Thursday, May 8, 2014

Pipe Size & Material Selection

Velocity of material which the pipes are holding.

                   Velocity of the gases and air =15 to 20 m/s
                   Velocity of steam                   = 40 m/s

Pressure drop should be minimized to get better efficiency of machine.

Generally we allow 1% of pressure drop in 100mt.length.

Pressure drop is inversely proportional to Dia. of the pipe.

Pressure drop is directly proportional to square of velocity.

Headloss (hl) = flv2/2gd,
                   Where f = friction factor.
                              L = equivalent length.
                                      Equivalent length for elbow = 1.5d
                                                                         For tee = 2d
                                                                     For valve = 5d.


MATERIAL USED IN BHEL:

For Pipes:
                   CS Material is SA106Gr.B
                   SS Material is A312TP321

For Fittings:
CS Material is A234WPB
                   SS Material is A403WP321

For Flanges:          
                   CS Material is A105 Gr2
                   SS Material is A182F321

For Gaskets:
 Permanent Gaskets.

For ‘O’ Rings:
                   Soft Iron, Stain less steel (AISI 304)


For Studnuts:
                   ASA193B7 (Stud material)
                   ASA1942H (Nut Material)

For Valves:
                   CS-Cast Steel Body.
                   SS-Internals.
                  

MATERIAL SELECTION:

·         Up to 415 deg.  We use Carbonsteel Material.
·         More than 415deg. & Less than 520 deg. W e use SS Material.
·         More than 520 deg. We use Alloysteel Material.
·         Below –20 deg. We use Low Carbonsteel material

COMMONLY USED PIPE JOINTS:

1)   Screwed Joints
2)   Welded Joints
3)   Flanged Joint 

TYPES OF SUPPORTS:  

1) Spring Hanger

2)   Spring Supports

2.1)   Guiding Supports

2.2) Pedestal Spring Support.

3)   Sliding Supports

4)   Rigid Supports (Anchors)

TYPES OF WELDING:  

1)   Socket Welding
2)   Butt Welding
3)   Lap Welding
  • Socket Welding is used for not more than 2” pipes.
  • Butt Welding is used for larger diameters. Butt Welding efficiency is 100%

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