Lockable Manhole covers have more than 100 anti-theft devices, mainly using six methods as follows:
- First: The coupling chains
- Second: The hinge connection
- Third: oral anti-spin technique method
- Fourth: bolt holes blocking skills
- Fifth: keys for the lock
- Sixth: fork joint linkage method
Wherein the first, two kinds and Manhole covers and frames are not able to lock together. It’s easy to open with the drill rod that is capable of chains, pry off the hinges.
The third type of lockable Manhole covers is that you just reversely rotate it into the right place to open and take covers.
The fourth type of Lockable Manhole covers: with bolts, nuts, blocked the hook hole, but as long as the iron wire with a bowed head on both ends is inserted into the groove of the bolt head under two ended side, to open and take the covers.
The fifth and sixth type: although the covers and frame can be locked each other into one, but with space and with high precision casting requires co-ordinated with new covers, the transformation of the existing wells cannot be used, costing considerably, but will not solve the “anti-rust “ problem. After half of year use, you also unable to open their own, cannot go down operations. Therefore, the above covers all types of anti-theft device, the effect is not ideal.