Mechanical connectors are present in many different areas of subsea oilfield equipment ranging from drilling BOP stacks through Christmas trees and flowlines to the latest concepts in modular completions.

They perform a very important interface and absolute integrity is required to prevent pollution. This is particularly so with their extensive use in modular template completions when many more such connectors are used than would be the case with more traditional methods.


In the case where diver involvement is acceptable, a very cost-effective and reliable type of connector is that of the type shown in Fig. 1. This uses individual tie-down screws which force (Fig. 1 is available in full paper)

wedge-shaped segments radially inwards against the tapered shoulder of the wellhead housing. Its mam advantages are low initial cost and reliability with no hydraulic components to denature after prolonged installation. However, it is labour intensive and obviously not suited to use in deep water and requlres longer to make up tight than hydrauhcally actuated types.


A type of connector using hydraulically actuated collet fingers is shown in Fig. 2. In this design, a number of hydraulic cylinders dnve a tapered sleeve which acts against the collet fingers, dnving them onto the matmg hubs.

Ths design is very versatile and is equally suited for use as a dnlling connector or a Christmas tree connector. In the unlocked position the clamp fingers open out at the bottom to provide a funnel whch Improves guidance when used as a wellhead connector. This feature is particularly useful during guidelineless drilling.

When greater imtial alignment is requlred as in the case of a tree connector, where internal stab mandrels are used, a lower skirt nng is employed to provide initial lateral clearance to prevent damage.

As the connector mechamsm relies on sliding tapered sleeves to denve its mechanical advantage, the effects of fnction have an unportant beanng on overall efficiency.

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