Randall Reports

INTRODUCTION:

The New Zealand Heavy Engineering Research Association (HERA) recently ran a series of seminars, introducing the upcoming move to AS/NZS2980 Qualification of welders for fusion welding of steels.

These very cursory notes are as a result of HERA’s seminar in Palmerston North, and many thanks are extended to Alan McClintock and Mikail Karpenko for their presentation.

SUMMARY:

NZS4711 and 4703 are being phased out, to be replaced by AS/NZS2980. This avoids the cost of updating the rather out-of-date 4711, and remedies the issue of having 2 standards covering a similar area.

AS/NZS2980 is also more useful, in that it covers a wide range of steel types (including high strength and stainless), material thicknesses and more welding processes.

NZS4703, covering stainless steel pipes for the dairy industry, has been incorporated into AS/NZS2980.

Existing NZS4711 and 4703 qualifications remain valid till their expiry date, then to be replaced with qualifications to AS/NZS2980.

New or renewal qualifications to NZS4711 will not be available from 01 April 2011.

Certifying officers will not be re-approved to NZS4711 after 31 March 2011.

MAIN ASPECTS OF AS/NZS2980:

The welder is to follow a qualified Welding Procedure Specification, defining variables such as type and position of weld, weld details, material group and dimensions, consumables, welding machine settings.

A more difficult position qualifies the welder for all joints considered easier to weld. For example, an overhead butt weld in plate qualifies for all plate positions except vertical down.

Weld qualification for welds at a particular material thickness qualifies that weld for a range of thicknesses. For example, material thickness “t” of less than 3mm qualifies for a thickness range of “t” to “2t”.

A weld in a particular material group qualifies that weld for a range of groups. For example, welds in quenched and tempered steels qualifies for that group along with carbon steel below 450MPa yield, fine-grain and cast steels, some nickel alloy steels and low-carbon steels.

Welder test certificate is for 2 years, subject to 6-monthly confirmation by that person’s welding supervisor that the welder has been working within the range of qualification. That welding supervisor would be a designated and responsible employee of the welder’s employer.

The certificate can be prolonged by the examining body for a further 2 years, provided that evidence can be provided of successful weld test or examination of 2 welds in the previous 6 months. The weld test exercise itself does not have to be re-done.

A self-employed welder should engage a supervisor at an independent examining body.

I was asked recently about the legality of a 3-axle simple trailer, versus the more usual 2-axle model. These 2-axle trailers are really useful, but are limited to carrying about a 15 tonne digger. Surely, a 3-axle model could carry an 18 tonne machine?

 

A simple trailer is like an over-grown car trailer, with a tandem axle set in the middle, and a rigid drawbar that transfers weight onto the towing vehicle’s coupling - usually around 4 tonne.

 

The gross weight for that tandem axle set is usually 14.5 tonne, as the axles are usually less than 1.3 metres apart. A 3-axle set is permitted to run at 18 tonne.

 

Clause 4.3(6) of the Dimensions and Mass Rule 41001 specifically limits the Gross Combination Mass for a truck and simple trailer to 32 tonne.

 

Sections 4.4 of that same Rule specifies that the Trailer : Truck Mass Ratio for combination vehicles shall be 1.5:1 or less - that is, the gross mass of the trailer must not exceed 1.5 times the gross mass of the towing vehicle.

 

That’s pretty straight forward for, as an example, a rigid truck towing a full trailer - the 1.5:1 ratio sets the maximum trailer weight at 60% of the combination, so if we are running at 44 tonne gross combination mass, the trailer is limited to 26.4 tonne.

 

This is where I should have checked my logic a little more closely, because my first thoughts for the simple trailer application went something like:

                         Maximum Combination Mass =          32 tonne

                        Trailer : Truck Mass ratio                    =          1.5:1

                        so maximum gross weight of trailer    =          32 tonne x 60%

                                                                                    =          19.2 tonne

                        typical trailer Gross Vehicle Mass      =          14.5 tonne on wheels plus

                                                                                                4 tonne on coupling

                                                                                    =          18.5 tonne

 

Conclusion: Not much point in having a 3-axle simple trailer, because you can’t utilise the full 18 tonne permitted for a 3-axle set.

 

Wrong.

 

Read the words and definition of terms more closely - Clause 4.4 refers to “gross mass”, which is defined as “…the mass of that vehicle and its load…which may be determined by adding the mass on the vehicle’s axles or axle sets.”

 

Note the subtle difference between these words and the definition for “Gross Vehicle Mass”, which is “…the gross vehicle mass specified…by the manufacturer…”

 

The 2-axle simple trailer mentioned above would have a manufacturer’s Gross Vehicle Mass of 18.5 tonne - that is, you can load it up to 18.5 tonne total - that is, 14.5 tonne on the wheels and 4 tonne on the coupling - and everyone is happy.

 

From the Trailer : Truck Mass Ratio aspect, however, things are slightly different.

 

The Mass Ratio considers the trailer’s “gross weight”, being the sum of the weights on its axles or axle sets - in this case, only 1 axle set, running at 14.5 tonne.

 

Therefore, for a combination mass of 32 tonne, the truck can run at 32-14.5 = 17.5 tonne, giving a mass ratio of 0.83:1 - well below the permitted maximum.

 

So, if we consider a 3-axle simple trailer with 18 tonne on its wheels, the truck can weigh 32-18 = 14 tonne, giving a mass ratio of 1.29:1, still below the maximum.

