When a compressor is operating efficiently, the seals are often overlooked as just another component. But when the seals repeatedly fail, causing unplanned downtime, a solution becomes imperative. Such was the case recently at Statoil’s K-Lab facility in Kaarsto, Norway.

K-Lab is the Norwegian state-owned oil and gas company’s test laboratory where auxiliary equipment for Statoil’s many production facilities is validated. Using an Ingersoll-Rand MGG-CBF-124 compressor, with original triple gas seals, K-Lab tests equipment such as gas metering systems, coolers and gas separators.

In early 2002, K-Lab indicated to Dresser-Rand that the triple gas seals suffered repeated hang-up problems, causing repeated delays. Statoil’s initial request was for D-R to contact the original manufacturer to solve the problem by mounting tandem gas seals to replace the triple seals. But after reviewing this option, D-R advised Statoil that this would not solve the hang-up problem on a compressor, which is repeatedly stopped and restarted for test sequences, such as is required at K-Lab.

Dresser-Rand is Statoil’s preferred supplier on compression and power generation equipment, through a comprehensive frame contract originally signed in 1996 and renewed in 2001. Consequently, solving the K-Lab dilemma was more than just an isolated challenge, but rather part of a long-term program to provide Statoil with the most reliable turbomachinery, and the lowest equipment life cycle costs.

The recommended solution was Dresser-Rand’s dry gas seals.

D-R presented to Statoil its development program for high pressure dry gas seals, and the very successful results obtained at a dynamic pressure of 200 Barg on a gas seal of larger diameter than the one required by the K-Lab compressor. This gas seal could solve the hang-up problem, while operating at the140 Barg dynamic pressure required by K-Lab.

Dresser-Rand dry gas seals were first introduced in 1995 to provide a less expensive gas seal offering superior reliability and performance. Developed by engineers at D-R facilities in Le Havre, France, the innovative seal features a patented groove design on the rotating seal face to maximize seal operation at a variety of operating conditions. A unique "swift tail" pattern of short grooves in combination with longer grooves provides optimum gas film stiffness at all operating speeds.

The risk of hang-up is minimized by a proprietary pusher ring design. The O-ring sealing on the housing is located in the sleeve. This design provides increased closing forces and prevents the seal from sticking in one position. For high pressures, this O-ring is replaced with a polymer ring.

Currently, more than one and a half million operating hours have been accumulated on Dresser-Rand compressors with D-R dry gas seals worldwide. A significant number of older units have also been retrofitted with the advanced seals, replacing the original oil film seals.

"Thanks to its "L" sleeve, the D-R dry gas seal has proved its ability to prevent hang-up in the toughest operating conditions everywhere it has been installed," said Emmanuel Landrin, a project engineer at Dresser-Rand in Le Havre. "Its effectiveness at 140 Barg makes it a good solution for Statoil, as well as for other equipment operators."