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Portable electrical appliances and equipment can deteriorate and become damaged, defective and faulty. It usually happens due to the incorrect selection of equipment and where electrical equipment is abused, misused and inappropriately stored.
If workers use equipment that is damaged, defective or faulty, this can increase the risks of death and serious injury from electrical hazards.
To prevent workers from being exposed to electrical hazards, portable equipment should be subject to frequent checks, inspections and testing.
There are different classes of portable electrical appliances and equipment. There are five classifications of electrical appliance (0, 01, 1, 2 & 3). Class I and Class II appliances are the two that are common in the workplace.
- The equipment has basic insulation and relies on an earth for protection.
- It is a higher risk, as the earth connection could be lost which would make the equipment live.
- It is known as earthed equipment.
- Examples include kettles, refrigerators, microwaves and toasters.
- Class I equipment will always need a full PAT test.
- Class II equipment is safer than Class I, as it does not rely on an earth for protection.
- It is protected by at least two layers of insulation.
- It is known as double insulated equipment.
- It is marked with a double square symbol.
- Examples include computers, power tools, lamps and photocopiers.
- Class II equipment will not usually require a full PAT test, but it will require insulation tests, a visual inspection and users checks.
Different types of inspection and test
Maintenance is critical in reducing the risks of faults, damage and deterioration. It is also a legal requirement under the Provision and Use of Equipment Regulations (PUWER) 1998 and the Electricity at Work Regulations 1989.
All portable electrical appliances and equipment should be on a planned preventive maintenance programme. The purpose of preventive maintenance is to ensure equipment is regularly maintained so that it remains effective and is safe to use.
It is important to remember that there are hazards associated with the maintenance of electrical equipment. These hazards should be identified by a risk assessment and suitable precautions put in place, e.g. disconnection and isolation of equipment.
There are three different types of inspection and test that form part of electrical equipment maintenance. These are:
- User checks – Checks that are carried out by the user of the equipment before and during its use.
- Formal visual inspection – A visual inspection is carried out by a competent person.
- Combined inspection and testing (PAT) – A formal inspection and specific tests are carried out by an electrically competent person.
User checks are carried out before and during the use of all portable electrical equipment. These checks are crucial, as equipment could become damaged or faulty between PAT testing periods. The aim is to identify and remove any equipment that could create a safety risk for the user.
A check should be completed whilst the equipment is disconnected and should include the following (this list is not exhaustive):
- Damage to the supply cable, e.g. cuts, cracking, heavy scuffing and fraying. It does not include light scuffing.
- Tape applied to join leads together.
- Damage to the plug, e.g. cracking and bent pins.
- Damage to connection points.
- Evidence of the coloured inner cables showing due to the outer sheath being improperly secured into the plug.
- Loose parts or screws.
- Damage to the equipment’s outer casing.
- Evidence of the equipment being used in unsuitable environments, e.g. corrosion and water damage.
- Signs of overheating, e.g. burns and discolouration.
- Whether a PAT label is present (if it is company policy).
It is not a legal requirement to record checks, but a checklist is recommended as a prompt for users. It is good practice to have a poster with pictures of typical defects and damage so that users know what to look for.
If any defects, damage or faults are identified during the check, the equipment must be taken out of use immediately. It must then be reported as per company procedures.
Workers should be given simple training and should have some basic electrical knowledge to carry out checks. They must be aware of how to identify faults, damage and defects. They should also know what to do if they identify any issues and who to report to.
Formal visual inspections
A formal visual inspection is an important part of maintenance, as it can identify some dangerous defects that could harm users. It can also be useful in determining the effectiveness of user checks. According to the HSE, formal inspections can identify up to 90% of faults.
A person who is required to complete formal visual inspections will need to be trained and competent. They will need to have the knowledge and experience to identify faults and damage. It doesn’t need to be an electrician, but the person doing the inspection will need to know what they are looking for. A higher level of competence is required compared to those completing user checks.
A formal visual inspection is more than an observation exercise. It involves a thorough inspection of the electrical equipment and can identify some defects that testing alone may miss. It’s an inspection of the appliance, plugs, cables, sockets and RCDs (if in use).
What is included in a formal visual inspection?
A formal visual inspection should include the same user checks.
It should also look at the following:
- Whether the equipment is being used in accordance with the manufacturer’s instructions.
- Previously reported damage, defects and faults during user checks.
- If there have been changes to the equipment or the circumstances in which it is used.
- Whether the equipment being used is suitable for the task and environment.
The above can identify trends that can assist duty holders in deciding the action to take, as a result of the inspection findings.
Inspecting a plug
A plug, and the cable which feeds into it, are particularly vulnerable to damage. Therefore, the interior of the plug must be checked during the formal visual inspection.
A standard three-pin plug consists of the following:
- A non-conductive cover such as plastic.
- Three pins, which are made of metal.
- The cable that enters the plug, which consists of inner wires, insulation and an outer sheath.
- The interior, which has the following components:
– A fuse – this prevents over current.
