Pump killers: How to fight the 13 most common centrifugal pump failures? Number 5.

In the series “Pump killers” we investigate the 13 most common causes of centrifugal-pump failure and take a look at the measures that can be taken to fight these ‘killers’. Every week we will share a new, even bigger, killer. Our goal: to reduce the number of victims by sharing our knowledge.

The comparison may well be true, but in this case it is certainly: what is bad for us humans is not good for a pump either. And this time we are talking about stress, in our case: leadership stress. This is the last time we'll get into this, I promise, but this pump killer is also a lot of attention in the various manuals. Those who read an installation, operation and maintenance manual when installing a pump, will know that it contains a lot of information about the correct way of connecting the pipes to the pump.

For example, it is stated that the pump may under no circumstances be used as a fixed point for the pipeline. It is also indicated that the permissible pipe forces on the pump flanges must not be exceeded.

Source: "Tension-free connected?" - Oveducon..

Unfortunately, in practice we see that many pipes are not connected stress-free to the pump, while aids are available for mounting flanges that are not “in line”. For the enthusiast, look on Youtube for: "flange alignment tool".

How does this phenomenon arise? Pipe stress, an excessive load on the flanges, is caused by pipes being insufficiently aligned and anchored before the flanges are mounted. Even when using bellows, the pump flange connection can be overloaded if there is insufficient support due to forces in the pipe.

Source: Fairfield Industrial Sales

This phenomenon is so unknown that it sometimes even requires a forklift truck to be able to disconnect a pipe from a centrifugal pump.

Source: Fairfield Industrial Sales

What are the consequences? As already indicated, the consequences can be major. The forces on the pump flanges can become so high that pump housings will rupture or pump flanges to break. With smaller stainless steel pumps, it is even possible that pump housings will deform due to excessive pressure on the flanges..

Source: "Broken by pipe stress" - source unknown.

In short: pipe stress not only causes damage to pump flanges, but even damage to pump housings, it also results in a shorter life of the mechanical seals and the alignment of the pump shafts becomes, to say the least, more challenging.

Source: "Feed Pump Pipe Strain" - Mechsol.com

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How can this be controlled? As a reader pointed out a few articles ago, pipe-stress is a bit of a neglect in pump technology. But there is certainly something that can be done about this.

To begin with, carefully follow the installation instructions from the pump manufacturer and make sure that the suction and discharge pipes are sufficiently anchored. Make sure that the support points cannot subside over time and that the thermal growth of the pump and / or expansion of the pipes that may occur, are taken care of in the correct ways..

Once the installation is put into operation, you are not finished yet, because then the pipework has to be checked for alignment a few more times. Only then will you know whether the pipework has been installed properly, because it can still change for various reasons!

Conclusion: laying pipes stress-free is a profession in itself that should certainly not be taken too lightly!

?We are curious about your experiences with this killer and / whether you have any additions to this article. Let us know in the comment section below!

Next week: number 4.