Pressurisation of Corridor in Pharma Plant 2

[remp]

Has anyone any rule of thumb numbers for leakage through doors, relative to pressure differences. Dealing with a pharma plant and presurisation of corridors?
The corridor in question requires a pressurisation system, and I would like to know how much air is required. The designer has stated that an air change rate of 16a/c per hour will do the trick, however he seems to be exhasuting 90% of the supply. Why would you exhasut a space if you are trying to pressurise it. Is there a rule in the pharma industry which states minimum air changes for a corridor. Each side of the corridor is tablet production/coating etc/...

Would appreciate some thoughts>>

 

[ChasBean1]

Hi again billyg,

Air exchange is not related to pressurization. The only requirement I know for corridors in any location is 0.05 cfm/ft2 ventilation (pretty low).

You can use supply and exhaust just because it's better for air circulation. The key to achieving a set pressure is sealing, gasketing & sweeps. You can achieve +0.05 in. w.c. in a corridor by supplying 50 cfm higher than exhaust or 500 cfm higher, depending on how tight the space is. Size only matters because the larger a space is, the more leakage it's likely to have.

I would design for supply to be 50-75 cfm higher than exhaust for each 100 ft2 of space. From there, seal everything tightly and use gaskets at doorways, and use adjustable door sweeps to obtain the right pressure.

 

[quark]

In addition to what CB mentioned, USP specifies a minimum 10 ACPH for class 100 000 areas (corridors fall into this category) and minimum 20 ACPH for class 10 000 areas. The value you considered seems to be quite OK. A positive pressure of 10 to 15 Pa is the guidance value followed world over for oral dosage facilities.

Once through system for oral dosage facility corridors is not a very strict recommendation and you can consider recirculatory system with proper filtration in your case.

The main problem with the corridor pressurisation comes from door openings. If you are logging the pressure values via BMS, you may end up with problems of irregular pressure profile.

10% of fresh air with 10ACPH AHU capacity is sufficient to take care of a pressure of 10 Pa (with all doors closed and leakage minimized by adjustable door sweeps and overlapping doors) as far as my experience is concerned.

Regards,


Eng-Tips.com : Solving your problems before you get them.

 

[235zzzo]

Hi!

Consider some additional points:

-Following the last Quark's post, you can get almost standard solutions to face the door openings problem.

- When there is any static pressure change, that is recognized by a (or several, in this case it is used the mean driven value) pressure probe/transducer which turns into a electrical signal (0~10 volts or 4 ~20 mA) to drive the ventilation group VFD. Then the flowrate is changed to recover the reference positive static pressure in the corridor, in every moment.

- This happens around the reference design ACPH imposed by the nominal/project conditions.

zzzo

 

[jherbert]

hi,

Why would 'dirty' (relative term) corridor air
feed into production space?

Production cleaniness is the goal, right?

Pressurisation of the 'cleanest'(relative)
production space(s) must overcome infiltration
from adjacent 'dirty' corridors, leakages, etc.
in the same as one would design an OR.

I would check the overall flow pattern.

as 235zzzo stated, the biggest challenge
is experienced during opening and closing
of the (hopefully interlocked) doors

cheers,

 

[quark]

Jherbert!

In oral dosage facilities (particularly tablets and capsules) that is a general practice to keep corridors positive with respect to the productin areas. This is to protect human from being exposed to the loose product (called as containment). Your point is valid as far as liquid parenterals are concerned and there you are more focused in saving the drug.

The cleanliness (relative) is acheived by having air locks between corridors and production areas where ever required.

Regards,


Eng-Tips.com : Solving your problems before you get them.

 

[235zzzo]

- First, I don't think corridor associated with any dirty functions at all!

- 2nd, the corridor is communication/circulation space to others production spaces, so it must be the cleanest space in the facility!

- Third, the architecture of the building must consider all those implications and sensitive relations between critical production spaces, therefore to consider compartimentatons wherever it's needed, like section doors along the corridor or those air locks, as Quark pointed out.

- Fourth, obviously, the ventilation system, as refered by my above post, should correspond to one per each locked area with a self control, as well. We are talking about 100 % treated fresh/new air systems, those buildings must be consider clean facilities, including specially the corridors, may I say. An obviously conclusion, if you have a problem in the corridor, that turns to be into many and very (!) serious problems to all the other communicating spaces.

- Finally, static pressure must be always positive in the corridors, in relation to the contiguous spaces.

zzzo

 

[235zzzo]

As an additional:

Arquitechure can solve the problem, once for all:
- two doors,
- a space in between, to enter into a production space, from the corridor,
- you open the first door,
- you close it afterwards,
- then you open the second, you are in and clean!

- Now, a small "secret", you should pressurize that small space in between with a ventilation system, and don't need any special control system, like the one above mention.

zzzo