PROCEDURE 1. Heating Ventilation and Air Conditioning
3. Air Handling Units (AHUs) 1 General specifications
3.6 Dampers
Dampers must be designed with profiled damper blades operating in opposite directions, with an additional seal mounted on external, rein-forced, polyamide, cogged wheels with slide bearings.
3.6.1 Coils
Air handling unit coils should have no more than eight fins per inch and be no more than six rows in depth to facilitate coil cleaning. Where more than four rows are required to obtain the cooling capacity, two coils should be placed in series. Spacing between the coils should be piped so that counterflow of air and water is achieved. Fins should be of the continuous, flat (noncorrugated) type.
SOP No. Val. 200.50 Effective date: mm/dd/yyyy
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Note: On large air handling unit systems, consideration should be given to bypassing the cooling coil with part of the return air to minimize the amount of reheat required. With coil bypass, pretreating the outside air for dehumidification may be required.
3.6.2 Notes
The HVAC specifications should state that before the activation of any air handling unit, all construction debris should be cleared away and the unit thoroughly vacuumed. Units should be vacuumed again before the instal-lation of cartridge or bag filters. Prefilters should be installed before initial unit start-up. Cartridge or bag filters should be stored in a clean, dry place and should be installed after room finishes are complete. If HEPA filters are contained within the air handler, these should also be installed at this time. Comprehensive cleaning guidelines for duct and equipment must be provided as part of the construction specifications.
3.6.3 Sealing
All ductwork should be sealed in accordance with SMACNA Class A rating, which requires all seams, joints, fasteners, penetrations, and connections to be sealed. Sealant should be FDA acceptable for the application, and non-hydrocarbon based. Leakage rates as low as 1% total airflow are not uncom-mon. All ducts passing through a clean room wall or floor should be provided with stainless steel sheet metal collars and sealed at the opening. Details of sealing methods should be provided on the design documents.
3.6.4 Leak testing
Before ductwork is insulated, the installing contractor should leak test each duct system at 125% of the operating pressure. Leak testing should be witnessed and signed off to signify approval. Acceptable leakage rates and leak testing procedures and reports should be based upon the SMACNA HVAC Duct Leakage Test Manual.
3.6.5 Insulation for HVAC ductwork
All insulation should be in accordance with the “fl ame-spread” and
“smoke-develop” ratings of NFPA Standard 255. Ductwork should be
SOP No. Val. 200.50 Effective date: mm/dd/yyyy
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externally insulated. The use of internal duct liner is not acceptable. Some criteria will not allow the use of fiber glass insulation even on the exterior of the ductwork. Whenever ductwork is exposed in clean spaces, it should be insulated with a rigid board-type insulation and jacketed with either a washable metallic or PVC coated jacket. Jacketed ductwork should be of sufficient density to minimize the dimpling effect when the jacket is applied. Flexible blanket insulation is acceptable in concealed spaces. No insulation should be applied on the ductwork until the leak test has been performed, witnessed, and approved. Rigid duct insulation should also be used in mechanical rooms.
3.6.6 Insulation of the ducts
The ducts must be insulated following the characteristics of the air inside:
T° ≤ 18°C should be insulated with armaflex thickness = 25 mm. The insulation must be glued on the ducts. The joints between two strips of insulation must be airtight (gluing of an insulation strip on the joints) to prevent condensation on the pipe. Return ducts, blow ducts (T > 18°C) should be insulated with rockwool or glasswool (thickness = 25 mm recovered by a metallized vapor barrier).
3.6.7 Marking of the ducts
The ducts and other equipment must be marked after insulation by:
Arrows to give the direction of the air flows
A red strip on the blow ducts
A blue strip on the return or exhaust ducts
A green strip on the fresh air
The number of the equipment (AHU, damper, sensors, etc.) cor-responding to the P&I
3.6.8 Damper
The regulation dampers — air flow (blow, return, or exhaust) by room or by intake or return opening — must be manual with mechanical locking (minimal looseness allowed) located in the ducts. The general dampers, or those for most important sections, must be similar to the dampers for air handling unit; a suitable model should be selected.
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3.6.9 Sound attenuators
Sound attenuators should not be used in systems requiring sanitizing because the perforated face (interior) of the sound traps can collect dust and microorganisms.
3.6.10 Humidifier
Humidifiers serving clean areas and process areas should use only clean steam for humidification. Carbon steel piping and headers are not accept-able; 316L grade stainless steel should be used. All humidifier components (main body, valves, piping, manifold, etc.) should be made of 316L stainless steel.
3.6.11 Air distribution
Standard type (turbulent flow) diffusers should be used in class 100,000 areas. Terminal HEPA filters should be used in the ceilings of the areas that are class 10,000 or cleaner.
3.6.12 Return or exhaust air
Ceiling return or exhaust is acceptable in class 100,000 areas. Low wall returns should be used in class 10,000 or cleaner areas. All returns or exhausts must be louvered, removable types.
3.6.13 Intake and return openings
The number and the location of the openings must be selected to have a good distribution of the changing of air (cleanless class, t° uniformity).
They must be designed following the requested air flows, velocities (at the opening and in contact with people), and level of noise.
The openings must be constructed with stove enamelled steel or stainless steel.
They must be mounted flush with the ceiling or the walls (or partitions) and sealed with paintable silicone.
Models should be selected as appropriate.
SOP No. Val. 200.50 Effective date: mm/dd/yyyy
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3.6.14 Intake or return openings with filters
In the classified rooms 10,000, 100, 100 with LAF (following F.S. 209E), the intake openings must be fitted with absolute filters. The number and size must be selected to obtain the same air velocity (±10%) for all the terminal filters of the same air handling unit. The absolute filters’ housing shall be airtight, mounted flush with the partitions, walls, or ceilings (maximum 2 mm of difference). The sealing gasket between the housing and the filter should be provided to prevent bypass of unfiltered filter. A manometer should be connected upstream and downstream of the filter housing and pressure drop measured. When the pressure drop across the filter exceeds the recommended change point, the filter must be replaced.
The recommended air velocity of a HEPA filter is 0.45 m/s. The HEPA filter and its housing must be tested mounted on site with the DOP. For return openings for powder production, the housing with HEPA filter must be fitted with a prefilter removable from the front. The recommen-dation is to use HEPA filter presealed in the housing located in a stainless steel frame.
REASONS FOR REVISION
Effective date: mm/dd/yyyy
First time issued for your company, affiliates, and contract manu-facturers
SOP No. Val. 200.50 Effective date: mm/dd/yyyy
Approved by: