Pipe Flange by Akram Megdad - Napis

7/22/2019 Pipe Flange by Akram Megdad - Napis

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Prepared and presented by:

Akram Megdad / Sr. Mech. Inspector


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Pipe Flanged joints are considered to

be weak joints in the piping system andmany considerations should be taken to

avoid failure.Lack of proper installation and inspection

could result in a little leakage

OR


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Types of flanged joints.

Methods of connecting flanged joints.

orces acting on the flanged joints.langed joints installation and inspection.Summary.

In this presentation I will talk about ?


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Methods of Connecting Pipe Flanges

A flange is used to connect a pipesection to a piece of equipment,

valve, or another pipe in a way thatwill permit relatively simple

disassembly. Such disassembly may

be required for maintenance,inspection or operational reasons.


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Methods of Connecting Pipe Flanges

There are three general methods used to join or connectlengths of pressure piping,

these are:

3 By the use of flanges.

1 By the use of threaded pipes and screwedconnections.

2 By the use of welded joints.


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Typical flange Joint Assembly

Flange assembly consist of :

Two flanges.

A gasket to provide a

seal between the flanges.

Bolting to keep

the assembly

together.


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Flange Types

There are several standard types of pipe flanges. Twoitems must be specified to completely define a flangetype.

Flange Type Attachment Method Face Type+

A flange type is specified by stating the type of attachmentand face.For example,"A weld neck flat-faced flange" The

type of attachment defines how the flange is connected to apipe section or piece of equipment (such as a pressure-vessel

nozzle). The type of flange face or facing defines thegeometry of the flange surface that contacts the gasket.


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Flange Attachment Types

Threaded Flanges

A threaded flange has pipe threads machined into its bore asthe flange is screwed to matching threads on the pipe end.Threaded flanges are used only for small-diameter piping

systems, up to 50 mm (2 in.) NPS (nominal pipe size) atlocations where pipe disassembly may be required formaintenance, field modifications, or to match specialty

fittings and valves.For hazardous services, a threaded flange may only be usedup to 38 mm (1-1/2 in.) NPS. However, based on SAES-L-009, Metallic Flanges, Gaskets, and Bolts,welded slip-on-type flanges are preferred over threaded flanges in screwed

piping systems.


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Threaded Flanges


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Slip-on FlangesA Slip-on Flange has an oversized bore, it is slipped overthe pipe OD and projects slightly beyond the pipe end,the flange is then fillet welded to the pipe OD, and also

between the flange bore and the pipe end.Based on SAES-L-009, Saudi Aramco requires that an ASMECode SectionVIII, Division 1, flange analysis to be performedif a Slip-on Flange is used for any of the following cases:

1 - Severe cyclic conditions.

2 - Design temperature greater than 230C (450F).

3 - ANSI Class 400 or higher rating.

4 - Pipe size over 600 mm (24 in.).



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Slip-on Flanges



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Socket-Welded FlangesA socket-welded flange is similar to a slip-on flange except ithas an oversized bore that is partially machined into the end

opposite the face, the pipe is inserted into the "socket" and theflange fillet is welded to the pipe OD, the diameter of the

smaller bore is the as the I.D. of the matching pipe. This type offlange is often used with high pressure systems that use smaller

diameter pipes (< 4 inches).Based on SAES-L-010, Limitations on Piping Joints, the

maximum size of socket-welded joints in hazardous services shallbe 38 mm (1-1/2 in.) NPS for new construction.However, as with threaded piping systems, SAES-L-009indicates that welded slip-on-type flanges are preferred over

socket-welded flanges in socket-welded piping systems.



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Socket-Welded Flanges



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Blind Flanges

A blind flange is a flat metal

plate without an opening orbore that is used to blockflow in a piping system.

It is used when a pipe end

or equipment nozzle mustbe blocked from flow.



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Lapped Flange

A lapped flange is not physically connected to the pipe, it isslipped over a pipe stub that has a flared end and the pipe

stub is welded to the major pipe section, the flared pipe end

has a machined face where the gasket is seated, the boltingholds the flanges and gasket joint together.Based on SAES-L-009, Saudi Aramco prohibits the use of lap-

joint flanges in severe cyclic conditions. Their use is alsolimited to special applications suchas :

To avoid welding dissimilar materials.

To facilitate lining up the bolt holes in underwater flanged joints.

The use of lap joint flanges is the exception rather than therule, the main advantage of a lapped flange is cost and then

only in high-alloy piping systems.



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Lapped Flange



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Welded-Neck Flanges

A welding-neck flange is normally referred to as the highhub flange and it is the strongestof the standard flange

attachment types, it is designed to transfer stress

concentration at the base of flange, the end of the flange isbutt-welded to the end of the pipe, the flange bore is sizedto match the pipe bore. A welding-neck flange is the most

widely used in refinery services because of its greaterstrength and ability to be used at high temperature and in

cyclic service.

Based on SAES-L-009, this is the preferred flange type inmetallic piping systems, 50 mm (2 in.) NPS and above.



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Welded-Neck Flanges


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Forces Acting on the Flanged Joints

PRESSURE

THERMAL

DYNAMIC


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PRESSURE

The flange rating should be adequate forthe required pressure and temperature

range to avoid over pressure on theflanged joints.


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THERMAL

Thermal expansion

will cause highbending moment andcould lead toalignment difficulties,leaks and fires.


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DYNAMIC

Dynamic forces should be taken in consideration to assurethe flanged joints integrity such as:

Processes related.

Controlled and unpredicted forces.

Piping lay out and configuration.

Modification to piping lay out.


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Flanged joints Installation and Inspection

Alignment

Surface finish

Gasket centering Bolting procedure


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Alignment

Flanged Joint misalignment caused by:

Low quality fabrication.

Field measurements mistakes.

And this will lead to:

Gasket damage.

Uneven load distribution.


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Surface finish

The surface finish should be the right one for theright gasket type.

No scratches, specially in radial direction.

Clean from foreign objects.


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Gasket centering

Check gasket dimensions for precision.

Gasket should be exactly centered.

Avoid touching the bolts.


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Bolting procedureUse the proper equipment.

Follow the right bolting sequence

to provide even load distribution.

Apply the required torque, No more No less.

W hat happens when bolts are over torqued ?

Cracked flanges.

Squeezed gaskets.


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Over torque cracked flange.


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SummaryRecognize that f langed joints are a cr itical

and potential hazard.Proper design material selection properinstallation careful inspection shall leadto the highest quality and save pipeflanged joints.


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Prepared and presented by:

Akram Megdad / Sr. Mech. Inspector

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Pipe Flange by Akram Megdad - Napis