Extremely high pressure testing at TWI's Cambridge laboratories entered a new era recently with the completion of a large subterranean pressure test pit. Serving the engineering needs of the oil and gas sector in particular it's believed to be one of the best equipped facilities of its type in Europe.
The advent of the new test facility has largely been triggered by a group sponsored project on strain based assessment of pipeline girth welds. The specimen under test will be both strained in bending and pressurised simultaneously.
The idea is not necessarily to take it to destruction up to 1000 bar are being applied. The pipe will be bent considerably, in four point loading and strained beyond its yield point. There'll be an intentional crack within it so the potential exists for rapid fracture. Without a remote pit like there is a risk of damaging adjacent laboratory equipment.
TWI has an impressive installation. Measuring eight metres by three in plan, the 2.5m deep reinforced concrete bunker comprises a metre thick floor with 700mm thick walls. The multi plate flat roof is made from eight 25mm thick steel plates, each of which is individually removable.
Two heavy section reaction beams - extremely thick section Universal Columns - can be bolted down across the pit at the same level as the roof, to enable four point bend tests to be conducted beneath.
Specimens will be craned into the chamber using a pair of 3t capacity A-framed gantries. So provisionally the pit will be able to accept specimens up to 6t in weight. Both hydraulic and pneumatic tests will be possible in either static or dynamic loading regimes.
Above the ground the entire installation is housed within a large steel fabricated building, equipped with mains and communication services. These include video monitoring and recording kit dedicated to receiving digital signals from in-chamber cameras and test piece instrumentation.
Inside the pit two large diameter conduits have been installed at mid-height in the northerly wall to allow access for all instrumentation and communication services to be run between the specimen and the control centre.
The facility is very suitable for testing a sample from a pipeline containing in-service damage to assess its fitness for continued operation.
Now that it has an established controlled facility, rather than building a temporary structure for each new project, TWI is expecting a number of short notice projects related to internal pressure testing and external loading.
To learn more about TWI's new pressure test facility please contact us.
