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Vol. 7
March Issue
Year 2006
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Articles


in Vol. 7 - March Issue - Year 2006
Manufacturing Tungsten Carbide Nozzles



Liners being loaded into a vacuum sintering furnace


CNC machining of nozzle jackets


Liner and jacket assembly

Offering low cost and therefore the potential of high margins, OE equipment suppliers in the international abrasive blast cleaning market are being targeted by Chinese, Indian and Far Eastern manufacturers of tungsten carbide blast nozzles.

Low cost imported nozzles may however be a false economy as these manufacturers cannot always offer the benefits of off-the-shelf stocks and the long working life that only high quality products can bring. Gordon McShannon of Hydra Mining Tools explains.
Without doubt the most critical factor in the efficient use of blast cleaning equipment is the blast nozzle. If a nozzle’s bore opens up too quickly or inconsistently, or if cracks or holes occur, it has to be replaced. Blast cleaning contractors have to have confidence that the nozzles they are using will give a long working life - an inferior product will impact directly on the profitability of any contract.
Many factors affect a nozzle’s productivity and longevity, chiefly:  the quality of the tungsten carbide powder used in the manufacture of the liner (an inferior material will wear away prematurely); quality in all stages of manufacture (to ensure a consistent venturi shape and orifice size) and the close fit between jacket and liner (which ensures that air and abrasive material cannot pass between the two, causing premature failure)
It is no coincidence that a high quality product is often the result of manufacturing experience and Hydra Mining Tools’ expertise in carbide manufacture extends back over 40 years.

High quality raw materials and manufacturing make the best nozzles
 
The majority of nozzle liners are manufactured in one piece from tungsten carbide, boron carbide or silicon carbide powder.  Over the years Hydra has developed the optimum blend of these powders or equivalents; every batch is first checked under laboratory conditions before being pressed into a mould. The powder is then sintered in a vacuum furnace, specially manufactured for just this purpose.
A typical cycle for producing a liner is to process it under vacuum at temperatures approaching 1500 deg. C. - the complete cycle taking some 12 hours.  The resulting liner is then one of the hardest materials known to man but quite fragile. It therefore has to be protected from breaking up or cracking in use with a jacket.
Jackets are manufactured from either aluminium or nylon. Soft, shock absorbing nylon jackets are proving more and more popular as they reduce the risk of accidental liner damage in use and are less prone to ‘jamming’ in the holder. Some customers prefer the best of both worlds - a traditional aluminium jacketed nozzle with a thin nylon outer sleeve or a combination steel/aluminium jacket. Regardless of material for greater accuracy, bore consistency and repeatability, as at Hydra, all jackets should be machined on CNC machines
The accuracy of both liner and jacket becomes apparent when the two are brought together, as it is here that a sloppy or over tight fit will cause premature failure when the nozzle is used. Once the fit has been checked, the two components are affixed, assembled and an end shim put in place to protect the exposed face of the liner. Finally, a part number or customer’s logo is stamped onto the outer jacket.

Experience in working with tungsten carbide

Hydra Mining Tools has been a leader in the manufacture of tungsten carbide cutting tools for mining and construction for over 40 years. The acquisition of a nozzle liner production facility and an investment at its Rotherham factory allowed the company to manufacture, in-house, a wide range of tungsten carbide, silicon carbide and boron carbide lined nozzles.  Since then Hydra has grown to be one of Europe’s leading manufacturers, exporting nozzles to over 20 countries.
In addition to manufacturing and stocking over 100 standard lines to European and US standards, Hydra also has the skills and facilities to design and manufacture special nozzles to meet particular requirements - ie. nozzles with brass jackets, special locating threads, larger bores, solid tungsten carbide nozzles with no jackets etc. Because of their experience and flexibility Hydra are often able to manufacture these Specials quickly and cost effectively.
 
We want them yesterday...
 
Blast cleaning contractors are notorious for leaving it until the last minute before ordering vital consumable parts. Hydra has therefore made special efforts to support its customers by carrying large stocks of nozzles ....so its customers don’t have to.  At any one time, between 7 and 8,000 nozzles are always held in stock at Rotherham ready for immediate despatch.




Author: Gordon McShannon
For Information:
Hydra Mining Tools International Ltd.
Rotherham Works, Wortley Road
Rotherham S61 ILZ, UK
Tel. +44.1709. 857500, Fax +44.1709.857501
E-mail: info@hydramining.com