Strength reduction of existing tubesheet by drilling few additional holes
Strength reduction of existing tubesheet by drilling few additional holes
(OP)
Hi...we have a case where we need to fix one perforated plate of 8 mm thickness below the tubesheet exactly alligned with the tube holes (Tubes no = 1000). Tubes dia is 19.05 mm and hole dia on perforated plate is 7 mm. Perforated plate will be fixed with the tubesheet by providing 10 nos of bolts. Drilling depth of bolts are around 38 mm inside the tubesheet (Bolt hole dia is around 12 mm). Holes will be drilled within the OTL. As per ASME calculation of existing tubesheet, thickness comes out to be 72 mm and provided thickness is 73 mm. So we don't have any margin available.
Will drilling of 38 mm length holes of some 10 no of locations have any effect on tubesheet thickness and strength?? What is the procedure of calculating the remaining tubesheet thickness without going for FEA analysis?? Our intension is to fix the perforated plates in the existing tubesheet only.
Will drilling of 38 mm length holes of some 10 no of locations have any effect on tubesheet thickness and strength?? What is the procedure of calculating the remaining tubesheet thickness without going for FEA analysis?? Our intension is to fix the perforated plates in the existing tubesheet only.





RE: Strength reduction of existing tubesheet by drilling few additional holes
I suppose you could weld studs to the TS rather than drill & tap?
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: Strength reduction of existing tubesheet by drilling few additional holes
So this plate will be a choke. Have you calculated the force against the plate? What about critical frequency?
Ten studs does not sound like very many to me. For 1000 tubes, I would want more than that.
Your holes do sound very deep. As long as your studs are run clear into the holes then there will be very little impact on the tubesheet.
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P.E. Metallurgy, Plymouth Tube
RE: Strength reduction of existing tubesheet by drilling few additional holes
RE: Strength reduction of existing tubesheet by drilling few additional holes
RE: Strength reduction of existing tubesheet by drilling few additional holes
Again, why so deep? Can you weld studs instead of drilling?
You might have a look at UG-43(d), maybe not specifically applicable to tubesheets, but...
Is drilling possible as installed? Well, yes anything is possible given proper resources ($$).
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: Strength reduction of existing tubesheet by drilling few additional holes