UHDE-STANDARD

Welding UN
WELDED JOINTS V416-01
FOR VESSELS AND EQUIPMENT Part1 (M)
Requirements Page 1 of 10
[Modified on: 29/08/2008]

Contents
1 Scope.................................................................................................................................................................... 1
2 Qualification......................................................................................................................................................... 1
2.1 Manufacturer's qualification ................................................................................................................................... 1
2.2 Procedure qualification test ................................................................................................................................... 2
2.3 Welder's qualification test ...................................................................................................................................... 2
2.4 Welding supervisor ................................................................................................................................................ 2
3 Joint details.......................................................................................................................................................... 2
4 Materials ............................................................................................................................................................... 3
4.1 General.................................................................................................................................................................. 3
4.2 Special cases and special materials ...................................................................................................................... 4
5 Preparation for welding....................................................................................................................................... 4
5.1 Weld preparation ................................................................................................................................................... 4
5.2 Protection of the workplace ................................................................................................................................... 4
5.3 Aligning and tack welding ...................................................................................................................................... 5
6 Welding................................................................................................................................................................. 5
6.1 Welding filler metals............................................................................................................................................... 5
6.2 Performance of welding ......................................................................................................................................... 6
7 Post-weld heat treatment .................................................................................................................................... 8
7.1 Stress-relieving and tempering .............................................................................................................................. 8
7.2 Partial stress-relieving ........................................................................................................................................... 9
7.3 Normalizing............................................................................................................................................................ 9
8 Post-weld surface treatment............................................................................................................................... 9
8.1 Mechanical treatment ............................................................................................................................................ 9
8.2 Chemical treatment................................................................................................................................................ 9
9 Repair welds ........................................................................................................................................................ 9
10 Weld quality requirements.................................................................................................................................. 9
11 Testing of the welds ............................................................................................................................................ 9

1 Scope
This Uhde standard outlines the minimum requirements for the welding of vessels and equipment in the work-
shop and on site. In addition to this standard and the codes and standards indicated in the purchase order, the
accepted standards of technology shall apply. Uhde standards UN 2000-01 Part 1 (M) and UN 2100-01 Part 1
(M) to be considered.

If the data contained in this Uhde standard are in contradiction to those specified in the purchase order docu-
ments, the latter shall take precedence. If data differ, the more stringent data shall apply. The applicable
codes and standards shall in any case be observed.

2 Qualification
Field welding and shop welding shall meet the same quality requirements.

2.1 Manufacturer's qualification

The manufacturer's workshops shall be equipped with the facilities required for the proper processing of the
materials and for the performance of the necessary tests. Regarding pressure-bearing components, the
manufacturer shall be in possession of the permit required according to the codes and standards. Uhde re-
serves the right to check whether these requirements are met.

© 2008 UHDE INDIA Technical Discipline: MQ

 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
FOR VESSELS AND EQUIPMENT Part1 (M)
Requirements Page 2 of 10

2.2 Procedure qualification test

Welding procedure qualification tests shall be performed according to the applicable codes and standards
prior to the start of fabrication unless the manufacturer's qualification permit already covers the materials to be
processed, the dimensions and the welding procedures to be used. The procedure qualification test reports
shall be submitted to Uhde upon request.

2.3 Welder's qualification test

Only welders tested according to the applicable codes and standards shall be employed. The qualification test
certificates shall be submitted to Uhde upon request. An identification symbol shall be allocated to each
welder.

2.4 Welding supervisor

To ensure the quality of the welds, the preparation and performance of the welding work shall be supervised
by qualified personnel of the manufacturer. Refer to section 6 for further details.

3 Joint details
Butt weld joints shall be preferred. All pressure-bearing welds shall be full-penetration welded or back-welded
on the root side. Back-welding shall be preferred for welds which are accessible from both sides.

Unless otherwise specified, fillet welds shall be performed with amin = 0.7 x smallest plate thickness. The min.
fillet throat thickness shall be amin = 3 mm. Deviations shall be agreed upon for special designs.

Open gaps of any type shall be avoided. Centering rings or insert rings which remain in the component are
only permitted if expressly approved by Uhde.

The transition between items of different wall thicknesses, joined by butt welding, shall be adapted by cham-
fering the larger wall thickness according to the codes and standards.

The minimum spacing between parallel butt welds shall be 6 s (s = vessel wall thickness) and 50 mm in the
case of plate thicknesses of < 10 mm.

For welded joints according to Figure 1, sketches a to e, min. spacing l may be reduced to 2.5 s. Sketch f ap-
plies to the spacing between nozzles and shell welds.

a b c d e f
Heating jacket con- Flange Tubesheet Skirt Skirt / flat head Nozzle
nection

I ≥ 2,5 s I ≥ 3 s, min. 50 mm

Figure 1. Welded joints

 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
FOR VESSELS AND EQUIPMENT Part1 (M)
Requirements Page 3 of 10
If the joint cannot be performed according to sketch f, the welds shall be arranged in such a manner that the
vessel seam is interrupted completely by the nozzle. This type of joint is only permitted if approved by Uhde in
writing. In such a case, the welds of pressure vessels shall be subjected to non-destructive testing. In addition,
a surface crack test shall be performed on the nozzle-to-shell welds after the pressure test. The test length,
measured from the nozzle edge, shall be d x s (d = nozzle diameter, s = vessel wall thickness in mm), but at
least 100 mm. (Refer ASME Section V, Articles 6 and 7).

