Success Story Details - International
- LNG tanks, Murgados, Spain
CONVEYING CRYOGENIC CONCRETE ON A LARGE TANK REQUIRED PRECISION PATIENCE AND PERSEVERANCE
WHAT YOU DON'T SEE IS THAT THE TEMPERATURE DIFFERENCE BETWEEN INSIDE AND OUTSIDE IS ABOUT 200°
In north-west Spain, two huge tanks for liquid natural gas (LNG) were set up in the harbour of Mugardos on the Atlantic coast.
The reason: rapidly growing demand for natural gas in Spain, rising twelve times faster than the average international consumption. The re-gassing plant in Mugardos would cover about 8% of domestic demand. The customer for the project was the supply company Reganosa, which entrusted the Belgian construction firm Tractebel with carrying out the construction works. NESCO, as the local subcontractor, was responsible for the concrete construct.
• Conveying cryogenic concrete on a large tank is not a task for the amateurs.
• Six of the largest truck-mounted concrete pumps in Spain were onsite to concrete the outer shell. With vertical reaches of up to nearly 63m the 4, 5 and 6-arm Putzmeister concrete placing booms towered high over the cupola area.
• The huge tanks, over 50m tall, were filled by special ships which could expunge their freight from the quay directly next to the tanks. Thanks to smooth logistics, the reliability of the concrete pumps and the professionalism of the machine operators, the arched cupola roof of the LNG tank was concreted within 24 hours.
Six of the largest concrete pumps in Spain with vertical reaches of nearly 63m were tasked with completing the monolithic arched cupola roofs of the tanks.
Six boom pumps delivered high strength, cryogenic concrete for LNG tanks. Each of the two round tanks are standing on a 1,6 m thick foundation with a diameter of 80m. The base plates each consist of 5.500m³ high strength concrete and are reinforced with over 830 tons of steel. In order to guarantee the best possible insulation (the temperature difference between inside and outside can reach nearly 200°C in summer), the LNG tanks installed on this foundation are surrounded by two shells. The base and walls of the inner shell consist of a special steel alloy with modified carbon content, while the ceiling consists of an aluminium-nickel alloy. A layer of perlite and insulating fibres was applied to cover the inner walls. The actual liquid gas tank, made of a steel-nickel alloy,was surrounded by this inner shell.
An LNG tank must be completely sealed against possible liquid leaks and must be optimally insulated against the environmental heat. Therefore, the construction of an expensive, double external shell around the actual liquid tank is absolutely necessary. Cryogenic concrete faces particularly high requirements in terms of tightness, crack formation and brittleness at low temperatures.
NESCO project manager Alberto Curto decided to use an entire fleet of Putzmeister concrete pumps, including 'Quads', 'Quintuplets and 'Sextuplets' for the concreting work. The final concreting of the formidable cupola, led to probably the most impressive appearance of large boom truck-mounted concrete pumps ever. Six machines manufactured by Putzmeister were involved, with vertical reaches from 58m to over 60m.
Each of the boom pumps had a precisely defined radius. After the edge reinforcement had been concreted on the upper collar of the concrete shell (structural engineers also speak of ring beams), the end hoses of the truck mounted concrete pumps were each connected to a pipeline which led to a mechanical Putzmeister concrete placing boom RV 10.
NESCO had suggested a 36-hour concreting process per roof arch. But thanks to an efficient concrete placement system, it was possible to cover the huge monolithic cupola in just 24 hours. A total of around 40 truck mixers were available to ensure continuous loading of the Putzmeister large boom pumps. They transported the concrete from two mixing plants in the region.
Concrete Takeaways :
• High quality, cryogenic concrete was delivered with precision and smoothness.
• Significantly less time was taken required than scheduled for covering the huge monolithic cupola.