For subsea applications, all parts of a pump have to be designed for the highest process security, reliability, and robustness. The pump seals have to withstand high absolute pressures and high temperatures. A newly developed mechanical seal can perform reliably at up to 1 000 bar a (15 000 psi a) and 180 °C (350 °F).
The exploration of subsea oil fields — those more than 3 000 m (9842 feet) below sea level — provides the oil and gas industry with a host of challenges. The mechanical sealing of subsea boosting pumps is not exempt from these challenges. For a new generation of subsea pumps, Sulzer and EagleBurgmann co-developed a mechanical seal that withstands the high absolute pressure and high temperatures (HP/HT) of subsea oil discoveries.
Sealing a hot process
The oil temperature of the subsea oil discoveries corresponds with the recovery depth and tectonic area of the oil field. It ranges from 70 °C to 180 °C (160 to 350 °F). The high temperature of the pumped media raises the temperature in the seal and can cause the pump barrier fluid to degrade or can cause deflection of the seal faces. In a joint project, the engineers of EagleBurgmann and Sulzer optimized a seal for HP/HT applications. Other industry sponsors backed the project as well. The goal was to develop an improved HP/HT solution and overcome the limitations of traditional mechanical seal design for subsea applications.
The following aspects were analyzed and enhanced:
- Pressurizing direction of the seal faces
- Secondary seal design
- Seal face material and mounting of the seal faces.
The new seal is a novel combination of an external pressurized seal, with a new secondary seal design, a cooling jacket, and a diamond coated seal face material. The new combination provides good results for high-pressure and high-temperature applications.