A New Generation Sealing – Bringing the Best of Subsea to the Surface
Nils Christian Mathisen
General Manager

This article focuses on how new metal sealing technology (metal to metal sealing, currently the main sealing principle from subsea technology ) can solve serious environmental issues (fugitive emissions), remove danger of damage to human and improve bottom line of today's businesses.

From the cold north of our world, from Norway, we bring a new sealing invention to the readers' attention. A flange sealing made out of one piece of metal. A metal to metal-seal, a sealing principle usually used subsea on extreme depths and pressures.

The inventors of this particular patented sealing technology has taken the best sealing principle from subsea - metal to metal sealing, and have taken it to the surface. The invention is called DeltaV-Seal, designed by the Norwegian company Pipeotech.

A sealing is in general not a product that brings much attention. Sealings are the consumables often selected at the last moment in a design project, having few expectations to it. Although this apparently insignificant consumable can have the most severe impact on human health, the environment and a factory's revenue, the focus on this consumable has traditionally usually been next to nothing.

When designing a piping system, flanges are usually defined as a leakage point. Seals are typically the weakest link in a piping system, and a common cause to fatal leakages, explosions, harm to people and leakages into the environment and consequently a significant cause to negative impact on the revenue of a business.

There are no reason a flange should be defined as a leakage point. A factory may have tens of thousands of potential leakage points. What do this do with corporate risk?

The challenges in the sealing market gave the inventors of this metal to metal-sealing an idea to challenge today's sealing technology. They wanted to develop a high quality, metal-to-metal sealing product, aimed to last many times the life time of a regular sealing, and last but not least - stop leakages.

There are so many gaskets in the market, what is so special about this new metal gasket?

First, the designers chose to develop the sealing based on a metal to metal design. In this way, sealing can be brought to a totally different level.

Special designed metal ridges are placed on each side of the sealing. When torque is applied on the bolts, the metal ridges deform, yield and adapt to the flange surfaces, without any damage or deformation of the flanges.

A metal to metal-connection like this gives the best possible tightness of any connection, and results in a sealing that becomes even tighter than the tightness classification "gas tight".

Prolong lifetime

What is interesting to see is that if you have any imperfections on the flanges, the ridges will deform individually to the surface and adapt perfectly to the flange surface landscape. In tests done with DNV GL, even scribes as deep as 0.3 mm across the whole raised face flange surface have effectively been sealed in helium tests.

So even if you may have old and worn flanges, you can use these metal seals to seal off damaged and leaking flanges. In this way you can prolong the lifetime of your current piping infrastructure.

Galvanic corrosion, cleaning of flanges

The metal seals are made in one piece of metal, water cut, using no heat that affects the sealing material properties. When installing the metal seals, the governing principle is to choose metal sealing in the same material as the flanges. In this way you avoid galvanic corrosion, which may save a business for substantial amounts of money.

When using a metal to metal-sealing, in same material as the flanges, this means that you neither need to clean the flanges when using this sealing. Using a metal sealing like the DeltaV-Seal, it simply does not contaminate the flanges like for instance graphite based seals do.

This issue alone can mean many hours saved within maintenance, for each and every flange pair, and for a factory consisting of thousands of flanges, this can save significant costs and also reduce risk significantly.

When time has come to do a scheduled inspection or to change of gasket, you simply loosen the bolts, you inspect the flange surfaces without having to spend hours on cleaning, you drop the new DeltaV-Seal in between the flanges and it centers itself on the bolts, guided by the outer centering ring. Then you torque the bolts according to procedure and you're done.

Leakage and fire tests

The results of the metal to metal sealing principle was clearly demonstrated when doing tests at the German test institute, AMTEC. The results of various tests shows that through this new metal sealing design you come as close to technically tight as possible, showing a leakage rate 10.000 times tighter than the requirements (VDI 2440 / "TA Luft" helium test). Even in a fire situation, showing leakage of only 1 % of the requirement in a direct fire situation (>650 C), resulting the metal sealing to become fire test approved (API 6FB).

Static sealing

It is through years of heavy use the force of a metal to metal-connection exposes itself. Since the metal sealing DeltaV-Seal contain no "soft" sealing materials like graphite, this means that the metal sealing is static , so it does not change its sealing properties over time, not even at high or low temperature, nor in a temperature cycling environment.

"Install and forget"

Since this is a metal to metal-sealing with no soft sealing material like graphite present, this means that once you have installed it, you do not need to retighten the bolts after you have installed the sealing using the correct installation procedure and torque. You neither need to go back after a week to do any retightening of the flange bolts. In practice, it is "install and forget".

This is a small but important feature of the new metal sealing that may change and simplify how you work, how you do installation, maintenance and service of your piping infrastructure.

World's first DNV GL type approval of a flange sealing

The advantage of having a static sealing was demonstrated when the designers of the DeltaV-Seal wanted to have a type approval of the metal sealing they had invented. The certifying body, DNV GL said that no such type approval had been done before through DNV GL. The type approval project was however initiated, and the DeltaV-Seal had to pass two simoultaneous tests, 1) minimum 10 million vibrations (23.5 Hz) and 2) minimum 0.5 million pressure pulse sequences, exposing the metal sealing from the inside with oil pressures sequencing from 0 to 78 bar, then 51 bar and then zero bar, all within one second.

The metal sealing endured the whole combined tests, taking five days continuously, making the DeltaV-Seal the world's first type approved flange sealing (DNV GL).

This demonstrates the power of a metal to metal sealing design, making it possible to bring tightness and endurance to a totally different level.

From gasket to tool

This new sealing technology is more a tool than a simple gasket product. It is a cost saver. Despite this is apparently just a piece of metal, with the unique sealing properties embedded in the design, with this tool bigger companies can save costs on operations and maintenance by millions in bigger plants. In addition, it practically eliminates galvanic corrosion and as a repair-tool you can prolong the lifetime of your existing piping infrastructure. Last but not least, it is a tool to practically eliminate the risk for harmful leakages from flanges for people and the environment.