Case story: Boosting productivity and cutting costs – at 12,000 psi
An international oil and gas company planned to build a challenging offshore gas production platform in Southeast Asia. Their new design, however, called for an increase from 8,000 psi to up to 12,000 psi in the working pressure of the platform's hydraulic tubes. Unfortunately, standard tubing of austenitic grade UNS S08904 – known as 904L – was incapable of handling pressures above 8,000 psi.
The Sandvik solution
Sandvik's proposal was to utilize super-duplex SAF 2507® tube, which could increase productivity by withstanding pressures of up to 12,000 psi – a 50 percent improvement over the standard 904L. In addition, because it is a lighter material, the super-duplex tube is easier to install and requires less welding. This simplified installation process was attractive not only for the oil and gas customer but also for the contractor who built the installation. Another advantage of SAF 2507® is its robust design, which makes it more suitable for marine environments with ambient temperatures of 30–35°C (86–95°F) and more resistant to crevice corrosion, pitting and chloride stress corrosion cracking.
"In choosing this grade they were able to achieve their target design and ensure higher productivity," says a Sandvik representative who helped the customer to determine the financial advantages in choosing SAF 2507® over 904L.
Comparing installation costs
While it may be difficult to quantify the financial gains of an increase in pressure from 8,000 to 12,000 psi, we can calculate the substantial decrease in installation costs enabled by the much lighter, stronger SAF 2507®. In the example below, we compare the costs of installing 200 meters each of standard-sized 904L and SAF 2507® instrumentation tubing.
|Grade and size, mm||Tube cost (USD)||Cost for welding (USD)||Cost for fittings (USD)||Total cost (USD)|
6.35 x 1.65
6.35 x 1.24
In this example, when welding and fitting costs are included, 904L yields a total cost of USD 8,069, compared with USD 7,640 for SAF 2507® – a cost reduction of USD 429. The lighter material of SAF 2507® also makes it simpler to install, and fittings made from SAF 2507® are used instead of welding's, which significantly reduces the risk of leakages.
* The prices listed were valid at the time of the installation. All prices are subject to change.
If the end-user had instead chosen 904L and also wanted to achieve pressures of 12,000 psi, they could have selected a non-standard size tube with 2.11 mm thick walls. However, such a choice would have required a high number of welded joints, further increasing the chance of leakages. Its corrosion resistance would also be inferior to that of SAF 2507®.
In the end, the lighter super-duplex material of SAF 2507® significantly reduced delivery and warehousing costs compared to the much bulkier 904L. The ease of installation, combined with 50% higher working pressures, solved multiple challenges for the customer, who now intends to use Sandvik super-‐duplex steel under similar circumstances in the future.