Levan Artilakva

Levan Artilakva — Engineering solutions

2SHLK-1420 crankshaft repair, Borsig load redistribution and NEUMAN & ESSER thermodynamic expertise.

03 — Engineering activity

Solutions for particularly complex equipment

A significant part of his professional activity is connected with the Severodonetsk Production Association “Azot” and Borsig, Esslingen, Halberg, Schwarzkopf and 2ShLK-1420 compressors.

2ShLK-1420 · 1986

Restoring a crankshaft main journal without dismantling

In 1986, melting of a main bearing on a 2ShLK-1420 compressor damaged the surface of its 550 mm diameter main journal. Conventional repair required dismantling the crankshaft together with the main motor rotor, with a total mass of 62 tonnes, and sending it to the manufacturer.

Levan Artilakva developed and implemented a method for machining the damaged journal in place. He designed a special lathe mounted on the compressor frame. The shaft retained its standard support at the sound main journal, while an installed steady rest supported it near the journal being machined.

The standard turning gear rotated the shaft through the ring gear on the main motor rotor. The end crank drove the longitudinal carriage feed: a pusher and Maltese cross transmitted its motion to the lead screw, providing intermittent cutting-tool feed synchronized with shaft revolutions.

The compressor frame thus served as the lathe base, the standard turning gear provided rotation, and the crankshaft itself drove the tool-feed mechanism. Rough machining removed 2 mm of metal, and finishing removed 0.1 mm. The solution made it possible to machine the damaged main journal without dismantling the heavy assembly.

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Borsig · 1988

Redistribution of dynamic loads

Another characteristic example of the engineering approach was the situation with a Borsig compressor when a crack was discovered in a critical part of the frame. Instead of ordering an expensive new frame from the manufacturer, with a three-year production time, and carrying out extensive work to replace it, an analysis was made of the dynamic loads arising during operation of the crank mechanism. On the basis of this analysis, it was proposed to reverse the direction of rotation of the main electric motor. Changing the direction of rotation changed the direction of action of the components of the dynamic forces and made it possible to unload the damaged section of the frame almost completely. The solution was based not on local reinforcement of the defective area, but on redistribution of forces within the entire mechanical system of the unit. This solution made it possible to fully restore safe, normal operation of the compressor within 10 working days. The absence of stress concentration was confirmed by strain-gauge monitoring of the damaged area of the frame under different compressor operating conditions. The Borsig compressor is an eight-row, six-stage opposed compressor with a capacity of 25,000 Nm³/h, a gas-mixture discharge pressure of 320 atmospheres, a power rating of 7.6 MW and a mass of 220 tonnes.

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NEUMAN & ESSER · 1999

Independent thermodynamic expertise

In 1999, during commissioning of a NEUMAN & ESSER compressor, the process parameters were found not to correspond to the specified values. In particular, the discharge temperature of stage IV exceeded the permissible value. The measures undertaken by the manufacturer's engineers did not produce a positive result. Levan Artilakva was invited as an independent expert. After carrying out a thorough thermodynamic analysis of the compressor parameters, he determined that the polytropic exponent calculated from the final parameters exceeded the isentropic exponent of the compressed gas. He concluded that the system was being heated externally and proposed changing the compressor process scheme by redistributing the gas flow. The problem was solved, and the manufacturer acknowledged an error at the design stage.

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