BOLTED

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bolt securing

Keeping up the pressure

3 October 2012
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Text: Linda Karlsson Eldh & David Wiles

photo: Martin Magntorn

Superbolt tensioners on pressure vessel

First published in Bolted #2 2012.

Customer: Ekström & Son
Weight: 80 tons
Temperature: 300 Degrees Celsius
Usage: Hydrogen plant
Total Pressure: 35 bar
Bolt size: M64x6

The Swedish company Ekström & Son is one of Europe’s leading manufacturers of pressure vessels. The pressure vessel is at the heart of any reactor. Its job is to hold gases or liquids at a pressure substantially different from the ambient pressure.
In the past, the bolting of the main flanges of a vessel for the hydrogen industry was a problem. Heavy hydraulic wrenches were needed to tighten the nuts and excessive tightening often damaged the gasket, causing leaks. The damaged gasket then had to be replaced, involving many hours of disassembly and reassembly for this part of the 80 ton vessel.

To avoid this, the company recently fitted 56 Superbolt high-temperature tensioners on the bolted connection of the vessel’s main flange. The tensioners, made with high temperature, high strength alloys, can be tightened with regular air tools.
Accurate preload permits the tensioners to distribute the
pressure evenly, preventing damage to the gasket.

After installation, the flange proved leak-proof during the first test. The engineering team saved almost two days of work by not having to disassemble the construction, retighten the bolted connection and re-test the vessel. This improvement prevented delays and the customer was very pleased with the results.

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