3 replies to this topic

[papaya]

I would like to know is it true that Flange Type Orifice Plate need to have rating minimum of 300lb even if the pipe rating is less than 300? I looked up ASME B16.36 ('07) could not find a clause saying minimum needs to be 300 but the document only covers 300 to 2500 class.

Can someone clarify if there is such requirement & if true what is the reason behind this requirement?

[ankur2061]

I would like to know is it true that Flange Type Orifice Plate need to have rating minimum of 300lb even if the pipe rating is less than 300? I looked up ASME B16.36 ('07) could not find a clause saying minimum needs to be 300 but the document only covers 300 to 2500 class.

Can someone clarify if there is such requirement & if true what is the reason behind this requirement?

Papaya,

FYI, not only for orifice plate but for other instruments as well such as flange mounted level/flow instruments the practice in some of the Oil & Gas Companies that I have dealt with is to have a 300# rating even if the line or system rating is 150#. I had the same query to my counterparts in the instrumentation group but I was not provided a satisfactory answer. There is no international code or standard that mandates this requirement.

The only thing that I can presume is that instruments may require more frequent maintenance than other components such as valves & frequent removal & installation would require a more robust construction which would lead to having a 300# rating. Another point would be that most instrument manufacturer's may have standardized the flange ratings as 300# and above for all flanged instruments.

Would like to know the opinion of a instrumentation engineer on this subject.

Regards,
Ankur.

[Qalander (Chem)]

I would like to know is it true that Flange Type Orifice Plate need to have rating minimum of 300lb even if the pipe rating is less than 300? I looked up ASME B16.36 ('07) could not find a clause saying minimum needs to be 300 but the document only covers 300 to 2500 class.

Can someone clarify if there is such requirement & if true what is the reason behind this requirement?

Papaya,

FYI, not only for orifice plate but for other instruments as well such as flange mounted level/flow instruments the practice in some of the Oil & Gas Companies that I have dealt with is to have a 300# rating even if the line or system rating is 150#. I had the same query to my counterparts in the instrumentation group but I was not provided a satisfactory answer. There is no international code or standard that mandates this requirement.

The only thing that I can presume is that instruments may require more frequent maintenance than other components such as valves & frequent removal & installation would require a more robust construction which would lead to having a 300# rating. Another point would be that most instrument manufacturer's may have standardized the flange ratings as 300# and above for all flanged instruments.

Would like to know the opinion of a instrumentation engineer on this subject.

Regards,
Ankur.

I also second Ankur's viewpoint with slight addition that this is

• For the sake of better Mechanical Integrity needs fulfillment,as well as
• Frequent operations reliability fulfillment

I also refer here that almost all

• the threaded tapping or connections employed for instruments related usage have much longer deeply inserted threads areas
• with much higher pressure withholding strengths and at times simultaneous vacuum withholding capability.

this signifies "good Engineering Practices" evolved over a period of Time.

Hope this helps in getting an insight on the issue.

Edited by Qalander (Chem), 16 March 2010 - 01:13 AM.

[papaya]

Thanks for the insight guys. Would like to know is this practice mandatory, or we can live with 150# instrument flange on a 150# line?

Also since ASME 16.36 doesn't provide info on 150# orifice flange, will a 150# orifice flange still meet the ASME requirements?

Edited by papaya, 16 March 2010 - 01:28 AM.