1.0 SCOPE
Roll flaring the end of pipe, also known as Van Stone Flanging, is a procedure which allows flanged connections without welding.  A loose Lap Joint or modified Slip-on Flange is placed on the pipe prior to flaring.  Approximately the last inch of pipe is then roll formed into a ring perpendicular to the pipe axis.  This ring, or lap, matches the raised face of a 150# or 300# flange.  Flaring is covered by ASME B31.3-93, Par. 306.4.2.

 

2.0 SIZES
Depending on the mechanical properties of the pipe being formed, equipment is capable of flaring the following sizes:

1/2" - 12" N.P.S.
Sch 5, 10 and 40

1/2" - 8" N.P.S.
Sch 80

3.0 FLARED LAP DIMENSIONS
Lap diameter and lap thickness are specified in ASME B31.3-93, Par. 306.4.2.  The Lap diameter matches the outside diameter of the raised face of a typical 150# or 300# flange per ASME B16.5.  The lap thickness, measured at any point, shall be at least 95% of the minimum pipe wall multiplied by the ratio of the pipe outside radius to the radius at which the lap thickness is measured.

4.0 MATERIALS
4.1   Carbon Steel
        ASME A-587
        ASME A-53
        GRADE A&B
        ASME A-106

4.2   Alloys
Stainless Steel  A-312, Types 304, 304L, 316, 316L, 309, 310, 317,                              321, 347
Nickel Alloys   Nickel 200, Alloy 400 (Monel®),
                           Alloys 600, 601, 625, 690 (Inconel®)
                    Alloys 800, 825 (Incoloy®)
                    Alloys C-276, B-2 (Hastelloy®)
Aluminum
                           3003, 5083, 6061-T4, 6061-T6, 6063-T6
Titanium           Grade 1, Grade 2
Zirconium         702 Grade

5.0 FLARED LAP SPECIFICATIONS
5.1   Facing
Most flared laps are smooth faced and will have an RMS 125 finish or smoother.   Depending on gasket selection, the flared lap can also be specified with concentric serrations.  APEX Piping Systems has a method of rolling concentric serrations while the pipe is being flared.  Each serration serves as an independent barrier.

5.3   Perpendicularity
As per ASME B31.3-93 Par. 335.1.1(c), alignment of the lap face shall not deviate from the indicated position measured across any diameter more than 1/16" per foot of diameter.

5.4   Lap Geometry
The radius (Dimension "R") is 1/16" for 1/2" thru 4" N.P.S. and 1/8" for 5" thru 12" N.P.S.  A larger radius is sometimes required for special applications.  Pipe flared for plastic lining applications normally requires a larger radius between pipe I.D. and lap which makes the O.D. radius larger as well.
T = Pipe Wall Nominal Thickness
t = Thickness of the lap after flaring.

6.0 BACK UP FLANGES
6.1   Back-up Flange Types
Since the process fluid does not touch the flange, selection of the back-up flange is based upon:
1.  Operating Pressure/Temperature
2.  External Corrosion
3.  Economy
As per B31.3-93, Par. 306.4.2 the flared lap is suitable for use in Normal Fluid Service.  In most instances, carbon, stainless, and non-ferrous metal laps will use one of the following types of flanges.  The lists starts with the lowest cost flange currently in use:

A.  A395 Ductile Iron - Approved for ASME B31.3 and ASME Section VIII use.

B.  A285 C Plate - Thickness must be calculated according to ASME B31.3 Par. 304.5 or from Appendix II of ASME Section VIII, Div. 1.

C.  A105 Slip-On (modified) - To allow for the Lap Radius per 5.4 of this specification above, this flange must be chamfered on the face I.D. as follows:
   Nominal Pipe Size           Chamfer
           1/2" - 1"                        3/16"
        1 1/2" - 3"                        1/4"
            4" - 12"                         3/8"

D.  A105 Lap Joint - More expensive than the Slip-On Flange but in small quantities may prove less expensive then chamfering the Slip-On Flange.

E.  Other Choices - Individual cases may indicate other options.         Some possibilities, in no particular order, include:
            Galvanized Carbon Steel
            Epoxy Coated Carbon Steel
            Stainless Plate Flanges

7.0   SAFETY
Loose flanged pipe systems should have a safety button attached 2" - 4" behind each flange.  This can be a drop of weld metal, a stud or any other mechanical stop which will prohibit the flange from sliding down the pipe where it could injure fingers or do other damage.

8.0   LIMITS ON FLARED LAPS
Per ASME B31.3 and reflecting industrywide usage, Flared Laps:
A.   Are not used with 400# or higher rated back-up flanges.
B.   Are not used in severe cyclic service.
C.   May be used in Category M service (ASME B31.3-93, Par.              M306.4), only in:
   a. 1/2" - 4" N.P.S.
   b. Sch 10 and above
   c. 400° F service and below
   d. Pressure/temperature ratings not to exceed those of ASME B16.5          Class 150, Group 1.1 Flanges.