Electromagnetic lifter for moving coils of hot-rolled steel and relevant operating method
An electromagnetic lifter includes at least two polar expansions shaped for transporting a horizontal axis coil of hot-rolled steel. The polar expansions are connected through a ferromagnetic circuit and respective cores around which solenoids are arranged. A detection coil is arranged around each of the cores suitable to detect the change in the flux linked to the coil, and a control unit connected to the detection coils compares the values detected by each of them in order to authorize or not the transport. The relevant operating method includes a first check that the difference between the values detected by the two detection coils is below a preset threshold, and in the affirmative a second check that the overall decrease in the linked flux is below a second preset threshold, the issuance of an authorization signal to the transport being possible only in case of positive outcome of both checks.
1. An electromagnetic lifter comprising
at least two polar expansions shaped for transporting a horizontal axis coil of hot-rolled steel,
said at least two polar expansions being connected through a ferromagnetic circuit and respective cores around which two magnetization solenoids are arranged,
characterized in that it further includes at each of said cores a single detection coil arranged around said core so as to detect the change in the flux linked to said coil of hot-rolled steel, as well as a control unit operatively connected to said detection coils and suitable to compare the values detected by each coil in order to authorize or not the transport.
2. The electromagnetic lifter according to claim 1 , wherein each detection coil is arranged close to the relevant polar expansion.
3. The electromagnetic lifter according to claim 2 , wherein the detection coil is made of enamelled copper.
4. The electromagnetic lifter according to claim 2 , wherein it further includes plates suitable to protect the detection coils from the heat transmitted by the coil of hot-rolled steel.
5. The electromagnetic lifter according to claim 1 , wherein it includes A/D converters arranged between the detection coils and the control unit.
6. An operating method for an electromagnetic lifter according to claim 1 , said method including the steps of:
a) activating the magnetization solenoids;
b) checking that the flux linked to the coil to be transported is sufficient to achieve an anchorage force greater than twice the weight of the coil;
c) initially lifting the coil and simultaneously checking that the difference between the values detected by the detection coils is below a preset threshold;
d) performing or not a second check that the overall decrease of the linked flux is below a second preset threshold, depending on the outcome of said first check; and
e) issuing or not a signal of authorization to the transport depending on the outcome of said second check.
7. The operating method according to claim 6 , wherein if the first check of step c) has a negative outcome step d) provides the issue of a signal for stopping the lifting operation and returning the load to the ground.
8. The operating method according to claim 6 , wherein if the second check of step d) has a negative outcome step e) provides the issue of a signal for stopping the lifting operation and returning the load to the ground.
9. The operating method according to claim 6 , wherein the preset threshold for the first check of step c) indicatively ranges from 3% to 10%.
10. The operating method according to claim 6 , wherein the preset threshold for the second check of step d) indicatively ranges from 3% to 10%.
11. The operating method according to claim 9 , wherein the preset threshold for the first check of step c) is 5%.
12. The operating method according to claim 10 , wherein the preset threshold for the second check of step d) is 5%.