NACE plates for vesels : necessary or not in my situation?

[mattegm]

Goodmoring guys,
i'm currently working for a hydrocyclone package consisting in some equipments like oil skimmer, hydrocyclone and nutshell filters for the treatment of oily water coming from desalters, separators etc..

The oily water cointains
- 200000 ppm of salt
- 1780 ppm2 H2S
- the system is working at the following pressure from upstream to downstream:
oil skimmer: atmospheric
hydrocyclone: 8 barg
Nutshell filters: 5 barg
Treated water out: 3 barg
- Temperature: max 60°C

All vessels are in carbon steel with internal lining of 375 micron in order to protect from salt.
Our client asked us to construct the vessels with NACE plates due to the presence of H2S.

I would like to know if this is necessary or not, considering that the CS is protected with the internal lining. I've purchased NACE M0175 but im' studying it..I think that the use of NACE plates,if not necessary, would increase fabrication price..

regards and thanks
MAtteo

[hellmanya]

Goodmoring guys,
i'm currently working for a hydrocyclone package consisting in some equipments like oil skimmer, hydrocyclone and nutshell filters for the treatment of oily water coming from desalters, separators etc..

The oily water cointains
- 200000 ppm of salt
- 1780 ppm2 H2S
- the system is working at the following pressure from upstream to downstream:
oil skimmer: atmospheric
hydrocyclone: 8 barg
Nutshell filters: 5 barg
Treated water out: 3 barg
- Temperature: max 60°C

All vessels are in carbon steel with internal lining of 375 micron in order to protect from salt.
Our client asked us to construct the vessels with NACE plates due to the presence of H2S.

I would like to know if this is necessary or not, considering that the CS is protected with the internal lining. I've purchased NACE M0175 but im' studying it..I think that the use of NACE plates,if not necessary, would increase fabrication price..

regards and thanks
MAtteo

can you specify the lining material?

[mattegm]

can you specify the lining material?

for internal lining: zinc rich epoxy (75 micron)+coaltar epoxy(150+150 micron); total film thickness 375 microns..

for external lining: zinc rich epoxy (80 micron)+cepoxy polyammide (120 microns)+Aliphatic poliurethane (120 microns); total film thickness 320microns..

regards

[zanjani]

Dear mattegm
when you read NACE MR0175 you will surely understand where It is required and where It's not,
NACE has detemined three regions. H2S partial pressure is the parameter that show service belogs to which region.
when it is lower than 0.05 psi it is in region 0, Normally, no special precautions are required for the selection of steels for use
under these conditions, for other regions there is special requirements and materials which is mentioned in NACE.

[mattegm]

Dear Zanjani,
considering the above data that are in my hand, can you advise the region where i am?
I have only the ppm of H2S in water..

I'm reading the specification but it's quite hard to understand where to look...

Will A516 Gr 70 for plates will be ok?

regards and thanks..

[hellmanya]

Dear Zanjani,
considering the above data that are in my hand, can you advise the region where i am?
I have only the ppm of H2S in water..

I'm reading the specification but it's quite hard to understand where to look...

Will A516 Gr 70 for plates will be ok?

regards and thanks..

1) As long as your water pH is greater than 4 ( for low h2S conentration) and pH is less than 7.8 ( for hish H2S generally 2000 ppm), the problem will not occur.

2) One more thing, presence of cyanide will aggravate the situation even in 6-7.5 pH & low H2S cocentration.
3) Steel with various strength grade will also show different results ( e.g. SA 516 Gr 60 will perform better as compared to Gr 65 or 70, refer NACE RP 0296)

Keeping this in mind, better go for HIC resistant Killed carbon steel.


Hope this will help

[mattegm]

1) As long as your water pH is greater than 4 ( for low h2S conentration) and pH is less than 7.8 ( for hish H2S generally 2000 ppm), the problem will not occur.
2) One more thing, presence of cyanide will aggravate the situation even in 6-7.5 pH & low H2S cocentration.
3) Steel with various strength grade will also show different results ( e.g. SA 516 Gr 60 will perform better as compared to Gr 65 or 70, refer NACE RP 0296)
Keeping this in mind, better go for HIC resistant Killed carbon steel.
Hope this will help

Dear Guys,
i've just returned from a meeting with client and i'm quite confused.
They insist to use NACE plates for vessel fabrication due to the presence of H2S=1728 ppmw.

In the material requisition of the project is mentioned only that:
- the package should comply to NACE specification

I have NACE in my hand but i'm not specialist on it, so i cannot see where i can find that, in my conditions, the NACE plates are not mandatory. If i find something that can confirm to me that in my case this is not mandatory i can tell the client "well, my package is compliant with NACE beacuse my working conditions does not request NACE certification for materials".

Another question is: does NACE spec affect also the fabrication procedure of an equipment like 100% RX on buttweld joint or Post Weld Heat Treatment? This is why client insist to have also these items but i don't understand if it is mandatory for NACE or is only a request by client. My package will follow ASME code for fabrication so 10% RX on welds and no PWHT.

An help would be very appreciated.
Thanks

[nnreddy]

Hi,

If H2S Partial pressure exceeds 0.05psi, the materials shall meeting NACE MR01-75/ISO15156 sour service requirements. Most of the mills can supply NACE compliance plate materials. When you procure the materials just specify that the materials shall meet the requirements of NACE MR-01-75/ISO 15156. Secondly NACE MR01-75/ISO15156 does not recommend internal lining.Please gothrough the standard aagain. In case of internal corrosion you need to have metallic CRA cladding or install sacrifical anodes.
Thanks
nnreddy

[mattegm]

Hi,

If H2S Partial pressure exceeds 0.05psi, the materials shall meeting NACE MR01-75/ISO15156 sour service requirements. Most of the mills can supply NACE compliance plate materials. When you procure the materials just specify that the materials shall meet the requirements of NACE MR-01-75/ISO 15156. Secondly NACE MR01-75/ISO15156 does not recommend internal lining.Please gothrough the standard aagain. In case of internal corrosion you need to have metallic CRA cladding or install sacrifical anodes.
Thanks
nnreddy

Thanks,
in my case what will be Partial Pressure of H2S?I don't have charts here in my hand..Can you help me?
regarding the mills, i know it's not a problem, maybe only a delivery time problem...What about the extra requirements during fabrication (like 100% radiography and PWHT?)

regards and thanks so much

[cytech]

Hi, Mattegm

Basically if the client requirement is to slow down the corrosion on the steel, you may proposed to install cathodic protection.

for the Cathodic protection you may submit the detail to the local vendor and ask to design the system and get approval from the client.