Cross welds are not permitted on pressure-bearing wall components. When welding stiffeners, connecting
plates, etc. within the area of pressure-bearing welds of vessels, the welded-on components shall be provided
with cut-outs according to Figure 2.

I ≥ 6 s, min. 50 mm
F ≥ 15 mm

Figure 2. Cut-outs on stiffeners

Pressure-bearing welds (e.g. circumferential and longitudinal seams of pressure vessels) may only be cov-
ered by welded-on items if agreed upon with Uhde. Semi-tube coils on vessel walls shall be routed across the
vessel welds over the shortest distance possible in order to maintain the testability of the covered welds to the
greatest extent possible.

A test hole of R ǩ“ shall be provided for design-specific, closed cavities, e.g. in the case of reinforcements of
cut-outs, welded-on block flanges, sheet metal linings, etc. Any such test holes shall be shown in the work-
shop drawings. After the test, the test holes on the equipment shall be sealed with greasy paste or wax.

The dimensions and shape of the welds and of the components joined by welding shall correspond to the
manufacturer's drawings approved by Uhde.

The manufacturer's drawings shall contain all welding data according to Uhde standard UN 2000-10 Part 1
(M). Field welds shall particularly be marked.

For the welding of clad steel, deposit welding, repair welds, and whenever demanded by Uhde, a welding and
testing schedule shall be elaborated on Uhde form UF V360-21 Part 1 (M) and submitted for approval.

The dimensions of the groove shape, the welding procedure, the welding filler metals and the weld build-up
per pass shall be described for all welds.

The joint details for vessels and equipment to be coated, lined or brick - lined shall be agreed upon.

4 Materials
4.1 General
The material certificates specified in the purchase order documents shall be furnished for all materials used.

Unless otherwise specified in the purchase order documents, killed steel shall be used and the C content lim-
ited to max. 0.25%.
 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
FOR VESSELS AND EQUIPMENT Part1 (M)
Requirements Page 4 of 10
The materials shall be processed, transported, stored and marked in such a manner that any confusion, dam-
age and corrosion are avoided.

Proper re-stamping of the materials shall be performed prior to cutting and machining. Tests for material con-
formity shall be performed in cases of doubt.

4.2 Special cases and special materials

It might become necessary to take special measures or to permit deviations from this standard in the following
cases:

• Vessels with wall thicknesses of > 30 mm

• Unalloyed steel with a min. tensile strength of > 450 N/mm²
• Alloyed steel such as 13 CrMo 4 4 and higher alloyed steel
• Fine-grained steel with a yield strength of > 320 N/mm²
• Risk of stress corrosion cracking.

5 Preparation for welding

5.1 Weld preparation
The weld may be prepared thermally and/or mechanically. Thermal treatment shall be followed by mechanical
treatment to remove any oxides.

Section 3 shall be observed for selecting the groove shape.

When employing thermal processes for preparing the welds on clad materials, the cladding shall be removed
mechanically to such an extent that the cladding will not be changed metallurgically during the welding of the
base metal.

The skin of a casting shall be removed in the area of the groove faces.

The groove faces shall be free of notches, occlusions, laminations, cracks and impurities.

The procedure shall be as follows:

• Notches caused by flame cutting shall be removed by grinding over a large area.
• Linear non-metallic occlusions which can cause difficulties when evaluating the ultrasonic test of the com-
pleted weld or which can cause disintegration of the material shall be removed by grinding and welding
(buttering layer).
• It is not permitted to leave large laminations in place. Discontinuities of < 20 cm² may be repaired by grind-
ing and welding (buttering layer). Discontinuities of ≥ 20 cm² shall be eliminated.

The method of repair shall be agreed upon with Uhde.

5.2 Protection of the workplace

The following shall apply when welding and thermal cutting are performed outdoors:

• The workplaces and workpieces shall be protected from inclement weather conditions (moisture, wind, low
temperatures) by suitable means.
• Welding shall only be performed on a dry base.
• At workpiece temperatures of < 5°C, outdoor welding shall only be performed after adequate measures
have been taken. The preheating temperature according to the welding schedule shall be observed.
 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
FOR VESSELS AND EQUIPMENT Part1 (M)
Requirements Page 5 of 10

5.3 Aligning and tack welding

After preparation, the seams shall be aligned, tack welded or clamped in such a manner that the misalignment
of the edges permitted according to the codes and standards is not exceeded and the specified root gap is
observed. Welding-on of erection aids shall be kept to a minimum. After removal of the erection aids, it must
be ensured that no cracks or any other type of damage start at these places. This shall be checked and con-
firmed by a magnetic particle test or a dye penetration test.

