When designing the structure of flame proof explosion-proof light fixtures, manufacturers often focus on the shape and strength design of the flame proof housing, but often ignore the design of fasteners, introduction devices, transparent glasses, hanging hooks, nameplates and other devices. Here we will mainly introduce three main design ideas for components, namely fasteners, introduction devices and transparent glasses.
The housing fasteners of flameproof explosion-proof light fixtures usually use bolts. Since there are mainly three types of flameproof gaps in the flameproof housing, the functions and installation precautions of bolts on different types of flameproof housings are also different.
A. Flanged joint
For flanged joints, bolts not only play a role in tightening, but also ensure that the effective length of the flat gap, the clearance and the flat surface roughness meet the standards.
B. Spigot joint (including cylindrical, cylindrical and flanged)
For the spigot joint, a. When the flameproof surface is only cylindrical, the bolts only play a tightening role; b. When the flameproof surface is not only cylindrical but also flat, the bolts not only play a tightening role, but also Also ensure that the effective length of the plane gap, the gap and the plane roughness meet the standard.
C. Threaded joint flame path
For the threaded joint, the bolts first play the role of tightening. Since it is easy to damage the flameproof surface when directly tapping the flame proof thread on the housing of the flameproof explosion-proof light fixture, the following matters must be paid attention to:
a. Try not to pass through the flameproof enclosure, and leave a margin of more than 3mm at the bottom of the screw hole when passing through the enclosure;
b. When using light alloy materials such as aluminum alloy as the flameproof housing, due to the low strength of aluminum alloy, when using bolts to fasten the flameproof housing that is frequently opened (such as replacing the light source during maintenance), it should not be For direct tapping on the aluminum alloy housing, the female thread and male thread should be embedded to prevent loosening to increase the strength of the screw hole and prevent the explosion-proof gap from failing due to rotten threads;
c. If the user does not need to open the flameproof casing when replacing the light source or other maintenance, and the bolts have been installed at the factory, you can directly tap the fastening screw holes on the flameproof casing, but the coarse thread cannot be used, and the thin thread should be used as much as possible. thread, and there is enough engagement to meet the tightening requirements.
In a word, when designing housing fasteners, it is necessary to first distinguish its role in the flameproof housing, whether it is only for fastening, or both for fastening and at the same time to ensure that the plane structure meets the standard of flameproof clearance, or whether it is both. To tighten, it is necessary to ensure that the threaded structure meets the standard of explosion-proof clearance, and then determine the maximum axial load of the bolt and select the appropriate bolt.
The introduction of cables or wires of explosion-proof explosion-proof light fixtures can be connected in the following two ways:
A. Indirect introduction: the way of connecting with flameproof junction box or flameproof plug-in device;
The cable or wire is first introduced into the junction box or plug-in device, and then the cable or wire that controls the lamp is led out from the junction box or plug-in device, and is fastened through the flameproof gland and connected to the flameproof housing of the lamp.
B. Direct entry: the connection method that directly inserts cables and wires into the main housing
The cable or wire is directly fastened through the flameproof gland and connected to the flameproof housing of the luminaire
explosion-proof light fixtures are inseparable from transparent parts, and transparent parts are the parts with the lowest strength in the housing parts, so whether the installation of transparent parts is reliable directly affects the safety performance of explosion-proof light fixtures. The following analyzes the three commonly used installation methods of transparent parts:
1. It is directly sealed in the casing and forms a whole with the casing. This method is simple, practical and widely used. The sealing material should be a temperature-resistant and oil-resistant rubber part, or use an adhesive such as epoxy resin to seal the transparent part in the casing and press it tightly.
2. With or without liner, directly fasten the transparent part in the housing. When the gasket is not used, the flatness of the joint surface of the transparent part is very high, and it is generally suitable for small flat glass and the joint part of the glass is ground at the same time, otherwise the glass will be unevenly stressed and easily broken.
3. Sealed or glued to a frame, which is fastened inside the housing, so that the transparent piece can be replaced as a whole. This structure is rarely used in lamps, and in some large-scale equipment where transparent parts are frequently replaced, the transparent parts and the frame are replaced as an integral part. The sealing between the transparent part and the frame can refer to the type 1.
In terms of structure, the force (generated by the internal explosion) of the transparent part should be directly transmitted to the metal housing as far as possible. It is inappropriate to transmit it to the metal housing through the pressure plate and/or screw of the transparent part. Can not be stressed, so as to ensure the reliable combination of the transparent part and the housing.