History was made last week when Dannevirke engineering company RCR Energy completed two steam locomotive boilers, the largest boilers built in New Zealand for more than 60 years.
They are for the Glenbrook Vintage Railway (GVR), a steam-operated 8km long tourist railway which carries 30,000 passengers per year between Glenbrook and Waiuku, south-west of Auckland, staffed entirely by volunteers.
Trains run on Sundays and public holidays between Labour Day and Queen's Birthday weekends and for special events such as Day Out with Thomas and charters.
When the GVR opened 40 years ago, motive power was provided by Ww 480, an ex-New Zealand Railways tank locomotive then more than 60 years old.
Weighing 52.5 tonnes, this was one of a class of similar locomotives employed all over the country on suburban passenger trains, shunting and near the end of the NZR career, hauling coal trains on the West Coast.
After years of faithful service by Ww 480, by mid-2013 major repairs were required on the boiler and a detailed cost estimate of the repairs were carried out.
As an alternative, two New Zealand manufacturers were asked to provide estimates for a new boiler.
Boiler designs today are much advanced on those last used by NZ and other railways in the 1950s.
These had mostly riveted joints, while today in commercial boilers, riveting is unknown, superseded by welding.
Although welded boilers had been recently built and operated successfully on locomotives in NZ these were smaller than the Ww type and used on duties less onerous than on the GVR.
As there was much conservatism and scepticism among NZ rail enthusiasts about the suitability of welded locomotive boilers, approaches were made to users of locomotives with welded boilers having duties similar to those of the GVR - Puffing Billy in Melbourne, and Queensland Railways in Brisbane. Both organisations were helpful.
Puffing Billy operates the most intensively worked steam locomotives in Australia or New Zealand, and through trial and error has refined the design of their many welded boilers to give excellent reliability.
Similarly, Queensland Railways operate a heritage fleet of steam locomotives more similar in size and duty to those of the GVR, with welded boilers built in-house and employing up to date features and welding techniques.
The QR boiler designer was engaged to draw up a welded version of the NZR Ww boiler design using proven QR features.
This design, and a detailed scope of works to design and build one or two Ww boilers, was forwarded to three New Zealand and one Sydney manufacturer for a quote.
Included in the evaluation was a visit to each of the tenderer's works and an assessment of their design capability, management systems and documentation, and an order was placed with RCR Energy for two boilers in view of the substantial per boiler saving and with GVR's second Ww locomotive, 644, in mind.
Several months of discussion between RCR Energy and GVR followed to refine the design with visits by GVR staff to RCR, with the details examined and signed off by certifiers SGS.
The codes to which the boiler have been built are very much more stringent than NZR boilers, which has been reflected in thicker plates and tubes, more robust inspection plugs and support of flat surfaces.
Once SGS had approved the designs, construction commenced and several visits were made to Dannevirke by GVR staff to inspect work in progress.
SGS also visited regularly and inspected the work done, compliance with the drawings and particularly weld quality.
The supply of boiler fittings andjoined small and large tubes was GVR's responsibility and many large non-standard size tubes had to be specially made in Germany.
The importer arranged for parts of the shipment to go to three other New Zealand heritage railways using the same diameter tube. Joining of the large tubes was a problem.
On one end of each the diameter is increased and on the other end decreased.
Hydraulic testing of the boilers to 150 per cent of normal working pressure presented no problems, and both were signed off as fit for service by SGS.
Now the real work by GVR starts - connecting the smoke box, installation, cladding, connection of pipe work and fitting of grate and brick arch, reassembly of the locomotive, painting, testing and final certification.
"Throughout the process, RCR Energy and its staff have been extremely cooperative, helpful and professional, and a pleasure to work with," John St Julian of GVR says.
"Personally I have found this to be a most interesting and satisfying project.
In railway preservation circles, this is really something, and provided the installation and commissioning of the boiler goes to plan, we will have achieved something that has eluded a certain much better known and very much better financed Australian example.
"I put this down to a well-researched and tight specification on our part and an extremely well organised and professional planning, design and control process by RCR, plus of course, absolutely first class welding skills. To this technocrat, most of the welds are things of beauty."