Shell and tube HX fabrication 1

[espnloser]

Hello All,

I would like to know if reaming is essential. Our specification calls for reaming. The vendor stated that their high quality machining equipment produces a hole finish of "125 to 250 ARH, which ordinarily exceeds requirements." If we wanted reaming it would be at a price but didnt say how much extra.

I am new to the job and trying to find out guidelines for this. TEMA has nothing about it. The whole "ordinarily" word throws me off.

If anyone with experience in dealing with HX vendors would be offer some advice, it would be appreciated.

thanks

Thanks

 

[rmw]

Reaming is only essential if you require a surface finish in the hole better than the mft'r can produce. You specify the finish and ovality you require, and it is up to them to meet it. If they have to ream, they won't give it away. If you can be reasonably assured (like by visiting and looking at some of their current jobs on their drilling machines,) that they can meet your requirements, then go with their promise.

Ask them for references from other customers who regularly have work in their shop(s) and get ahold of their inspectors and check with them.

However, you should have some kind of inspection process of your own to look at the holes before the tubes are inserted (actually before the TS is taken off the drill) to accept or reject based on what you specify.

The word "ordinarily" is their escape clause if something messes up on your TS, they can shrug their shoulders and say "ordinarily this doesn't happen." Make them build you the Hx you want. Don't, however be putting a lot of extraneous requirements that you don't really need. It all costs by the weight and time involved to make it.

rmw

 

[workermonkey]

i'm also young and new at this stuff, but my experience would be that if the hole is the right size for expansion then who cares if it's reamed. TEMA wants everything double grooved anyway and if these tubes are roller expanded the reamed finish is unnessecary. we ream our holes because the drill we use is less than accurate. we under drill the hole size and then ream it out to the proper diameter for expansioin.

 

[panduru]

Thanks workermonkey, your argument sounds not only convincing but perfect from the technical point of view as well.

The user generally can specify the state in which he wants the equipment delivered rather than how that has been brought about by the manufacturer.

On the other hand, "ordinarily" is a commercial term almost always included to protect the interests of the party. That should not really "throw you off," because you will be seeing a lot of it in the course of supply management.