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IFR with double wiper secondary seal.

Friday, September 14, 2018   By: Karsadi [652] 4 Stars
Greetings for all friends.

To plan for the perfection operations of storage tank with Naphtha content.
I will design an Internal Aluminum Floating Roof Tank with a vapor mounted type, which is equipped with a Fix. Aluminum Geodesic Dome.
To determining of Internal Floating Seal will be install the combination of Mechanical shoe primary seal which is equipped with a Secondary seal where the secondary seal is planned to be installed with double wiper seal or using a secondary seal which is equipped with two sets of wiper seal.
The question is? For my confidence and to increase my knowledge, hopefully from friends can share knowledge and information as your comment.
Is my design still permissible by API 650 standards and habits in Internal Floating planning, is it a common design or special design?
Hopefully somebody will be give opinions and explanations as comments.
It is wrong design or correct design? and if allowed by standard,
what the benefits and disadvantages if compared with secondary seal type with single Wiper.
Previously we thank you very much for the attention and knowledge that you can share.
Best Regards

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Wednesday, September 19, 2018   By: Dunedin [1843] 1 Stars
Since this tank is a CFRT, i.e. Fixed Roof with Aluminum Dome, I do not consider a Secondary Seal absolutely necessary.

The main purpose of a Secondary Seal is to protect the Primary Seal from the elements, wind, rain, snow, etc. but as you have a roof on the tank, this will protect the Primary Seal.

A Mechanical Shoe type of Primary Seal is ideal.

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Wednesday, September 19, 2018   By: Orlando Costa [201] 2 Stars
From what I understand in your text, you have a tank with an external EFRT floating roof with a aluminum dome Aluminum Geodesic Dome.

And you want to install another seal on the EFRT or replace the existing one. I see no reason for this. As Dunedin said a secondary seal is not necessary because the dome already serves as a protection against the weather.
I just recommend using a consecrated and approved stamp template, checking who they used. You can see more in API 650 Appendix H.

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Saturday, September 22, 2018   By: Karsadi [652] 4 Stars
Dear, Sir

If you think of a secondary seal as weather seal, then it is enough to plan EFRT with the weather secondary seal only and do not need to consider being IFRT.

With technological advancements to reduce emissions and leaks due to evaporation, the EFRT is installed vapor tight secondary seal,

Many ways to overcome losses due to emissions and leaks due to evaporation among them I planned to Fix Geodesic roof using N2 gas blanketing method, to maintain the N2 in the tank, then the construction of the vapor tight fix roof tank and using the standard API 650 annex G.

To make the vapor tight Aluminum Dome fix roof to maintain the expected operating life it is not easy and not many vendors can carry out according to API 650 annex G.
to overcome the above, emissions and leaks due to evaporation,
My opinion of design with combining EFRT construction with Mechanical Shoe and IFRT with double wiper seal.

That is the meaning of my post and I am waiting for comments and suggestions.

Best Regards

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Sunday, September 23, 2018   By: Karsadi [652] 4 Stars
Dear Mr. Orlando Costa,

Sorry, maybe my last posting are unclear and I repeat, as follows

The main objective of this storage tank design is to accommodate Naphtha products and in an effort to overcome due to evaporation losses due to emissions, an IFRT tank is planned with Al IFR HC full liquid contact type as per API 650 annex H, because of tank operation is equipped with N2 blanketing , then I need to maintain the N2 pressure in the tank, so it is chosen with the addition of the fix. Al Geodesic Dome with tight vapor type as per API 650, annex G. and for completeness, I plan to install primary seals with mechanical shoe type and above it is installed with a single wiper secondary seal.

For alternative of tank construction with the same functions, I intend to change the HC design. IFR from liquid full contact becomes a vapor contact, in this construction a double Wiper Seal will be installed over the primary Mechanical Shoe type.

if Al IFR vapor contacts are planned, does it need to be equipped with pressure / vacuum vent as presuure balance between below and above the skin deck.

According to my understanding, this is best and challenges others how and please argue.

Best Regards

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Tuesday, September 25, 2018   By: Dunedin [1843] 1 Stars
Nitrogen Blanketing on a tank fitted with an IFR is not a factor in selection of the seal system. My earlier comment is valid.

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Tuesday, September 25, 2018   By: BABRTs 973 [53] 5 Stars
Why would one want to use nitrogen blanketing on a floating roof? If emission control is the goal, a well designed roof with minimal avenues for emissions with a liquid mounted mechanical shoe seal and secondary would be about as emission free as could be achieved. And jurisdictional and environmental regulation would drive how the emissions are controlled.

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Tuesday, September 25, 2018   By: Dunedin [1843] 1 Stars
Control of the moisture content of the stored product that is the reason for the nitrogen.

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Published on ast-forum.com


Atmospheric Design Pressure
By: Fathi [46]

The whole story is to avoid brittle fracture=

Test temperature shall be equal or warmer than Minimum Metal Design temperature at Test pressure.

I would limit my minimum testing temperature for a tank (or even for a vessel or a piping system) by the =

Temp = maximum of [ Min(lower shell) , Min(shell# 2) ....Min (Upper shell) ]

For a Shell# i the minimum is function ( of shell tickness , Material group ) and this can be found in API 650 , Fig 2-1

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