tubesheet hole diameter

[abangbikerz]

we just received a tubesheet from machine shop for our heat exchanger project. i do a dimensional inspection after the tubesheet arrived, and find out that the tube holes are out of the tolerance given by the design. its oversized by 0.2-0.3mm where tolerance only allowed +0.05 from design dimension. client decides to reject the tubesheet. Dont know if that deviation does make a significant effect to the operation and reliability of that heat exchanger. is it appropriate to reject the tubesheet??

 

[austsa]

You need to review the tubesheet calculation and see if the increased hole size still meets code requirements. You'll also need to look at how much the tube expansion is increased by and whether this increase can be tolerated.

 

[TD2K]

Were these tolerances part of the order for the tubesheet from the client? It sounds like they should have but I've seen orders go out where not all the specifications were identified and you can't after the fact try to impose new ones on the supplier.

If they were part of the purchase order, before doing a bunch of work you might want to talk to the client first to see if they will possibly accept the tubesheet if it's not in compliance with the specifications they issued for it even if the suggested calculations show it's in compliance with the necessary codes and will work.

 

[jtseng123]

Are you asking your client to endorse the non-conformance ? or you will endorse it ? Is the tolerance too stringent or common industrial practice ?
You need to have strong technical basis and willing to take the whole responsibility in case it fails during operation prior to going against your client. Even you can pursade client to accept it, people will question the credibility of your engineering.

 

[abangbikerz]

im not going to go against my client decision. they have spoken. so be it. just i got bashed by production department for reporting this non conformance to my superior and making it an issue. to them this problem is not a problem at all. FYI im a newbie in this field.

 

[DRWeig]

bashed by production department for reporting this non conformance to my superior

Side issue there for which I am compelled to comment:

In my organization, the bashers would be severely disciplined or terminated. Nobody gets bashed for reporting a discrepancy of any kind up the appropriate channel.

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

 

[Brandon181]

TEMA table RCB-7.41 lists tube hole diameters and tolerances. In my opinion, it is important that those tolerances are maintained for many diffent reasons, however I do not have any personal operation experience dealing with an exchanger with oversized tubesheet holes. Perhaps you might find these articles helpful:

Tubesheet Hole Article 1

Tubesheet Hole Article 2

 

[GenB]

It's the client's call. they specified you deliver. it the TS's are rejected based on non-conformance(it may be okay per Code), it's a non conformance to the client's specifications. The machine shop has to deliver to you they are the losers.