6 Welding
The welding procedures shall be adapted to the material, design and operating conditions.

The following are approved welding procedures:

• Shielded metal-arc welding (SMAW)

• Gas tungsten-arc welding (GTAW)
• Active-gas metal-arc welding (GMAW)
• Inert-gas metal-arc welding (GMAW)
• Submerged arc welding (SAW)
• (Tungsten) plasma-arc welding (PAW)
• Other welding procedures:

Other procedures may be employed if procedure qualification tests have been performed and Uhde's approval
has been obtained.

Welds performed by the GMAW procedure (active-gas metal-arc welding and inert-gas metal arc welding) on
components subjected to high stresses and/or on pressure-bearing components require Uhde's special ap-
proval.

6.1 Welding filler metals

The chemical composition of the welding filler metals shall be compatible with the base metal and the operat-
ing conditions. The filler and the base metals shall be of the same type as far as this is possible from the met-
allurgical aspect. Proof of certification shall be furnished for the electrodes used.

It must be ensured that the filler metals specified in the approved documents of the manufacturer are used.
Other welding filler metals may only be used if approved by Uhde.

If any confusion of the filler metals is suspected, the manufacturer shall furnish proof of the filler metals used
by suitable test methods.

For the joining of components of different ferritic materials, the filler metal corresponding to the lower alloyed
base metal shall normally be used. When joining components of different austenitic materials, a filler metal
corresponding to the higher alloyed base metal shall be used.

When joining components of ferritic and austenitic materials, an austenitic filler metal of a higher alloy than the
base metal or a nickel-based filler metal shall be used. If the workpiece is subjected to operating temperatures
of > 300°C or to heat treatment, a nickel-based filler metal shall be used.

6.1.1 Special requirements

In addition to the requirements outlined in this section, special demands can be made on the welding filler
metals in special cases as regards analysis, limits of analysis and structural constituents.
 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
FOR VESSELS AND EQUIPMENT Part1 (M)
Requirements Page 6 of 10

6.1.2 Shielding gas

The following shielding gases shall be used:

• GTAW: argon; welding-grade argon; helium; an Ar-He gas mixture, if necessary. For root protection: argon;
helium; Ar-He gas mixtures, if necessary; anti-slag gas (90% N2, approx. 10% H2)
• GMAW (active-gas metal-arc welding): CO2 or a gas mixture of Ar, CO2 and O2.
• GMAW (inert-gas metal-arc welding): argon; welding-grade argon or an argon mixture with an oxygen con-
tent of max. 1%.
Other types of shielding gas shall be agreed upon with Uhde.

6.1.3 Storage and stock keeping of welding filler metals

It must be ensured that

• the filler metals used are undamaged, that their sheaths are dry and that they are stored in dry rooms,
• the filler metals are free of oil, grease, rust and impurities.

6.1.4 Drying
Prior to use, rod electrodes with mainly basic sheaths, which are used for the welding of unalloyed and low-
alloy steel, shall be dried according to the instructions of the manufacturer, but for at least 2 hours at 250°C
and temporarily stored at 100 to 150°C. They shall be removed from the drying oven in small quantities and
kept in a heated flask at 100 to 150°C until use.

This also applies to rod electrodes of higher alloyed austenitic materials and nickel-based materials with rutile-
bearing sheaths. The drying temperature and drying period shall correspond to the manufacturer's specifica-
tions. Agglomerated welding flux for submerged-arc welding shall be treated as basic rod electrodes.

6.2 Performance of welding

The specified energy per unit of length, preheating and temporary storage temperatures shall be observed.

Quick cooling shall be avoided. This particularly applies to materials which are susceptible to hardening.
Components which are welded at a preheating temperature of > 50°C may only cool down gradually (meas-
ures to be taken: e.g. covering by means of insulating mats).

6.2.1 Tack welds

Tack welds need not be removed prior to welding if the starting crowns and end craters are ground and/or the
tacks are completely fused during welding. When welding an erection aid to a component, the welding re-
quirements met by the component shall also apply to the erection aid. Welding shall be performed with at least
2 layers.

6.2.2 Welding of root, filler and top passes

Striking the arc on the surface of the workpiece is not permitted. The arc may only be struck on the groove
face, the existing bead or on an auxiliary plate.

The root pass of welds which are welded from one side shall be protected from the admission of air by means
of shielding gas (e.g. anti-slag gas) and/or treated mechanically after welding.

The root pass of welded joints of austenitic components shall be performed by the GTAW procedure under
shielding gas and using an additional welding wire. Deviations herefrom require Uhde's written approval.
 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
FOR VESSELS AND EQUIPMENT Part1 (M)
Requirements Page 7 of 10
The root pass shall be checked for defects and back-chipped prior to back-welding. In the case of high-tensile
steel, steel susceptible to cracking as well as austenitic materials, the back-chipped root shall be subjected to
a non-destructive test.

Gouging or grooving out the root pass thermally is only permitted if the root pass is subsequently ground.

Prior to welding the filler and top passes, the preceding passes shall be cleaned from welding slag. Lack of
fusion, pores and occlusions shall be eliminated by grinding.

The top pass shall be free of notches and shall only be a little wider than the groove. In special cases, notch –
free transitions of the welds may be required. In the weld areas concerned, the working steps shall be per-
formed according to the specifications contained in the manufacturer's drawing (standard symbols or text).
Normally, notches shall be removed by grinding.

