What terms should be included in a chemical filter purchase specification?

Procurement specifications convert project requirements into executable and acceptable procurement documents. Chemical filters are different from particle filters. If the specification only states size, air volume and 'high removal efficiency', the supplier cannot judge what media should be used, and there is no clear criterion for acceptance.

An executable chemical filter procurement specification is recommended to cover the following contents: pollution characteristics, system conditions, structure and interfaces, performance and testing, supply and acceptance, maintenance and changes. The more specific the terms are, the fewer disputes will follow.

Describe pollution characteristics and protection goals

This is the starting point of the specification and the basis for deciding on filter material selection.

target gas. List the names of specific gases that need to be treated, such as sulfur dioxide, ammonia, toluene, formaldehyde or other components. If there are multiple pollutants in the project, they should be listed separately and the priority should be stated. For specific identification methods, please refer to Discussion on why chemical filters should be selected according to the target gas .

Inlet concentration range. Describe regular concentrations, peak concentrations, and fluctuations. Concentration data comes from on-site testing or process data. If there is no data for the time being, it should be marked 'to be tested and confirmed' instead of omitted directly. For specific investigation methods, please refer to whether to do air sampling before choosing a chemical filter . Discuss

Protect the target. Clarify whether it is equipment anti-corrosion, personnel health, process protection or odor removal, and give the outlet concentration requirements or allowed removal efficiency. Different detection methods and media selections correspond to different targets.

Use location. Indicate in which system the filter is installed, such as fresh air unit, return air section, FFU, equipment-side air supply unit, or other locations. The location affects the structure and interface requirements of the filter segment.

State system conditions

The performance of a chemical filter is affected by system conditions, and the specifications should include these inputs.

Handle air volume. Describe the design air flow through the filter section and the possible operating range. Is it the total air volume of the system or the air volume of a single unit, series or parallel connection. Please refer to the specific caliber Discussion on whether the chemical filter air volume should be selected based on the total air volume of the system or the air volume of a single unit .

Temperature and humidity range. List operating temperature, relative humidity and possible condensation risk. Some chemical media are sensitive to humidity, and high humidity or droplet environments may affect capacity and life. For specific environmental impacts, please refer to Discussion of how long chemical filters last .

Available resistance. Explain the allowable initial resistance and final resistance range of the system fan. If there is insufficient margin, you may need to select a lower resistance option or adjust the fan. For specific calculations, please refer to Discussion of how much the added resistance of the chemical filter will increase the fan's electricity consumption .

mode of operation. Continuous or intermittent operation, hours of operation per day, whether there are seasonal or shift changes. These affect cumulative loads and replacement cycles.

Specify structure and interfaces

For the chemical filtration section to be installed into the system, the interface must be clear.

Dimensions. The clear opening, usable depth, overall dimensions and tolerance requirements of the mounting frame are given. Don't just write the old filter size. For specific measurement methods, please refer to Discussion of what dimensions should be covered in chemical filtration retrofit field measurements .

Sealing method. Clarify whether it is a gasket seal or a liquid tank seal, the location of the sealing surface, the pressing method and the compression requirements. Please refer to the specific directions to confirm Discussion on whether the chemical filter gasket should face the inlet or outlet side .

Airflow direction. Indicate from which side the air enters and exits, and whether there are any wind path turns inside the equipment. For specific confirmation methods, please refer to Chemical filter airflow arrow unclear discussion on how to confirm.

Installation and maintenance space. Specify disassembly and assembly paths, access door dimensions and operating space. When the space at the equipment end is tight, the feasibility of replacing the filter material should be stated in the specification.

Clarify performance and testing terms

Performance requirements cannot just be written as a general efficiency value.

Filter media type. Indicate the type of media, such as ordinary activated carbon, impregnated activated carbon, special chemical adsorbent or composite filter material. Different filter materials target different target gases and have different prices and capacities. For specific differences, please refer to Discussion on why the chemical filter quotation should indicate the type of filter material .

performance basis. The supplier is required to provide efficiency, capacity or penetration data corresponding to the target gas, and indicate the test air volume, concentration, temperature and humidity and detection method. For specific reporting requirements, please refer to Discussion of why chemical filter performance reports list specific target gases .

Test report form. Clarify whether it is a unit-by-unit report or a batch report, whether number correspondence is required, and whether local leak detection or sealing inspection data is included.

Acceptance method. Specify which items should be tested during on-site acceptance, such as air volume, pressure difference, outlet concentration and sealing status. The location of sampling points and detection methods should be agreed in the specifications. For specific methods, please refer to Discussion of sampling points for chemical filter performance verification .

Agreed supply scope and information

The quotation and scope of supply must correspond to avoid subsequent additions.

product range. Does it only provide the filter element, or does it include the frame, seals, and mounting accessories? Is spare filter media included? Please refer to the specific inquiry parameters. Discussion of what parameters need to be provided for a chemical filter inquiry .

List of information. List the information that needs to be provided, such as specifications, drawings, inspection reports, installation instructions and maintenance manuals. The information must correspond to the product number.

Packaging and shipping. Describe packaging requirements, shipping directions, and arrival inspection requirements. Please refer to the specific directions to confirm Discussion on whether the transportation direction and installation direction of chemical filters must be consistent .

Arrival acceptance. Specify what items to check upon arrival, such as model number, label, appearance, and packaging status. For specific inspection methods, please refer to Discussion of what appearance and labels to check before installing a chemical filter .

Maintenance, changes and warranty

Long-term operation requirements should also be reflected in the specifications.

Change criteria. Clarify the basis for replacement, whether it is outlet concentration, cumulative load, operating time or comprehensive judgment. For specific management methods, please refer to Discussion on why the chemical filter replacement cycle cannot be calculated as half a year .

Spare parts requirements. Whether long-term supply of spare parts is required, how to agree on the replenishment cycle and price.

Change management. How to notify and re-verify if filter media, structure or supplier changes. For specific principles, please refer to Discussion on how to check chemical filter manufacturer selection recommendations with project requirements .

Warranty Terms. Clarify the warranty scope, period and handling methods. Warranty terms should correspond to performance requirements and acceptance conditions and cannot be independent of technical terms.

Project judgment example

When purchasing a chemical filter for a certain project, the specification only stated the size, air volume and 'acid gas processing', but did not indicate the specific gas name, inlet concentration and outlet requirements.

After the goods arrived, it was discovered that the supplier had configured the medium according to conventional acid gases, but the project actually dealt with mixed acid gases, and the concentration of one of the components was higher than the conventional level. After operation, the outlet concentration does not meet the standard, and the filter material needs to be replaced.

After supplementing the specification, the target gas composition, concentration range, export requirements and detection methods were clarified, and the re-purchase plan met the requirements.

This case illustrates: The more complete the terms of the procurement specification, the more targeted the supplier’s plan will be, and the more evidence-based the subsequent acceptance will be. involving When selecting a chemical filter product series , it is recommended that the pollution characteristics, system conditions, interface requirements and acceptance methods be provided to the supplier for verification.