Clean Room Controls

[krb]

Can anybody give me some information on what types of controls are required for a Class 10,000 cleanroom? I'm sure of temp and humidity controls, but what about monitoring, room pressurazation, air flows etc.? Is there anywhere I can find this information? We are using standard package units with HEPA filters.

 

[quark]

ISO 14644is the new bible for that. What sort of manufacturing facility is yours? The airflow should be such that flow should occur from more critical to less critical areas. In pharmaceutical companies a pressure difference of 15 pascals is maintained between two adjascent rooms.

You can refer MCA Orange Book also.The installation of HEPA should be terminal and room exit from risers.



Regards,

Repetition is the foundation of technology

 

[VEEKRISH]

It is my experience when doing Pharma / Clean room jobs that as the HEPA Filters (at the Terminals) tend to get loaded, the Supply Air Quantity tends to drop. I have overcome this by using CONSTANT VOLUME FLOW RATE CONTROLLERS. There are good ones available which are System Powered and requires no external power source. This maintains the constant air quantity over a certain range of pr change. I find it a bif help. May be you should consider it too.

 

[krb]

Thanks to all for the information. The facility repacks bulk material into individual packages. We are installing the HVAC systam and had some questions as to what the engineer had designed for the controls system. Your responses have helped answer our questions.

 

[farraj]

can any body tell me if we can use packeg unit in clean room &after that we use hepa filter

 

[SAK9]

I would like to correct VKRISH post as follows.As the filters load up,the system static pressure drop increases and the fan speed needs to be increased to cater to the increased static pressure loss.This may be achieved with a flow measurig station at the AHU outlet which would sense the drop in air flow with increased system pressure drop.This deviation from set point would drive up the variable speed drive of the AHU motor increasing the fan speed and the fan static pressure.

Constant Volume Controllers are useful when the system static pressure fluctates normally on the plus side.The volume regulation is achieved by varying the damper opening based on system stsatic pressure(usually spring or bellows operated).They waste energy on a system fitted with HEPA filters.

 

[ChasBean1]

SAK9, negative. As the filters load, terminal boxes open to maintain a given flow rate. If the central AHU is also trying to maintain a flow rate as sensed at the unit itself, there will be a mismatch in the flow required at the terminal devices versus the flow required by the AHU. The central AHU should only control to a given duct static pressure and not to a given flow rate.

ferraj: Yes. The packaged unit should control to maintain a certain duct static pressure. Beware of minimum flow rates and direct expansion (DX) cooling.