How to choose between whole room purification and local purification?

This question looks like a comparison of options, but it is actually closer to a true-or-false question: What exactly do you want to protect, and how long is the exposure path?

I have seen many projects, and as soon as I started, I asked how much it would cost to build an entire room at level 100. After further questioning, I discovered that only the final assembly process of the product was really exposed, and the previous handling, caching, and loading were all in a normal environment. In this case, it costs a lot of money to build a whole room of 100 levels, but the effect is limited. I have also seen the opposite situation. The product is exposed in the open area throughout the entire process, but only one workbench is purchased, and the subsequent processes are all streaked.

Off in both directions. The key is not which solution is more advanced, but whether the exposure path and purification boundary can be aligned.

First look at how long the exposure path is

The most essential difference between whole room purification and partial purification lies in the scope of protection.

If the product is exposed only briefly during a process and then immediately enters a closed container or package, then local protection is usually sufficient. A clean workbench, a clean booth, or adding an EFU to the equipment can solve the problem.

But if the product comes down from the previous process and is exposed all the way through transportation, temporary storage, assembly, and testing, then it is not something that can be partially covered. If any section in the middle is not protected, the cleanliness saved in the front will be in vain. In this case, either the entire room should be controlled, or the exposure section should be shortened to the shortest possible time.

Therefore, before choosing a solution, it is recommended to spread out the process flow diagram and mark out the exposed sections of the product section by section. After marking, the answer will basically come out.

On which side is the pollution source?

Another dimension of judgment is the location of the pollution source.

Where the particles come from determines where they should be blocked. If the pollution mainly comes from the outside, such as a dirty room background, dust carried by the air entering the door, or drifting from the workstation next door, then whole room control or regional isolation is more direct. If the contamination comes from the product itself or nearby equipment, such as debris generated during assembly and dust from mechanical friction, then local exhaust or workstation protection may be more appropriate.

The fear is to reverse the direction. The equipment itself is producing dust, but it only supplies air to the whole room. The particles are blown to the entire room as soon as they are generated, and the measuring points exceed the standard everywhere. On the contrary, the external environment is very clean and the dust generated by the equipment is concentrated at one point, but the filtration level of the entire room is raised to a very high level. Money is spent, but the source is still there.

As mentioned in What is the Difference Between Cleanliness Grade and Filtration Efficiency ? Space grade evaluates particle concentration, while filtration efficiency evaluates product performance. Determining the location of pollution sources is a matter of space and cannot be solved by upgrading filters.

How people, materials and institutions move

Just because it looks clean statically does not mean it will be clean in production.

The movement of people, unpacking of materials, and movement of robots will all cause instantaneous particles. The whole-room plan must include these dynamic loads into the air supply volume, while the local plan depends on whether the protective boundary can block the disturbance caused by these movements.

Give an example. If someone passes by an open workstation frequently, the air curtain of some workstations may be disturbed. At this time, you must either change the location of the workstation, add a fence, or expand the protection range. Just increasing the wind speed on the workbench sometimes stirs up more surrounding air.

How to Establish a Partial Clean Zone in an Open Workstation . This situation has been discussed in detail in In situations with high personnel density and frequent movements, the management of local boundaries often requires more attention than the equipment itself.

Investment should not just be counted as equipment money

The cost structure is different for whole room plans and partial plans.

The whole room purification involves the building envelope, air conditioning system, air supply and return ducts, and ceiling FFU array. The initial investment is large and the operating energy consumption is also high. Local purification equipment itself is cheap, but if the workstations are scattered and the number is large, it will add up to a lot, and the maintenance of each unit must be arranged separately.

There’s something else that’s easy to miss: the cost of renovations and expansions. Once the whole room plan is built, it is very troublesome to change the layout. The partial solution is relatively flexible, and it is convenient to move to a different location or add another piece of equipment. This is worth considering for production lines with fast product replacement.

How to convert the clean area area into air supply demand has been discussed in the air volume calculation. The calculations for the whole room and the local area are different. The whole room should be calculated based on volume and air exchange, while the local area mainly depends on the protected area and target wind speed, and cannot be mixed.

Combination plan of background and part

In actual projects, there are not many purely whole-room or purely partial projects, but more combinations of the two.

The background area should be ISO 7 or ISO 8 to ensure a stable environment; key workstations should be superimposed with local protection to achieve ISO 5 or even higher. This not only controls the scale of investment, but also protects sensitive links.

In the combination plan, pay attention to the two sets of airflows not to fight. The direction of local air supply, the direction of background air supply, and the position of the return air outlet should be looked at together. If the background wind blows laterally, the boundaries of local protected areas may be washed away. If the local wind is too strong, it may interfere with the airflow organization in the background area.

The same idea applies to the device side. The EFU equipment-end fan filter unit is responsible for the fine protection of the interior or part of the equipment. The overall environment of the room is controlled by FFU clean air supply products are maintained. When the two cooperate well, each can take care of its own task without interfering with each other.

How to match the filter

Regardless of which option is chosen, filters should be selected based on target particle size and pollution load.

The HEPA and ULPA filter pages have parameters for different levels of products. For local protection at the equipment end, the size and resistance of the filter must match the EFU box; for the whole room plan, the total air volume and air pressure balance of the FFU array must be considered. If partition control is required, The FFU group control system can configure operation strategies by region and time period.

Aili Industrial has manufacturing capabilities in motors, fans, control systems, sheet metal, air filters and complete machine assembly. The types of equipment involved in the whole room and partial solutions are different, but the core components can be matched in the same system, and the interfaces and parameters are relatively easy to align.

Scene judgment

In a medical device assembly workshop, products are cleaned and packaged before final assembly. The cleaned parts are placed in sealed turnover boxes, which are not opened until the assembly station, and the bags are sealed immediately after assembly is completed. In this case, only partial protection of the assembly station is enough, and the entire room can be maintained in a normal clean environment.

In another project, after the product comes out of the injection molding machine, it needs to go through three processes: trimming, inspection, and assembly. The entire process is exposed, and is temporarily stored on open shelves in the middle. This kind of exposed path is difficult to cover with local protection, so the regional division and air supply design were finally made according to the whole room plan.

The products of the two projects are similar, but the exposure paths are different, and the solution choices are completely different.

Key points for selection and acceptance inspection