How do the ULPA liquid tank and the knife edge cooperate?

The reliability of the liquid tank seal ultimately comes down to the pairing of the knife edge and the tank body. The two seem to be as simple as 'plugging in', but in actual projects, problems often lie in this coordination relationship.

Just because the knife edge enters the groove does not mean that the seal has been formed. If the insertion depth, uniformity of four sides, eccentricity, and tank continuity are not up to standard, there may be gaps in the liquid seal path. These problems may not necessarily be visible during installation. They will be discovered only when leaks are detected, which will increase the scope of troubleshooting. For specific failure troubleshooting methods, please refer to the instructions related to the failure of the liquid tank seal ULPA.

Dimensions must be checked in sets

The liquid tank and the knife edge are two sets of drawings, and they should be looked at together when checking.

Groove width and groove depth. The width of the groove body must be able to accommodate the thickness of the knife edge and leave space for the sealing liquid. The depth of the groove must ensure the designed insertion depth. If the groove width is too narrow, it will be difficult to insert the knife edge, and the sealing fluid may be squeezed out; if the groove width is too wide, the gap between the knife edge and the groove wall will be too large, and the stability of the liquid seal may be affected.

Knife edge position. The position of the knife edge relative to the installation datum plane should correspond to the position of the tank body relative to the filter element datum plane. When two sets of drawings use different datums, the dimensions may appear to be qualified individually, but they may not match up when put together. Checking with the same benchmark before placing an order is more reliable than confirming separately.

Blade height. The height of the blade determines the maximum insertion depth. The groove depth and knife edge height must match to ensure that the designed insertion depth can be achieved while leaving a margin.

Four corner structure. The four corners are the locations where deviations of the knife edge and the groove body are prone to occur. Just because the dimensions of the straight sides are acceptable does not mean that the four corners fit properly. During verification, the four corners must be confirmed individually. For specific measurement methods, please refer to the relevant instructions for high-efficiency filter size measurement.

How to control eccentricity and height difference

Even if the dimensions are correct, eccentricity and height differences during installation may affect the seal.

eccentric. When the filter element is placed in the installation frame, if the position is offset, the knife edge on one side may be close to the groove wall and the gap on the other side is too large. Under long-term operation, the side close to the tank wall may be worn or deformed, and the liquid seal on the side with a large gap may be unstable. When installing, try to keep the filter element centered, and use positioning structures to assist if necessary.

Height difference. If the installation frame is uneven or the support structure has a height difference, it will cause the filter element to tilt and the insertion depth on the four sides to be inconsistent. If one side is inserted too shallowly, the sealing path may be interrupted; if the other side is inserted too deep, it may hit the bottom of the groove or squeeze out the sealing fluid.

Support flatness. The supporting surface under the filter element should be flat to avoid tilting of the filter element due to support problems. Device-side applications such as The EFU equipment-end fan filter unit has a compact internal space, and the processing accuracy and installation status of the supporting surface need to be carefully checked.

Effect of compression method. The distribution and tightening sequence of the pressing parts will affect the stress state of the filter element. Tightening a single angle first may cause the filter element to tilt or the frame to deform, which will affect the relative position of the knife edge and the tank body. Tighten gradually in the order required by the design to avoid local overpressure. For specific compression requirements, please refer to the instructions related to the compression degree of the gasket.

Preserve verifiable results

After assembly is completed, you cannot judge whether the fit is in place by just looking at the appearance.

Check insertion status. Observe the state of the four edges of the knife entering the groove body, and confirm that the insertion depth is basically uniform and there is no obvious eccentricity or inclination. Marking or measurement methods can be used to assist in confirmation.

Complete installation status leak detection. The sealing path is scanned according to project requirements, covering all four sides and corners. The matching position between the knife edge and the tank body is the key area for leak detection. For specific methods, please refer to the relevant instructions for troubleshooting liquid tank seal failure.

Reconfirm after disassembly and assembly. If the filter element is removed and then reinstalled, the interface status may change. The sealing status after disassembly and assembly needs to be rechecked, and the leak detection conclusion before disassembly and assembly cannot be used.

Records archived. The knife edge size, tank size, installation status and leak detection results are saved accordingly. involving For the selection of ULPA ultra-high efficiency filters , the interface data should be included in the technical documents.

Project judgment example

A certain project required the replacement of a ULPA filter element. The appearance and dimensions of the new filter element were similar to the original product. However, after installation, it was discovered that air leakage continued at a section of the edge.

The investigation found that the position of the tank body of the new filter element deviated from that of the original product - although the length and width of the outer frame were the same, the position of the tank body relative to the reference plane was about 2 mm different. This deviation results in insufficient insertion depth of the knife edge on this side and interrupts the liquid seal path.

Treatment method: Compare the drawings of the original filter element and installation frame, recheck the tank position and knife edge size, and confirm the source of the deviation. After replacing the filter element with a matching size, the retest was normal.

This case illustrates: The coordination between the liquid tank and the knife edge cannot only depend on the outer dimensions. The interface parameters such as the slot position, knife edge position, and insertion depth must be checked in sets. involving HEPA/ULPA air filters is the same. The selection logic for

Selection and Acceptance Checklist

About Aili Industrial’s liquid tank matching packages

The core of the cooperation between the liquid tank and the knife edge is to align the interface data on the filter element side and the box side under the same benchmark. If this work can be completed during the planning stage, the on-site installation will be much smoother.

Aili Industry has independent manufacturing capabilities in filters, fans, control systems and sheet metal processing, and can provide ULPA ultra high efficiency filter、HEPA high-efficiency filter and supporting air supply equipment. For liquid tank sealing projects, the installation frame structure, knife edge size and working conditions can be combined to assist in checking the tank position, knife edge height and insertion depth. When the filter is matched with equipment such as FFU and EFU, the sealing interface and installation matching dimensions can be uniformly confirmed to reduce matching deviations on site caused by inconsistent benchmarks.

When enquiring, provide installation frame drawings, knife edge dimensions and operating conditions to help confirm the appropriate liquid tank matching solution. The specific configuration is subject to the technical documents and drawings confirmed by the project.