The basis of design shall be series GB gasket seal bag-in / bag-out filter housing constructed by CFI or approved equal. All housing components shall be factory assembled and tested in accordance with accepted requirements and approved by the Owner or its representative.
The housing shall be constructed from 14 gauge and 11 gauge type T-304 stainless steel (as standard). The CFI construction method shall provide adequate reinforcement to withstand a negative or positive pressure of at least 20” water column (w.c.) or the Owner’s specified and scheduled operating system pressure, whichever is higher. The housing shall be side servicing for filter installation and removal. Housing design shall allow air to enter and exit the housing without changing direction. The housing shall accommodate standard sized filters that do not require any special attachments or devices to function properly during or after installation. Prior to leaving the factory, each filter housing module as well as the entire assembly shall be tested to insure its integrity in accordance with ERDA 76-21, paragraph 6.2.2 housing construction. “Nuclear Air Cleaning Handbook”, Table 4-2 for filter fit, mechanical function, for filter sealing surface flatness, and tested under system operating pressure by means of pressure decay test.
Welding and Cleaning:
All pressure retaining welded joints and seams shall be continuously welded, (CFI-standard). Housing shall be free of all burrs and sharp edges. All weld joints and any portion of any gasket setting surface shall be ground smooth and flush to base metals. All welding shall be visually inspected by a procedure having each welder operator qualified in accordance with ASME Boiler and Pressure Vessel Code Section IX. All welds shall be visually inspected by qualified factory personal in accordance to ANSI/AWS D9.1-1990, (“Specification for Welding of Sheet Metal”).
All hardware used in the manufacture and assembly of the filter housing shall be a minimum of 300 series stainless steel (i.e. nuts, bolts, washers, springs, etc.), except for the brass nuts used for filter clamping device and the aluminum hand knobs used for filter access door retaining. (aluminum hand knobs are used to protect against galling of stainless steel threaded parts) per ERDA 76-21, Section 6.2.2 housing construction.
Removable Gasket Seal Filter Clamping Mechanism:
The filter clamping device (locking tray) shall be operated by means of a standard wrench and from outside of the housing front. The filter clamping mechanism shall be located on the clean air side of the filter / adsorber (i.e. downstream), leaving the filter sealing mechanism to be located in clean air. The sealing mechanism shall be self-aligning and adjustable by means of springs used in a dual compression bar assembly. The filter clamping device shall produce a minimum of fifteen hundred (1,500) pounds of pressure per filter element to insure a proper and uniform filter to frame seal along its gasketed surface. The filter clamping device shall be driven by a type T-304 stainless steel 1/2-10 acme threaded shafts and 1/2-10 brass acme nuts to prevent galling. The filter clamping device shall seal each filter individually with maximum of ten (10) foot-pounds of torque.
Filter Access Doors:
Each filtration element location shall be provided with an access door to remove the filtration element and replace it with another. Access doors shall be single-wall type. The filter access door shall be sealed to the housing front by means of a skinned silicone closed cell sponge gasket. Silicone gasketing shall not have a memory during prolonged compression, (i.e. it will never lose its shape or composition during compression) and shall be replaceable. Each access door shall be rigid and provided with at least (4) four tie-down latches. The access door shall be designed such that, when removed, no sharp projections remain.
Filter Access Ports:
Each filter access port shall have a bag clamping ring (also called a bagging ring). The bagging ring shall have a smooth hemmed edge to insure safe installation and removal of the filter change out bag. The bagging ring shall be seal welded to the housing front around the filter access port. It shall be designed with two (2) raised ridges to stretch the shock cord of the filter change out bag elastic mouth around the bagging ring. The bagging ring and filter change out bag shall be concealed behind the removable filter access door when in the installed position. The filter access door shall be clamped in place with the use of 2” machined aluminum hand (star shaped) knobs which do not require tools to furnish the necessary torque required to specified tightness.
Filter Removal Rod:
A filter housing that is two or more filters deep shall be equipped with a filter removal rod assembly. Filter removal and manipulation is through the filter change out bag.
Filter access handedness shall be by the side (right hand, left hand or both) of the housing where the filters are to be accessed. The handedness shall be determined as if a person were standing inside of the housing and is facing in the downstream direction of the air stream (i.e. the air is hitting the person in the back).
Filter Change-out Bag:
The filter change out bag shall be constructed of (8) eight mil thick LP-375C Class 2 PVC flexible material and shall be yellow in color. The filter bag shall be matted on one side to reduce static and shall be semi-transparent. The filter bag shall have a clear portion at the mouth for visual purposes and two (2) two glove ports for filter manipulation. The filter change out bag is retained to the bagging ring by means of a safety strap for an air tight and secure seal. (All system straps and change out bags shall be furnished by CFI and shipped boxed inside system).
Factory Testing and Quality Assurance:
The filter housing shall be manufactured under CFI’s quality assurance program that addresses the workmanship requirements of ASME NQA-1 “Quality Assurance Program Requirements for Nuclear Facilities”. All production welds shall be visually inspected per CFI’s standard procedure (C-2012 “Visual Inspection of Welds”) which incorporates workmanship acceptance criteria. The filter housing shall be tested for filter fit, filter sealing, and surface flatness. Each housing module and the complete pressure boundary shall be leak pressure tested by the “Pressure Decay Method” in accordance with ASME N510-1998, “Testing of Nuclear Air Cleaning Systems,” paragraphs 6 & 7, at standard conditions or under the operating pressure and temperature, whichever is greater (both filter sealing surface and overall housing are tested).