safety of work in this case. Except for obvious defects (deflections, cracks, detachment of elements, etc.) superstructures and pillars can have latent defects which raise the probability of crash. Therefore one of the major problems is maintenance of reliability and fail-safety of building designs of galleries during all service constituent 20-60 years.

ANALISIS OF DESIGNS

      One of the ways of solving the problem is the analysis of the reasons of emergency states and crashes. The analysis of set of emergency states and crashes of conveyor galleries has allowed us to establish following their basic reasons:
      1. Mistakes of the project;
      2. Defects of installation of designs;
      3. Bad quality of iron hire;
      4. Long-term service without general overhaul and inspections;
      5. Non-observance of requirements on anticorrosive protection;
      6. Non-observance of norms of fire safety;
      7. An overload of bearing designs.
      One reason (47, 4 % of cases) or a combination of two reasons (43, 0 % of cases) is enough for the crash of conveyor galleries. So the organization of reliable inspection system and supervision at all stages of existence of design can prevent crashes. This most perspective way demands much time for realization, and also perfection of normative and legislative base.
      Other way of the prevention of emergency states is application of the most reliable and durable types of designs which allow to lower or to prevent influence of some cause of accident.
      As constructive solution superstructures of galleries belong to one of three groups with bearing designs from steel frame with parallel girths, welded H-bar or the metal shell structure of rectangular and round section combining bearing and protecting functions [2].
      Experience of application of conveyor galleries with metal shell structure has shown that their durability and maintainability is appreciably lower than at galleries of other types. Discrepancies of installation, heterogeneity of metal on all length of the gallery, the high speed of corrosion in the bottom part of shell structure are typical for them. Degradation of bearing of shell structure owing to intensive corrosion deterioration demands reinforcing of design. However it is impossible to make reinforcing of shell structure. So for maintenance of the further work installation of a steel frame with parallel girths around the shell structure is necessary. The given type of reinforcing is irrational. It means, that it is necessary to take into account their low durability and high cost of repair-and-renewal operations at designing the given type of galleries in the sequel.
      Among bearing designs from steel frames the most perspective are designs from tubes. Application of tubes allows to lower influence of the corrosive environment at the expense of reduction of a specific surface of designs. The influence coefficient of a section type for speed of corrosion for tubes is equal 1; for the closed box-type section - 1,1; for a sheet, single hire or the joist web - 1,4; for a compound hire - 2,0 [3].
      Such solution theoretically will allow to lower speed of corrosion in 2 times as against a compound hires which are most distributed. Beside that it is difficult to put a qualitative anticorrosive covering on compound hire. So there will be sites of the raised corrosion wear between its elements on the surfaces unprotected by a covering. Painting of tubes is more technological. Therefore quality of a covering will be higher and cost of its spreading will be lower. According to preliminary calculation application of tubes allows to raise durability of a design on 40 %.
      Increasing of cost of erection works at 10% at the expense of its complication and increasing of materials consumption of bearing designs on 13 % are the lacks of such constructive solution. To define defects of elements of tubular designs is much more difficult than at a hire. Beside that the price of tubes exceeds the price of a hire and increasing of demand for them will bring the deficiency and additional growth of the price.
      The bearing designs from welded H-bar under floor are alternative. Underfloor positioning of bearing designs allows to isolate them from the influence of temperature at a possible fire. Erection, protection by anticorrosive coverings and repair of such designs are most simple of all. It allows to lower capital and operational expenses, but materials consumption of designs grows.
      One more important detail is that the term of erection of such design is much lower than at bearing designs from shell structures or frames. So such design can provide fast restoration of functioning of gallery at possible crash.
      Without application of the control over a condition of building designs of conveyor galleries and duly (1 time in 3 years) restoration of an anticorrosive covering it is difficult to predict their durability and safety. In this case the engineer increases bearing ability of designs of gallery to compensate the accelerated corrosion wear that damages the ecology.
      Practical research of the given constructive solutions in conditions of Avdeevka by-product coke plant confirms their efficiency and reliability.

List of literature

      1. Ткачев В. С., Остапенко М. А. Оборудование коксохимических заводов. – М.: Металлургия 1983. – 360 с.
     2. Руководство по проектированию транспортерных галерей / Ленингр. Промстройпроект Госстроя СССР. – М.: Стройиздат, 1979. – 104 с.
     3. Шевяков В. П. Проектирование защиты строительных конструкций химических предприятий от коррозии. – М.: Стройиздат, 1984. – 168 с.

© DonNTU 2008 Ageev