How to control space stability in a 100,000-level dust-free workshop
For the above-mentioned interference factors, the class 100,000 dust-free workshop should consider the stability of the differential pressure control from many aspects such as design, installation, commissioning, and operation. The control method in practical applications is discussed below.
1. The return air volume of the circulation unit should meet the requirements, and can be automatically adjusted to ensure a fixed value air supply, that is, the design total air volume needs a margin for adjustment. When the air volume decreases during use, the air filter resistance can still be adjusted to the required The air volume and the set value of the supply air can be determined on the basis of the static pressure difference test balance during the debugging process.
2. The fixed value adjustment of the pressure difference is based on the balance of the air volume test. That is, when the static air condition is satisfied, the automatic return air valve opening degree is set higher than 50%. The return air hand valve makes the indoor pressure difference close to a given value. When there are a large number of rooms controlled by a unit, special attention must be paid to the commissioning. Due to the mutual influence of the branch pipe air volume, this commissioning step is a repetitive process and is gradually approached. In the process of setting values, after all the rooms have met the requirements after testing, they can be fixedly sent back to the wind hand valve, and then put into the differential pressure automatic control system.
The functional section and order of arrangement of some purification air-conditioning units in Class 100,000 cleanrooms should not be ignored. Generally, the air volume calculated according to the air-conditioning load of indoor equipment and envelope structure is less than the circulating air volume calculated according to the purification level. The amount of air supply should be based on the circulating air volume required to meet the air-conditioning purification level. The fresh air volume of the clean air conditioner is the sum of the air volume of the system equipment and the air volume that maintains the positive pressure of the system. Do not consider the positive pressure air volume.
Class 100,000 dust-free workshops are not able to use a surface cooling section for air conditioners with low fresh air volume (caused by equipment exhaust air, when the fresh air volume is greater than 50% of the circulating air volume). To ensure the design of the air volume temperature, a two-stage surface cooling method is used, that is, two table cooling sections are connected in parallel with the chilled water system at this time. At this time, the efficiency of the second-stage surface cooler will be very low, but it is necessary to ensure the air temperature. The middle section of the air-conditioning unit is indispensable. The service door in the positive pressure area should be opened in order to reduce air leakage. The flow section should be installed in the middle section between the fan section and the intermediate efficiency filter section to prevent the wind speed at the outlet of the fan from being too high. High air volume is too concentrated to blow through the middle-efficiency filter bag.