• BS 2971 Class 2 Arc Welding of Carbon Steel Pipework  {Gas Pressures less than 17 barg}
• BS 2633 Class 1 Arc Welding of Carbon Steel Pipework 
• BS 4677 Arc Welding Of Austenitic Steel Pipework. 
• BS 806 Boiler Pipe Work (Refers to BS 2971 and BS 2633) 
• PD 5500 Unfired Pressure Vessels (Formally BS5500) 
• BS 2790 Shell Boilers 
• BS 1113 Water Tube Boilers 
• BS 5169 Air Receivers 

UK pressure systems regulations
Items that come under the UK pressure systems regulations must be 'properly designed and constructed so as to prevent danger', and items that are repaired or modified should not give rise to danger. The Health and Safety Executive Guidance Booklet to the regulations interprets this statement as meaning the manufacture or repair of any item should be carried out to suitable codes and recommends the use of British Standards or other equivalent National Standards. 

European Pressure Equipment Directive
For inspection category 2 and above all welding procedures and welder qualifications have to be approved by a Notified Body (an Inspection Authority Notified by a European member country under the Directive), or a Third Party Organisation similarly approved under the Directive. All qualifications approved by these organisations have to be accepted by all parties for work carried out under the directive providing they are suitable for the application and technically correct. 

Welding Procedure Specifications
This is a simple instruction sheet giving details of how the weld is to be performed, its purpose is to aid the planning and quality control of the welding operation. EN ISO 15609 (formerly EN288 Part 2) specifies the contents of such a specification in the form of a list of items that should be recorded, however only relevant information need be specified, for example only in the case of a procedure requiring heat input control would there be a necessity to quote travel speed or run out length for manual processes. 

1. Produce a welding procedure specification as stated above. 
    
2. Weld a test piece in accordance with the requirements of your specification. The joint set up, welding and visual examination of the completed weld should be witnessed by an Inspection Body. The details of the test such as the welding current, pre-heat etc., must be recorded during the test.
    
3. Once the welding is complete the test piece must be subject to destructive and non destructive examination such as radiography and mechanical tests as defined by the welding procedure standard. This work can be carried out in any laboratory but the Inspection Body may require to witness the tests and view any radiographs. 
    
4. If the test is successful you or the test body complete the appropriate documents which the test bodies surveyor signs and endorses. The necessary documents are as follows:- 

Forms E1, E2, E3 may be referred to as the WPAR (Welding Procedure Approval Record) or WPQR (Weld Procedure Qualification Record).

• Change in parent material type. 
• Change of welding process 
• The diameter range for pipe given by the welding standard is exceeded. Typically 0.5xD to 2xD. 
• The thickness range is exceeded. Typically 0.5xt to 2xt. 
• Any other change required by the welding standard. 

Complete a weld test as stated in 2) above. The test should simulate production conditions and the welding position should be the position that the production welds are to be made in or one more severe
For maximum positional approval a pipe inclined at 45 degrees (referred to as the 6G position) approves all positions except vertical down. 

Test the completed weld in accordance with the relevant standard to ensure that the weld is clean and fully fused.
For a butt weld this is normally a visual examination followed by radiography. 

Once the test is completed the E4 form has to be completed by you or the test body and signed by the test bodies surveyor. 

Note The above changes that require a new welding procedure may also apply to the welders approval, refer to the standard for precise details. 

Welder Approval Without A procedure
BS 4872 is for the qualification of welders where a weld procedure is not required either by the application standard that governs the quality of production welds or by contractual agreement. Typically applied per BS2971 for welding of boiler pipework less than 17 bar g and 200°C. Basically the same rules mentioned above for the welder approval apply. 

Acceptance Standards
In general welds must show a neat workman like appearance. The root must be fully fused along the entire length of the weld, the profile of the cap should blend in smoothly with the parent material and the weld should be significantly free from imperfections. Reference should be made to the acceptance standard for precise details. 

What information should they include?

 Sufficient details to enable any competent person to apply the information and produce a weld of acceptable quality.  The amount of detail and level of controls specified on a WPS is dependant on the application and criticality of the joint to be welded.

 For most applications the information required is generally similar to that recorded on a Procedure Qualification Record (PQR) or Welding Procedure Approval Record (WPAR), except that ranges are usually permitted on thicknesses, diameters, welding current, materials, joint types etc.

 If a WPS is used in conjunction with approved welding procedures then the ranges stated should be in accordance with the approval ranges permitted by the welding procedure.

 However careful consideration should be given to the ranges specified to ensure they are achievable, as the ranges given by welding procedure standards do not always represent good welding practice.  For example welding positions permitted by the welding procedure standard may not be achievable or practical for certain welding processes or consumables.

 EN ISO 15609-1 (formally EN 288 Part 2)  European Standard For Welding Procedure Specifications
EN ISO 15609 Defines the contents of a Welding Procedure Specification in the form of a list of information that should be recorded.  For some applications it may be necessary to supplement or reduce the list. For example only in the case of a procedure requiring heat input control would there be a necessity to quote travel speed or run-out length for manual processes.

 ASME IX  American Boiler and Pressure Vessel Code
QW 250 Lists the variables for each welding process, all the variables stated should be addressed.  The range permitted by the WPS is dictated by the PQR or PQR’s used to qualify it. 

Typical Items That Should Be Recorded On W.P.S:-

     Common to all Processes        .

