Safe and Efficient Offshore Valve Replacement
As a natural result of use and the unavoidable deterioration of seal material over time, the repair or replacement of valves on offshore natural gas platforms is inevitable. Often, the need for repair or replacement is identified through planned inspection and testing. Sometimes, however, a valve failure is only discovered when a leak is indicated on platform sensors.
Various types of valves serving different purposes are installed on offshore platforms, including trap valves, shutdown valves, subsea isolation calves (SSIV), and topside piping, valves and instrumentation.
Regardless of the type of valve or its application, replacing it will involve complete removal of the old before installation of the new unit. Repairing in situ may only require taking it apart. Before this work can commence, the pressure and pipeline content (normally hydrocarbons) must be removed from the pipeline or section where the faulty valve is. This can be done by either decommissioning (bleeding down) the entire pipeline and then recommissioning (refilling and restoring pressure) after the work is completed, or by isolating the section where the valve will be repaired or replaced.
Depressurisation can be costly as valuable production is lost (pipeline inventory plus loss of production during the extended period of time required to depressurise the pipeline). Moreover, the removal of pipeline inventory can create significant environmental challenges, which further escalate the overall costs and complexities of the repair or replacement process.
An alternative to depressurisation of the entire pipeline is isolation of the section on which the valve repair or replacement is to be carried out. Localised pipeline isolation offers several advantages as both production downtime and loss of pipeline product are kept to a minimum, with associated environmental and economic benefits. A wide range of methodologies, both intrusive (such as hot tapping and plugging) and non-intrusive (inline plugs, use of inline valves), can be used to isolate pressurized pipeline sections. Both intrusive and non-intrusive methods are well accepted in the industry, with the choice of one over the other being largely governed by factors such as location and accessibility of the pipeline, operating pressures, pipeline inventory, etc.
This white paper outlines how non-intrusive double block and monitor plugging technology provides a double barrier isolation for gas export lines during valve replacement, satisfying regulatory requirements and operators’ concerns about safety, time, and cost.
Download this white paper to find out more.