Marine drilling platforms are used to support offshore oil and gas production equipment and are equipped with riser tensioner cylinders that are supported by air-filled, high-pressure vessels that pose a combustion hazard. Replacing the air with inert nitrogen improves platform safety.
Riser tensioner cylinders extend and retract to compensate for the rise and fall of the platform caused by waves and wind. The cylinders keep constant tension on the risers. The tensioners prevent damage to the riser due to platform movement.
Air is a combustion hazard
The tensioner cylinders are typically air over oil hydraulic cylinders. High-pressure air is used as a dampener over the hydraulic oil. The cylinders are supported by up to 25 air pressure vessel banks holding 70.6 ft3 (2000 liters) in each vessel and up to 4350 psig (300 barg) per tensioner. A high-pressure compressor maintains the pressure in the vessels to account for leakage. The high-pressure vessels are filled with air which can support combustion. If these vessels were to rupture during a fire, they would release over 500,000 cubic feet of air to fuel the flames. Replacing the air in these vessels with inert nitrogen significantly improves platform safety as nitrogen does not support combustion.
Nitrogen as a safe alternative
An on-site nitrogen generator is a smart choice for providing inert, high-pressure nitrogen as an alternative for air. A Parker nitrogen generator safely separates oxygen and nitrogen from a compressed air supply. The generator is delivered as a complete skid that includes nitrogen membranes and a high-pressure booster to deliver 4500 psig of 95% pure nitrogen. Nitrogen at this purity will not support combustion, and will, in fact, suppress a fire. Once located on the platform, a Parker nitrogen generator is simple to install. Supply the system with electricity, and connect the onboard compressed air systems to the inlet of the generator, and the outlet to a set of storage vessels. A bank of storage vessels is recommended to act as a buffer for flow fluctuations.
Read this marketing application for additional information on using nitrogen as a replacement for air for riser tensioners.
This post was contributed by Gas Generation Technology Blog Team Members, Parker Hannifin.