There is no national standard or law that stipulates the requirements or actions before a tool or piece of equipment is used for rental purposes. Rental companies, however, have a legal responsibility to take all reasonable steps to ensure that equipment is not only fully operative, but that it is safe and without risk to the health of personnel who operate it and for others who might be affected by its operation. This responsibility extends even in the event of a fault or defect in the equipment, because the rental company as well as the manufacturer is likely to be sued.
Relying on a customer to advise on any misuse or damage to the equipment is clearly unacceptable. The rental company should conduct regular inspection and testing of equipment as part of best practice considerations. And, if an accident occurs, the rental company would be required to clearly demonstrate that it took all reasonable steps to prevent the accident. Inspection and safety testing programs should therefore be regarded as part of due diligence procedures for any rental company.
For rental and service companies, a number of reasonable steps are recommended to ensure the safety of their electrical equipment.
- Purchase of safety equipment
- A system for inspection and test
- Identification and training of appropriate personnel
- The use of suitable test equipment
- A suitable area for testing
- A defined series of tests
- A results recording system
Purchase safe equipment
Rental tools and equipment purchased directly from manufacturers or their authorized representatives need to be constructed so that they meet electrical safety requirements. This can usually be verified by product packaging or labelling, or by contacting the manufacturer and gaining certificates of conformity.
Second-hand equipment must be closely inspected before purchase and particular attention should be paid to modifications that may have been made by the previous owner. Any such modifications may invalidate any manufacturers' declaration of safety. It is advisable to ensure that the appropriate electrical safety testing is undertaken to confirm that no danger or risk is posed.
For full liability protection, traceable records of inspection and testing programs provide proper records to prove that all necessary steps have been taken to ensure the safe operation of all rental equipment supplied.
Identify and train appropriate personnel
Testing and inspection should be carried out by personnel who have sufficient knowledge of what to look for and to carry out the procedures without danger to themselves or others. They should also have the ability to identify possible safety problems on new or unusual equipment and to make valid judgements based on test results. Ideally such personnel should be supplied with full and up-to-date copies of manufacturers' and employers' safety manuals.
The use of qualified electricians is not necessarily called for, but it is suggested that a designated person (or persons) be identified with responsibility for testing. Suppliers of equipment to rental companies often give advice and training. Test equipment manufacturers also offer comprehensive training on testing systems and procedures.
Use suitable test equipment
Safety testers capable of carrying out appropriate tests to ensure the electrical safety of products are available from a number of manufacturers. Specialist test equipment is available that has been designed and developed to meet the specific test needs of the rental industry. Test equipment itself should also be tested at least annually, both for safety and calibration. Most manufacturers or calibration houses are capable of providing this service.
Find a suitable testing area
Electrical safety can be hazardous if simple precautions are not taken. Such testing should not be carried out just anywhere. Identify a discrete place in the shop and ensure that it is clearly identified as a testing area. The following list provides a number of recommendations for test areas in the workshop where high voltage tests are undertaken.
- A separate test area with an emergency stop switch
- No risk of the operator being knocked, disturbed or distracted by colleagues or the moving of equipment in the general vicinity.
- A workbench constructed of wood or other insulated material
- No conducting surfaces or objects that could be grounded and provide a conductive path to ground.
- The floor should be covered with insulated matting, such that the tester cannot walk off this mat in a single pace from the normal working position.
- Warning signs and a red warning light should be placed at the test area entrance, forbidding entry of unauthorized personnel.
- The electrical installation should conform to the relevant wiring regulations and the test instrument connected to the mains with GFI protection.
A defined series of tests
Because some faults cannot be detected by visual inspection alone, it is imperative that the requisite testing of rental equipment is undertaken before and after use.
There is little guidance available on the type of testing to be undertaken, although such factors as the type, size and usage patterns of equipment need to be considered, alongside technical factors such as whether the item is Class I (metal case) or Class II (double insulated).
In addition, some guidance on ‘in-service’ testing and recommended pass/fail levels for rental products is provided by manufacturing test standards for new products, by reference to the appropriate UL and international standards.
Clearly, only when the recommended tests and appropriate pass/fail parameters for rental tools have been identified can any decisions be taken on the type of test equipment required. For example, routine testing of small rental appliances might comprise relatively simple ‘go-no go’ testing with an instrument capable of providing an unambiguous pass/fail indication. At the other end of the scale, perhaps for larger tools and pieces of rental equipment, possibly incorporating integral ‘no volt’ switches, it might be more reasonable to run a more comprehensive series of tests with dedicated pass-fail limits set according to the type of equipment under test.
Against this background, the following list of tests represents a sensible series and order of tests that can be incorporated in testing programs for most types of rental equipment.
- Visual Inspection
- Ground Bond
- Hi Pot or Dielectric withstand
- Functional Test (Load)
Visual Inspection
A visual inspection needs to be thorough, a quick ‘once over’ is unsatisfactory. The tester should inspect the mains plug, mains cable, equipment cable clamp and the outer casing of the equipment itself. The tester should be looking for:
Mains plug:
- No damage to case
- Sleeved pins present
- Correct approval marks
- Insulation of cable OK
- Clamp gripped to sheath and no movement or rotation
- Connections OK
- Correct fuse
Mains cable:
- No significant cuts
- No significant damage other than minor scuffing
- Suitable specification cable is being used
- Correct labels are in place
Equipment:
- Cable clamp in equipment has no movement or rotation
- Insulation is protected
- Clamp is gripped to sheath
- No cracks or holes in casing that give access to electrical components or impair safety
- No evidence of ingress of water, solvents, grease or other liquids that could impair safety
Ground continuity test
This test verifies the integrity of the protective conductor (earth) and every part on the conductive case, which is designed to be earthed. This measurement is carried out at less than 12V with a test current at least 1.5 times the design current of the unit under test. The resistance measured should not exceed 0.1 Ohm.
Dielectric withstand Hi Pot Test
The test is designed to detect that gaps or clearances between conductive parts and earth are sufficient and that degrading, such as pin holes, cracks in insulation and other protective devices have not resulted through production processes and/or wear and tear. The test applies high voltage to the product so as to check insulation between the live conductors and earth. For Class 11 equipment the high voltage is applied between the conductors and the outer surface of the product. The test voltages for hand held operated tools are 1250V for Class 1 equipment and 3750V for Class II equipment. The maximum permitted resistive leakage is 5mA.
Function test (Load)
This test measures the current consumption of the equipment while it is running. A higher than specified consumption is indicative of mechanical wear on bearings or shorted turns in the windings. Abnormally low current consumption could be the indication of an open circuit or ruptured fuse.
Results recording system
It is recommended, that the results of inspection and testing be carried out for two reasons. First, to prove due diligence if a problem arises. Second, by recording test results and thus becoming aware of any trend towards a failure threshold, or a sudden change in test value, the rental company can anticipate future problems.
Electric shocks can ruin lives and also threaten company reputations. By following a few simple steps most electrical accidents can be avoided.
John Jansen is vice president of Clare Instruments, Tampa, Fla. The company has published a guidance document: Ensuring the Electrical Safety of Equipment in the Service and Rental Industry, available free from Clare by calling (813) 886-2775 or e-mail: [email protected]. Visit Clare on the Web at www.clareinstruments.com.
Specialist instruments test the electrical safety of all types of rental equipment and tools.