• Procedure number
• Process type
• Consumable Size, Type and full Codification.
• Consumable Baking Requirement if applicable
• Parent material grade and spec.
• Thickness range.
• Plate or Pipe, Diameter range
• Welding Position
• Joint Fit Up, Preparation, Cleaning, Dimensions etc.
• Backing Strip, Back Gouging information. 
• Pre-Heat (Min Temp and Method)
• Interpass If Required (Maximum Temperature recorded )
• Post Weld Heat Treatment. If Required (Time and Temp)
• Welding Technique (weaving,max run width etc.)
• Arc Energy Limits should be stated if impact tests are required or if the material being welded is sensitive to heat input.

Sketches
A sketch of the joint configuration is required which should include the basic dimensions of the weld preparation.  Some indication of the run sequence is also beneficial, particularly if the correct sequence is essential to ensure the properties of the weld are maintained. 

Production Sequence
Whilst this is good practice it is not a requirement of either ASME 9 or EN288 Part 2; it could be issued as a separate QA procedure if preferred.

Non Destructive Testing
A WPS is primarily concerned with welding not N D T, this activity should be covered by separate N D T procedures.

The Clarke 90EN MIG Welder

That's just 90 amps. But it's a natty little welder that can do both gas and gasless welding. The knobs at the bottom marked "+" and "-" are for attaching the earth wire and power feed to the gun. The wires can be changed over to go from gasless to gas shielding welding. (The photo shows the set up for gasless with a positive earth).

Machine Mart claims "Power settings from 24 - 90amps. Welds mild steel up to 4mm thickness." Which seems quite a lot for such a little welder so I thought I'd put it to the test. I set it up with 0.8mm steel wire and Argon/CO2 mix shielding gas.

The welder works very well on thin metal. Here are some welds on 1.5mm sheet at different power settings (which are marked below the welds). I'd assumed the order of increasing power would be 1min, 1max, 2min, 2max. But I admit I haven't read the manual. The order of increasing power appears to be 1min, 2min, 1max, 2max.

The results are just as good as more expensive welders for 1.5mm steel, although the welder did seem a little more sensitive to wire speed settings than my normal 155 amp welder.

The duty cycle is worse for this one as well, but I normally spend 10 minutes preparing for every 1 minute welding so for car welding so that wouldn't be a problem for me.

Let's try some 2mm sheet

Back to the point of the exercise. With the power cranked up to maximum I had a go at 2mm sheet steel. I welded very slowly to try and get as much heat as possible into the weld. It ended up looking quite neat.

The penetration was reasonable. It took a little time for the metal to heat up, so the first 15mm is a bit marginal, but once I'd got going the penetration was perfectly acceptable.

Had I been using a more powerful welder I'd have rejected the weld, turned the power up another notch and welded a bit faster which would have improved the penetration at the start. But since we were already at max I'll be kind and accept the little welder's attempt at 2mm steel.

3mm sheet

So already wanting more power I decided to try some 3mm steel.

With the the power still set at maximum I tried butting two sheets of 3mm steel together. Maybe welding even more slowly would be enough to get some penetration.

Nope - no sign of any penetration on the reverse.

I tried a bend test in the vice. It took a bit of hammering to break the weld, but when it did break the weld broke in two which means it was less strong than the steel it was trying to join together. Penetration turned out to be very poor, with the weld barely penetrating a quarter of the way through the sheet.

So we can't weld 3mm sheet never mind 4mm.

Let's try adding a V and a root gap to the 3mm sheet.

Thick sheets are hard to weld, so it's probably not unreasonable for the manufacturers to expect us to do a little preparation.

Here I've tapered the edges of the 3mm sheet to create a 90 degree V. Also I've spaced the two sheets apart by 1mm (root gap). That's about all I can do to help the poor welder. The weld looks neat, how's the penetration?

Once again the penetration was quite good once the welder got going. But for the first 15mm the welder couldn't get the metal hot enough and penetration was poor. Again, even with the V and the root gap I find myself reaching for another power setting.

I tried another bend test. This time the parent metal broke rather than the weld, which is a good sign that some of the weld was OK (apart from that first 15mm where there just wasn't enough heat - there the weld broke before the metal).

It seems unfair to even ask the welder to try anything more than 3mm, never mind claim that it can manage it.

In TIG welding an arc is formed between a nonconsumable tungsten electrode and the metal being welded. Gas is fed through the torch to shield the electrode and molten weld pool.  If filler wire is used, it is added to the weld pool separately. 

TIG Welding Benefits

•  Superior quality welds
•  Welds can be made with or without filler metal
•  Precise control of welding variables (heat)
•  Free of spatter
•  Low distortion

Shielding Gases

•  Argon
•  Argon + Hydrogen
•  Argon/Helium

Helium is generally added to increase heat input (increase welding speed or weld penetration).  Hydrogen will result in cleaner looking welds and also increase heat input, however, Hydrogen may promote porosity or hydrogen cracking.

GTAW Welding Limitations

•  Requires greater welder dexterity than MIG or stick welding
•  Lower deposition rates
•  More costly for welding thick sections

Weld Discontinuities

•  Undercutting
•  Tungsten inclusions
•  Porosity
•  Weld metal cracks
•  Heat affected zone cracks

TIG Welding Problems

•  Erratic arc
•  Excessive electrode consumption
•  Oxidized weld deposit
•  Arc wandering
•  Porosity
•  Difficult arc starting

The cohesiveness of the molten metal, the pressure of the flame, the support of the weld metal already deposited, and the manipulation of the rod all combine to keep the molten metal in the puddle from running or falling.