PUW Suface Finish 1

[Spayball]

hey Looking for a bit of help here.

Surafce Finish for a Purified water system, I know the ASME BPE 2007 standard calls for a surface finish of between 0.38 to 0.64 micron Ra for mechanically polished parts.

But what i am wondering does this surface finish need to be the same in the pre treatment unit.( Hense the pre treatment stage) The closest surface finish i can get is 0.8 Ra microns. i want to know if this is acceptable and any supporting references would be great.

Thanks

 

[quark]

The main reason for specifying surface finish in PW line is to restrict the growth of biofilms in the system. Now, as the common bacteria lie in the range of 0.2 to 0.4 microns, the above said surface finish doesn't allow a colony to form on the pipe surface. The generation units (either IX or RO or UF) have many uneven surfaces and restricting pipe finish is like adding a drop of water in an ocean.

The common practice is to have better surface finish from the moment purified water is generated.

 

[Spayball]

Thanks quark. But what i ment to say is that it is only the pipes prior to the pre treatment that shall be of a surface finish of 0.8Ra microns. And every part of the system (RO , EDI and UV shall be within ASME BPE 2007 standard. So would this matter since all colonys would be destroyed during the PW generation.

hope this makes sence !!

 

[quark]

Hi Spayball,

Most of the rules relating to pharma/biotech or implied and we have to choose the best practically viable option.

Unlike product contact (in which case raw, inprocess and finished material all hold good) water has a definite stage after which we say PW, HPW or WFI. In your case, PW classification comes into picture after the water quality is complied with respect to conductivity, TOC and TVC. So, we can exactly say the water is purified after UV system.

So, I would take care to have good surface finish after this step. However, it is quite possible to maintain the required surface finish in UV housing and the pipe upstream side of the UV. So, they can also be finished to the specified surface finish.

0.8 microns Ra is a good finish and I don't see any problem with it. Probably, I will have a look into BPE 2007 (as I didn't have my hands on it yet) in a couple of weeks and let you know.

 

[Spayball]

hey quark,

Thanks for you supporting comments, got the go ahead from validation to proceed with piping,

thank again

 

[quark]

I have gone through the document. Your query is not specifically addressed. Moreover, it basically refers to sterile applications. Purified water limit for TVC is 100 cfu/ml and this is quite high.

I would suggest reading SD-2 (Scope and Purpose) in page no.9 for pointers with respect to the issues that were not specifically mentioned. Having said that, I would prefer strict controls where ever possible. Please refer to page nos. 11 to 14.

Today, I came across with a fellow who is in the technical subcommittee of ASME BPE 2007 sufrace finishes. I put forward your question along with some other concerns I have. Let us see what we can hear from the horse's mouth.

 

[Spayball]

Great Quark,

Would be most greatfull to hear what ASME BPE technical guy will say.

And yes i had read through the relevant sections, Hygienic design connections,dead legs etc have been taken into consideration.

Keep me posted.

Thanks

 

[quark]

Got the reply. They are suggesting us to refer to ISPE Baseline Guide for Water and Steam. The new version is at draft level. However, ISPE is very pragmatic and though they directly doesn't address this question, they give you options.

On a personal note, (mind you they clearly mentioned that it is not official), the BPE member concurs with our idea.

Good luck,