January 9th, 2011
The majority of pipe connections are welded joints. However, at some locations in pipeline, installations it is necessary for the pipe to be able to be dismantled for maintenance. This may be at the location of a valve or pump, or just because it is necessary to get to something behind the pipeline. This is where it is necessary to install flanges in the pipeline which allow a section of pipe to be unbolted and removed.
If, however, the pipe has had to be constructed from special materials to cope with the corrosive properties of the liquid or gas being transported then these flanges can be expensive if made entirely from the same material. One solution is to employ lap joint flanges where the flange ring is made from a different material to the stub pipe it is fitted onto. At Chemipetro we manufacture a range of lap joint flanges of various sizes.
One advantage of a lap joint flange is that as it is not welded to the stub pipe and is free to rotate. Like a swivel ring flange it can twist to ensure it aligns correctly when the joint is assembled.
This all makes lap joint flanges seem the ideal solution, low cost and easy to fit. There are, however, problems. The fatigue life is also only one tenth that of a standard weld neck flange. Also, the gasket face sealing the pipes is the end face of the pipe lip and is therefore limited in size. The pressure rating of the joint is therefore limited making them no good for high pressure joints.
Tags: flange, Flanges, weld neck joints, welded joints
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August 15th, 2010
One of the most fundamental problems faced in any industry is how to join two pieces of material together. A layman asked this question would probably immediately think of glue. This is possible even with steel, where welding is effectively gluing two pieces of metal together.
There are however two fundamental problems with any sort of glued joint. The first, the joint is only as strong as the glue itself. To help overcome this with welded joints the ends of the pieces are shaped to form a V. This gives the weld a greater surface to form on and so make the bond stronger.
The second problem is that any glued joint is permanent and does not allow for anything to be dismantled should maintenance be required.
To dismantle a joint it should be connected by a removable fastening. This is where the humble nut and bolt come in. By providing flanges on the end of a pipe or a pipe fitting, and by bolting the two flanges together, a strong but removable coupling can be achieved.
But what sort of nut and bolt should be used? In concept they may all be the same but in practice they can be very different, from a simple threaded rod which is cut to length, to a 12 point ferry head unit. The choice of nuts can also be bewildering from the simple hexagonal to a bi hexagonal 12 point self locking type.
Whatever your need we at Chemipetro can provide a wide range of fastenings to meet your specific requirements even if it is a non standard and unique type.
Tags: Flanges, pipe fitting, Pipe Flanges, welded joints
Posted in Pipe Flanges | No Comments »
April 15th, 2010
As a supplier and manufacturer of high-quality pipe flanges for the petrochemical industry, we at Chemipetro understand the importance of caring for our flanges and pipe fittings once they’re installed.
All flanges need regular maintenance, or you will start to get decreased performance from other components on your site. It’s essential you eliminate problems at their source, as soon as they arise. Not only will this improve plant efficiency, it will create a safer working environment and save on running and repair costs. A large number of fires and explosions start as a result of leaking or poorly welded pipe fittings.
No matter how high the quality of the alloys, it is essential you protect flanges, gaskets and other components from their environment as much as possible. This starts by reducing corrosion to an absolute minimum. Using corrosion resistant alloys, such as super duplex, has reduced corrosion substantially – but the annular seal on the outer diameter of flanges can still be vulnerable to moisture and dirt. Once these creep in, eventually it will lead to corrosion and degradation around the gasket area.
You should also remember that welded joints are more vulnerable to corrosion than other areas of pipe fittings, even if tough stainless steel alloys are used. Excessive corrosion of flanges is dangerous, and if they have to be replaced it can lead to plant shut-down. To reduce this risk, use flange protectors to stop dirt and moisture attacking the joints.
While strong, corrosion-resistant alloys like duplex steel will ensure you get long life from the pipe flanges you buy from us atChemipetro, they will last even longer if you remember these few basic rules.
Tags: corrosion resistant alloys, Pipe Fittings, Pipe Flanges, Super Duplex, weld neck flanges, welded joints
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