PRINCIPLE OF OPERATION
The Retrotec systems have 2 types of panel systems than temporarily seal off a doorway in the enclosure so that the variable speed blower can be installed. First, the static pressure existing across the doorway is measured, then the blower is turned on to pressurize the enclosure to the maximum pressure that could occur once the room is full of agent. The airflow required to establish this pressure is measured and the process is repeated in the other direction. These 2 readings are used to calculate the size of the hole in the enclosure . The computer then calculates the agent loss rate that would occur after discharge.
Each retrotec blower will measure up to about 9 square feet of leaks in any size building. The system was designed specifically to be quickly reversible so measurements can be made in the other direction. This eliminates a host of site, operator and equipment errors.
Accuracy is 5% of the measured flow rate. The system was calibrated according to ASTM standard E 1258-92 and CGSB 149.10 and meets all requirements of NFPA. Flow measurement is by a balanced annular piezometric pickup.
Room pressure gauges are specially calibrated to +/- 1 Pascal. An error of 1 Pascal in 15 will change the result by about 3%.
WHY REVIEW ENCLOSURE INTEGRITY? it’s mandatory.
For the past six years most new halon system have been approved using a door fan and computer to predict the retention time of the enclosure instead of using a discharge test. Now, “clean agent” manufacturers recommend door fan tests because:
NFPA 2001 says “: 4-220.127.116.11″ A discharge test is generally not recommended;…” NFPA 2001, requires the enclosure be tested. Appendix B covers the door fan test.
4-7.2.3* Review Enclosure Integrity. All total flooding systems shall have the enclosure examined and tested to locate and then effectively seal any signifigant air leaks that could result in a failure of the enclosure to hold the specified agent concentration level for the specified holding period. The currently preferred method is using a blower door fan unit and smoke pencil. If quantitative results are recorded these could be useful for comparison at future tests.
NFPA 2001, requires re-evaluation and possible retesting every twelve months.
4-4 Enclosure Inspection. At least every 12 months, the enclosure protected by the clean agent shall be thoroughly inspected to determint if penetrations or other changes have occurred than could adversely affect agent leakage or change colume of hazard or both. Where the inspection indicates that conditions that could result in (an) inability to maintain the clean agent concentration (exist), they shall be corrected. If uncertainty still exists, the enclosures shall be re-tested for integrity in accoredance with 18.104.22.168. Exception: An enclosure inspection is not required every twelve months if a documented administrative control program exists that addresses barrier integrity. This is an important service to the end user and a cost effective one for the contractor with a door fan to provide.
Clean agent discharge testing is expensive, disruptive and takes a lot of time. By comparison initial door fan testing takes one to two hours by one man and costs very little.
Door fan tests show a lot more than just the ability of the enclosure to hold the agent. The test demonstrates containment levels on all planes and elevations allowing the tester to point out problems that may arise regarding fire containment, smoke control, dust control, energy control and agent exhaust deficiencies.
Door fan tests give the client a better “picture” of his facility – you can service his needs better differentiatig your service from your competitors – you look better.
If an agent discharge is required, the door fan test can quickly and cheaply prevent a discharge test failure by predicting discharge results in advance and pinpointing problem areas.