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Equipment kits and technology for rehabilitation of water-supply and canalization systems

Introduction

The development of trenchless methods of laying and rehabilitation of different underground engineering services with the tube outer diameter 800mm max in Russia and abroad is conditioned by increase of city high-density built-up, economical reasons and ecological requirements. In well-developed countries the share of trenchless laying and restoration works in city areas has reached 40% and has stable upward trend.

In recent years a great number of tunneling complexes of various actions (puncture, punching shear or drilling) and different level of design have been developed.

The most spread as driven elements in methods of puncture and punching shear have air-percussion machines - air-hammers (impact moles). This class of machines that has been developed in the middle of sixtieths in the Institute of Mining (Siberian Branch of Russian Academy of Sciences), nowadays is being produced in Russia, C.I.S., Germany, USA, Swiss, England. Air-percussion machines are being used for soil hole-making (diameter up to 200mm), close-end steel pipeline plugging (diameter up to 300mm) and open-end - up to 800mm; pipeline cleanup from soil; rehabilitation of failed pipelines (up to 500mm); underpinning with cylinders; cleanup of nipped pipelines etc. Some foreign companies producing air-hammers ("Tracto-Technique", "Dich-Vich", "Terra", "Essig", "Usiba", "MTM" and others) do not develop new pneumopercussion machines and equipment complexes with a view to improve energy and operational attributes. Apparently they use the results of Russian research, that were published in open press owing to patents expired.

By now in the Institute of Mining of Siberian Branch of Russian Academy of Sciences has been gathered extended experience in the field of development of air-percussion machines and equipment kits of different purposes for constraint operations. Significant contribution to solution of this problem was made by V.A.Grigouraschenko, B.V.Studishnikov, K.K.Toopitsin, A.D.Kostilev, K.S.Gurkov, V.V.Kamenskiy, V.V.Klimashko, V.D.Plavskikh, S.K.Toopitsin, A.L.Isakov, A.V.Sukhushin, V.A.Kozlov, A.S.Savelyev, V.A.Kharkin, E.G.Jarkov and other scientists and operatives.

Equipment kits and technology for rehabilitation of water-supply and canalization systems

Technology for rehabilitation of water-supply and canalization systems and development of the equipment kits for its implementation provide:

- replacement of the steel, iron, concrete, reinforced concrete, asbestos-cement pipelines (up to 500mm) with plastic ones in different soil conditions;

- performing replacement works from existing manholes with the interval between them 50m and more;

- accessibility to driven element (impact mole) in case of its failure for repair or replacement

- - ability of air manifold placing in the replacement pipeline.

The trenchless technology substance:

Draw cable is laid through the failed pipeline from the inlet manhole to output, one end of which is connected to pull winch at the output manhole and another - to driven element (impact mole) in the inlet. The base of the driven element is the special air-percussion machine - "air-hammer". On its head the tapered reamer with holding jig for new plastic pipeline mounting is located. Draw cable is attached to the head of air-hammer while the safe-haulback cable - to the rear. Pull winch is driven by an air engine therefore a single power source can be used. In terms of safety in operation air engine is rather than electric. Its performance allows to change pulling power on draw cable according to pressure of supplied compressed air from 10 to 150kN. Air engine has "steam-engine" speed-torque characteristic that is torque is a constant and even increase while speed-down till full stop. This characteristic is very important since constant draw cable tension provides stable air-hammer performance and transfer maximum impact load to the reamer. Draw cable tension compensates air-hammer kickback and provides steady-state mode operation. Besides, fluctuating load transfer to the new hole sides is eliminated. Thereby the hole firmness enhanced along with accessibility to the air-hammer in case of its failure. At this rate for the air-hammer repair or change it is necessary to release the pull winch catch and pull it out with the safe-haulback cable.

Compressed air is supplied to the pull winch first, then to the air-hammer, the latter starts to transfer impact load to replaced pipeline, and, concerning chosen process flow chart destroys and forces it into the surrounding soil or knocks it out to the outlet manhole. To decrease reduction range of destroyed pipeline the leading grooving as stress concentrators are made on its sides. The air-hammer, making, pulls attached to its holding jig plastic pipeline into the new-made hole. Separate link-ups or segments of the pipeline are built up with threaded connection or welded to string, which is chuted to manhole through the inclined hole from surface. Under the welding process heating unit completely closes internal diameters of pipeline segments, making impossible placing the compressed air manifold in the new-made pipeline. In this connection the design of air-hammers provides ability of air manifold connection to the machine's head. Thus air manifold is laid in the replaced pipeline instead of new as in the first case. As the air-hammer advances, air manifold is taken up at the output manhole while its length decreases, therefore the losses of compressed air are reduced. Concerning development of the equipment kits, implementing aforecited flow charts, it is necessary to take into account large quantity of requirements and boundary conditions, exercising a significant influence to design of machines and devices composing the kit. These requirements are determined by certain building task (excavation elimination; arrangement, mounting and disassembling of driven elements etc. in constraint conditions of existing manholes), physio-mechanical properties of solid ground and geometrical adjectives of destroyed and new-laid pipeline. Several requirements, appeared in the process of equipment kits development, come into collision between themselves. Therefore the key criteria was detected - energy-adequacy of simultaneous forces, produced by an air-hammer and pull winch.

Trenchless technology of failed pipelines rehabilitation and equipment kits for its implementation had passed long-term trial-industrial testing. The examples of equipment kits, made by Institute of Mining SB RAS, Novosibirsk Joint-Stock Company "Siblitmach", Omsk Joint-Stock Company "Polyot", are run in Moscow, S. Petersburg, Omsk, Novosibirsk, Novouralsk and Barnaul see equipment kits realization chart. In 1994-1996 more than 50km of canalization pipelines (diameter - from 160 to 355mm, material - concrete, iron, and sewer tile) have been rehabilitated. The field of experience has verified the ability of new technology application in any soil conditions.

The kit capacity is rated by the driven element (impact mole) traverse speed and plastic pipeline segments buildup rate. The operating time, rated on the Novosibirsk and Moscow objects, yields the following quantities (averaged by diameter of new-laid pipeline - 255mm, site length - 25m, material of replaced pipeline - sewer tile, iron):

engineered traverse speed, mph - 9
time share of net machine operation for driving single segment, % - 25
time share of development and final operations in general time distribution, % - 45

On the ground of listed figures the kit monthly capacity reaches 200-210 running meters. Accordingly, the annual rehabilitation work load including all-shift working time losses (vacations, holidays etc.), will amounts to 2000 running meters. The warranty service life period of driven element (air-hammer) - 2 years.

Conclusion

A large scientific-engineering problem, having significant economic importance, has been solved. It is enclosed in the series of special-purpose air-percussion machines and equipment kits which allow to mechanize the process of trenchless laying and rehabilitating of underground engineering services: open-end steel pipeline plugging (diameter up to 820mm) with following cleanup from soil by the self-propelled soil-withdrawal device and rehabilitation of water-supply and canalization systems (diameter up to 500mm).


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