Main contractor OAO Metrostroy awarded JSC GRPM the contract to supply crane support for the construction of a new 120m-diameter cooling tower as part of upgrade works at the nearly 40-year old facility.
As the cooling tower needed to be built to a height of 150m, this presented some unique complications for set-up of the Terex Comedil CTT 331-16 tower crane selected for the job.
Firstly, the standard free-standing height for the CTT 331-16 tower crane is only 92.6m. So for this particular job, high resilience steels adapted for operation at low temperatures were used in each tower section to increase the maximum set-up height to 158.6m.
In addition, the extreme weather conditions in the area meant that using typical anchoring methods for the crane at this height were not feasible.
If attempted, the steel bracing rods normally used would buckle under the high wind loads due to the extra length.
For this reason OAO Metrostroy decided the crane must be positioned so that it would be inside the cooling tower as it was constructed.
However this solution presented it’s own challenges for the JSC GRPM’s tender for the project, specifically for the set-up and disassembly of the crane.
When erected to its maximum height the CTT 331-16 is normally tied in using three tie-collars to guarantee the self-climbing framework’s stability.
However, any bracing on the crane could only be attached to the cooling tower as it was being built, and the cooling tower’s walls would not be strong enough to anchor three tie-collars.
JSC GRPM Saint Petersburg’s equipment supplies director Andrey Chukichev explained: “We were sure that the CTT 331-16’s height, lifting capacity and manoeuvrability were an ideal match with the cooling tower’s impressive overall dimensions.
“However, it was clear that we had to work fast to provide the competitive ‘turn-key’ solution that Metrostroy needed to stand a chance in winning the race for the job.”
The distributor brought in the Terex Cranes applications team to help design a cost-effective solution, and after analysing the situation, they realised the wind shielding provided by the tower meant they only needed two tie-collars.
Using this evidence a solution involving the two tie-collars being anchored to the base of the cooling tower’s perimeter was designed.
This necessitated eight pairs of 40mm thick steel cable anchors, which were pre-stressed to 17t per cable to compensate for stretching and the increased pressure caused by the unusual lengths and inclines needed.
The team also designed a bespoke jib-dismantling device so that the crane’s 65m boom and telescopic cage could be disassembled from within the cooling tower’s structure.
OAO Metrostroy’s Paul Kolpakov commented: “The Terex Cranes team’s recommendation corresponded exactly to what our company needed. We asked for a full ‘turn-key’ crane proposal including the purchase of the crane, plus the skilled, responsive support of applications specialists and local sales and service teams from start to finish.
“This is what we got, and working together for seven months on this project was a good experience.”
