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Home Environmental Light-weight welded cylinders for motor transport

Light-weight welded cylinders for motor transport

Description

Pollution of the environment with toxic fuel combustion products constitutes 70% of the total pollution in large cities. Utilization of natural gas (methane) as a motor fuel reduces emissions of CO, hydrocarbons and nitrogen oxides, and eliminates emissions of lead compounds. Moreover, the equivalent amount of gas is 2-3 times as cheap as that of petrol.

Cylinders with a working pressure of up to 19.6 MPa are employed to run cars on compressed methane. Automotive cylinders made from carbon and low-alloy steels with a specific weight of 1.25 and 1.86 kg/I are used currently in trucks and buses in Ukraine. To use cylinders in cars and agricultural machines, their specific weight should be no more than 0.7- 0.8 kg/I, which can be achieved through increasing strength of a structural material by using tubes of nickel-containing steel 20KhN4FA for hot sealing of bottoms and necks.

The E.O.Paton Electric Welding Institute developed design and technology for manufacture of combined welded cylinders with a specific weight of 0.60-0.65 kg/I (Fig. 1). The gas-tight casing consisting of longitudinally welded skin 1 and two stamped bottoms 4 of the same thickness with butt joints 3 is made from high-strength alloyed steel sheets by TIG welding in argon atmosphere. In sheets 3-6 mm thick the ultimate deviation in thickness is 3-4 times as low as in tubes, and the process of their production at metallurgical enterprises is well-managed. The resulting joints are characterized by a fine-crystalline structure and smooth transition from the weld to base metal along the fusion line. Assigned chemical composition and comprehensive treatment of the longitudinal weld provide its full strength and impart it a high structural and fatigue strength.


Fig. 1 Schematic of combined cylinder with
a welded casing made from sheet steel


Fig. 2 Appearance of combined welded cylinders

Given that stresses in the cylindrical part of the casing are twice as high as in hemispherical bottoms, reinforcing composite skin 2 with a wall of the assigned thickness is formed on it by transverse winding with tensioning of glass fibers impregnated with an epoxy binder and polymerization at increased temperatures.

In the cylindrical part of the casing, the composite skin induces circumferential compressive stresses, which partially compensate for circumferential tensile stresses in metal at a working pressure, thus resulting in improvement of performance of a cylinder. Decrease in thickness of the steel casing wall by reinforcing it with the cylindrical composite skin provides decrease in the specific weight of the automotive cylinders. This method can be employed to manufacture automotive cylinders of different size-types in wall thickness, diameter and length, which can be varied both by varying length of a rolled billet and by circumferential welding of several skins. Welding of the skins can be performed by the arc methods and by the pressure method, e.g. flash butt welding and magnetically impelled arc welding.

Innovative Aspect and Main Advantages

The combined cylinders with a capacity of 20, 30 and 60 I (610, 845 and 1575 mm long) subjected to hydraulic tests withstand the internal pressure of not less than 52 MPa, which is more than 2.6 times higher than the working pressure. Depending upon the steel casing wall to combined skin thickness ratio, the combined cylinders can be made with a diameter ranging from 200 to 400 mm. They can withstand from 15,000 to 24,000 cycles of an internal pressure loading. The safety factor for strength does not decrease after 15,000 cycles and remains at a level of more than 2.6. The given quantities of the loading (fueling) cycles provide a minimal (15 years) and maximal (20 years) service life of a cylinder, based on less than 1000 loading cycles a year.

The technology for manufacture of the combined cylinders with a welded casing, capacity of 28-50 I and diameter of 219 mm was mastered by Kyiv enterprises, and is being mastered in Fastov (welded cylinders 335 mm in diameter with a capacity of 50, 70 and 100 I) and in Simferopol (360 mm diameter cylinders). The structural material for the cylinders is a relatively inexpensive sheet steel 30KhGSA, which contains no deficit alloying elements and has been produced in Ukraine for a longtime.

Stage of Development

Design of the cylinders and technology for their manufacture are covered with:

  1. Ukraine Patent 61162
  2. Ukraine Patent 55385
  3. DSTU and M/ECER 110-00:2002

Contact Details

Contact persons: M.M.Savitsky, A.A.Savichenko
E.O.Paton Electric Welding Institute
11 Bozhenko Street, 03680, Kyiv-150
Tel./fax: (38 044) 289-1739; 271-2328
E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

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