Special agreements shall be made for the welding of materials coming into contact with hydrogen sulphide,
high-pressure hydrogen or urea.

6.2.3 Cleaning and grinding

After completion of the work, slag, scale, annealing colours, welding spatter and other impurities shall be re-
moved from all welds. It must be ensured that the tools used for this purpose do not adversely affect the mate-
rial of the component concerned (measures to be taken: e.g. only brushes of stainless steel shall be used for
cleaning stainless steel; only suitable grinding disks shall be used for austenitic materials - the disks shall not
be used for other types of material).

After completion of the workpiece, any inadvertent arc strikes on the surface shall be smoothed by grinding.
The wall thickness shall not be less than the specified min. wall thickness. After grinding has been completed,
austenitic materials shall normally be subjected to erosive pickling and passivation. Deviations herefrom re-
quire a separate agreement.

At Uhde's request, the manufacturer shall furnish proof of the absence of cracks in the ground areas. The
erection aids shall not be removed by knocking them off or by flame cutting. After removal of the erection aids,
the areas to which they had been welded shall be ground. Proof of the absence of cracks shall be furnished by
a surface crack test. (Refer ASME Section V, Articles 6 and 7).

6.2.4 Welding of clad steel

Refer to sections 5.1 and 6.1.

Electrodes for the welding of buttering layers may also be used for the welding of filler passes and, if the cor-
rosion resistance is adequate, for top passes.

An agreement shall be made if treatment of the weld surface is required.

6.2.5 Welding after cold forming

If welding is required on steel which has been cold formed by more than 5%, proof shall be furnished that
welding is permissible.

When welding edged plates of C steel, the distance of the welds from the area of cold forming shall be at least
R + 2 x s (R = edge radius, s = wall thickness).
 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
FOR VESSELS AND EQUIPMENT Part1 (M)
Requirements Page 8 of 10
6.2.6 Tube-to-tubesheet welding
Uhde standard UN V416-02 Part 1 (M) applies to tube-to-tubesheet welding.

6.2.7 Application of heat during welding

When determining the preheating temperature and the filler pass temperature, the special characteristics of
the material, the welding parameters, design, wall thickness and the corrosion attack by the process fluid con-
cerned shall be taken into consideration. The temperature ranges to be observed shall be specified in the
manufacturer's drawings. The preheating zone beside the weld shall be 4 x wall thickness, but at least 100
mm. During welding, the wall temperature shall be monitored continuously by means of thermochrome cray-
ons, surface thermometers or thermocouples and recorded upon request. The preheating zone shall be cooled
in still air. In the case of steel which is sensitive to welding, consideration shall be given to the question as to
whether heat treatment is required immediately after welding while the steel is still hot.

The preheating temperature shall be agreed upon for special welding work, e.g. deposit welding, repair weld-
ing, etc.

6.2.8 Marking of welds

All welds on pressure-bearing components shall be marked by the welder by means of his stamp. The type of
marking to be used on steel which is susceptible to cracking and on components with special surface require-
ments shall be agreed upon.The marking of austenitic components of wall thicknesses of < 6 mm may only be
effected by engraving or with coloured crayons which are free of oil, grease, sulphur, chlorine, tin, zinc, arse-
nic, lead and copper. Uhde reserves the right to check the works' certificates of the manufacturer of the mark-
ing means.

7 Post-weld heat treatment

If post-weld heat treatment is required, the heat treatment temperature shall take into consideration the heat
treatment already performed on the blanks. The specified heat treatment data shall be taken into considera-
tion when procuring the blanks.

The annealing process to be used, the annealing temperature, the heating rate, the holding time, and the cool-
ing rate shall be specified in the drawing or in an annealing schedule.

7.1 Stress-relieving and tempering

Stress-relieving shall be performed after all welding work has been completed. The following parameters shall
apply to the performance of stress-relieving:

• Deviations from the stress-relieving temperature between the individual measuring points should be kept
as small as possible (reference value: ± 15°C).
• Unless otherwise specified in the material data sheets or by Uhde, the following shall apply to tempera-
tures exceeding 400°C:
§ Heating rate
≤70°C/h for wall thicknesses up to 50 mm
≤ 50°C/h for wall thicknesses exceeding 50 mm
§ Cooling rate
≤ 50°C/h for wall thicknesses up to 50 mm
≤30°C/h for wall thicknesses exceeding 50 mm
§ In the case of closed chambers or complex structural components with large differences in wall thick-
ness, the heating and cooling rates shall be determined taking into consideration the max. permissible
thermal stresses of the various cross sections of the components. The heating and cooling rates shall
be controlled via the max. permissible difference in temperature (e.g. 20 to 30°C).
• The holding time shall be 2 minutes per mm material thickness, but at least 30 minutes.

Stress-relieving schedules shall be prepared for materials which are subjected to high stresses, severe corro-
sion attacks and multiple stress-relieving. These stress-relieving schedules shall specify the designation of the
 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
FOR VESSELS AND EQUIPMENT Part1 (M)
Requirements Page 9 of 10
component concerned, position of the temperature measuring points, heating and cooling rates, holding time,
position of the test specimens and the furnace atmosphere.

