Heat Exchanger Fabrication Question?

I posted this in Chemical Engineering section but might be more appropriate here.

In a dilemma about exactly how tubes are stuffed in a multi baffle plate heat exchanger. The half plate baffles are already stitch welded on inside of exchanger pipe.

With only a 1/64" clearance in holes for tubes I cannot fathom how one would insert a 35 ft tube thru the full length of a pipe with half baffle plates every 8 ft..

It seems like you would need a broom handle type wood stick aligned thru full length of pipe thru each baffle and then use it as a guide for the tube.

I don't know, have you had any experience around heat exchanger fabrication?

Appreciate your comments and advice,
Kelly