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UWG Group deploys digital levelling gauge

Posted: 13 August 2003

The DLG measures pitch and roll using high precision inclinometers, calculates resultant tilt and azimuth (relative to the principle axis of the instrument) and then displays the findings on an easily readable LED display. The instrument is housed in a suitable casing for subsea deployment and is mounted on an adjustable table to facilitate calibration.

The unit is operated via a light sensitive switch, and after a suitable period the display is terminated and the unit reverts to sleep mode to conserve battery power and prolong its operational life.

In its standard form, the DLG can provide in excess of 2,000 sets of readings and can remain in sleep mode for approximately three years, making the design appropriate for both temporary and permanent installations.

The DLG was incorporated into the installation program of the Nini and Cecilie templates primarily for the economic advantages it offers over other potential options.

The client wanted to monitor the pitch & roll of the templates during and after the pile driving operations.

Traditionally, a ‘bulls eye’ instrument could have been used for this application, however the accuracy of such an instrument can be relatively poor and the readability is often subject to interpretation when observed via an ROV.

The potential alternative of reinstalling a gyro during pile driving breaks was deemed to be uneconomic due to the high cost of the instrument and the specialist survey technician required. In addition, such a route would have delayed the installation process considerably.

The compactness, acute accuracy, simplicity and re-usability of the DLG design proved ideal for these template installations.

During the pre-mobilisation calibration, the DLG was calibrated to the subsea gyro module. This allowed the client to obtain a calibrated pitch and roll while allowing the gyroscope to be demobilised prior to commencement of the pile driving operations.

The vibrations from the pile driving operations tested the DLG to far beyond the operational limits of other electronic devices, but the client was able to obtain the critical data necessary to confirm successful conclusion to operations.

The ROV pilots noted that the visibility of the digital readout was far superior to other devices and they were able to fire up and read the DLG from a greater distance (3m approx.) than any other devices with which they had previously worked. This capability permits the DLG to be placed along the main axis of any subsea structure without concerns regarding the ROV’s ability to activate and read the gauge.

Gary Maddern, UWG’s Project Engineer and Template Installation Supervisor says: “This project perfectly demonstrated how UWG’s DLG has the flexibility and durability to be used on most subsea installations. The accuracy is second to none and highly visible display will ensure that we will be seeing more of the DLG in the near future”.

UWG Group provides: Deep Water Riser Engineering - Equipment Sales and Rental - Well Systems Engineering - Well Construction, Intervention and Decommissioning.

Proven innovators in many disciplines, UWG Group member companies include UWG Ltd, Team Energy Resources Ltd, Claxton Engineering Ltd, 2H Offshore and WellCut Inc.

The Group employs approximately 160 staff worldwide.

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Posted by Richard Price, Editor

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