Uhde reserves the right to check the arrangement of the instruments and measuring points prior to the start of
stress-relieving.

If production test plates are stress-relieved separately from the workpiece, it must be ensured that the stress-
relieving of the production test plate is comparable to that of the workpiece.

If the stress-relieving temperature is controlled by measurements taken in the furnace chamber, Uhde re-
serves the right to demand that a stress-relieving test be performed when it is doubtful that the temperature in
the furnace chamber is uniform. Workpieces may be withdrawn from the furnace at temperatures below 300°C
if cooling in still air is ensured.

Workpieces of very different thicknesses and workpieces of materials which are susceptible to cracking shall
remain in the closed furnace for at least ½ h at temperatures below 100°C before they are withdrawn. The
workpieces to which the above applies shall be agreed upon.

Welding and forming work which must be performed after stress-relieving shall be agreed upon in detail and
approved by Uhde.

7.2 Partial stress-relieving

Partial stress-relieving of the welds requires Uhde's approval. The width of the zone being stress-relieved
shall be at least 6 x wall thickness, but at least 50 mm on either side of the weld. The axial course of heating
shall be influenced by means of adequate insulation to prevent the resulting thermal stresses from damaging
the base metal. Uhde may demand proof by calculation.

7.3 Normalizing
Normalizing of welded components requires Uhde's written approval.

8 Post-weld surface treatment

8.1 Mechanical treatment

Refer to section 6.2.3.

8.2 Chemical treatment

In the case of high-alloyed steel and nickel-based alloys, the annealing colours shall be removed from the
workpiece by pickling.

Depending on the application, either pickling pastes or pickling baths may be used. If approved by Uhde, pick-
ling can be replaced by sand/shot blasting.

The surface treatment shall be performed according to Engineering Standard UN V416-03 Part 1 (M).

9 Repair welds
The welding and testing procedures used in fabrication shall also be used for repair welds. Uhde shall be
informed about repair welds with a depth of > 20 mm and a length of > 300 mm on materials according to
section 4.2 and when repair welds have to be performed in difficult positions. The last paragraph but two of
section 3 applies to deviating welding procedures.
 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
FOR VESSELS AND EQUIPMENT Part1 (M)
Requirements Page 10 of 10

10 Weld quality requirements

The requirements specified in the codes and standards for pressure vessels shall apply.

11 Testing of the welds

Refer to the codes and standards and to the technical specification.

Reference standards
Uhde Standards
UN 2000-01 Part1 (M) Pressure vessels, general specification
UN 2100-01 Part1 (M) Tubular heat exchangers, general specification
UN 2000-10 Part1 (M) Title block's for manufacturers drawings
UN V416-02 Part1 (M) Tube – to – tubesheet joints
UN V416-03 Part1 (M) Surface treatment of austenitic stainless steels after welding
Uhde forms
UF V360-21 Part1 Welding procedure and testing schedule
 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
for vessels and equipment Part 2 (M)
Examples Page 1 of 45
[Modified on: 29/08/2008]

Contents
Page

1 Scope.................................................................................................................................................................... 1
1.1 Handling ................................................................................................................................................................ 1
2 Examples for welded joints of similar steels .................................................................................................... 2
U1 Heads and shells ................................................................................................................................................... 2
U2 Flanges.................................................................................................................................................................. 3
U3 Nozzles.................................................................................................................................................................. 4
U4 Pad type connections, inserted.............................................................................................................................. 8
U5 Jacketed vessels ................................................................................................................................................. 11
U6 Nozzles penetrating the jackets........................................................................................................................... 13
U7 Half-pipe coil jacket.............................................................................................................................................. 14
U8 Skirts, legs, support brackets............................................................................................................................... 15
U9 Joints of shell-to-flat-head or shell-to-tubesheet .................................................................................................. 20
U 11 Agitator to coupling flange joint............................................................................................................................ 25
U 12 Weldring gaskets ................................................................................................................................................. 29
U 13 Attachment welds ................................................................................................................................................ 30
3 Examples for welded joints of dissimilar steel ............................................................................................... 31
U 51 Attachments welded to cladding .......................................................................................................................... 31
U 52 Weld joints of loose liner...................................................................................................................................... 32
U 53 Components of carbon or low-alloy steel to be welded to austenitic steel ........................................................... 36
U 54 Configuration of dissimilar-steel welds................................................................................................................. 38
U 55 Vessel nozzles with alloy cladding or lining ......................................................................................................... 44

1 Scope
This Uhde standard is a supplement to Uhde standard UN V416-01 Part 1(M) “Requirements”, and covers the
requirements for weld joint of similar and dissimilar steels.

1.1 Handling
Individual sheets of this Uhde standard may be used as specification if a respective note is included. In this
case, it is not necessary to change the numbering of the page.

The details marked
in this Uhde standard require an agreement between purchaser and manufacturer. The
latter is requested to make proposals which require written approval prior to the performance of the welds.

