Subsea Critical Equipment: Reducing Test Times with Nitrogen Gas Compressor Systems

For critical subsea applications, the highest performing equipment is needed to ensure maximum operational safety. Because the equipment must perform reliably in extreme environments, it undergoes rigorous testing to guarantee product integrity before installation.

The challenge facing manufacturers is production slowing down due to time-consuming testing and fill times. Nitrogen gas compression technologies could address these challenges by reducing wait times and optimizing equipment deployment.

The Important Role of Leak Testing

Subsea x-trees, a key component in offshore oil and gas fields, monitor and control subsea good production and flow. Subsea trees can also manage gas injected into a well when they are fixed to the wellhead of a completed well. A subsea x-tree’s typical operational life is 25 years, so it is imperative that it meet specific test criteria prior to being deployed, including:

Hydrostatic pressure testing (up to 30,000 psi)*
Flushing and contamination monitoring (to SAE AS4059 B to F)*
Nitrogen gas leak testing (up to 18,000 psi)

Before project deployment and completion, the x-tree undergoes one last nitrogen leak test. To accelerate this testing phase, high nitrogen flow rates are used to fill the large internal volume of the x-tree, quickly bringing it to the target test pressure. This critical step requires the use of a nitrogen compressor built for rapid filling, otherwise, manufacturers could experience unnecessary slowdowns.

Understanding the needs of the subsea market, Haskel designed a nitrogen gas compressor and booster system to meet the expedited testing requirement. Our rapid fill system has demonstrated a reduction in test time up to 40-50%.

Typical Pressurization Time by Volume

Optimizing Large Volume Fast Filling with Nitrogen Gas Compressors

While nitrogen gas compressor designs vary by manufacturer, all Haskel nitrogen gas compressor booster systems are designed for safe, cost-effective, and reliable rapid filling of large volume components in preparation for underwater leak testing. Our standard equipment design features include:

An electrically driven, 3 stage 5000 psi nitrogen compressor feeding into four Haskel AGD-152 boosters mounted in parallel.
Storage cylinders that mount onto a common skid or supplied separately with multi-bank units for a specific location near the test cell. Eliminates the need for costly bottled gases.
Compressor and boosters mounted on a base plate and housed in a noise-attenuated enclosure, minimizing distractions to work environments.
System controls that mount into the unit or on a remote console. Controls include automatic stop/start, relief devices, pressure isolation, vent valves, high/low gas inlet shut down, high temperature shut down, low oil pressure shut down, hours run meter, and emergency stop.
Source gas from an on-site nitrogen generator or liquid “boil off” system that uses low-pressure nitrogen (typically 4- 10 bar) to boost the gas to any target pressure up to 18,000 psi (1241 Bar). Produces a nitrogen output of 90 scfm up to 12,000 psi or 70 scfm at 15,000 psi.
Safety relief devices that are standard on all gas booster systems for maximum operational safety.
PED category 1V compliance.

In addition to the standard product features, Haskel supplies hydrostatic test and flushing systems to work in conjunction with the manufacturer’s specific nitrogen test equipment systems.

With its rapid fill capabilities, the Haskel nitrogen gas compressor optimizes large volume component testing by reducing fill time by approximately 40%.

A Custom Use Case for Nitrogen Compression

While the Haskel nitrogen gas compressor system is standardized, that design is merely a starting point. We understand that each customer has specific requirements and modifications that can help optimize performance in a specific application.

Operator safety takes top priority, especially as the demand for higher pressure testing (above 12,000 ps) increases. Recent customizations include additional features to guarantee safe operations. For example, Haskel designed an “operator safe” control panel allowing the unit to be controlled remotely by relying on solenoid-controlled valves to operate the compressor and boosters. This added feature helps minimize the operator’s exposure to high-pressure gas by separating the operator from the test bay.

Built specially for critical subsea applications, Haskel’s nitrogen compression system increases efficiency while maximizing operational safety.