The standard gasketed ANSI flange has been used successfully by the offshore oil and gas industry for decades. But while the operational demands of the oil and gas industry upstream and downstream have changed over this time, the design of the ANSI flange has not. Its weight and size, especially at high pressures, means it is not well suited to offshore application where space is typically confined and congested, and weight often equates to added cost.

Moreover, it is susceptible to leakage, so does not conform readily to today’s industry-wide drive to reduce leaks and emissions, for improved health and safety and environmentally-sound operation, as well as optimised performance and production.

The design of the conventional gasketed flange is at the root of its problems. Relying on substantial bolt force to hold the two flange faces together and compress a gasket to create the seal means the higher pressures often characteristic of offshore applications typically demand sizeable bolts and flange sections, adding up to a cumbersome connection.

On top of this the conventional flange is essentially an inefficient seal, using 50 per cent of the bolt load to compress the gasket, leaving only 50 per cent to hold the pressure. And because this is a dynamic connection, factors such as thermal expansion and fluctuating cyclical loads can cause movement between flange faces, which impacts on the gasket, compromising seal integrity and resulting in leakage.

Increasingly recognised by the global oil and gas industry and now being introduced in Australia by Vector International, technologies such as the Techlok clamp connector and SPO Compact Flange offer huge benefits in terms of size and weight. They are quicker and easier to make up, require only minimal maintenance, and are leak-free. In short they provide the integrity of a welded joint with the versatility of a mechanical one.

Importantly, both the SPO Compact Flange and Techlok clamp connector incorporate an internal seal ring instead of the ANSI flange gasket and do not rely on bolting to maintain joint integrity. The SPO Compact flange, like an ANSI flange, uses radial compression but, importantly, combines this with a wedging action. So where the conventional flange places the loading on the bolts and joint integrity is largely dependent on bolt torque, the SPO Compact Flange technology places 90 per cent of the loading on the heel area to ensure a rigid, full contact between seal faces, which remains static regardless of load fluctuations, meaning that once it is pressure-tight it remains pressure-tight. Indeed, in over 50,000 applications worldwide the SPO Compact Flange claims to have never leaked in service.

The Techlok clamp connector, on the other hand, is designed as a clamp rather than a flange – consisting of hubs, sealring, clamp segments and bolting – and deploys a pressure-energised metal-to-metal seal. Whereas a gasketed ANSI flange is being in effect forced apart by the pressure in the line, this internal pressure actually reinforces the Techlok seal, to the extent that its strength can usually exceed the burst pressure of the connected pipe. In further contrast to the flange, the Techlok bolts are transversely mounted (the hubs are drawn together as the bolts are tightened, by the wedging action of the two clamp segments, compressing the sealring), and are almost completely isolated from the operating loads.

Both the Techlok and SPO Compact Flange provide pipe connections that, set up correctly, offer reliable leak-free performance and are able to withstand pressures in excess of 40,000 psi in temperatures from -254°C to 950°C. Moreover, their designs enable the seal diameter and bolting to be minimised, resulting in considerably smaller, lighter-weight compact connections – typically 70 to 80 per cent smaller and lighter than ANSI flanges for the equivalent pressure rating. This in turn means significant space and weight savings, which are particularly valuable in offshore developments.

Another benefit of these compact connectors is that the maintenance requirements involved are minimal. The SPO Compact Flange will remain pressure-tight, and the Techlok clamp connector does not require periodic tightening or any special maintenance, while in both cases the inner sealring is protected from corrosion. Minimised bolting requirements also makes installation quicker. Several Techlok connectors, for instance, can usually be made up in the same time as one ANSI flange.

The benefits of the technology are compelling in themselves but are particularly important in the offshore oil and gas sector, where both the SPO Compact Flange and Techlok clamp are well-proven. Both products are in evidence in multiple applications on offshore pipes and pipelines, platforms and FPSOs from the United States and Canada to the North Sea, Middle East and Asia.