Velocity profile test of Ultra clean ventilation (UCV)

[mechbuild]

I was told to perform the velocity profile test for ultra clean ventilation system of operating theaters.
Based on HTM procedure, the velocity to be measured at 2 mtrs from finished floor level but no air velocity detected at this level with fan anemometer.

The procedre does not say the clear method of measuring the velocity.

I would appreciate if any body can advice me on this.

 

[walz]

If air at 2 meter height has some velocity, it should be detected. If its not, then you need to get more sensitive anemometer.

 

[mechbuild]

Thank yo Walz.
We achieved required air flow by balometer,based on these, we should achieve the required velocity at 2m above FFL.
The face area of the hepa filter is 2.8m x 2.8 m and according to HTM, this area to be divided into number of small grids each of 2.8 cm x 2.8 cm.

May be due to large face area, we are unable to get the velocity at 2m above FFL. If we measure the velocity at each grid at 2m above FFL, by covering this area upto 2m, we may get the reqired velocity profile. But I don't know that this way of measurement is acceptable or not.

 

[walz]

Air movement in a duct is different than moving free in the room, there was a similar question asked here about calculation of this air velocity. Can you tell me the velocity range which you are required to achieve.

One idea is that you measure the airflow instead of veloity at 2 meters height. then divide the airflow with the inlet area of the flow measuring device to get your velocity.

 

[mechbuild]

I think you are quite right, I was also thinking the same.
I will perform the velocity profile soon.

Thanks a lot for your valuable advice.

I would appreciate if anybody else willing to say anything in this regard.

 

[mechbuild]

Hi,
The ultra clean ventilation canopy of operating theater is divided ino two zones and specific velocity to be maintained at 2m & 1m from FFL in each zone as follows as per HTM 2025.

74 fpm average velocity at 2m from FFL for the complete face of the hepa filter

40 fpm average velocity in the central zone at 1m from FFL.

We have a balometer that can measure air flow at 1.75m from FFL.and this air flow can be converted into velocity by dividing face area of the hepa filter.

We can apply the similar method for the central zone to measure the velocity at 1m from FFL.
I dont know the acceptability of the above method to verify the velocity profile.
I would appreciate if anybody correct me if i am wrong.
Thanks.

 

[walz]

If you have measured the floe ... means you have the velocity...

there is no instrument that can actually measure the flow, flow is always measured by other parameters on which it depends..

so your flow to velocity conversion is reliable

 

[mechbuild]

Thanks Walz for yor advice.
By using balometer, I achieved a good result at 1.75m from FFL, approximately the velocity was 82 fpm.

But for central zone, where velocity to be measured at 1 m from FFL, there is no stndard hood available of this size for measuring the velocity. Can you please suggest me suitable method to measure the veloccity.

 

[walz]

One idea could be that... the instrument used for velocity measurement should be oriented in such a way that it can detect the velocity.


May be your instrument should be aligned perpendicular to the velocity of air.

Try to feel the direction of air movement at central zone and then change the orientation of your instrument perpendicular to that flow. Or just at 2 m height try changing the orientation till at some angel you read the flow.