Recent subsea developments In the West of Shetland have highlighted that conventional installation practices can give rise to initially unforeseen problems at a later date One of these problems In particular IS the practice of connecting a pipeline end manifold (PLEM) to a rigid line on the lay vessel and then laying the pipe and PLEM to the seabed Having to access this site later and perform work on the PLEM can be difficult as the PLEM to pipeline interface is a standard flange The practice of recovering the PLEM and flowline to the surface can be a high risk operation and may not be possible due to other lines crossing over the line to be lifted
As a result of this problem a new concept for a remote standard flange separation and connection has been developed and is illustrated in this paper The tool has the versatility to be used on any standard flange system and can therefore be utilized on joints previously Installed by divers The basic philosophy of the system includes full ROV based operations, standardisation and flexibility by using the same Interfaces, optimisation of both CAPEX and OPEX by the minimisation of permanently Installed subsea hardware
The tooling solution designed for the connection and disconnection of a standard API or ANSI flange was borne from a specific project to re-instate pipeline end manifolds to rigid flowlines The basic characteristics of the system is summarised by the data below (Available in full paper)
The remote flange connection system is based on a set of tools which can all be operated by a standard work class ROV The main tools in the suite are
An alignment skid which can move the PLEM in any direction to allow the two flange faces to be brought together
A Laser Alignment System to allow the final alignment of the two flanges
A Nut Magazine to captivate the nuts of each flange
A Bolt Magazine to captivate the studs of each flange and provide a torque interface
A Torque Tool to perform the controlled tightening of all studbolts
An ROV interface skid to allow all tools to be operated including the external pressure testing of each flange joint after torqueing
Water Lift Bags to provide support along the free span length of flowline and allow some pipe orientation to be performed
The Alignment Skid comprises a series of frames which can manipulate the PLEM to its correct position for connection to the flowline (see Figure 1) A pipe stand is attached to the front of the lowest frame into which the rigid flowline is placed The pipe stand contains a neoprene lined cradle which can elevate the pipe vertically a total of 450 mm and allows the pipe to rotate up to ± 7° about the in-line axis The cradle is free to rotate through this angle allowing the flowline to find its natural position The cradle of the flowline support is angled to hold the flowline at an approximate angle of +5° from the seabed
