after how many hours do you think should be changed?

Looks like it is worn way too thin. How many hours did you get out of this transit elbow ?

Wow,way to scary.That's a perfect example of why bbcp's blast net works.The rock and fluids could have went right into the mixer drivers legs.

Not so nice if that happends when you pump at the 8:th level in a building, and you placed the pump on a street crowded with traffic. That will be: "just another day at the work".....

you got your money worth out of this one...

a little duct tape, hes good to go at least to 200mph

Do you not hard face the inside of your swing 90 and your 1st 90 to your reducer?

success and a concrete pumping very hard consistency ...! this curve has pumped about 3100 hours ... I had never happened before, and guys are still at work ... and anything can still happen ....

For those using a thickness tester a point to note-the obvious place here to test would be the outside radius of the bend, however with the introduction of a grout/washout T point, the pipe will wear most opposite this T point. This is because the forces are greater against the opposite wall of the T with the  T full of concrete.  

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i think you can get the ball back

Yes.. Thinks so to... Use some ductape :-)

I don't think Duck and a Coke can will do it, perhaps Duck and a paint can. Or cut up a 5 gallon pail that you have on the pump and Duck it.