Curious as to what people's or even manufacturers views are of:

"When or what does it take for a concrete pump to be officially decommisioned from service?"

Great question. There is no rule that I know of up to this point.

When its towed to the BONE YARD. Todds Right. We have all seen them run to the bone before shut down then stripped to nothing for parts.

Define decommissioned and you'll have your answer. 

I have seen some old whitemans that the insurance company would not insure, and that condemned them.

According to Australian standards it's the upto the Engineer to deside if a boom is fit for service so as long as you can get an engineer to sign an inspection report it's fine to work! As for line pumps no real law so work it until it won't pump anymore! I know of a 76 model boom still pumping here in vic! 

Decommisioned meaning taken out of service indefinitely due to safety concerns.

The only thing i can think of is roll over, a catastrophic accident or boom failure leading to an insurance company writing off the machine.

But in an ideal world, where the machine has had no comprimise on the upkeep, would a machine ever be decommission a machine because of:

1. too many operating hours,
2. over a certain years old, or,
3. concerns about its presentation (eg. rusty, dirty, noisy, smoky, leaky etc).

Cyclic loading of boom componentry only gives you so many cycles of movement. so when is the limit established as one can say of for scrap metal?

excessive pitting or rust, metal fatigue would cause a boom to be condemned, hydraulic side can all be replaced! As far as I'm aware no age or hour restriction exists! Most booms see the scrap heap when it's no longer profitable to keep in good working order! 

pitting or rust can be repaired, cut and replacesd. Metal fatigue is generally not considered until something catstrophic happens. The cost to analyse every fragment of the placing boom and support structure by far outweighs the pros of keeping a suspect machine.

I would still think that cases to decomission may be:

1. insurance company writes of the pump due to unsalvagable accident, 
2. road traffic authority issues it with a defect notice with way too many problems,
3. the emmission laws pass to increase progressive annual registration for vehicles that emit high co2 emissions to thepoint where it becomes very expensive,
4. maybe the main hydraulic pump gives way passing shrapnel through the whole system especially with FFH,
5. machine caught with a hot load of mud.

Otherwise those 1976 models, can you forsee it still working in 5-10 years time?

What about the new pumps can you see them pumping concrete beyond 2050? 

Why would you want to run a piece of equipment, that is 20+ years? If you buy a new pump, you have the tax write off, you are covered under warranty,  and you get a state of the art machine. Once it gets to a certain age, the needed repairs become more and more costly, and knowing from experience, wont be done.  So in my opinion, trade it in, buy new and avoid decomissioning

Even after trade in, it ends up in someones hands. yourmissing the point as to where the life of it ends.

Is there a standard ? I have seen wrecked pumps repaired to like new . Year , pump hrs , dot repairs , hyds, and rust are all repairible as long manufacture part support is there. The older pumps with no parts support just get parked or sold to third world countries . Great question . Maybee and manufactor rep. or boom inspector will reply with there thaughts.

I own a 84 Elba 31 M , and I'm contemplating scrapping it now that one of my operators blew one of the hydraulic pumps and had a boom party gone bad . Barrels and all pipe solid , the only thing clean is the putzmiester hopper .

Just not worth putting the money into a old machine that everyone complains about , but I will miss the simplicity of it .

schwing say their pumps have an expected working life of 30years or at least they did not sure if that still applies! 

todays pumps and chassis design life is around 10-15 years. The smaller booms under 32 m do last longer.

I was just looking at the transCrete web site, it says some of their pumps are still working daily at 40 years old