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A brief introduction to the waterproof seal structure design of a hydraulic cylinder product.
The design of the “waterproof ring” (usually an O-ring) of the hydraulic cylinder is different from that of the “dustproof ring” in terms of function and location, but together they constitute a complete sealing and protection system for the hydraulic cylinder. Its core function is “static sealing” to prevent water, dust and other substances from entering the end of the hydraulic cylinder and causing rust and other problems.
I. Location and Function
Location 1: Threaded or stepped connection between the guide sleeve and cylinder barrel
Location 2: Connection between the gland and guide sleeve
Core Function: These two locations are the mating surfaces of hydraulic cylinder components, serving as static seals. Their main function is to prevent external water, moisture, corrosive liquids, dust, etc., from seeping into the hydraulic cylinder through the assembly gaps of these metal parts.
II. Differences and Connections between Dust Rings (Dynamic Seals)
Dust Rings (Dynamic Seals): The core protection is on the surface of the piston rod, a moving part, and involves dynamic, active scraping and cleaning.
O-rings (Static Seals): The core protection is on the mating surface of parts, and involves static, passive filling and sealing.
III. A Discussion of the Waterproof Ring Structure Design of a Hydraulic Cylinder Product
Briefly discuss the problems with the waterproof ring design of a hydraulic cylinder product. Functionally, this structure is sound and meets the design requirements. However, feedback has arisen during actual assembly: the gland cannot be screwed into the cylinder thread, and tightening it after screwing it in is difficult. See the diagram below for details:
The structural design failed to consider assembly feasibility, resulting in the gland mating with the waterproof ring 1 immediately upon being installed on the guide sleeve mating surface. Previously, in selecting the O-ring compression amount for the hydraulic cylinder, we mentioned that the compression amount for waterproof sealing should be 15%–25%, or even higher.
This led to a situation where, due to excessive compression, the gland could not be properly inserted, and the waterproof ring’s position was on the same cross-section as the threaded inlet, making assembly extremely difficult. Even after the threads were properly engaged, the significant friction between the waterproof O-ring and the gland’s inner bore caused further tightening difficulties, ultimately requiring a complete structural overhaul. See the diagram below:
The structural optimization is also simple. One way is to change the waterproof O-ring 1 to the gland, so that the initial 80% of the thread engagement will be very smooth, which can greatly reduce the assembly difficulty.
Another method is to process the inner hole of the gland into a stepped shape. During the initial thread engagement, the waterproof ring and the inner hole of the gland do not rub against each other, thereby reducing the assembly difficulty.
★★★Review of selected articles in our hydraulic cylinder engineering newsletters:
- What are the common installation methods of hydraulic cylinders?
- How to select a hydraulic cylinder? Here are the precise selection steps!
- Hydraulic cylinder buffer device, common faults and solutions
- How to test internal leakage in hydraulic cylinder?
- Disassembly and assembly methods and precautions of hydraulic cylinder
- Why does the hydraulic cylinder get strained? How to solve it? Let me tell you everything!
- Why is the hydraulic cylinder still leaking oil after replacing the sealing ring
- Difference between single-acting cylinder and double-acting cylinder. How to choose?
- Disassembly methods and precautions of hydraulic cylinder
- Hydraulic cylinder: The relationship between the force, pressure and cylinder diameter, how to choose a type？