Abstract: This paper introduces the principle and characteristics of AHU and AHU+HEPA air conditioning system. Then a pharmaceutical plant clean room purification air conditioning project AHU + HEPA form of design and application, the application of variable air volume valve is introduced, and details of the relevant verification debugging program content!

Keywords: clean room, purified air conditioning AHU + HEPA variable air volume valve, debugging purified air conditioning system is different from the ordinary comfort air conditioning system, the difference is mainly on the temperature, humidity and cleanliness has more stringent requirements, and cleanliness is affected by many factors. In the pharmaceutical plant, in addition to the above requirements, there is the control of differential pressure, and to ensure that the relevant functions in line with GMP requirements, before production by the quality assurance department to line the relevant verification test.



I. Air-conditioning system type and airflow form

The air-conditioning system of this pharmaceutical plant is AHU+HEPA form air-conditioning system, i.e., whole-air duct central air-conditioning system; the air of class B and C purified air-conditioning system in the plant is sent to the room after three-stage filtration by primary (G4), intermediate (F8) and high-efficiency filters (H13), with primary and intermediate filters set up in the air-conditioning unit AHU, and high-efficiency filters set up in the high-efficiency air supply outlet at the end of the system.



II. AHU air handling units

Purification of air-conditioning system AHU air-handling unit using double-layer metal insulation wall plate in the form of structure, the outer wall plate material for the color steel plate, the inner wall plate material for the stainless steel plate, the function of the section includes: fresh air section, primary filtration section, the surface cooling section, fan section, heating section, humidification section, intermediate filtration section, the air section, and so on.

1. Air conditioning system fan interlocking relationship

When running start first open the blower, then open the exhaust fan; stop closing first off the exhaust fan, then off the blower. The new air duct is equipped with electric air valve, and its corresponding air conditioning unit fan interlock, when the fan is closed, the interlock electric air valve

2. Temperature and humidity control

Temperature sensors are set on the return air duct to meet the indoor temperature and humidity requirements in summer by adjusting the amount of chilled water in the surface cooling section and the amount of hot water in the heater: in winter, the indoor temperature and humidity requirements are met by adjusting the amount of hot water in the heating section and humidifying the humidifier humidifying the volume. In order to ensure the indoor air supply to control the cleanliness, the air supply duct is equipped with airflow sensor to control the motor frequency conversion device, by adjusting the fan speed, change the fan pressure to adapt to the system due to changes in filter resistance and other elements brought about by changes in the air volume to ensure that the air supply is constant.

3.Fire safety

The power supply of all fans of the air conditioning system is interlocked with the fire alarm system. When a fire is confirmed to have occurred in the plant, the air conditioning and ventilation system will accept the shutdown signal issued by the fire control center, and can automatically cut off the power supply of all fans and feed back the shutdown signal to the fire control center.



III. Air volume balance control

In the pharmaceutical plant, between different clean areas and clean rooms and non-clean rooms need to maintain a certain pressure difference, the maintenance of the pressure difference is mainly through the balance of air volume to control, that is, the air supply, return air, exhaust air volume adjustment. The plant in the air supply valve using a fixed air volume valve, return air, exhaust air using variable air volume valve. General differential pressure control in accordance with the current pharmaceutical plant.

After the relevant specification requirements are as follows:

Differential pressure between clean areas at all levels is ≥10Pa: Clean area and non-clean area pressure difference is ≥10Pa.

To the plant of a pure room as an example: the system has a total of four rooms, respectively, personnel airlock 2, material airlock 1, pure room 1. Personnel airlock 1 defined as level D, the number of air changes to take 15 times, an area of 6m, room height 2.8m, the air supply air volume to take S1 = 250ma / h: personnel airlock 2 defined as level C, the number of air changes to take 3O times, an area of 6m, the room height 2.8m, then the air supply air volume to take S2 = 500ma / h: material airlock is defined as a level C, the number of air changes to take 30 times, an area of 12m, the room height 2.8m, then the air supply air volume to take S2 = 500ma / h: material airlock definition for level C, the number of times to take 30 times, an area of 12m, the room Height 2.8m, the air supply air volume S3 = l000m3 / h; purification room is defined as C-level, the number of air changes to take 30 times, an area of 128m, the height of the room 3.8m, the air supply air volume S4 = 14600m / h. Total air supply air volume S = S1 + S2 + S3 + S4 = 250 + 500 + 1000 + 14600 = 16350ms / h; return air volume R2 The total air volume S=S1+S2+S3+S4=250+500+1000+14600=16350ms/h; the return air volume R2 is 500m³/h, R3 is 1100m³/h, R4 is 12400m³/h: the room exhaust air volume P1 is 350m³/h, P4 is 2000m³/h; so that the air supply=return air+exhaust air.

