Code of practice for the use of high pressure jetting equipment by divers

Summary

High-pressure water jet systems are water delivery systems which have nozzles or other openings whose function is to increase the velocity of water or other liquids. Solid particles may also be introduced, although the exit in all cases is in a free stream. High pressure (HP) water jetting is utilised in the diving industry for a variety of cleaning tasks and, in some instances, as a cutting tool.

Typical uses of HP water jetting equipment include:

• marine growth removal
• paint coat removal
• supporting seabed material removal by breaking down clays and stiff soils for air lifting
• breaking up consolidations within pipework
• breaking up of drill mud and grout spillages on the seabed.

HP water jetting equipment may also be used as a cutting tool. In certain applications it can cut concrete and steel either with or without the addition of an abrasive material such as grit or copper slag.

Grit entrainment in HP water jetting is commonly used to support weld inspection through the removal of the obscuring paint coatings.

HP water jetting equipment can be used from pressures of a few hundred psi up to many thousands of psi, subject to the safe working pressure (SWP) of the system and the actual requirement for the task.

For the purpose of marine growth removal in the offshore diving industry, HP water jet systems typically have a SWP of 345-690 bar (5,000-10,000 psi). Sometimes pressures as high as 1,000 bar (14,500 psi) may be used.

For the purpose of concrete or steel cutting, with or without grit entrainment, HP water jet systems typically have a SWP of 690-1,700 bar (10,000-25,000 psi).

Ultra-high-pressure (UHP) water jets operate above 1,700 bar pressure. They are being increasingly used by the offshore industry for the removal of surface coatings, cleaning and cutting.

Contents

• Scope
• Definitions
• Introduction
• Equipment
• Protection of Personnel
• Operational Procedures
• Avoidance of Accidents During Underwater HP and UHP Water Jetting Operations
• References
• Appendix 1 – Diving Medical Advisory Committee Recommendation – Accidents with High Pressure Water Jets (DMAC 03 – January 1981)
• Appendix 2 – Advice to Attending Medic or Doctor
• Appendix 3 – Useful Contacts
• Appendix 4 – Extract from IMCA Safety Flash 05/11 – Diver Safety – High Pressure Water Jetting Operations
• Appendix 5 – Extract from IMCA Safety Flash 06/07 – Diver Injury Using Cavitation Blaster

Version history

May 2024, Rev. 1.2 – Page 2, references and bookmarking updated; no change to content

October 2021, Rev. 1.1 – Minor additions to guidance

July 2013, Rev. 1 – Updated to incorporate ultra high pressure jetting equipment and two safety flashes

August 1998 – Initial publication