reduced ID fittings

[pipe15]

We ordered standard B16.9 fittings but some of them came with a reduced ID. For example, an 8" - Schedule 160 tee. The nominal ID that we expected would be 6.813". What was supplied was a tee with an ID of 4.96". We did not find this out intil system flow testing. We were not getting the flow that our hydraulic modeling predicted. The tee was UTed and subsequently cut out. My question is what should we have specified in order to get a tee with the expected ID?
thanks
Mark

 

[MikeHalloran]

A 'full bore' fitting?
Honestly, I don't know if there's an industry standard in any industry for specifying what you want, except maybe to add language to the PO that a ball of a given size has to fall through the lumen.



Mike Halloran
Pembroke Pines, FL, USA

 

[LittleInch]

That's certainly a large bore reduction.

Surprisingly B 16.9 6.2.2 says "6.2.2 Bore Diameter. Bore diameters away from the ends are not specified. If special flow path requirements are needed, the bore dimensions shall be specified by the purchaser."

So do exactly that - " 8" schedule 160 tee with minimum main bore of 6.8" diameter "

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Gator]

I'm not clear on how a fitting with such a heavier wall got welded into the system and flow tested without anyone noticing and questioning such a difference in wall thickness.

 

[pipe15]

Gator, the ends of the fitting were properly counter-bored from the vendor in order to meet the Code required mismatch criteria.

 

[moltenmetal]

We frequently see tees, caps and similar BW parts which are made to at least one schedule heavier than required, then back-tapered at the BW ends to match the ID of the required pipe schedule. We suspect they're actually fittings for a heavier schedule which were under-tolerance on wall thickness.

 

[DVWE]

Unfortunately there is nothing preventing a fitting manufacturer from making lighter wall fittings from heavier wall fittings, as long as the BW ends meet the wall thickness requirements of what the fittings are qualified to and stamped.

 

[canadapipe]

I've seen this quite a lot as it's typical for many fittings to be forged from much thicker material in order to maintain the minimum required wall thickness. DVWE is quite correct in his statements and this is a very typical industry practice, though typically haven'd seen that much of an ID reduction.

What you would want to spec the supplier is typically called a "through bore" fitting which you would then get you what you should expect. In addition I'd probably ask for fabrication drawings to approve as in some cases the outer dimensions are changed to meet this criteria.

 

[MikeHalloran]

I remember having a flow problem in the seawater system of a nice yacht being built on the opposite coast.

ISTR that most of the system was nominally 3" PVC, but somewhere in the middle of it the builder had installed a fitting called a "king nipple" that was found to have a bore under 1.5" diameter. That limited the flow, and in turn the exhaust system cooling, which is how it became my problem. It took a week of phone calls back and forth, and actual attempts to roll a ball through the system a section at a time to discover the root cause.

I never did get a ride on the yacht, but we got the system working okay with a bigger nipple, so it was a happy ending.





Mike Halloran
Pembroke Pines, FL, USA