PAO Testing Protocol | HVAC Validation Procedure

Rahul Kashyap
2

PAO Testing Protocol | HVAC Validation Procedure

By means of an aerosol generating equipment, a sufficient amount of said aerosol must be injected, which may be PAO (Poly Alpha Olefin), to the air system at the strategic point before the air outlet in the filter. Then the concentration of aerosols must be verified upstream of the filter. Record the average speed with which the air passes through the filter to verify the results of the sample.

When this concentration of PAO (Poly Alpha Olefin) presents acceptable values,> 10 <80 micrograms per litter, according to ISO 14644-3:2005 Annex B, scanning continues downstream of the filter, over the entire front surface of the filter and frames, at a 3 cm distance from the filter face and at a recommended average speed of approximately 5 cm/s.

If during the PAO (Poly Alpha Olefin) scan values ​​that exceed the limits established for the designation of leaks are recorded, according to ISO 14644-3: 2005 - B.6.2.6, the scanning probe will be maintained in said sector, in order to stabilize the reading and confirm the detected leak.

ISO 14644-3: 2005 - Annex B.6.2.7, recommend stake as criteria of acceptance, minor vanishing points or equal to <0.01% penetration of the concentration of challenge spray injected. When the integrity and water tightness test of filters, subsequent tests will be invalid, taking into account the provisions of standard 14644-1 and 2 in relation to pre-test conditions for classification and re rating, respectively.

In accordance with the provisions of the IEST-RP standard-CC034, a silicone sealant is used and the leaks must not exceed 5% of the front surface of the filter mantle, nor present a side greater than 38 mm. (length or width). After the repair is complete and the sealant has dried, the Scan again to verify the absence of leaks outside the allowable values.

The standard establishes a procedure very precise to determine a integrity and tightness test of HEPA / ULPA filters. Effectively complete those steps in field work largely requires measure of our ability to use the appropriate criteria. When we talk about criteria appropriate we mean that the filter integrity tests do not we usually perform on a "test bench”. On the contrary, we usually we use laminar flow, a biological safety cabinet, be installed in the air handling units, be installed sandwiched in the ducts, or it may be the very common case that the filters are housed in terminal modules a ceiling level, "as is the case we decided to analyse this, there are many factors that we must take into account when conducting a test of integrity and tightness of a filter, either HEPA or ULPA, the ones that concern us most are those that are directly related to "generation, concentration and stability" of the aerosols upstream of the filter, prior to scanning.

Most of the time the decision goes through previous experiences and in similar situations where aerosols PAO (Poly Alpha Olefin) were injected from air treatment units using aerosol generators hot chamber (many times over injecting the amount of aerosols), and due to the existence of leaks in the air ducts there is an escape of the aerosols that contaminate the facilities which lead to suspend the tests.

knowing the installation with which will work, we will be able not only to proceed effectively with the measurement, but we will have the ability to use the results in favour of optimizing the systems and the plants it supplies, improving the quality of procedures and consequently of the products.

 

 

 

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