© 2008 UHDE INDIA Technical Discipline: MQ

 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
for vessels and equipment Part 2 (M)
Examples Page 2 of 45

2 Examples for welded joints of similar steels

Item Figure Application Requirements Notes

U1 Heads and shells

For type of groove
refer to
Uhde-Standard
UN V416-01 Part 1(M)
U 1.1 Section 3

Tapered transition for 1)

plates of unequal wall
thickness. If cladding is required, the
tapered transition shall be
arranged on the external
U 1.2 side.

For non-pressure ves- a = 0,5 s1 If surface protection

sels with flat heads. but min. 3 mm from inside is required,
the surfaces shall be
smoothed by grinding.

U 1.3

For non-pressure ves- For pressure vessels only For type of groove
sels with conical heads. with double-welded butt refer to
joint; the related design Uhde-Standard
standard must be ob- UN V416-01 Part 1(M)
U 1.4 For pressure vessels in served. Section 3
exceptional cases.

When plates of unequal 1) For type of groove

wall thickness are refer to
welded and the joint is Longitudinal weld: Uhde-Standard
accessible from one e1; e2 ≤ 0.1 s2 UN V416-01 Part 1(M)
but max. 2 mm
U 1.5 side only. Section 3.
Circumferential weld: The offset e2 shall be
e2 ≤ 0.1 s2; max. 2 mm such that the root pass
can be welded prop-
e1 ≤ 0.2 s2; max. 5 mm erly

When plates of unequal 1) For type of groove

wall thickness are refer to
welded and the joint is Longitudinal weld: Uhde-Standard
accessible from both e1 ≤ 0.1 s2; max. 2 mm UN V416-01 Part 1(M)
sides. e2 ≤ 0.2 s2; max. 4 mm Section 3.
s2 - s1 ≤ 0.3 s1; If full penetration by
U 1.6 max. 6 mm the back-welding
method and a suffi-
Circumferential weld: cient transfer of
e1 ≤ 0.2 s2; max. 5 mm forces is ensured,
e2 ≤ 0.4 s2; max. 10 mm higher offset values
s2 - s1 ≤ 0.4 s1; are admissible for
max. 10 mm non-pressure vessels
 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
for vessels and equipment Part 2 (M)
Examples Page 3 of 45

Item Figure Application Requirements Notes

When plates of different 1) For type of groove

wall thicknesses are refer to
welded. For pressure The values of U 1.5 or Uhde-Standard
U 1.7 U 1.6 are exceeded.
vessels refer to the UN V416-01 Part 1(M)
design standards. Section 3

1) If cladding is required, the admissible offset depends on the cladding thickness.

U2 Flanges
For pressure vessels, The flange face nor-
process equipment and mally needs not be
piping. machined after weld-
ing.

U 2.1 Welding Neck Flange For type of groove

refer to
Uhde-Standard
UN V416-01 Part 1(M)
Section 3.

Flanged nozzles and PN ≤ 10 bar For type of groove

piping. DN ≤ 500 refer to
Uhde-Standard
UN V416-01 Part 1(M)
U 2.2 Section 3.

Non pressure vessels s1 ≤ 8 mm If necessary, the

of carbon-steel. a ≥ 3 mm flange face shall be
machined after weld-
ing.

U 2.3

Non pressure vessels For vessel shell flanges: If necessary, the

s1 ≥ 5 mm (for austenitic flange face shall be
steel ≥ 4 mm) machined after weld-
h ≤ 6 s1 ing.
a = 0.7 s1 ≥ 3 mm This applies also for
b ≤ 3 mm for s1 ≥ 5 mm plain collars of Lap
b ≤ 2 mm for s1 < 5 mm Joint flanges.
U 2.4
 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
for vessels and equipment Part 2 (M)
Examples Page 4 of 45

Item Figure Application Requirements Notes

Pressure vessels s1 ≤ 30 mm The flange shall be

b ≤ 3 mm if s1 < 16 mm machined after weld-
b ≤ 4 mm if s1 ≥ 16 mm ing. For temperatures
above 150°C a vent
bore shall be provided.
Single-bevel groove weld
a (mm) pe · di (bar mm)
0.7 s1 ≤ 10 000
1.0 s1 ≤ 20 000

U 2.5

Single-J groove weld

for pe · di = unlimited
alternatively
s1 ≤ 10 mm > 10 mm
t = s1 = s1
R = 6 mm = 8 mm

see U 2.5 see U 2.5 see U 2.5

U 2.6

U3 Nozzles
Nozzles accessible from both side
Minimum wall thickness of the nozzle pipe s1 ≥ 3.2 mm
2) a = 0.7 s1 but
a ≥ 3 mm if s2 ≤ 15 mm
Nozzles protruding a ≥ 5 mm if s2 > 15 mm
from the internal side h ≥ s1
for
s1 ≤ 14 mm
s2 ≤ 30 mm This requirement only
U 3.1 applies to
s1 < s2
 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
for vessels and equipment Part 2 (M)
Examples Page 5 of 45

Item Figure Application Requirements Notes

2) s = 0,5 s1 If s1 larger than s2 the
a = 0,5 s1 weld dimensions shall
Nozzles protruding h ≥ s1 comply with s2.
from the internal side
for This applies also to s1
< 14 mm if the nozzles
s1 > 14 mm are used for the rein-
s2 ≤ 30 mm forcement of wall cut-
outs
U 3.2

