The types of solutions where grout is required to be injected, and a remotely operated vehicles (ROV) is used as the method of placing, and injecting the hardening medium are many and varied.
- Pipeline supports.
- Pre-lay pipe sleepers.
- Central crossing supports for pipelines or cables.
- Stabilisation to pipelines or cables.
- Pipeline protection.
- Under base grouting; valve box protection.
- Structural grouting to offshore platforms or piles.
- Template grouting.
- Clamp or brace grouting.
An understanding of ROV operation of what can and cannot be done by the ROV is paramount in preparing the solution to be installed and injected using the ROV as the method of installation.
The aim is to keep the operations simple with use of one manipulator, which is a twist or push/pull operation.
Metholdolog of design
Visual ability to evaluate all attachments and or aspects of the solution in its final position pre/post injection must be one of the main considerations when considering the methodology of design for ROV utilisation.
In other words we design for the work to be carried out by ROV; we do not adapt an existing design or solution for ROV installation. ROV grouted solutions have been used worldwide to 1000 metre water depth for structural grouting to offshore structures and pipelines
How to make the installation method user friendly for ROV installation. Example: Free span correction. The sketches' below are an illustration of the depth of thought that has to be gone into to achieve a total package.
You will note the additional aids to the structure to, retain, ensure shape is maintained and the item is easily handled to ensure the ROV can manoeuvre around for ease of placing. Note the means of cutting the grout flow line is easyand in a location that is very ROV friendly.
The technique to permit grouting of piles by ROV was initially developed and presented to industry during the mid 80s; today this is a documented procedure that industry accepts as a normal procedure.
The ROV has to interface with the section of hose to connect to the location or connection where the grout hose has to be inserted or connected.
It is therefore critical for the grouting contractor to provide the correct information at fabrication stage of the structure, and to consider how the ROV is going to perform its function. Access and viability are the main criteria for the connections to be made successfully.
Steel wore down lines
While self-supporting hoses may be produced specifically for this type of work, to date they have generally not been used because of cost and limited application makes them an expensive asset. Hence steel wire or polypropylene down lines have been used to support, deploy and recover the grout hose to/from the deck of the execution vessel.
A slight variance at one TLP project saw the grout hose ('tail') deployed at the end of a drill string that was assembled over the side of the vessel of execution. A drill collar was used at the bottom to minimise movement of the rigid 'string'.
While the work vessel and support services are a major influences on the type of hose deployment scheme used, because of the deck space required for winches or other methods of hose storage and deployment.
The method of mdeployment becomes more critical for water depths of 1500 metre and more. It is critical at any water depth to consider the ability of the ROV to interface with grout hose tail.
The ROV interface system of grouting by attaching a hose to a subsea connection or receiver at any depth. The technique has been very effective and has been widely used on many projects over the past 25 years.
Applications include pile grouting, grouting of templates, and jackets, under base grouting to gravity structures, together with maintenance and repair of clamps and braces to structures.
ULO commenced providing the service of utilising industrial fabrics to create a shape or form to contain a cementitious grout in 1964 for the civil construction industry.
With the major discovery and development of oil in the North Sea in the late 1960s. The use of fabric formwork was seen as a major development for utilisation by the offshore oil industry, to support subsea pipelines.
ULO formed a joint venture and established a base in Aberdeen to provide a service in this area, and the name 'COLOS' became synonymous with the oil industry boom in the North Sea.
ULO's presence in the Middle East commenced in 1978 and expanded into India in 1981. The Far East has been supported since 1975.
With rising prices in Europe it was decided to open the manufacturing base in the Middle East in 1988.
From the Middle East all products are manufactured and sent to the various locations world-wide.
Further development of using new ideas to achieve the same solutions are being developed at all times, as well as ROV installed solutions.
The ULO products range gives an insight into some of the solutions. As 90 per cent of the products manufactured are individually designed. The range is a guide to assist in considering the final solution.
Over the past 12 months, ULO has been concentrating on raising the standard of supporting documentation and case studies. Equally it has been trying to concentrate on improving on site execution times. This is difficult as the principles and safety aspects offshore cannot be short cut. Equally the chemical action of mixing cementitious grouts has not and cannot be changed.
ULO has already been at the cutting edge of ROV and Diverless Placing Systems and sees more development in this area in the future.
ULO is a privately owned company with over 35 years experience in providing products, solutions and services to support and protect subsea pipelines, cables and structures world-wide.
ULO over the past 35 years have developed many specialised and unique solutions. ULO is continuously expanding the horizons of developing systems for the ever changing offshore construction industry globally.
ULO enjoys a unique relationship with consultants, engineers, clients and contractors to provide the correct technology to solve the specific solutions required.
Enter X at www.engineerlive.com/iog
R S Miles and H W Lee, ULO Systems LLC are with ULO Systems LLC, Sharjah, United Arab Emirates. www.ulosystems.com