Counterbore Planning

Client Requirements

In the welding of high specification pipelines, the internal fit is subject to stringent requirements. Misalignment must be controlled to avoid stress concentrations and to avoid root defects. Seamless line pipe can be subject to significant shape and wall thickness variations, while longitudinally, welded pipe is normally prone to ‘Out of Roundness’.

Counterboring can be a good method of matching the bores to improve fit-up and welding productivity, with the added benefit that reduced wall thickness variation can improve AUT logistics. But there can be difficulties in implementing a counterboring solution, where insufficient wall thickness is available, or where internal size/concentricity variations mean that there are large variations in the amount of material to be removed. Removing a large amount of material can also increase stress concentrations. Reactive changes to counterboring size can impact production logistics.

Services Provided

Using 2D laser profile measurements, OMS can simulate, analyse and optimise counterboring operations, in order to determine the best counterboring strategy ahead of time. This allows the customer to plan ahead, manage risk and control production costs and schedules using advance knowledge of the best counterboring parameters to get the job completed.

Results can be predicted, problem pipes identified, and production challenges can be foreseen and managed. Listings can be prepared identifying target counterboring parameters for pipes, together with margins available. Pipes with little margin available can be identified. This enables project managers to foresee and manage production issues in an optimal way.

Benefits

If pipes are known to have good geometry, counterboring may be quite straightforward. But if wall thickness margins are tight, or when pipe geometry is poor, risks and difficulties can emerge. Here, only by measuring pipes ahead of counterboring operations can the full benefits of counterboring be gained, while reducing risks and pitfalls.

OMS uses laser measurement tools to profile all pipe ends. These measured profiles are fed into a software optimisation process. 2D profiles enable a simulation engine to calculate the amount of material removed and the wall thickness remaining, under counterbore diameter setting. This allows the counterbore diameter to be optimised for the best possible result across all pipes. Where it is not possible to counterbore all pipes at a single diameter, the software automatically analyses ranges of counterbore diameters to optimise the fewest possible counterboring size groups, outputting a tally list of pipe identities and diameter groups.

Practical machining tolerances such as counterbore centering, diameter tolerance and wall thickness margins can be taken into account within the simulation, as the optimiser seeks the best way to utilise all pipes. HiLo limits control the step size between counterboring group sizes so as to avoid any sequencing logistics.

Problem pipes are automatically identified. All pipes are compared to specifications, and any out of specification pipes can be listed.

Project managers can use this advance knowledge to plan ahead, deciding a strategy based on full knowledge of the factors involved in the solution. Listings of pipes and counterbore sizes can be provided on site so that production staff can implement the solution.