Chapter 84 is the core chapter in the HS classification system covering machinery, mechanical appliances, and their parts, including power machinery, pumps, compressors, valves, bearings, transmission devices, etc. Goods in this chapter generally have mechanical motion characteristics and are used for energy conversion, material conveyance, or processing. Mechanical seals, as shaft sealing devices for rotating equipment that prevent fluid leakage, are basic mechanical components and are therefore classified in this chapter. Heading 8484 covers seals used in machines or equipment, including gaskets of metal combined with other materials, mechanical seals, and similar devices. Mechanical seal specifically refers to a device consisting of two end faces perpendicular to the rotating shaft that are kept in contact and slide relative to each other under the action of fluid pressure and a compensating mechanism to prevent fluid leakage, commonly used for rotating shaft sealing in pumps, reactors, compressors, etc. Code 848420 consists of 6 digits: the first 2 digits 84 indicate Chapter 84 (machinery, mechanical appliances, and their parts); digits 3-4, 84, indicate heading 8484 (gaskets and similar joints of metal sheeting combined with other material or of two or more layers of metal); digits 5-6, 20, indicate subheading 8484.20, specifically referring to mechanical seals. This subheading is further distinguished from other seals (such as gaskets, O-rings, etc.), emphasizing its working principle of mechanical end-face sealing. Mechanical seals are classified under 848420 rather than the adjacent 848410 (gaskets of metal sheeting combined with other material) or 848490 (other seals), because their core feature is dynamic sealing achieved through the contact of a rotating ring and a stationary ring end face, with an axial compensating mechanism, making them precision mechanical components rather than simple static gaskets.

Product Name: The standard name of the declared goods should use 'mechanical seal' or a specific model number, avoiding the generic term 'seal'. Use: Describe the equipment to which the mechanical seal applies, such as 'for centrifugal pump shaft sealing' or 'for reactor agitator shaft'. Brand: Fill in the manufacturer or brand name; if no brand, write 'no brand'. Model: Fill in the product model or specification code to facilitate customs identification of the specific product. Material: Materials of main components, such as rotating ring/stationary ring (silicon carbide, graphite, hard alloy), auxiliary sealing rings (nitrile rubber, fluororubber). Structure Type: Describe the structural form of the mechanical seal, such as single face, double face, balanced type, unbalanced type. Working Principle: Briefly describe the sealing principle, such as 'end face contact, spring compensation'. Product Name: Mechanical seal; Use: For centrifugal pump shaft sealing; Brand: XX; Model: MS-200; Material: rotating ring silicon carbide, stationary ring graphite, auxiliary seal nitrile rubber; Structure Type: Single face unbalanced type; Working Principle: Spring-loaded rotating ring and stationary ring end face contact to achieve sealing. Misdeclaring mechanical seals as 'gaskets', leading to incorrect classification under 848410. Incomplete material declaration, failing to distinguish materials of rotating ring, stationary ring, and auxiliary sealing rings. Vague use description without specifying the equipment, affecting customs review.

The core basis for classification is the function, working principle, and structural characteristics of the goods. A mechanical seal must have a rotating ring and a stationary ring, achieve dynamic sealing through end face contact, and have an elastic compensating element. If it is only a static sealing gasket or O-ring, it should be classified under other headings. Material should also be considered, but mechanical seals are usually composed of multiple materials, so they are classified by function. 848410 Gaskets of metal sheeting combined with other material: This code refers to static sealing gaskets made of metal sheeting combined with other materials (such as asbestos, rubber), with no relative motion, whereas mechanical seals have a dynamic sealing function. 848490 Other seals: This code is a residual subheading applicable to seals not elsewhere specified, such as O-rings, oil seals, etc. Mechanical seals are not classified here because there is a dedicated subheading 848420. 841391 Parts of pumps: If a mechanical seal is imported as a dedicated part of a pump and declared together with the pump, it may be classified as a pump part, but a mechanical seal imported separately is still classified under 848420. 848790 Machine parts: This code applies to machine parts not elsewhere specified. Mechanical seals already have a specific listing, so they are not classified here. Does it have a rotating ring and stationary ring end face contact structure? Is it used for dynamic sealing of a rotating shaft? Does it contain an elastic compensating element (such as a spring)? Is it imported separately rather than as part of a complete machine? Does the material affect classification? Usually not; classification is by function.

What is the difference between a mechanical seal and an oil seal? Are the HS codes the same? A mechanical seal achieves sealing through end face contact and has a rotating ring and a stationary ring, classified under 848420; an oil seal is usually a lip seal, belonging to static or low-speed sealing, classified under 848490 or other codes. The working principles and structures are different, so the codes are different. How to determine whether a mechanical seal should be classified under 848420? The key is whether it has an end face sealing structure: two end faces perpendicular to the rotating shaft are kept in contact under the action of fluid pressure and a compensating mechanism. If so, it is classified under 848420; if it is another sealing form, consider 848410 or 848490. When declaring a mechanical seal for import, how should the material be filled in? The materials of the rotating ring, stationary ring, auxiliary sealing rings, spring, and other components should be filled in separately, such as rotating ring silicon carbide, stationary ring graphite, sealing ring fluororubber. Material affects review but does not change classification. Can a mechanical seal be classified as a pump part if it is a part of a pump? If imported separately, even as a part of a pump, it should still be classified under 848420, because that subheading already specifically lists it. If imported together with a complete pump, it is classified as a pump. Are HS codes for mechanical seals consistent across countries? The first 6 digits of the HS code are globally uniform, but countries may subdivide the later digits differently. For example, the US HTSUS is 8484.20.00, and China is 84842000; the first 6 digits are the same. What should be noted when checking the tax rate for mechanical seals? Tax rates change, so the latest customs tariff should be checked. Reference can be made to the General Administration of Customs of China or international trade databases, noting MFN rates, general rates, and free trade agreement rates. What are the common classification errors when declaring mechanical seals? Common errors include: misdeclaring as gaskets (848410), oil seals (848490), or pump parts (841391). Judgment should be strictly based on working principle and structure. Are special documents required when exporting mechanical seals? Generally no special documents are required, but if a brand or patent is involved, an authorization letter is needed. Depending on the destination country's requirements, a certificate of origin, etc., may be required.