– The cable grip – this secures the outer sheath of the cable into the plug.
– Inner wires – these wires are secured to terminal screws in the plug.
- Earth – The earth wire is for safety and prevents the appliance from becoming live. The wire’s outer insulation is green and yellow stripes.
- Live – The live wire provides the current and holds the voltage (e.g. at 230v). The wire’s outer insulation is brown.
- Neutral – The neutral wire completes the circuit. The wire’s outer insulation is blue.
Inspecting inside a plug
A visual inspection of a plug’s interior should include the following:
- Any signs of damage to the plug, e.g. cracking, overheating (burns and discolouration) and water damage.
- The correct rated fuse is installed and it hasn’t melted. It should also check that a proper fuse is in use, e.g. not a piece of wire or nail.
- An earth wire is fitted for a Class I appliance.
- The inner wires, including where there is an earth, are present and secured to the correct terminal. The inner wires should not be visible outside of the plug.
- The terminal screws are secured and tight.
- There are no bare wires visible, only where they attach to the terminals inside the plug.
- The cable grip is secured and holding the outer sheath of the cable tightly.
The above will not apply to moulded plugs where only the fuse can be checked. If equipment fails an inspection, it should be taken out of use and reported. A formal visual inspection can be part of a PAT test, which is combined with testing.
PAT testing (combined inspection and testing)
PAT testing is also known as combined inspection and testing. It consists of a formal visual inspection and testing.
It should include checks to ensure that:
- The supply cables are of the correct polarity.
- The fusing is correct.
- The cables and cores have been effectively terminated.
- The suitability of the equipment for the environment it is used in.
Although formal visual inspections can identify a high percentage of faults, some cannot be identified without testing.
PAT testing does not need to be carried out by a qualified electrician. However, those who carry out PAT testing will require more training and competence than those who only carry out visual inspections.
The level of training and competence required to PAT test will also depend on the equipment, the risk and the environment.
PAT testing competence
As you have learned, the HSE recognises two levels of competency:
- The person completing the test doesn’t necessarily require electrical skills.
- The person will need to know how to use the testing equipment. There should be robust testing procedures.
- The testing equipment is easier to use, e.g. it gives either a pass or fail result, which does not require an interpretation.
- The person will require electrical skills, technical knowledge and experience to complete the test.
- The testing equipment is more sophisticated.
- The readings given require interpretation.
If there are not trained and competent people within the organisation, an external company can be used. If duty holders appoint external PAT testers, they must check their training and competency.
Testing of portable electrical appliances and equipment can identify faults that formal inspection alone cannot.
PAT testing – tests
Whether testing is required, and the type of testing, will depend on the type of electrical equipment and its class. It will also be based on the findings of the risk assessment.
New portable electrical appliances and equipment will not require a PAT test if it is supplied in a safe condition. However, new equipment will be subject to visual inspections and user checks.
There are many different types of portable appliance and equipment tests which are carried out by using specialist equipment (PAT tester). There are different types of PAT tester.
The tests that are commonly carried out are earth continuity tests, insulation resistance tests, lead polarity tests, current leakage tests and functional checks.
Earth continuity tests
- Earth continuity tests are carried out on Class I appliances and extension cables.
- Earth continuity tests are also known as earth resistance tests and earth bond tests.
- The test measures the connection between the earth pin in a plug to the case of the appliance.
- A test current is applied to exposed metal parts of the appliance. It may be difficult to test plastic Class I appliances; in some cases, only an insulation resistance test will be possible.
- The reading is given in Ohms (Ω), which measures resistance.
- The equipment will typically pass if the reading is less than 0.1 Ohms. The pass value is (0.1 + R (resistance)). However, this will depend on the equipment being tested.
Insulation resistance tests
- An insulation resistance test is carried out on Class I and Class II equipment.
- It measures the resistance of the insulation that surrounds the live parts of the equipment.
- The test method will depend on the class of equipment being tested.
- If Class I equipment does not pass the earth continuity test, the insulation resistance test should not be carried out.
- It involves using a test voltage of between 250Vdc and 500Vdc.
- Higher voltages may cause damage to sensitive equipment. Therefore, a lower voltage test may be required.
- The reading is given in Megaohms (MΩ).
- Typically Class I appliances will pass if the reading is above 1MΩ and Class II should be over 2MΩ.
Lead polarity tests
- Lead polarity tests are not performed on the appliances themselves.
- It checks that the leads have been wired correctly.
- It is performed on extension cables and detachable leads.
Current leakage tests
- These tests measure current to see if there is any leakage out of insulated areas.
- It is often used as an alternative to insulation tests.
- There are different current leakage tests, which will depend on the type of portable electrical appliance.
- The reading is given in milliamps (mA).
- Values should not exceed 5mA for Class I appliances or 1mA for Class II appliances.
- Different appliances will have different pass marks. These can be found in the IET Code of Practice.
- A function check is carried out to see if the portable appliance is working properly.