2) a = 0,7 s1 but

Nozzles which do not a ≥ 3 mm if s2 ≤ 15 mm

protrude from the inter- a ≥ 5 mm if s2 > 15 mm
nal side (such as m ≥ s1
drains, internals, lining)

U 3.3 s1 ≤ 14 mm
This applies only to
s2 ≤ 30 mm
s1 < s2

2) s = 0.5 s1 If s1 is larger than s2,

a = 0.5 s1 the weld dimensions
Nozzles which do not m ≥ s1 shall comply with s2.
protrude from the inter-
nal side (such as This applies also to s1
drains, internals, lining) < 14 mm if the nozzles
are used for rein-
s1 > 14 mm forcement of wall cut-
s2 ≤ 30 mm outs.

U 3.4

alternatively

2) These welds shall only be used for atmospheric vessels.

 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
for vessels and equipment Part 2 (M)
Examples Page 6 of 45

Item Figure Application Requirements Notes

Pressure vessels z ≈ 0.3 s2 Back welding is re-

quired; weld with
s2 ≤ 10 mm notch-free transition.
3)

U 3.5

Pressure vessels z ≈ 0.3 s2 Weld with notch-free

transition.
s2 > 10 mm Ensure adequate wall
3)
thickness s1.

β 45° to 60° ≥ 30°

b
U 3.6 (mm)
2 to 4 4 to 6

Preferred for enameled s2 > 4 mm in case it must This type requires

vessels be enameled approval on a case-to-
case basis. The
s2 ≤ 12 mm necked-out section
must be such, that the
material properties are
U 3.7 not affected.

This applies also to
cases where the weld
is accessible from one
side only.
3)

Nozzle accessible from one side only

Minimum wall thickness of nozzle pipes s1 ≥ 3.2 mm
DN ≤ 300 s2 = 3 s1 If s2 > 16 mm, single-J
z ≈ 0.3 s2 groove is permitted.
s1 ≤ 14 mm
3)
s2 ≤ 30 mm Weld root pass by the
gas-shielded method.

U 3.8

3) The internal edges of the nozzle pipe shall be rounded. For radius refer to Uhde Standard UN 2000-01 Part 1 (M) clause 3.4.3
 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
for vessels and equipment Part 2 (M)
Examples Page 7 of 45

Item Figure Application Requirements Notes

DN ≤ 100 s2 ≤ 3 s1 The shell section ad-

jacent to the nipple
s1 ≤ 7 mm Weld root pass by the weld shall be
s2 ≤ 30 mm gas-shielded method. subjected to ultrasonic
testing.
Permitted only in ex-
ceptional cases which Ensure adequate
require the approval of nipple length
U 3.9 the purchaser. (> 6 s1)

3)

For nipples and nozzles Additional measures The shell section ad-
subjected to higher required for full penetra- jacent to the nipple
loads; da < 100 mm tion welding shall be weld shall be sub-
agreed upon on a case- jected to ultrasonic
They are subjected to to-case basis. testing.
special approval.
3)
s2 ≥ t + 3 mm
t ≥ 3 mm
s1 (mm) x (mm)
U 3.10 Weld the root pass by the
≤ 4.5 8

> 4.5 to 8 4 gas-shielded method.
> 8 to 16 ≈2

Special type with drilledHole and weld depth must For s1 ≥ 4 mm, the
root for nozzles and be arranged such as to following dimensions
nipples which have a ensure proper drilling to may be used:
diameter (d < 50 mm). the root.
β = 30°
c ≥ 1.5 mm
Type normally used for R ≥ 4 mm
U 3.11 high-pressure vessels. d1 = d2 + 2 mm
In case of larger diame- d = d1 + (4 to 6 mm)


ters, this weld type is The shell section ad-
subjected to approval jacent to the nipple or
of the purchaser. nozzle welds shall be
subjected to ultrasonic
testing.
3)

Reinforced types of nozzle

For pressure vessels If the nozzle is accessible 3)

from both sides, the weld
Nozzle reinforced by edge shall correspond to
means of pipes of lar- Figures U 3.5 to U 3.6; if it
ger wall thickness shall is accessible from one
be preferred to reinforc- side only, it shall comply
ing rings. with Figure U 3.8.
U 3.12

3) The internal edges of the nozzle pipe shall be rounded. For radius refer to Uhde Standard UN 2000-01 Part 1 (M) clause 3.4.3
 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
for vessels and equipment Part 2 (M)
Examples Page 8 of 45

Item Figure Application Requirements Notes

Used for nozzles which s3 ≤ s2 For use in hydrogen

are accessible from h ≥ 0.7 s3 service, the weld de-
both sides, configura- α = 60° sign shall correspond
tion according to Fig- a = 0.5 s3 to Figure U 3.14.
ures U 3.1 to U 3.4 3)

U 3.13

Pressure vessels 3)
s3 ≤ s2
b + s1 = s3
b ≥ 7 mm
β ≥ 20°
a = 0.5 s3
z ≈ 0.3 s3
U 3.14

