are Mechanical seals WITH CRN common for mixing tanks (pressure vessels) ?

[wydim]

Hello,

I'm from a Canadian Manufacturer. We're designing a mixing tank (with vertical agitator) 30 psig (registered pressure vessel with CRN).

Is someone familiar with mechanical seals that have a CRN ? is it common ? is it required to have a CRN ? and what are the code/law requirements for these seals. I'm working with John crane for the top mixer mechanical seal (API plan 53A. Seal model 5620VP) but he does not have a CRN for the seal. Another similar tank 30 psig (also for the same project) also requires a simpler seal (type 32). Still no CRN available.

What have you guys experienced in the situation ?

best regards,

 

[MJCronin]

You state: .... "and what are the code/law requirements for these (mechanical) seals."

It is my understanding that any mechanical seal has the same status as a gasket regarding ASME Certification. That is to say, the component is crucial to maintaining the pressure boundary, but certification is not part of the ASME vessel code.

I would assume that CRN has the same certification requirements.

An interesting internet blog on mechanical seals seems to address this issue:

Mechanical Seals

It should be noted that the mechanical seal is not considered to be part of the pump pressure vessel and therefore does not fall under the pressure vessel rules. Seal manufacturers have several pressure ratings for their products. API 682 recognizes a static pressure rating, a dynamic pressure rating and a hydrostatic pressure test rating (see the SealFAQs version of these definitions). Each seal OEM seems to use a different and proprietary method for determining these pressure limits.

http://www.sealfaqs.com/?tag=api-682

Please enrich this forum and string .... tell us what you find out

Best regards




MJCronin
Sr. Process Engineer

 

[wydim]

MJCronin, thank you for your response, I like the quote you have copy/pasted from the article in the link. It works in my favor...
BUT, I would like a 'real' explanation/justification from an official source text... or other designer experiences with mechanical seals on mixing pressure vessels

for my Canadian friends :
the province of Quebec law (B-1.1, r. 6.1 - Règlement sur les installations sous pression) references the canadian code (CSA B51). And the CSA B51 has the following definition for FITTING

Fitting — an appurtenance attached to a boiler, pressure vessel, or piping, including such items as valves,
gauges, and controlling devices. It can include other pressure-retaining components installed in a piping
system within the scope of the Act.

according to table 1 : a mechanical seal is a Category H fitting.
category H fittings must be registered

also figure 1a or 1b shows a decision tree that ends with Category H fitting and inspected by manufacturer.

 

[TBP]

Who is requiring the CRN - the customer, or the provincial inspection authority? It wouldn't be the first time that an end user had specified a unicorn...

I would consider shaft seals to be in the same category as packing and gaskets - and I've never heard of CRNs for either of those. My recollection of the code/standard wording is to the effect of "suitable for the service conditions".

 

[wydim]

Hello TBP,
thank you for your reply,

nobody (not the customer, not the AI) is requiring the CRN. It's just me being cautious as a design engineer to supply a product that operates within the applicable law, that's all.