February 29

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How Pipe-Laying Vessels Use Tensioner Pads

The United States produces 9 million barrels of oil every day.

Offshore drilling accounts for around 30 percent of U.S. oil reserves.

All of this extraction is made possible by an intricate network of subsea pipeline, which wouldn’t be possible without the vessels that lay these pipelines as deep as 9,100 feet below sea level.

J-Lay cranes are capable of withstanding the incredible water pressure incurred at these depths, allowing for the placement of piping very deep in the ocean. And custom rubber products crafted to the specifications of the vessel allow these difficult constructions to take place.

These pipe networks depend on custom-molded rubber products, such as tensioner pads. When you're working with this kind of pressure, custom rubber rollers are essential for the smooth, safe movement of pipes during welding. They allow pipes to be moved without incurring tears, breaks or other damage that leads to leakages.

S-Lay Process

With an S-Lay crane, the other type of pipe-laying vessel, rubber tensioner pads allow the crane to maintain a delicate balance of tension and forward thrust that preserves the integrity of the pipes in a subsea construction, which requires incredible precision.

Using dynamic positioning — which incorporates computer-driven motion sensors and gyrocompasses — S-Lays place great lengths of pipes while exerting enormous amounts of pressure on the pipes to maintain their positioning. In order to preserve the piping, tensioner pads help stop the crane from causing severe damage, counterbalancing the crane’s force.

An article on offshore pipe-laying published by the Laboratory of Computational Methods and Offshore Systems (LAMSCO), describes the process for a S-Lay well:

"In the S-Lay method, as the laying barge moves forward, the pipe is eased off the stern, curving downward through the water until it reaches the touchdown point. After touchdown, as more pipe is played out, it assumes the ‘S’ shaped curve. To reduce bending stress in the pipe, a stinger is used to support the pipe as it leaves the barge. To avoid buckling of the pipe, a tensioner must be used to provide appropriate tensile load to the pipeline. This method is used for pipeline installations in a range of water depths from shallow to deep…The tension is applied to the pipe by tensioners on the barge which are usually arrays of rubber wheels or belts which surround the pipe and apply an axial force to the pipe through the friction generated between the tensioner and the pipe external coating.”

The LAMSCO report reinforces the importance of high quality tensioner pads. They help prevent breaks and unevenness, which in turn helps prevent disastrous results — both financially and environmentally. Cheap pads or ones that are substandard can cause irreparable buckling, costing operations money, time, and countless headaches.

The supreme importance of tensioner pads is part of the reason that they are frequently custom molded. The sizes and shapes of vessels and pipes vary, as do the geographical and meteorological environments that the tensioner pads must excel in. They must do this while maintaining their strength and flexibility, as well as their ability to resist wear in harsh subsea conditions.

Because these pads can be overlooked and must be customized, it’s important to work with a shop like Mark Tool, that can not only create custom tensioner pads, but produces a surplus so replacement parts are always available.

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