U4 Pad type connections, inserted

Non pressure vessels; a = 0,7 s2
spherical, cylindrical h ≥ s2
and flat sections
s2 = 5 to 16 mm

If pad type flanges with

a larger diameter D are
welded to shells, it is
essential that an ade-
quate diameter Da be
provided.
U 4.1
alternatively
Standard weld for spheri-
cal and flat sections

3) The internal edges of the nozzle pipe shall be rounded. For radius refer to Uhde Standard UN 2000-01 Part 1 (M) clause 3.4.3
 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
for vessels and equipment Part 2 (M)
Examples Page 9 of 45

Item Figure Application Requirements Notes

Spherical, cylindrical s = 0.35 s2

and flat sections, a = 0.5 s2
16 < s2 < 30 mm h = 1.3 a
If pad type flanges with
a larger diameter D are
welded to shells, it is
essential that an ade-
quate diameter Da be
provided.

U 4.2
alternatively
standard weld for
spherical and flat
sections

Pressure vessels z ≈ 0.3 s2 if s2 < 16 mm

s2 ≤ 30 mm b = 2 to 3 mm it is possible to use
single-bevel groove
If pad type flanges with welds with back-
a larger diameter D are welding.
U 4.3 welded to shells, it is
essential that an ade-
quate diameter Da be
provided.

Spherical and flat sec-

tions, irrespective of the
wall thickness s2.

U 4.4

For spherical, cylindri- z ≈ 0.3 s2 If s2 > 16 mm, a dou-

cal and flat section if b = 2 to 3 mm ble-bevel groove weld
the flange must be is required.
plane with the internal
side.

U 4.5 s2 ≤ 30 mm
 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
for vessels and equipment Part 2 (M)
Examples Page 10 of 45

Item Figure Application Requirements Notes

For spherical, cylindri- z ≈ 0.3 s2

cal and flat sections if b = 2 to 3 mm
the joint is accessible
from one side only. Weld root pass by the
gas-shielded method.
s2 ≤ 16 mm
U 4.6

Pad type connections, set up

Non pressure vessels; a = 0.5 s2 ≥ 5 mm Tapped hole penetrat-

z = 0.7 s2 ing the pad or blind
For spherical, cylindri- thereby covering s2 hole.
cal and flat sections if
For pressure vessels,
h ≤ 3 mm use tapped blind hole.
s2 ≤ 30 mm

For h ≤ 1 mm
(such as inspection
holes), the following is
required:
a = 0.5 s2 ≥ 3 mm
U 4.7

alternatively
For spherical and
flat section

Non pressure vessels; h2 ≤ 3 mm, otherwise it Tapped hole penetrat-

must be adapted ing the pad or blind
For spherical and cylin- hole.
drical section if a = 0.5 s2 ≥ 5 mm
z = 0.7 s2 thereby cover- For pressure vessels,
h1 ≤ 15 mm ing s2 use tapped blind hole.
s2 ≤ 30 mm
e = 0.5 s2 ≥ 10 mm

U 4.8

alternatively
For spherical and
flat section
 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
for vessels and equipment Part 2 (M)
Examples Page 11 of 45

Item Figure Application Requirements Notes

Non pressure vessels; h2 ≤ 3 mm, otherwise it Tapped hole penetrat-

must be adapted. ing the pad or blind
For spherical and cylin-
hole.
drical section if
s1 ≈ s2
h1 > 15 mm a = 0.5 s2 ≥ 5 mm For pressure vessels,
s2 ≤ 30 mm a1 = 0.5 s2 ≤ 6 mm use tapped blind hole.
z = 0.7 s2 thereby cover-
ing s2

U 4.9

U5 Jacketed vessels
For vessels if α ≈ 45° Full penetration weld
s2 ≤ 15 mm β = 45° to 60° for root pass required
b = 2 to 3 mm This type is also used
for pipes.

U 5.1

s2 ≤ 15 mm
1. for instance, if the
shell must be
enamelled.
2. for instance, if the
vessel must be
heat-treated with-
out jacket.

U 5.2
 UHDE-STANDARD
Welding UN
WELDED JOINTS V416-01
for vessels and equipment Part 2 (M)
Examples Page 12 of 45

Item Figure Application Requirements Notes

s2 ≤ 15 mm β = 45° to 60° If the stress is low,

1. for instance, if the b = 0 to 4 mm fillet welds with
shell must be a = 0,7 s2 are also
enamelled. admissible.
2. for instance, if the
vessel must be
heat-treated with-
out jacket.
U 5.3

s2 > 15 mm c = according to the de- This type is also used

sign calculation but > s2 for pipes.
If the stress is low,
R ≥ 5 mm fillet welds with
h ≥ 0.5 s2 a = 0,7 s2 is also ad-
b = 0 to 4 mm missible.
β = 45° to 60°

U 5.4

Jacket welded in sec- a ≥ 0.7 s2 Subject to approval on

tions b ≥ 1.5 s2, but min. a case-to-case basis.
6 mm
β ≥ 10° if s2 ≥ 10 mm
alternatively:
The fillet welds a1 must be
calculated
a1 ≥ 0.7 s2
U 5.5