How does clean air supply coverage affect the number of equipment?

Clean air supply coverage is a commonly used parameter to estimate the number of FFU or supply air terminals, but it cannot be used alone without the effective air outlet size, target airflow and return air conditions of the equipment. If the coverage rate is calculated incorrectly, the number of equipment may deviate greatly; if the coverage rate is sufficient but the air flow path is wrong, the workstation protection may still be insufficient.

The following will start from the coverage definition, effective area, calculation of the number of devices, and layout verification.

First distinguish between installation coverage and effective air supply coverage

Coverage usually refers to the ratio of the air supply area to the area of ​​a room or area. But the air supply area has two calibers:

• Installation coverage : The area where FFU or air supply end is arranged on the ceiling, including the part occupied by the equipment frame and keel;

• Effective air supply coverage : The area that can actually filter the air supply needs to deduct the equipment frame, frame and ceiling keel.

The FFU shell frame, ceiling keel and lamps will occupy the area; the actual area that can filter the air supply is usually smaller than the external area. If coverage is estimated based on the installation area, the effective air supply capacity may be overestimated.

For the distinction of area diameter, please refer to How should we look at the effective air outlet area of ​​FFU? , first clarify the area definition and then calculate the coverage.

Coverage cannot be directly applied to a fixed ratio

Different projects and different airflow forms have different coverage requirements. The coverage logic of one-way flow areas and non-one-way flow areas is different, and the cleanliness level and pollution load will also affect the demand. The entire room area cannot be calculated directly according to a fixed ratio.

If you are still unclear about the choice of airflow form, you can see How to choose between whole room purification and partial purification ? First confirm the plan level, and then fall to the coverage calculation.

The effective air outlet area determines the coverage capacity of a single device

The effective air outlet area of ​​a single FFU depends on the filter size and box structure. Two FFUs with the same appearance may have different actual air supply areas due to different filter frames and internal structures.

When calculating the number of devices, the effective air outlet area should be used instead of the box external area. For specific judgment, please refer to How should we look at the effective air outlet area of ​​FFU? . If the area caliber is used incorrectly, different average wind speeds and coverage rates will be calculated for the same air volume.

Basic logic of device quantity calculation

The number of equipment can be estimated according to the following steps:

• Determine the area to be protected;

• Determine target coverage;

• Confirm the effective air outlet area of ​​a single device;

• Calculate the amount of equipment required;

• Check target wind speed and total air volume;

• Check return air capacity and ceiling loads.

During the calculation process, the target wind speed and total air volume need to be checked together with the coverage rate. For the conversion of face wind speed and air volume, please refer to How to convert face wind speed and air volume?。

The relationship between coverage and airflow continuity

Coverage is not just an area ratio, but also affects the continuity of protection. Gaps, frames, and keels between equipment can create air supply gaps. If critical workstations are located right on the boundary of the gaps, even if the total coverage is sufficient, the protection may not be sufficient.

When laying out, the position of the workstation and the position of the air supply surface should be matched to ensure that the key operating positions are within effective air supply coverage. For on-site performance with insufficient number of FFU, please refer to What are the on-site manifestations of insufficient FFU quantity?。

Quantity calculation also needs to check system capabilities

After the area coverage is met, the target wind speed, total air volume and upstream return wind resistance must be checked. The actual measured air volume of different equipment may be different. After batch installation, each area should be confirmed through balancing debugging instead of just counting the number of units.

If excessive air volume causes disturbance, please refer to Is excessive FFU air volume good for cleanliness? . To check the filter resistance and fan operating point, please refer to Why should we look at the complete performance curve when selecting FFU?。

Ceiling layout and equipment arrangement

The arrangement of FFU will affect coverage and usage effects. Common layout methods include full cloth, checkerboard cloth and partial concentrated cloth. Different arrangements have different coverage and airflow continuity, and the selection needs to be combined with the workstation location and airflow direction.

Light fixtures, piping, fire sprinklers, and structural beams should not obstruct air supply and maintenance. Insufficient maintenance channels will increase subsequent expenditures. This is reflected in what later expenses will be increased due to insufficient maintenance channels . There is a more detailed analysis of

Connection with clean area air supply needs

The coverage calculation ultimately comes down to air supply demand. The area of ​​the clean area cannot determine the air supply volume alone, but also needs to be combined with the air flow pattern, pollution load and exhaust conditions. For details, please refer to How to convert the clean area area into air supply demand?。

If the project is constructed in phases, please refer to What are the expansion conditions for using independent modules in clean systems? , unify the ceiling module and equipment interface in advance.

Equipment selection and terminal matching

Please refer to the room background air supply FFU clean air supply products , please refer to the local protection of the equipment side. EFU equipment side fan filter unit . The logic of division of labor between the two lies in The division of labor between device-side EFU and room FFU is explained in detail.

Filter selection should correspond to target particle size and actual resistance.The HEPA and ULPA filter pages have parameters for different levels of products. When selecting, check the efficiency of the specific model at the target air volume. If you are still unclear about the difference between space rating and filter efficiency, you can read What is the difference between cleanliness level and filtration efficiency?。

If multiple devices require partition duty and troubleshooting, they can be combined FFU group control system provides unified management.

Project judgment example

For a certain project, the coverage rate was estimated based on the ceiling installation area and was deemed to meet the requirements. On-site measurement found that the actual effective air outlet area was smaller than the installation area, and there was an air supply gap at the junction of workstations. Adjustment method: Recalculate based on the effective air outlet area, add some FFU and adjust the layout so that key workstations are within effective air supply coverage. The wind speed at the workstation recovered after adjustment.

Another project has adequate coverage, but the station granularity is still high. The investigation found that the return air channel was blocked by shelves, the air flow was short-circuited, and the air volume was insufficient in some areas. Adjustment method: Clean the return air channel and rebalance the air volume in each area instead of continuing to increase the number of FFU.

These two situations illustrate that the coverage rate affects the number of equipment, but it must be comprehensively judged based on the effective air outlet area, return air conditions and work station layout.

Key points for selection and acceptance inspection

Aili industrial equipment supporting support

Air supply coverage ultimately depends on the number and arrangement of equipment. Aili Industrial has collaborative capabilities in fans, motors, filters, control systems and complete machine assembly. It can check the number, arrangement and total air volume of FFU based on the project protection area, target wind speed and effective air outlet size to avoid insufficient coverage or equipment waste caused by estimating the installation area. Specific models can be viewed FFU clean air supply products , supporting equipment can be viewed EFU equipment end fan filter unit , please refer to the filter package. HEPA and ULPA filters。