Modular Filter Changing Procedure
- Step 1
With the system operating to create a negative pressure, attach changing HEPA filter module to vacuum source and to the downstream ports of all filters installed in the series. Activate the vacuum source and deactivate exhaust blower. Loosen bolts securing the upstream flange to the ductwork.
- Step 2
Create an 1/8" to 1/4" gap between the flange on the ductwork and the upstream flange on the module. Slip a piece of polyethylene plastic, minimum 6 mil thickness, through this slot and then tape the polyethylene to the pipe extending from the module. (The vacuum ensures that all airflow is inward).
- Step 3
Repeat the above procedure, encapsulating both upstream flanges in plastic and securing the plastic to the duct. Loosen the bolts on the downstream flanges and encapsulate in plastic. Shut down vacuum source and disconnect from module. Cap this opening with the cap provided.
- Step 4
Remove the filter module. For added safety, a plywood or metal blankoff can be permanently attached to the flanges on the filter modules prior to disposal. Dispose of module properly
- Step 5
Place new module into position.
- Step 6
Connect vacuum source to maintain a negative pressure between the adjacent flanges. Remove the plastic from the flanges on the ductwork one at a time and reinstall the SAFEMOD.
All modules are tested at the factory and labeled with airflow direction, efficiency, and pressure drop. However, to complete the installation, an in place test is recommended utilizing the upstream and downstream test ports provided for the SAFESCAN section.
A Comparison of Scanning Methods
- Testing filters by the probe method rarely detects pin-hole leaks
- Testing filters with the SAFESCAN detects pin-hole leaks
The SAFESCAN scanning section shall be manufactured with all components capable of being incinerated and shall replace a portion of the SAFEMOD housing such that the flange to flange dimensions are the standard 27". It shall consist of an aluminum frame, guide bars, and aluminum tubes (10), mounted such that the total filter face is scanned by moving the tubing inward and outward using the end of the tubing outside of the module. A 2-1/4" plastic funnel, with internal ridges to create a "tornadic" effect, is mounted to the end of the tubing with a 90 degree plastic elbow. The fitting, supporting the tubes in the housing, shall guide the tubes and funnels while scanning and shall be capable of creating an airtight seal when the scanning is complete. The outside end of the tubes shall be capped with aluminum caps when not in use.
The SAFEMOD (patent number 7,010,960) containment filter modules shall be as manufactured by Nextek, LLC, Raleigh, North Carolina, and shall include a HEPA/CARBON filter, bubble tight isolation dampers, etc., (as required by system). The system, when installed, shall enable the changing of the modules by maintaining a constant negative pressure in the system cavity, when any seals are broken, to ensure that all leaks are inward. All vacuum connection ports shall be on the downstream (clean) side of the filter.
The filter modules shall be constructed of materials capable of being incinerated at 1200 degrees Fahrenheit and shall consist of .090" aluminum sheeting, with welded corners. The inlet and outlet flanges shall be 0.1875" aluminum welded to the inlets and outlets and shall be punched with 5/16" diameter holes evenly spaced, quantity to be such that the holes are no more than 4" linear inches apart. The test ports shall be pipe nipples with removable aluminum caps, and shall be designed to easily permit in-place testing. An aluminum vacuum port on the downstream side, similar in construction to the test ports, shall be welded on the outlet side of the module.
Neoprene rubber gaskets, 40 - 60 durometer, shall be affixed to the inlet and outlet flanges of each module. A label, indicating the efficiency, test cfm, and direction of airflow shall be affixed to the module casing. In addition, the test standard utilized for this test shall be prominently displayed.
The HEPA filter modules, if a pre-filter is desired, shall contain a 25% efficient polyester filter held in place by clips affixed to the inside of the aluminum housing. The HEPA filter shall be 99.99% Efficient on a 3 micrometer, mono-dispersed DOP particles (IEST-RP-CC001.3, Type C) and constructed with a frame capable of being incinerated, aluminum separators or separator less, and polyurethane sealant. The filter shall meet the requirements of IES-RP-001-86 for their type A filters, The initial pressure drop across the HEPA filter module shall not exceed 1.3" at rated flow.
The HEPA filter shall be caulked in place with RTV-108 silicone sealant, and held in place with aluminum clips affixed to the inside of the aluminum housing. After the pre and HEPA filters are secured in place, the assembly shall be scan tested with a poly-dispersed Dioctyl Phalate smoke in accordance with IEST-RP-CC034.1, Type C, and shall have a minimum efficiency of 99.99%.
The CARBON Filter Module shall contain an activated carbon filter and a 25% efficient polyester post filter held in place by clips affixed to the inside of the of the aluminum housing. The CARBON filter shall be constructed with components, capable of being incinerated, with the carbon sealed in pleated ABS plastic trays and affixed to either a wood board or ABS plastic frame. The carbon shall be selected to provide the most efficient capture of (name the type of gas contaminant - see selection chart). The filter shall be securely held in place and sealed to prevent bypass with RTV 108 silicone rubber adhesive/sealant. The assembly, when completed, shall be tested in accordance with ANSI/ASME N510 - (latest edition), and have a minimum efficiency of 99.99%.
The dampers shall be a positive seal, bubble-tight type and shall be tested at 10" w.g. pressure. The design pressure of the damper shall be 10" water gage. Damper housings shall be cylindrical and constructed of 10 gage T-304 stainless steel. Blade shall consist of two 10 gage plates with a closed cell silicone rubber gasket between them. Blade seal shall occur when the silicone gasket seats against the inside of the 10 gage housing wall. The damper shall be all weld design. All "pressure" retaining weld joints and seams requiring only intermittent welds by design shall not be continuously welded. As a minimum, all weld joints and seams shall be wire brushed and/or buffed to remove heat discoloration, burrs and sharp edges. All welding procedures, welders and welder operations shall be qualified in accordance with ASME Boiler and Pressure Vessel Code, Section IX.
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