Metal-to-Metal Sealing for High Pressure Subsea Production System(SPS) Bolted Flange Connector

Metal to metal seal is one type of static seal used in high pressure Subsea Production
System (SPS) Bolted Flange connector. Static sealing elements, as their classification implies,
remain stationary relative to the surfaces they are sealing against. The subsea system can be
located many miles away in deeper water and tied back to existing host facilities in shallow
water. Due to the deeper water, higher challenges and problems need to be considered such as
high reservoir pressures, low sea-bed temperatures, large variations in water depth range, flow
assurance challenges, geo-hazard issue like gas hydrates, rough metocean condition,
remoteness and hydrostatic pressure. The first objective is to analyze how leakages occur in
SPS Bolted Flange connector. Bolt, flange and seal are the three main components in Bolted
Flange connector that can contribute to the excessive leakage. Once excessive leakage
happens in the deepwater, there will be loss in productivity, marine pollution and other
important effects that need to be highly considered. From the literature reviews, main factors
due to the seal that can cause leakage are inadequate overall flatness, inadequate smoothness
and seal ring breakage can be concluded. The second objective is to propose and demonstrate
the applicability of metal to metal sealing of SPS Bolted Flange connector for deepwater
application. Temperature, pressure, industry design codes, life expectancy, leakage integrity
and maintenance and accessibility are the key elements in selection of metal seal for SPS
Bolted Flange connector. For this project, metal O-Ring has been chosen as the design for
metal seal inside SPS Bolted Flange connector because its characteristics meet the deepwater
and subsea requirements. The comparison has been made between Stainless Steel AISI 321,
Alloy 600 and Alloy X750 by calculating the pressure exerted on the metal seal. All these
materials satisfy subsea requirement but Stainless Steel AISI 321 has been chosen for metal ORing
inside Bolted Flange connector due to cost consideration.