What Is a Waterproof Screw?
A waterproof screw is a type of screw that features a sealing component on its seating surface (located behind the screw head) to create a waterproof seal, closing the gap between the screw and the fastener.
These sealing components go by various names depending on the screw manufacturer, such as sealing rings, shield rings, or O-rings. However, they all serve the same purpose. Typically, there is a small gap between the screw’s seating surface and the object it’s fastened to, which can potentially allow water or organic solvents to penetrate.
Waterproof screws are equipped with sealing components that are water-resistant and hermetically seal the gap between the screw and the object being fastened. These screws are commonly used to protect electronic circuit boards in household appliances from water splashes and to prevent rainwater from entering outdoor machinery.
Uses of Waterproof Screws
Waterproof screws find applications in safeguarding precision equipment and water-sensitive devices from water infiltration. They are particularly crucial for the following types of equipment:
– Precision equipment susceptible to water damage (e.g., computers, weighing equipment, medical devices).
– Equipment used in outdoor environments (e.g., weather instruments, solar power generation equipment).
– Equipment in locations where water exposure is likely, such as dishwashers.
When purchasing waterproof packing and screws separately, there’s a risk that they may not be the correct size or may not provide an effective seal. Choosing waterproof screws with included waterproof sealing components ensures a high level of waterproofing.
Principle of Waterproof Screws
Waterproof screws are specifically designed to withstand exposure to water. The screw body (the threaded part) is typically made from rust-resistant stainless steel. The seating surface behind the screw head is fitted with a sealing component that matches the size of the screw body, creating a seal between the screw and the fastened object.
These sealing components are often constructed using nitrile rubber, which is resistant to water and can also withstand solvents like petrol and alcohol. This makes it effective in preventing the penetration of fats, oils, and other liquids.
However, nitrile rubber is susceptible to corrosion by certain organic solvents, such as ethyl acetate and ether. For applications requiring resistance to these solvents, waterproof screws made of fluoroplastic (PTFE) should be chosen.
Other Information on Waterproof Screws
1. Proper Use of Waterproof Screws
Waterproof screws are primarily designed for use in areas exposed to water, such as external covers. Improper use may result in damage to the mating nut or the product or equipment assembled with the waterproof screw.
To prevent this, several considerations should be kept in mind:
– Ensure that the tightening force remains within permissible limits to avoid damaging the waterproof screw or mating elements.
– Repetitive forces, such as those caused by vibrations, should not exceed permissible limits for both the screw and the mating member.
– The seating surfaces of the waterproof screw must fall within permissible ranges to prevent the object being fastened (e.g., metal, wood) from caving in.
– Fastening with waterproof screws should not cause damage to the object being fastened.
2. Fastening Conditions for Waterproof Screws
When fastening waterproof screws, careful selection of fastening conditions is essential. Generally, the fastening force applied by a screw results from the screw itself undergoing elastic deformation and stretching to return to its original length. The force required to pull the screw is generated during the screw-tightening process, and the screw’s helical shape enables torque to be converted into pulling force.
Fastening with a screw is akin to moving a heavy load straight up, requiring significant force. However, sliding the load down a gentle slope necessitates much less force. Using a trolley with smooth-rolling wheels further reduces the effort required. Similarly, fastening waterproof screws involves overcoming resistance during tightening, and adequate axial force may not always be achieved. When securing components subjected to substantial external forces with waterproof screws, careful consideration of fastening conditions is crucial.