Hi All,

I've got a B16.5 Cl900 20" WN flange and a 20" Blind Flange on a vessel.

Design pressure: 137.8 bar
temperature: 120 deg C
material: Gr.1.1 (SA105)
Corrosion allowance: 3mm

To B16.5 pressure rating is 137.96 bar which shows up in the report for the WN Flange, but for the Blind it's 137.796 bar. Which means it's lower than the design pressure

30| 40| 137.800 | 137.967 | 153.060 | 107.950 | No Calc |
40| 50| 137.800 >>> 137.796 | 153.060 | 107.950 | No Calc |

As they are standard flanges I did not perform a calculation.
Does PV Elite take CA. into account? If so how does it do it as there is no calculation?
How can I get around this?

Thanks
Istvan

Hello IstvanSzeifert

B16.5 only gives at table for the pressure-temperature rating. It does not take into account the corrosion allowance, neither does it consider what type of gasket is employed. If the box is checked (in PV Elite) to treat the flange as a standard B16.5 (or B16.47) flange, or blind, the pressure at the specified temperature is included in the vessel design summary from the table in B16.5 (or B16.47). The code does not address the issue of corrosion allowance or gasket factors for standard off the shelf flanges.

I hope this has anwered your question.

Hello Ray,

It is a standard flange, and as I said it above it does use the pressure from the table in B16.5 if it's a weld neck flange. But, if it's a blind flange it uses a lower value.


Weld neck Flange: 30| 40| 137.800 | 137.967 | 153.060 | 107.950 | No Calc |
Blind Flange: 40| 50| 137.800 >>> 137.796 | 153.060 | 107.950 | No Calc |

Weld neck Flange is 137.967
Blind Flange is 137.796

As per your reply these should be the same.

The biggest problem is that our design pressure is 137.8. Which means one of them is sufficient, the other one isn't. I don't know how PV Elite got to the value of 137.796

Hello IstvanSzeifert,

Basically there is no sperate tables for WN and blind flange temp and rating, if you are using any of the class flanges of any type in that class you are going to refer same rating table and the value should come same for both the flanges irrespective of their type,

So, their is no problem in using that blind flange which you are talking about unless you have confirm it manually with code requirment,

The PVElite output you are getting is erroreous,

Regards,
Hitesh Pawar

Dear Istvan,

Is it a case of static head?

If not then send your PV Elite file to the COADE tech support and we will review it and get back to you.