Efficient retrieval and seafastening of concrete mattresses

Nils Olav Åkre Hauge, Ole Kristian Lund og Mathias Meek

Background

• 40 000 concrete mattresses in the North Sea• Protect pipelines and infrastructure

• Falling objects• Trawler/anchor• Erosion

• Termination plan 5-2 years before the lie expires

The scope of this project

• Safe and cost-effective method• Without use of divers• Without using mattresses loops over water• ROV friendly• No damage to personnel or equipment

• Seafastening on board Edda Freya• Make the most out of the deck space

Existing methods of retrieval and seafastening

• Retrieval• Reverse installation• «IMF»• Speed Loader• Wet Storage/Recovery Basket• Subsea grab• Subsea Container

• Seafastening• Base frame and a Speed Loader• To Speed Loaders• Twistlock

Own methods of retrieval and seafastening

• Retrieval• Further development of the «IMF»• Further development of «Wet Storage/Recovery

Basket»• Roller Method

• Seafastening• Power screw• Bolts

The evaluation process

• Efficiency• Safety• Cost• Manageable• Seafastening• Structure

• Further development of the «IMF», combined with Twistlock

Relevant regulations

• The law of petroleum (PTIL)

• DNVGL-ST-E273

• NS-EN 1993 Eurocode 3

• NORSOK R-002

• Norwegian Maritime Code

• DNV – Rules of Classification of Ships

• Traffic rules

Selected method

• Lifting frame• «VI-SO Clamp»

• Container• «Twistlock»

Rigging

• Hand Calculations• Shackle• Pad eye• Weld• ROV hooks• Straps

• Ansys• Pad eye• VI-SO Clamp

Structure Calculations

• Hand Calculations• Buckling Calculation

• SAP2000• Lifting Frame• Container

Seafastening

• Mathcad• Twistlock

Conclusion/Suggestions for further work

• Time- and cost effective method• Expensive investment cost• Satisfying all requirements provided by DeepOcean• Develop a new «VI-SO Clamp» with higher load capacity

Mass (kg)MaterialRevDescriptionQtyItem

1800,3Steel, Mild 350x250x16 L=6468211253,1Steel, Mild 350x250x16 L=300032

43,7Steel, S3551PL 16 x 350 x 2504314,1Steel, S3551PL 22 x 125 x 8012488,3 1Padeye4532,2 1VISO clamp Tandemloc46

2,9Steel, Mild AS 2465 - 3/4 x 2 UNC16714,6Steel, S3551PL 20 x 155 x 15548

Drawing no.:

Client:

Project title:

Drawing title:

Sheet:

This document is the property of DeepOcean and shall not be reproduced, copied, disclosed or used in any manner without written permission of DeepOcean.

Lifting Frame

HVL

Bachelor

NO.ENG.DR.18.005 Lifting Frame

USE - Issued for USE

Approved by:Checked by:Drawn by:

Rev.:

ADate:

27.04.201826.04.201825.04.2018

Anders VikebøØrjan GloppenNils Olav Hauge

Projection:

Status:

1 of 7

Gen. Tol. -NS-ISO 2768 U.S.O.: m

Gen. Welding -Tol. NS-EN ISO 13920 U.S.O.: B

Gen. Machined surface -roughness U.S.O.: 6,3

1

713

3500

6500

Total weight: 3249,2 kg

100 % MPI100 % UT1 Coat Primer 1 Coat Paint No SystemRAL1003To be punctured

5

6

4

2

3

7 (TYP) (TYP)

3125489 1000

(TYP)(TYP)

60°

71,0

3

71,03

8

4