IV. Application of variable air volume valve systems

The return and exhaust air of the pharmaceutical plant is controlled by variable air volume valves. Variable air volume valve has many forms, at present in the pharmaceutical plant application is more butterfly valve and venturi valve. Venturi valve control is more accurate and stable, less maintenance problems, but the initial investment cost is higher. Therefore, the project inside the selection of the butterfly valve. The whole control valve consists of VAV box, room differential pressure transmitter, differential pressure controller and actuator. General shape for easy installation and connection, using rectangular or circular. In the differential pressure controller, the room differential pressure value is compared with the room set value through the sensor. If there is any difference between the measured value and the set value, the actuator adjusts the opening of the dampers in the VAV housing to achieve the set value. Before leaving the factory, different VAV units are individually set according to the room differential pressure value and different VAV units are tested for functionality using a special program.

V. Hot and cold media

Refrigerant: The refrigerant used in the air-conditioning system is 7℃/12℃ chilled water, provided by the chilled water unit: Heat: The heat medium used in the air-conditioning system for heating is 70℃/50℃ hot water, provided by the steam heat exchanger unit, the steam is supplied by the boiler, and the air-conditioning system humidification is carried out by steam with a humidification capacity of 0.1MPa.



VI. Verification and commissioning

At the end of the construction and commissioning of all utility equipment, the air conditioning system needs to be verified and commissioned to ensure that the relevant parameters meet the design and GMP specifications. The scope of commissioning is mainly to: confirm the completion of other commissioning activities: document confirmation; installation checks to confirm that the system meets the requirements; functional checks to confirm that the operation meets the intended requirements and meets the safety requirements. Utility confirmation mainly refers to the confirmation of the cooling and heating sources, steam, etc.. Documentation checks include drawings, operation manuals, certificates of conformity, material certificates, equipment data sheets, such as air ducts, need to have duct leakage leakage detection records, high-efficiency filters need to have installation records, fans, air-conditioning units need to have a stand-alone test run records, the room air volume adjustment test records, noise, illumination, temperature and humidity test records, the above information needs to be provided by the supplier.



The function check includes the following aspects :

1. HEPA integrity check test tool for the photometer and aerosol generator, the method is: remove all the diffuser, the aerosol generator connected to the filter upstream of the injection port, adjust the upstream aerosol into the concentration, the use of a photometer in the distance from the filter 25 ~ 30mm scanning the entire filter, record the leakage rate (penetration rate shall not exceed 0.01%).

2. Noise confirmation

Test tools for noise meter, in the normal operating conditions of the equipment, the test noise does not exceed 75dB.

3. Illuminance test

Test tools for illuminance meter, method: in each room diagonally off the ground about 0.85m, according to 1 ~ 2m spacing points, 30m within the measuring point from the wall 0.5m, 30 square meters above, the measuring point from the wall 1m.

4. Air volume and the number of air changes to confirm

Test tools for the calibrated wind speed / wind volume instruments, folding ruler or laser rangefinder instruments.

5. Room temperature, differential pressure and relative humidity distribution confirmation

Install the data logger approximately 4 inches above the floor and as close to the center of the room as possible. Test for 5 min, record 1 time/min temperature, relative humidity. Use a differential pressure meter to measure the pressure difference between neighboring rooms.

6. Room Dust Particle Confirmation (Static)

The testing tool is a tested dust particle counter, and according to IS014644-1, the number of sampling points and the amount of sampling in the room are confirmed, and the sampling position is confirmed before the test is conducted.

7. Self-cleaning confirmation
The purpose of the test is to confirm that the cleanliness of the room can be restored to the specified level within a specified time, applicable to non-unidirectional flow system. The testing tools are calibrated dust particle counter, smoke generator, stopwatch. The number of sampling points depends on the room volume. Set the dust counter to record 1 time/min, place it in the designated location and turn it on. The sampling location should be 0.8m above the ground and 0.8m away from the equipment, and should avoid the exhaust and return air outlets. Use a smoke generator to introduce additional particles into the room, the initial number of particles in the room depends on the room level.