Boiler Tubes - Allowable Deflection.

Hello All,

We have a recently manufactured 5 ton per hour, 10 bar, diesel fired steam boiler that has just been installed. The boiler was manufactured to EN 12953 specifications. The third party inspector has stated that some of the tubes are deflecting to degree that requires them to be replaced - this deflection being about half the tube diameter over a length of 3.5 m (just over 11 feet). The tube ends are expanded and welded. The manufacturer has responded that the code is silent concerning the allowable tolerance on tube deflection, and some of the background research I've done has not shed any light on this either.

If anyone has experience in this regard, or can point me to a code or specification that deals with this, I'd appreciate any advice.