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Different Types of Anchor Bolts
Different Types of Anchor Bolts

A bolt out of the blue


At times the problems look so difficult and complicated but solutions are simple if right stake holders are involved in resolving.

Gas turbine foundation is the most important concrete foundation of a combined cycle power plant. Starting right from design engineering to pouring of concrete, a group of specialist very carefully review and approve the every aspect of design including the details of concrete pouring methodology.

The following incident happened at one of the projects in UK where I was worked as Lead Civil Engineer. After pouring the concrete and removing the form work it was realized that anchor bolt locations of gas turbine foundation are displaced from their required position by 13 mm. This was a very serious problem and everyone starting right from Project Director to the Surveyor who gave the line and level of the bolts were worried and signs of panic was visible on everyone's face.

Anchor bolt comparison

Everyone started giving their reasoning as to how the anchor bolts could have moved while pouring the concrete. After lot of deliberations it was clear that anchor bolts were in correct position before concrete was poured. However during the operation of pouring concrete, the bolts have moved. But the big question was how?

Following are the possible reasons.
anchor bolts 3Anchor bolts are kept in position by templates and the templates in turn are fixed to form work. Concrete is poured through concrete pump trucks. Some times while pouring concrete on sides, the form work along with the template has given way thereby disturbing the position of anchor bolts.

After finding out the reason why the positions might have shifted it was necessary to find out a solution for this unusual problem.

Many times, problem ring different bells for different stakeholders of the problem. One group of people might have thought, how to realign the location by rework. Another group might have thought how to realign the gas turbine base frame. A third group might have thought what we can do with the anchor bolts to resolve the problem. Instead the Gas turbine manufacturer was notified of the "as built" positions of anchor bolts and was requested for suggesting a solution. What the gas turbine manufacturer told us was music to our ears. They said they will take care of the problem. According to the manufacture the holes in gas turbine base frame have a tolerance of +/- 6 mm and since the base frame was under fabrication at that point of time the manufacture agreed to locate the holes with required adjustments to suit to the as built position at site.

Everybody breathed a sigh of relief. The solution was that simple.

Last modified onTuesday, 09 August 2016 19:18
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  • Dilip
    very interesting story.
    I have a question
    Was there any specific problems later while actual positioning of the CTG frame, since the manufacturer's telorance limit was +/- 6.0mmand the actual shift was 13 mm?

  • While fabricating the GTG base frame itself the manufacturer made the wholes as per the location details provided to him by Site. Therefore there was no problem while installing the GTG at site. There were no problems reported from site even during the warranty period.

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