5 replies to this topic

[JKM]

Dear All,

 

I am modifying my query. As per API 521 (page 137, 6th Edition, 2014), It is quoted as below

 

" If unit knockout drums are provided upstream of the main flare knockout drum, these upstream drums need not to meet the droplet size criteria required at the flare tip because knockout drum shall be designed to do so. However some credit can be taken for liquid holdup in the upstream drum to achieve the required liquid holdup capacity specified above. If the upstream flare knockout drum shall have any required remaining liquid holdup capacity."

 

Our intention is to minimize the KO Drum SIze. Considering above I am taking droplet size to be 1000 micron to have the lower Vessel ID. Additionally I am designing the vessel of hold-up time of 15 mins. only.

 

 

Considering above I would like to ask as below:

1. I would like to know whether it is acceptable to have higher droplet size and less than 20-30mins. hold up time. Whether this rule stated above in reality acceptable. Please share our opinion.

 

2. Additionally I would like to know your opinion/suggestion, that how can I minimize the KO Drum the size. 

    Kindly let me know if there are other alternates to reduce the size.

 

Regards

JK 

Edited by JKM, 15 January 2018 - 11:37 PM.

[Bobby Strain]

You can find a sample at my site that will provide you a proper size. You can find it on the home page within the text, not in the Menu. Just Google my name. You must, however know the liquid holding capacity. You can compare designs with the cost index provided by the calculation. You must also provide the required droplet size to be removed. API suggests that you use 300 micron. And, be careful, because the KO drum may already be too small! Or you may not have sufficient information on the design basis to offer any other size. So, you must be careful not to take on any liability for your company.

 

Bobby

Edited by Bobby Strain, 15 January 2018 - 02:04 PM.

[Pan Nata]

High liquid droplet diameter will may cause burning rain.

 

Actually, its not "negotiable" to reduce your Flare KO Drum size. You just have two options, increasing your vessel ID to get lower vessel length (ensure it is still higher than minimum required length) that's mean you are not lowering you drum size at all or reducing your inlet flowrate to Flare KO Drum but you have to install another flaring system (Drum+Stack) to ensure your required flaring rate well-handled.

[JKM]

Dear Bobby and Pan,

 

Thanks a lot for your reply.

 

Regarding burning rain, it will not occur as there is in addition to this KO Drum, there is one Main KO Drum which ensures the final droplet entraining to Flare is limited to 300 micron.

 

Let me know if you come across similar situation.

[Bobby Strain]

You should not change a client design that you are given. Especially in the size of flare system knockout drums. You probably don't have enough information to offer an adequate size. You can't arbitrarily assume that 1000 micron droplet is a sound design basis. You won't find information anywhere to support your assumption. Engineering should be sound. Not based on assumptions. Assuming stuff for your design is a good way to wind up in court with your client.

 

Bobby

Edited by Bobby Strain, 18 January 2018 - 10:21 AM.

[JKM]

Hi Bobby,

 

Thanks a lot for your advice. First, I am taking not assuming it arbitrarily. It is stated in the API 521 (page 137, 6th edition). This estimation is for the BIDDING only.