When to use slip on flanges?

Slip On Flanges are preferred by some contractors, over the Weld-neck, because of the lower initial cost. However, this may be offset by the added cost of the two fillet welds required for proper installation. The strength of the slip-on flange is ample for it’s rating, but its life under fatigue conditions is considered to be only one-third that of the weld-neck flange.

The slip on flange may be attached to the end of a piece of pipe or to one or more ends of a pipe fitting. The slip-on flange is positioned so the inserted end of the pipe or fitting is set back or short of the flange face by the thickness of the pipe wall plus 1/8 of an inch. This allows for a fillet weld inside the SO flange equal to the thickness of the pipe wall without doing any damage to the flange face. The back or outside of the flange is also welded with a fillet weld.

It is welded both inside and out to provide suffcient strength and prevent leakage.

Slip-on flanges are all bored slightly larger than the O.D. of the pipe. They are preferred over welding neck flanges many users due to their lower intial cost, but final intallation cost is probably not much less than that of the welding neck flange because of the additional welding involved.

ADVANTAGES OF SLIP ON FLANGES:

Blind flanges have the face thickness of a flange, a matching face type, and similar bolting pattern. Blind flanges can also be used to seal a nozzle opening on a pressure vessel. Because it is bolted, the blind flange provides easy access to the interior of a vessel or pipe, unlike a cap that is welded. Figure 4.25 represents the drawing symbol for the blind flange.

What is plate flange?

Plate flange is also named plain flange, flat flange and slip on flange etc. A plate flange is a flat, circular disk that is welded onto the end of a pipe and allows it to be bolted to another pipe. Typically used in fuel and water pipelines, the two plate flanges will be bolted together with a gasket in between them. The plate flange will have bolt holes all around the perimeter and will be used to create junctions, tees and joints.

When building a pipeline, the length of the pipes used are not always known. By manufacturing the products separate from the plate flange, the welders can cut the pipe to length and weld a plate flange in place to join the pipes at any needed length. The plates can also be welded to the pipe on a slight bias, allowing two pipes to be joined that may not be precisely lined up.

WHAT IS A FLANGE?As a general rule, welding neck, slip-on, and socket weld flanges are used for high-pressure applications that require long-lasting flanged joints. Threaded flanges can be used with a lower pressure piping system, and if vibrations are not present.