Can anyone explain this?

Approx 150m into the line, sheared completely yesterday afternoon. Pipe thickness was checked in February and all acceptable etc. It hasn't actually sheared on the weld, its sheared through the bend itself. Never seen anything like this before, happened to anyone else?

Were using a Schwing 3500, with a 2800 as a back up if things go wrong!

Not sure of the pressures its being pumped at, but its only pumping slowly as supply is awful so we try to keep the concrete in the line moving for as long as possible until we have a wagon on site for a straight switchover.

I would understand a clamp blowing or even blowing on the weld, but the bend shearing like it has is very strange IMO.

I have done quite a few high rises and long line pours. I have found from my experience that when I break something, it is for two reasons. 1) The pipe was super thin and couldn't hold the pressure and broke there. 2) Mechanical loading. (I have broke almost everything due to this.) If you get the pipe line moving, it is only a matter of time before something gives. I have broken bends the same way that you have. I have done two different things to fix this. I have purchased Conforms .500 wall bends to give me a stronger bend. I have also made thrust blocks around the bend and used restraints to control excess movement. Think back, was your line moving in this area? Did you see a lot of flexation in the line near that bend? I would guess that this was the issue.

I also just noticed that you are using metric pipe as well. Metric pipe ends cannot handle the pressure of HD ends. Check the max line pressure on your pump. Metric pipe is rated at 85 BAR. The elbow looks to be a cast one in the picture. Excess movement can still crack the end of the bend and then the mechanical forces rip it off.

All pipes were tested for wear in the walls in february and all passed with flying colours, so wall thickness wasn't the issue here. All pipes are bought direct from Schwing UK and is approx 9 months old..

Dipstick,

Thanks for the response. This is another project I am working on, the old project with the 1.3km of line went smoothly without anything like this happening.

Its an interesting point with regards to this 85bar pipeline, and something I will now investigate right away.

EDIT:

Just looked at our spec sheet for the pipe, and it has a working pressure of 85 bar (from new) and a burst pressure of 170bar. Looked at the concrete pressure the Schwing 2800 pump produces and its 106? 

We love a challenge ;-)

I'm not entirely sure how they work if i'm honest but if the burst pressure is 170bar, and the maximum pump pressure is 106bar, how would it burst?

You should at least consider going to the HD pipeline instead of the metric. The HD ends are rated for more pressure. The burst pressure is nice data to have but the issue here are the ends and clamps. The ends and clamps will fail before the pipe (when new). It all has to do with the ends. I would also suggest larger bends in your system line. This will help with the surge and movement. I sent you a PM, I can help and Dipstick is also a good source. I would stay away from cast pieces in your system as well.

The HD ends are also more likely to be of a higher quality and not sourced from a lower quality factory due to the lower volume using HD.  Buying the Con Forms Hevi Duty system for high pressure or high rise is going to save you in the long run.  You won't wear out the elbows near the end, they stack better for high rise applications, allow for higher pressures and are built in the US.

Conforms pipe is poor as well, trust me I know. Pipe producers have no concern regarding quality, pipes are hand welded while water quenched which inveriably leads to issues.

If you think all pipe is the same and Con Forms pipe has "no concern for pipe quality"?  I question your experiences.  Do you have any specific reference or incident?  No one is perfect in building anything but you should make a trip to Port Washington, WI and see what goes into making the Con Form pipe and elbows versus the crap coming in from overseas.  And their purchase of Esser had nothing to do with manufacturing the highest quality pipe in the world?  No one makes a higher quality product in the world than Con Forms and Esser.  And they are constantly striving to improve as well.

Elbow only as good as the pipe before and after it!