3 replies to this topic

[maria_no]

Hi everyone,

I need your help on finding some standards or good engineering practices about the flow-rate needed for nitrogen (no steam is available) emergency snuffing of a furnace. So far, I didn't find anything on API 560 and skimming through NFPA codes. Informally I was able to find that the volume needed should be 3 times the volume of the radiant section, but I found also two options for the time required to displace this nitrogen volume: 5 or 15 minutes. The difference is relevant in the design of the system since nitrogen will be supplied by bottles. Thank you in advance.

Regards,

M.

[Satyajit]

Hi Maria,
Please give details of the furnace . For simple fired heater, low pressure snuffing steam is enough for purging.
For a balanced draft furnace, normally both ID and fD fan are run to purge the furnace.
Hope you got your answer.
Regards,
Satyajit

[maria_no]

Hi Satyajit,

Thanks for your answer, but I'd like to know how to calculate the flowrate of nitrogen for snuffing purpose. The furnace is natural draft fired heater. Do you need any further detail?

Regards,

M.

[ankur2061]

Hi Satyajit,

Thanks for your answer, but I'd like to know how to calculate the flowrate of nitrogen for snuffing purpose. The furnace is natural draft fired heater. Do you need any further detail?

Regards,

M.

Maria,

Per ANSI/API STD 560 clause 15.3.1.3 "Purge connections shall allow for a flow rate providing a minimum of three firebox volume changes in 15 minutes".

This would be the minimum flow rate for any kind of snuffing. You are free to provide a design margin on this flow rate say 25% for the design of your snuffing system.

Hope this helps.

Regards,
Ankur.