ASME VIII Div 1 Lethal Service Requirement 2

[Gcooper79]

Hi All,

We are supplying an ASME VIII Div 1 pressure vessel (wall thickness 15mm) containing process gas consisting of over 500ppm H2S. There is nothing in the clients specifications to state the vessel requires PWHT and they have not specified that the vessel is lethal service. After PO award and during discussions this week, the client has stated that the vessel requires PWHT.

As far as my limited knowledge of the code, PWHT is not required due to the thickness and according to para UW-2a, the vessel only requires PWHT if the end user has stated that the vessel is lethal service. Is the H2S quantity enough to automatically consider the vessel to be lethal service or does the client specifically need to state the vessel is lethal service? If they do need to state it, is there anywhere in the code this is written and also a definition of lethal service?

thanks,

Graeme

 

[SJones]

https://www.eng-tips.com/search.cfm?q=Lethal+service&action=search

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[david339933]

Yes, they need to state it. UW-2.
Definition: End note 42.

 

[SJones]

I would start typing the variation order.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[hacksaw]

Definitely lethal service. Check your piping materials and the instrument installation requirements.

500 ppm will drop you on the ground. It is deadly.

 

[georgeverghese]

A PV with 500ppmv H2S isnt what the oil/gas industry would typically consider to be in lethal service. Especially when in well ventilated surroundings. Maybe toxic, but not lethal.

 

[JStephen]

I have run into a similar situation where the customer did not want to use the words "lethal service" but did want to specify PWHT, full radiography, etc. I'm not sure if there's some liability issue that motivates this or what. An ordinary person would assume that any compressed hydrocarbon would qualify as "lethal service" but for some reason, it needs to be nerve gas or something before that kicks in.

 

[SJones]

@JStephen

Could it be a financial issue: once a purchaser declares lethal service, the price premium adds up to more than simply asking for the bells and whistles of lethal service without declaring it as such? It certainly occurs with “sour service” - declaring sour service tends to cost more than simply specifying the necessary requirements without the declaration.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[Gcooper79]

Thanks for the replies. I’ve emailed the client to advise the end user needs to determine if it’s lethal service or not. As it stands, PWHT is not in our scope of supply. If they want PEHT, we will raise a VOR for it.

Thanks,

Graeme

 

[hacksaw]

Courtesy of OSHA

200-300 ppm Marked conjunctivitis and respiratory tract irritation after 1 hour exposure.

500-700 ppm Staggering, collapse in 5 minutes. Serious damage to the eyes in 30 minutes. Death after 30-60 minutes.

700-1000 ppm Rapid unconsciousness, "knockdown" or immediate collapse within 1 to 2 breaths, breathing stops, death within
minutes.

1000-2000 ppm Nearly instant death

 

[Some Curious Guy]

Speaking from my experience, end users are hesitant to define a service as " lethal " . Maybe they run into some jurisdiction problems and legal liability if they use the term " Lethal " . However they define all the requirements usually expected with lethal service ( PWHT , Extra NDE's etc ) in the UDS or Requisition or their Specs without mentioning the term "Lethal".
Per my little knowledge on metallurgy I think Sour Service also requires some free water content to cause hydrogen damage. Most end user specification contain a table specifying limits on ph of water , H2S content , other cyanide / sulphide content to classify the service as low , medium or high severity H2S service. The responsibility of defining this is with the owner / EPC. Vessel manufacturers are not expected to know the fluid contents. Hence you are well within your rights to demand a change order if there was nothing defined in the Purchase order specifications. At the same time do not try to be too aggressive in your approach. Let your sales team handle this effectively and negotiate better terms. Remember You also need to make a good business relationship with your Client / End user.

 

[MJCronin]

Eng-tips has discussed this whole ASME "lethal service" topic before ...

It is a hot potato frequently flipped between the client and the engineer.... Who decides ?.... What are the rules ????.

Some cranky old senior citizens (who are probably off their meds) have expressed strong emotions

I still feel the same way that I did way back in 2011 ... There should be a General Guideline issued by someone or some organization with expertise in toxicology

https://www.eng-tips.com/viewthread.cfm?qid=308653

I would like to hear the opinions of others on "Who Should Determine if a vessel should be designed for Lethal Service ?"

We all understand what ASME says about this .... But the client frequntly "delegates" this responsibilty to the engineering firm!!!

MJCronin
Sr. Process Engineer

 

[EdStainless]

The owner can 'delegate' whatever they wish, but the ultimate responsibility is still theirs.
If the engineering firm does not insist on sign off on such items, then they are not practicing due care.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[KevinNZ]

Australia and NZ have the Hazard level of the fluids all coded up, AS 4343. You calculated the Hazard level and then all sorts of statuary rules start to apply.

 

[georgeverghese]

Even nasty hydrogen fluoride service vessels in HF alkylation units in refineries are typically not classified as being in lethal service.

 

[Christine74]

Yes, I've also seen a vessel in hydrofluoric (HF) acid service that was not assigned "Lethal Service", but the manufacturer was required to comply with all of ASME Section VIII's requirements for Lethal Service. This is a common practice for vessels in H2S service as well.

As long as all of ASME's Lethal Service requirements are met, is there any particular reason why the nameplate needs to have an "L" on it?


-Christine.

 

[Gcooper79]

Hi Christine74,

No, there is no requirement to have it ‘L stamped’. The only reason I mentioned it was because the client was insisting PWHT was performed on the vessel (this was not agreed pre PO, nothing in datasheets or specifications). As such, I stated the code does not require PWHT unless the vessel is designated ‘lethal service’.

Graeme

 

[Christine74]

I'm not a metallurgist but I've never seen a data sheet for equipment in H2S service that didn't specify PWHT as a requirement. I think someone dropped the ball so you need to give them a Change Order for the additional scope. If they decline make them put in writing that neither PWHT or Lethal Service is required for this vessel.


-Christine