Automatic testing of overload protection device in a rescue hoist
An automatic field load check testing system includes a computer communicating with and commanding a rescue hoist. A processor of the computer commands the rescue hoist to wind to build a load on a cable. As the tension builds a sensor monitors an overload clutch to determine if any friction discs in the overload clutch slip as the load builds. When the load reaches a minimum clutch slip load, the load is relieved. Where the friction discs slip before the load reaches the minimum clutch slip load, the overload clutch fails the test. Where the friction discs do not slip before the load reaches the minimum clutch slip load, the overload clutch passes the test.
1. A method of testing an overload clutch, the method comprising:
activating, with a processor of a computer, a motor of a hoist, the motor driving a cable drum through the overload clutch;
loading the cable to a minimum clutch slip load with the motor;
sensing a load on the cable and communicating the load to the processor; and
monitoring the overload clutch with a sensor, the sensor configured to sense slippage of a friction disc of the overload clutch and to generate a slip signal in response to slippage of the friction disc.
2. The method of claim 1 , further comprising:
recalling, from a memory of the computer, a state of the cable, the state indicating whether the cable is conditioned.
3. The method of claim 1 , further comprising:
generating a successful iteration count based on a number of times overload clutch does not slip in response to the cable being loaded to the minimum clutch slip load; and
comparing the successful iteration count to a minimum iteration count.
4. The method of claim 3 , further comprising:
subjecting the overload clutch to an additional load iteration based on the successful loading iteration count being less than the minimum iteration count.
5. The method of claim 4 , further comprising:
providing a test status indication based on the slip signal.
6. The method of claim 5 , wherein:
the test status indication is of a test fail based on receiving the slip signal at the processor; and
the test status indication is of a test pass based on not receiving the slip signal at the processor.
7. The method of claim 1 , wherein the step of monitoring the overload clutch with the sensor, the sensor configured to sense slippage of a friction disc of the overload clutch and to generate the slip signal in response to slippage of the friction disc comprises:
monitoring the overload clutch for a slip vibration profile; and
generating the slip signal based on the sensor sensing the slip vibration profile.
8. The method of claim 1 , wherein the step of sensing the load on the cable and communicating the load to the processor comprises:
routing the cable through a traction sheave disposed between the cable drum and a cable guide through which the cable exits the rescue hoist; and
sensing the load generated on the traction sheave by the cable with a load cell disposed in the traction sheave.
9. The method of claim 1 , wherein the step of loading the cable to the minimum clutch slip load with the motor further comprises:
abutting a bumper disposed at a terminal end of the cable against a cable guide through which the cable exits the rescue hoist; and
rotating the cable drum with the motor to cause the cable drum to reel in the cable with the bumper abutting the cable guide.
10. A method of initializing a hoist, the method comprising:
determining, with a processor of a computer, a status of at least one pre-test factor of a hoist;
conducting at field load check test of an overload clutch of the hoist based on each of the at least one pre-test factor being true, the field load check test comprising at least one loading iteration comprising:
activating, with the processor of the computer, a motor of the hoist, the motor driving a cable drum through the overload clutch;
loading the cable to a minimum clutch slip load with the motor;
sensing a load on the cable and communicating the load to the processor; and
monitoring the overload clutch with a sensor, the sensor configured to sense slippage of a friction disc of the overload clutch and to generate a slip signal in response to slippage of the friction disc.
11. The method of claim 10 , wherein the step of determining, with the processor of the computer, the status of at least one pre-test factor of a hoist comprises:
recalling, from a memory of the computer, a state of the cable, the state indicating whether the cable is conditioned; and
indicating a first pre-test factor is true based on the state indicating that the cable is conditioned.
12. The method of claim 11 , wherein the step of determining, with the processor of the computer, the status of at least one pre-test factor of a hoist further comprises:
comparing a time interval since most-recent test to a test interval, the test interval being a set time period between field load check tests of the overload clutch; and
indicating a second pre-test factor as true based on a difference between the time interval since most-recent test and the test interval.
13. The method of claim 11 , further comprising:
indicating, with a user interface of the computer, that the first pre-test factor is false and that the cable requires conditioning based on the state of the cable indicating that the cable is not conditioned.
14. The method of claim 10 , further comprising:
generating a successful iteration count based on the number of loading iterations where overload clutch does not slip in response to the cable being loaded to the minimum clutch slip load; and
comparing the successful iteration count to a minimum iteration count.
15. The method of claim 14 , further comprising:
subjecting the overload clutch to an additional load iteration based on the successful loading iteration count being less than the minimum iteration count.
16. The method of claim 15 , further comprising:
providing a test status indication based on the slip signal.
17. The method of claim 16 , wherein:
the test status indication is of a test fail based on receiving the slip signal at the processor; and
the test status indication is of a test pass based on not receiving the slip signal at the processor.
18. The method of claim 10 , wherein the step of monitoring the overload clutch with the sensor, the sensor configured to sense slippage of the friction disc of the overload clutch and to generate the slip signal in response to slippage of the friction disc comprises:
monitoring the overload clutch for a slip vibration profile; and
generating the slip signal based on the sensor sensing the slip vibration profile.
19. The method of claim 10 , wherein the step of sensing the load on the cable and communicating the load to the processor comprises:
routing the cable through a traction sheave disposed between the cable drum and a cable guide through which the cable exits the rescue hoist; and
sensing the load generated on the traction sheave by the cable with a load cell disposed in the traction sheave.
20. The method of claim 10 , wherein the step of loading the cable to the minimum clutch slip load with the motor further comprises:
abutting a bumper disposed at a terminal end of the cable against a cable guide through which the cable exits the rescue hoist; and
rotating the cable drum with the motor to cause the cable drum to reel in the cable with the bumper abutting the cable guide.