GB1517955A - Method of applying a tension to a pipeline during construction and daying thereof - Google Patents

Abstract

1517955 Laying pipelines under water H N EAGLETON J D LORMAND and J S HERRING 4 Aug 1976 [24 June 1975] 26787/75 Heading F2P To prevent damage to e.g. a coated pipeline 16a during laying under water 54 from a lay barge 50, especially in the region of the bend 66 near the bottom surface 52, tension greater than a predetermined minimum is induced in at least the bend portion 66 by internal pressurization, e.g. using air. Two pigs, of which one 12b is shown diagrammatically, are sealable within the pipeline 16a and maintain the air pressure in the bend portion 66 and to the rear of it, i.e. in the already-laid portion 62, and are progressively moved forwards as more pipe is laid. Air may be supplied from a drilling platform 58 or another barge, e.g. via a valve 60 and riser 56 connected to the rear end of the pipeline 16a; alternatively the rear end of the pipeline 16a may be closed and pressure supplied from the front end of the pipeline 16a, through the pigs, or from a source within one of the pigs. In use the rear pig is sealed and the forwards one moved forwards progressively as more pipe is laid, with or without pressurization of the space between the pigs, and the rear one moved forwards as necessary to maintain pressure in the desired region. The pigs may be connected or separate and may be directly or remotely controlled; they may also be suitably valved for different applications.