- The appliance is plugged into the mains supply to see if the equipment controls work and that it is functioning normally.
As you can see, some technical knowledge is required to understand these tests. Anyone who is carrying out any of these tests on portable electrical equipment must be competent.
PAT testing equipment
During the test, the appliance is plugged into the PAT tester. A test lead is attached to the earth point or metallic parts (depending on the test and equipment class). The equipment is then switched on, but not always connected to the mains power. This is an oversimplification of a procedure that is used for a pass/fail PAT tester. The actual procedure will depend on the PAT tester in use and the company’s processes.
Simple PAT testers, that give a pass or fail result, usually consist of a basic earth continuity test and insulation resistance test. These PAT testers do not typically give readings. However, some pass/fail units have a reading display and will provide the result of the test.
There are more complicated PAT testing units that will provide more detailed results. For example, those that display several results and those which are downloadable. These units will require more competence to be able to conduct the tests and to interpret the results.
Duty holders need to ensure that the PAT testing equipment, and the tests, is suitable for the equipment and the risks. They also need to ensure that the PAT testing equipment is calibrated.
What if the equipment fails?
A company must have clear failure criteria and standards in their procedures. Appliances can fail a PAT test for all different reasons and it may not always be due to a fault, e.g. error in PAT testing procedures and incorrect interpretation of results. Regardless, an appliance that fails a PAT test must not be used. If there is any doubt, a competent external contractor may be required to assist.
If the equipment fails one test but passes another, it should be treated as a failed result. If equipment fails during the PAT test, it must be removed from service immediately. Although not mandatory, it is recommended that PAT labels are applied that indicate that the equipment has failed its test.
If there is a risk of the failed equipment being used, the plug should be removed where possible. This prevents workers from using potentially dangerous equipment. The person who is conducting the PAT test must notify relevant personnel that the equipment has failed. Who will need to be notified will depend on the company’s reporting procedures.
If a portable electrical appliance fails a PAT test, it may need to be repaired before it can be put back into service. Repairs to any electrical equipment must be carried out by someone (internal or external) who has specialist knowledge and expertise. Repairs must be carried out properly to ensure that the electrical equipment is safe and does not cause harm to users.
Cut cables can be repaired by using couplers, but it is recommended that new sections of cable be used rather than trying to carry out repairs. Again, anyone repairing electrical cables must be competent.
If items cannot be repaired, or if there is not someone competent to complete repairs, then replacement equipment may be required. It is particularly important to replace cables that have been damaged or have deteriorated.
Fundamentally, any electrical equipment that cannot be repaired must be disposed of safely and correctly.
Frequency of PAT testing
There is not a legal requirement to PAT test, nor is there a legal set frequency. There is a common perception that portable electrical appliances and equipment must be tested annually, which is incorrect.
The inspection and testing regime, along with the frequency, will be based on the findings of the risk assessment. It is dependent on the type of electrical equipment (e.g. the class and category) and the environment it will be used in. For example, power tools used on a construction site will require more frequent inspection and testing than electrical appliances in an office.
Factors that should be considered when determining the frequency of PAT testing:
- The electrical equipment type.
- The equipment’s class, e.g. Class I (earthed) or Class II (double insulated). Double insulated equipment reduces the risk.
- Whether the equipment is handheld. Handheld equipment increases the risks, as a person holding it can receive an electric shock if there is a fault.
- The manufacturer’s recommendations.
- The initial integrity and soundness of the equipment.
- The age of the equipment. Older equipment can be more of a risk, as it requires more maintenance.
- The environment where equipment will be used. The risks will increase where equipment is used in harsher conditions, e.g. wet and dusty environments.
- The likelihood of the equipment being damaged and foreseeable misuse.
- The frequency of use and duty cycle of the equipment.
- Any modifications or repairs to equipment that could affect the risk.
Whether the equipment has been subject to damage, defects or faults (as per the findings of previous maintenance records).
The HSE’s guidance HSG107 (maintaining portable electrical equipment) has suggested initial intervals for checking portable electrical equipment.
PAT testing labels
There is no legal requirement for PAT testing labels (or stickers) to be applied to portable appliances and electrical equipment.
However, they are useful and usually contain the following information:
- The appliance identification number.
- The signature or initials of the person who carried out the PAT testing.
- The date of the PAT test.
- Whether it has passed, failed or being inspected. Different colour labels are available, e.g. green for pass, red for fail and black for inspection.
- Some also have a re-test date. The HSE does not recommend this, as the PAT tester is not responsible for determining the frequency of tests, the duty holder is. The frequency of PAT testing is determined by risk assessment. However, a re-test date can be added to the label where the duty holder has informed them of the frequency of tests.
Labels are useful but if they are used, the following should be taken into account:
- Labels can be removed, can peel off and can wear. If they are used by the company, they should be checked regularly, e.g. by users.
- The writing of the labels must be legible. They must be written in ink that will not come off or smudge.
- Labels must be applied to an area on the equipment that will not interfere with its function or create a hazard.