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Piping Fittings

ELBOWS OR ELLS Elbows are used to change the direction of pipes.

These are categorized in different types in three

basic types.

1. On The Basis Of Radius:

2. On The Basis Of Angles:

3. On The Basis Of Shape:

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Piping Fundamentals For Fresher Engineers

There are two types based upon radii. Short radius (SR) and long

radius (LR). The elbows normally used are long radius (LR) with

centerline radius of curvature equal to 1.5 times the nominal pipe size

for NPS and larger sizes. Short radius (SR) elbows with centerline

radius of curvature equal to the nominal pipe size are also available.

1. On The Basis Of Radius:

90 Elbows Banded Equal Pipe Fittings

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2. On The Basis Of Angles

Elbows are available in standard 90and 45.

45 Elbows Banded Equal Pipe Fittings

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3. On The Basis Of Shape:

Elbows are also available according to requirements in uniformand changing radius. Changing radius elbows includereducing

elbows. Reducing elbows make a 90change in pipe with change

in line size. Reducing elbows have centerline radius of curvature

1.5 times the nominal size of the pipe to be changed to the longer

end.

These are not used in engineering practice due to cost

factor. Where reducing elbow is required, we change line

size before using elbow.

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Return changes direction of flow through 180and is used to construct

heating coils, vents on the tanks, etc.

We dont use returns in engineering practice in

pipelines, as these are expensive. Where we need

to bend the pipe for 180,we use two elbows.

Return

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FLANGES

Aflange is used to join pipe, valves or a vessel

within a system. They are available for:

Butt-Welded Systems.

Socket-Welded Systems.

Screwed Systems.

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Types of flanges are:

Welded Neck Flanges Slip On Flanges

Screwed Flanges

Socket Welding Flanges

Orifice Flanges Blind Flanges

Reducing Flanges

Lap Joint OR Van Stone Flange

Expander (Increaser) Flange Lap Joint OR Van Stone Flange

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Welded Neck Flanges

Welded neck flanges are used for high-pressures, cold or hottemperatures. They have two types:

1. Regular

2. Long

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Regular welded neck flanges are used with butt-welded fittings. They

are seldom used for pipes. Regularity of the bore is maintained.

Regular

Long

Long welded neck flanges are primarily used for vessel and equipment

nozzles. The hub thickness is greater than the diameter of any pipe that

may be bolted to the flange. They are seldom used for pipes. Regularity

of the bore is maintained.

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Slip On Flanges It is properly used to flange pipe. The pipe slips into the flange prior

to welding both inside and outside to prevent leaks. Slip-on flanges

can be used with long tangent elbows, reducers and swages. Theflange is poor resistance to shock and vibration. It introducesirregularities in the bore.

It is cheaper to buy than the welding neck flanges.

The pipe or fitting is set back from the face of flange to a distance isequal to the wall thickness i.e. = 1/16, so as to provide thenecessary expansion space for the fitting or pipe end.

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Screwed Flanges

They are made of steel and are confined to special applications.Their chief merit is that they can be assembled without welding.This explains their use in extremely high-pressure services

particularly at or near atmospheric temperature. Screwed flanges areunsuitable for conditions involved in temperature or bending

stresses of any magnitude particularly under cyclic conditions whereleakage through the threads may occur. Seal welding is sometimesemployed to overcome this problem.

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Socket Welding Flanges

They are normally used for small size piping systems with high-pressure applications. Their initial cost is about 10% greater than

that of slip-on flanges. Their static strength is equal to but their

fatigue strength is 50% greater than double welded slip on flanges.

Internally welded socket flanges are mainly used in chemical

processing piping systems.

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Orifice Flanges

They are widely used in conjunction with orifice

meters on measuring the rate of flow of liquid or gases

Blind Flanges

It has no bore and is used to close ends of piping systems.

Blind flange also permits easy access to a line once it has

been sealed.

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Reducing Flanges

or Reducers

The reducing flange is described in the same manner as a reduceri.e. the large end first, the reduction second. Suitable for changing

line size but should not be used if abrupt transition would create

undesirable turbulence.

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Expander (Increaser) Flange

or Expander

Alternative to using reducer and welding neck flange.

Useful for connecting to valves, compressors and pumps.

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Lap Joint OR Van Stone Flange

If costly pipe such as stainless steel is used, as the flange can be ofcarbon steel and only the lap joint stub-end needed be of the line

material.

Stub-end must be used in the lap joint and the cost of two items

must be considered. If both stub and flange are of the same material,

they will be more expensive than a welding neck flange.

They are only used in Butt-welded systems.