Compact pipe flange offers benefits in size, weight and leak resistance.

The ANSI flange has provided the industry with a suitable sealing technology for decades--often to great success--but the demands of the oil and gas industry have changed during this time while the ANSI flange has not. Cost-efficiency, environmental responsibility and optimum health and safety are three issues facing 21st century operators and contractors which is why it is important to recognize the advantages of compact pipe connection technology. Advantages The compact flange provides everything that a standard flange does not--space saving, reduced weight and, perhaps most importantly, a guaranteed leak-free connection. The reduced dimensions of the compact flange are achieved by reducing the seal diameter, which in turn, reduces the cross-section area of the seal faces. Second, the gasket is replaced by a sealring which works with the seal faces, not against them, to ensure face-to-face mating, so that only low seating forces are required to compress the seal faces. With lower pressures needed, both the size and number of the bolts can be reduced. ultimately providing a smaller, lighter-weight connection (70-80 percent smaller and lighter than ANSI flanges in the case of Vector's products). The key advantage of the compact flange over the ANSI flange is that it will not leak, thus providing cost savings both in terms of avoiding lost product and maintenance, as well as improving health and safety. In a compact flange, only a small amount of the total bolt pre-load is used to compress the seal. The major part of the bolt pre-load is transferred through the mating flange faces, creating a static face-to-face connection unaffected by the internal pressure or the external loads acting on the flange, Once pressure-tight after assembly, a compact flange, being a static connection, will always remain pressure-tight. Vector's flange Vector's SPO Compact flange takes the compact sealing principle still further, essentially providing a double seal--face-to-face mating and internal sealring--making it one of the leading products of its kind. Indeed, in more than 50,000 applications worldwide, it can boast to have never leaked in service. Vector's design is unique in that the flange faces include a slightly convex bevel with the highest point (the heel) adjacent to the bore, and an outer wedge around the outside diameter of the flange. As with the ANSI design. the flange is made up by tightening bolts which pulls the two connector halves together. When assembled, the flange faces first make contact at the sealring, then at the heel. As the pre-tension increases, the pressure at the heel increases, until full face-to-face contact is achieved, and the bevel is closed. An environmental seal is created at the outer wedge. The full face-to-face contact makes a completely static joint with no relative movement between seal faces. The seal created at the inner diameter of the flange faces is a fully qualified seal. Independent of the heel seal, a second seal is the sealring, which is compressed inside groves on the flange faces, according to dimensions and their tolerances. Should any accidental leakage occur at the heel, the internal pressure acting on the sealring inside the flange forces it toward the outer-diameter, intensifying the sealing action. Further, the external wedge barrier prevents ingress of corrosive agents from damaging the bolts or the internal sealring, making the compact flange ideal for use in harsh operating conditions, like those offshore, and when interfacing different metals with a potential for galvanic corrosion. This is a key advantage over the ANSI flange, which is susceptible to the effects of corrosive elements with ramifications for seal integrity. The no-leak capabilities of the SPO compact flange have been proven recently during modification work on Norsk Hydro's Troll C Floating Production Unit (FPU) to tie it into the Fram West field on the Norwegian Continental Shelf. Conventionally, the modification work would have required welding, but with the significant man hours, preparatory work and procedures required to create a gas-tight habitat in which welding could commence (all of which inherently drive the cost of construction). Norsk Hydro looked to alternative options. Typically, flanged spools are not accepted as a construction method for such piping modifications and welding is preferred because it is guaranteed not to leak. However, in this instance, Vector's compact flange design was accepted as an alternative to a fully welded system, due to its static design which guarantees no leaks, and the need for welding was reduced. A further recognition of the flange's strength is that it has been accepted by the Norwegian Petroleum Directorate as suitable for applications on risers above sea surface--where traditionally only welded joints are permitted--regarding its strength and integrity as equal to a girth weld. The application on Troll C is one example, SPO compact flanges are in operation on piping systems with design temperatures up to 720[degrees]C and down to -175[degrees]C. and pressures up to 15,000 psi, exceeding the ANSI pressure classes 150 to 2,500. In medium to high-pressure piping and in situations where volatile substances are being transported and leakage is unacceptable, compact flanges such as Vector's SPO Compact flange prove themselves to be the optimum connection method. Yet despite this, the comfort factor with the traditional flange design leads to a propensity toward the ANSI flange. With issues of assured joint integrity and reduction in hydrocarbon emissions more important than ever fur the industry (indeed, the Norwegian Petroleum Directorate has recently announced it is making moves to reduce leaks, following the rise in the number of gas leaks on the Norwegian Continental Shelf), compact technology like Vector's has a valuable contribution to make in reducing leaks, as well providing weight and space savings for operators. There certainly seems to be a trend developing--compact flanges are now the connectors of choice in the North Sea and there are widespread applications for compact technology with deepwater development. making it reasonable to suggest their use could increase on such projects, By reducing the topside weight of tension leg platforms required to access deep water petroleum reserves, the Department of Commerce's National Institute of Standards and Technology (NIST) estimates $250,000 could be saved per meter of water depth--a significant cost saving. Compact pipe connection technology provides greater efficiency, safer operation and is more cost-effective than the ANSI flange, but typically the technology is still only specified in situations where leaks are absolutely critical. The benefits are clear--it is time for the industry to start taking advantage of them. www.thru.to/pgj Circle #201