 

Our 3-axle trailer would have a tare weight of around 4.0 tonne, so the laden weights would be something like:

                         Mass on axles                                      =          18.0 tonne

                        plus mass on coupling                         =          4.0 tonne

                        less tare weight                                   =          4.0 tonne

                        gives a payload                                   =          18.0 tonne

 

Conclusion: Yes, you may carry an 18 tonne machine on your 3-axle simple trailer.

 

Subsequent note to self: Read those words more carefully.

From the list of impending rule changes coming from the New Zealand Transport Agency, the long-talked about 50 tonne combination mass legislation is expected to be introduced late 2009.

This increased mass limit is touted as being for “high productivity vehicles”.

I wondered what effect this increase might have on the Road User Charges that applicable vehicles would incur, on the basis that no alterations are envisaged to the Dimensions and Mass Rule other than the maximum permitted combination mass - that is, axle and group ratings continue unchanged.

This effectively means that the only rigs that may run at 50 tonne are:

                                    3-axle rigid truck and 4-axle full trailer

                                    4-axle rigid truck and 4-axle full trailer

                                    3-axle tractor unit and 5-axle B-train

The other combinations - including a 4-axle tractor unit with quad semi trailer - are ruled out as axle group ratings will be exceeded.

Using the estimated weights in the following tables and the current Road User Charges, the calculations for each combination of RUC cost per tonne payload show an interesting trend - every one of them gives an increased RUC cost per tonne, of 16-21%.

So much for “high productivity”!

What this tells us is that there will have to be rather more changes than just the Gross Combination Mass - the Road User Charge scale of fees, for one!

Example 1 - 3 axle truck, 4 axle full trailer

          44 tonne GCM        Truck                       Trailer                  Combination

          Tare (tonne)                9.0                            6.5                           14.0

          Payload (tonne)         12.0                          16.5                          30.0

          Gross (tonne)             21.0                          23.0                          44.0

          RUC                       $369.93                    $184.80                    $554.73

          $ / tonne Payload                                                                       $19.46

 

          50 tonne GCM        Truck                       Trailer                  Combination

          Tare                            9.0                            6.5                           15.5

          Payload                     13.0                          23.0                          34.5

          Gross                         22.0                          28.0                          50.0

          RUC                       $432.14                    $349.47                    $781.61

          $ / tonne Payload                                                                $22.66 (+16%)

 

Example 2 - 4 axle truck, 4 axle full trailer

          44 tonne GCM        Truck                       Trailer                  Combination

          Tare                           10.5                           6.5                           17.0

          Payload                     11.5                          15.5                          27.0

          Gross                         22.0                          22.0                          44.0

          RUC                       $237.00                    $162.42                    $399.42

          $ / tonne Payload                                                                       $14.79

 

          50 tonne GCM        Truck                       Trailer                  Combination

          Tare                           10.5                           6.5                           17.0

          Payload                     14.5                          18.5                          33.0

          Gross                         25.0                          25.0                          50.0

          RUC                       $348.71                    $240.25                    $588.96

          $ / tonne Payload                                                                $17.85 (+21%)

 

Example 3 - 3 axle tractor, 5 axle B-train

          44 tonne GCM       Tractor        1^st Trailer      2^nd Trailer      Combination

          Tare                            8.0                5.5                5.0                  18.5

          Payload                      9.0                9.5                7.0                  25.5

          Gross                         17.0              15.0              12.0                 44.0

          RUC                       $192.99         $93.23         $103.09           $389.31

          $ / tonne Payload                                                                       $15.27

 

          50 tonne GCM       Tractor        1^st Trailer      2^nd Trailer      Combination

          Tare                            8.0                5.5                5.0                  18.5

          Payload                     11.0              11.5               9.0                  31.5

          Gross                         19.0              17.0              14.0                 50.0

          RUC                       $268.49        $127.22        $172.63           $568.34

          $ / tonne Payload                                                                $18.04 (+18%)

While this isn’t exactly related to Engineering, it does restore my faith in people, and shows how a few tools that we use all the time at work can actually be very handy!

 

Last Saturday, I was washing my house’s soffits and guttering, using my Raven Telescopic Water Brush - NZ-made, by Raven Products in Auckland.

 

I must have been a bit over-zealous with tightening one of the plastic extension collars, because it broke. I had to stop part-way through the job, of course.

 

After thinking for a little while about the futility of fixing things these days, I decided to be a bit cheeky, and see what happens if I see about getting a replacement.

 

With my digital camera, I took a photo of the broken part. Next, I used Google to find Raven Products and got their website. I then sent an email to their Technical Services Department, wondering about the possibility of getting a replacement, with the photo as an attachment.

 

Upon checking my messages on Monday night, behold! a reply from Richard Mitchell, Raven Sales and Marketing Manager, sent that morning and asking me to confirm my postal address so that they could send the piece.

 

I duly replied, giving my address and confessing that now I’ll have to complete the job. I also asked how I could make payment - might a cheque be acceptable?

 

Come Tuesday night, another reply from Richard, commiserating with me that cleaning the house is the down-side, but also saying to not worry about payment for this one - one of the perks for buying NZ made.

 

So, what tools have we used?             - digital camera,

                                                            - Internet,

                                                            - Google,

                                                            - email.

 

What have we learned?                      - these electronic gizmos can be useful,

                                                            - buying NZ-made can be good,

                                                            - most folk we deal with are great.