Thursday, October 23, 2008


1.0 AIM:
The basic aim behind this exercise is to provide Terminal HEPA Filters for the Compression Area, with Overhead Feeding Room & Airlock and provide temperature and humidity control so that the product passing through shall remain under the same conditions as that of manufacturing areas.
Based on the actual observations of the present operating system it was decided to form the System Design Basis on following assumptions:
1.1 To provide Terminal HEPA filters in the Supply air path so as to achieve most effective Air Filtration System within the given limitations.
1.2 The air changes will be kept as minimum 25 air changes per hour.
1.3 Pressure Gradient shall be maintained from Passage to Compression Area to prevent cross contamination and to prevent ingress of untreated external air.
1.4 Heating Coil with Hot water shall be provided to maintain the required Relative Humidity.
1.5 The return air risers shall be provided with Grilles for pick up of room Air.
1.6 The motor of Air- Handling Unit will be provided with frequency drive so as to control the air quantity through variation in fan speed.
2.0 System Designation & Areas Covered under designated System:
2.1 System Location: Contractor Company
2.2 System Designation: AHU - XX
2.3 Areas covered:
3.0 Design Parameters:
3.1 Area, Height & Volume:

3.2 Out Side Conditions:

3.3 In Side Conditions:

3.4 Fresh Air Quantity: 60 CFM
3.5 Lighting Load: 1.5 Watts / Sqft.
3.6 Roof Insulation:
Sun Exposed Roofs shall be insulated with 50 MM THK Expanded Polystyrene / Equivalent
3.7 Chilled Water Temperature - Not to exceed 8.50C at Inlet to Chilled Water Coil
3.8 Equipment Load, Occupancy, Room volume, Design Air changes and air quantity requirements.

4.0 Calculated Refrigeration Load & Air Quantity:

Note: 1. FA – Fresh Air
2. Deh. – Dehumidified Air Quantity
(i.e. Calculated Air Quantity based on Area Heat Load)
3. TR – Refrigeration Tonnage
(Calculated on the basis of Area Heat Load)
4. AHU Capacity – Air Quantity in CFM.
(Selected from Higher of Design Air Changes required &
Calculated Air Quantity based on Area Heat Load)
5.0 Differential Room Pressure Gradient:

6.0 Air Filters:

7.0 Temperature & Humidity Control:
Temperature and Relative Humidity Control to achieve the desired room conditions is achieved by a combination of Cooling and Heating Coil. Sensible & latent heat is removed from the Air Stream by the Chilled Water Cooling Coil. A three way proportionate balancing valve with temperature controller has to be provided at the chilled water cooling coil outlet connection.
The sensor of this valve senses the return air temperature and humidity proportionately controls the chilled water flow to chilled water coil in such a way that when the room temperature drops and/or the Relative Humidity decreases, the chilled water flowing through cooling coil is reduced proportionately to the setting and when the room temperature or Relative Humidity rises, the chilled water flowing through cooling coil is increased proportionately to the setting to achieve desired range of room temperature / Humidity.
The necessary Re-heat is provided to maintain desired Room Temperature through a heating coil. A Three Way proportionate balancing valve is provided at the outlet of the hot water coil, to regulate the hot water flow control as per the temperature requirements.

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