Is this Sour Service 1

[bmoorthy]

We have a Pipe carrying water under pressure 15 Bar

The out side of the pipe is exposed to Sour Gas (pressure in MM of water coulum)

Is this coming under the scope of Sour service?

 

[Unotec]

If the gas is "sour" as per your definition, then yes, it would fall under the cour scope

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>

 

[rustbuster]

Not nessecarily, Sour Service is defined in NACE MR-0175. The partial pressure of H2S may fall below the curve based on concentration and pressure.

 

[SJones]

Rustbuster - there is no curve of concentration verus pressure defining sour service in MR0175/ISO 15156. If the pipe is exposed to an H2S containing environment then, by the definition given in ISO 15156-1, 3.19, it could be in 'sour service'. What the thread is driving at is: will the pipe require to have additional manufacturing and testing controls for H2S service? bmoorthy has to review ISO 15156 and reach a conclusion.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/

 

[gr2vessels]

bmoorthy,
The exposure of the water pipe to the sour gas does not qualify to be subject of the NACE MR0175, as per the Clause 7.1.1, due to the low partial pressure you have mentioned (assuming is less than 30 mm water column of H2S partial pressure and in absence or other contaminants, low ph, etc..). However, if the partial pressure is above the limit of 30 mm water column, then your pipe may qualify for the sour service classification.
Also, for my curiosity, where is that few mm H2S partial pressure coming from, obviously not from the atmospheric environment / pressure...
cheers,
gr2vessels

 

[SJones]

But sub-clause 7.2.1.3 then goes on to point out a number of other issues.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/

 

[strider6]

pipe exposed on the external surface to H2S? where does it come from the gas? is the pipe inside a vessel or other equipment?

S,

Corrosion Protection & Corrosion Control

 

[adrianviorel]

strider6, it could be that our collegue is speaking about some furnace/boiler coils, subject to flue gas. It de-pends on the used combustibles.

 

[bmoorthy]

The situation expressed is from process data shet of waste Heat Recoery Unit and Fired heaters

 

[gr2vessels]

bmoorthy,
As above, if the H2S partial pressure exceeds approx. 30 mm water column, then the environment is required to be classified as sour service. As you know, the effects of H2S on steels could be classified as those that require external stress, such as sulphide stress cracking (SSC), and those that do not, such as hydrogen induced cracking (HIC), and corrosion. The presence of carbon dioxide in the flue gas together with the sour environment tends to increase the corrosion rate in the steel; it may also increase the susceptibility of the steel to both SSC and HIC, with the effect on HIC being more pronounced. The fact that the sour environment is on the low pressure side of the stressed pipe makes no difference, the damage will occur, depending obviously on the extent of exposure to the flue gas components, pressure and temperature, the pipe material compliance with the NACE requirements (0175 or 0103 as applicable).
cheers,
gr2vessels

 

[bmoorthy]

The Tubes!! are made from A 106 Pipes. Finned. steel Finns. Resistance welded.

So do we insist on Hardness below the Finned Tube Resistaance welds? (If indeed the Partial pressure is in excessof 30 mm of water column)

 

[gr2vessels]

yes.
gr2vessels

 

[bmoorthy]

WHRU and Fired Heaters have plate flanges (to connect various sections) and the boxs are traditionally fabricated as per API 560. the gasket joints have the ladder tape (Kind of fabric tape) and get bolted with A 307 or A 325 or even commercial grade bolt nuts.

It is the coil (Which contains the water) that gets pressure tested with all the vigour, whilst the shell side, which is essentially considered structure with insulation/refractory does not get tested for leaks from gasket joints. This is the industrial reality.

There seem to be no guideline for this at all.

The point i am trying to make is, if the flue gasses that exert parrtial pressure greater than 30PPM of water column due to H2S, should there not be leak test for this joints.