Section 12 Installation

12.1.1 Specification covering the installation procedures are to be submitted for approval.

12.2.1 Specifications, plans and data are to comply with Ch 1, 5.3 Plans and data to be submitted 5.3.1 and Ch 1, 5.3 Plans and data to be submitted 5.3.2. Additionally, for installation, data is to be submitted specifying sea bed preparation, extent and means of execution and survey prior to pipe-laying.

12.2.2 The construction specification is to specify the tolerance within which the pipeline is to be laid. A tolerance of 100 metres from the nominal centre line of route is anticipated, however wider tolerance may be permitted if sufficient reason is demonstrated. In areas congested by existing pipelines or cables tighter tolerances may be mandatory. A tolerance greater than the surveyed width of route will not be permitted. The closest approach of a pipeline to an obstruction or potential hazard to the pipeline, is to be not less than 500 metres.

12.3.1 The equipment used for operations are to be agreed by LR for the processes specified.

12.3.2 Individual pipes, equipment, fittings and sub-assemblies are to be handled and stored with care, especially components with anodes or heavy anode bracelets. No components are to be stored in a manner to cause damage or deformation.

12.3.3 All components and sub-assemblies are to be inspected before installation and be approved to the satisfaction of the Surveyor.

12.3.4 The laying, tie-in, etc. of the pipeline and its associated fittings and equipment is to be carried out in accordance with approved procedures which are to prevent any damage or unscheduled loading or stressing of pipe or coating.

12.3.5 The installation of the riser is not to introduce any unscheduled loading and the transfer of loading to riser supports is to be shown to be in accordance with design specifications.

12.3.6 All monitoring systems are to be operated and calibrated to the Surveyors satisfaction during all laying and installation operations.

12.4.1 The material used for coating of field joints is to be compatible with the pipe coating. Where the field joint coating is to be identical to the pipe coating, then a similar coating application procedure should be used.

12.4.2 A procedure for field joint coatings is to be prepared indicating the surface preparation required, conditions for coating application and criteria for acceptance or rejection. A procedure for the repair of damage to coatings under field conditions, again with acceptance or rejection criteria, should be produced.

12.4.3 Where a metallic sheet cover is used to protect the field joint it should be such as to provide a smooth outer surface. Consideration is to be given to taping over the cover to prevent corners being raised.

12.5.1 Pipelines can be trenched into the sea bed primarily:

• to increase the stability of the pipeline;
• to protect the pipeline from damage from impact;
• to minimize the obstruction to trawling activities by the pipeline.

12.5.2 It is the normal requirement that pipelines are to be trenched and buried. However, for large diameter pipelines, trenching may not be necessary if:

• the pipeline is at least 16 inches in diameter;
• it can be demonstrated that the pipeline has sufficient stability.

12.5.3 It will not be necessary to trench any part of a pipeline which is within an installation safety zone provided it can be shown that the pipeline has sufficient stability.

12.6.1 When assessing a span to decide its significance, both static and dynamic stresses, together with operating stresses, are to be considered. In particular fatigue effects are to be investigated.

12.6.2 Consideration should be given to reducing the length of a span to well below the critical length for vortex shedding excitation by providing intermediate supports to the pipeline span by means of grout bags, sand bags, mattresses or gravel dumping.

12.7.1 As soon as is practicable following construction of a pipeline, a survey of the entire pipeline is to be carried out. The purpose of this survey Is to:

1. determine the 'as-buiit' co-ordinates of the pipeline;

2. ensure that the pipeline has been constructed within the permitted corridor;

3. ascertain whether the pipeline has been satisfactorily trenched or buried where applicable;

4. ascertain whether any part of the pipeline is unsupported;

5. examine the condition of the pipeline and in particular the weight coating, following construction;

6. ensure that any debris has been removed.

12.8.1 In general, pipeline or cable crossings are to be avoided. Where a pipeline or cable crossing is essential, the operator of the pipeline or cable to be crossed is to be consulted and the method, location and timing of the crossing is to be agreed by both operators. Possible interaction of the cathodic protection system of two pipelines is to be considered.

12.8.2 The crossing is to be constructed in such a manner that a physical separation between the two pipelines exists at all times.

12.8.3 The pipeline crossing is to be subject to full examination during the post-construction survey and during each subsequent survey of the pipeline.