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Grundfos pumps it up

30 września 2009

Tekst: David Wiles

zdjęcia: Getty images, martin magntorn and grundfos

Grundfos, one of the world’s largest pump manufacturers, had a problem. A combination of vibrations, high temperatures and corrosive liquids meant that the nylon locking nuts at the heart of its machines were coming loose. The result for the Danish company, with its global reputation for quality and reliability, was sometimes pump failure. But in a chance encounter they stumbled upon what they describe as a brilliant fix for their predicament.

boat spraying water

First published in Bolted #1 2009.

Grundfos is one of Denmark’s largest companies with 18,000 employees around the world, of whom about 5,000 work at its sprawling headquarters, set among gently rolling hills in the northwest of the country. The company is the world’s largest manufacturer of circulator pumps, and also produces submersible pumps for pumping groundwater and so-called CR pumps for use in industry.

It was the latter that were suffering from the failure of the nylon locking nuts. “This loosening of the nuts was a huge problem,” says Segment Director General Industry Morten Gylling. “It is the smallest component in the pump but it is also one of the most important.”

While the nylon locking nuts worked well up to a certain temperature, once over about 80 degrees the nylon simply will not lock anymore. “And then if you have a lot of vibration the locking nut will also lose the pretension of the rotating assembly over time. We had quite a lot of failures on pumps due to this loosening,” says Grundfos’ Chief Engineer Per Frost Vedsted. “We needed a new design that would get rid of these problems.”

So Grundfos’ engineers set about solving the problem and came up with a number of potential solutions, but none proved to be ideal. And then in a chance encounter at an industrial seminar they came across Nord-Lock.

“There was this Junker test demonstration which caught my colleague’s interest,” says ­Vedsted. “We invited this company to come to Denmark so we could see it with our own eyes, and I think it took about half an hour before we were convinced that this could solve our problems.”

Grundfos’ long sought-after solution was Nord-Lock’s bolt securing system.
“It is fair to say that their concept was brilliant – but it didn’t match our applications,” says Gylling. Grundfos needed washers that were both harder and had a smaller inner diameter, and so engineers from both companies worked together for more than half a year to come up with today’s solution using the high-performance alloy Hastelloy (SMO254).

From ordering 50,000 Nord-Lock washers that first year, Grundfos is now using 500,000 a year. And with the solution set to be used in a new pump range, that figure could be over 1 million within the next two years.

“This is a great example of two companies coming together to achieve something remark­able,” says Gylling. “Nord-Lock has a brilliant concept, while Grundfos has the knowledge of the market and the corrosion material expertise. By joining forces in an open and honest relationship we achieved something that was a breakthrough technology. Nord-Lock couldn’t have done it, Grundfos couldn’t have done it. But by joining the forces we have a winning solution.”


Applications: Pressure boosting, boiler feeding, wash and clean, temperature control
Industries: Mining, marine, machine tool, off-shore, fire-fighting, pharma, petrochemical
Construction materials: Cast iron, stainless steel, titanium
Temperature range: up to 120°C (standard), up to 180°C (variant)
Flow range: 1–180 m3/h
Bolt securing: Nord-Lock


This is how Grundfos benefits from Nord-Lock washers:

  • Lower lifecycle cost – even if the initial investment is higher
  • Better control of the pretension on the rotating assembly
  • Lower friction – lubricants can be used
  • No wear, such as that caused by heat, vibration and corrosives
  • A tailor-made solution was made possible through company collaboration.

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