Seal Rings

Destec seal rings are used both as original equipment in client products and as a direct replacement for existing joints that have proved troublesome. They are built on Destec's own experience in high pressure, high temperature metal-to-metal static sealing, using a modified cone ring design that gives strong leak tightness under severe pressure, temperature, thermal cycling and shock. When converting an old joint to a Destec seal, Destec's engineers carry out the design work to established codes and standards, and the practical site work is handled by Destec's own on-site machining service using portable machines, so the modification and rebuild can happen in place. Sizes currently in service range from 10mm up to 2150mm. The higher the pressure, the more effective the seal becomes, since internal pressure intensifies the sealing action, and the all-metal design can be used at high temperatures, limited only by the material selected: options run from carbon and alloy steels through to Inconel, with a range of coatings for lubrication.

The sealing system holds up under severe pressure, temperature and vacuum conditions, and is suitable for nuclear applications. Its added flexibility also copes well with cold quench conditions and thermal cycling, which is where conventional compressible joints tend to leak. Because the design is compact and lighter than conventional flange arrangements, fluid seal areas and joint loads come in lower too. On dismantling, the all-metal seal ring reverts to its original form and is ready for reuse, and every seal ring of a given size is interchangeable with no pre-fitting required. Seal rings up to 850mm diameter are supplied as a double cone ring, with standard sizes stepped in 5mm increments to closely match the bore, or a purpose-designed seal ring where an exact match is needed. Rings over 200mm diameter can include a central rib, which keeps seating stress high while keeping the ring's overall width down. To speed up assembly, seal rings can be retained in one of the flanges, which helps in difficult working conditions such as connecting flexible hoses on a work barge, and retainers can also be fitted for ROV removal using a collet that grips the bore. Destec seal rings can also be designed with orifice plates, chokes or blinds built in, and where corrosion or erosion is a concern, sleeves can be fitted in the bore for protection, including for use with lined pipe. A heavy duty range is available for deep sea applications, designed to handle high external pressure and high flange shear loads without needing spigots. PTFE coatings on the seal rings are colour coded by base material for easy identification: violet blue for low alloy or carbon steel, olive grey for martensitic steel, ruby red for austenitic steel, grass green for nickel chromium (X750, 718, 725), black for duplex and super duplex, and light orange for nickel chromium 625 plus.