Risk Based Frequency of Portable Appliance Testing

Edition 5 of the IET Code Of Practice (The official guide to PAT Testing) encourages the duty holder to carry out a risk assessment and gives various examples. In Chapter 7 of this handbook, we provide both a way of carrying out a risk assessment and a Table based guidance on how the frequency of maintenance can be worked out.

The main factors to be taken into account are as follows:

 

·         The equipment construction i.e. Class I or II

·         Equipment Type i.e. stationary, portable, handheld etc

·         Environment i.e. office, school, factory etc

·         Previous failure rate on site

 

Note: The failure rate refers to the average failure for the whole site and not for that particular appliance. For example, if out of 200 appliances on site, around 5 fail when inspection and testing is carried out, then the failure rate would be (5 x 100)/200 = 2.5%.

 

We can now assign the following risk weighting (RW) to these factors.

Class of Construction
Class 1	RW = 4
Class 2	RW = 2

Type of Appliance
Handheld	RW = 4
Portable	RW = 4
Movable	RW = 4
Stationary/IT	RW = 2
Fixed	RW = 1

Environment
Construction	RW = 20
Factory	RW = 8
Used by Public/Customers	RW = 5
School	RW = 4
Office/shops	RW = 1

Previous failure rate
Greater than 10%	RW = 4
Between 1 and 10%	RW = 2
Less than 1%	RW = 1

If previous failure rates are not known, then one has to use other information to decide on your risk weighting. For example, if this is a hairdresser, and in previous years there have been no PAT testing failures then a RW of 1 can be used to start with. However, if there is no previous information, then start with a RW of 2.

 

To work out the frequency of testing for any particular appliance, one would simply multiply these RW’s together to give us a risk factor (RF) and use the guidance below to work out the frequency of inspection and testing.

Suggested Frequency of Inspection and Testing
RF of less than 20	Inspect every 2 years, test every 4 years
RF between 21 and 100	Inspect every year and test every 2 years
RF between 101 and 200	Inspect and test every year
RF between 201 and 400	Inspect and test every 6 months
RF greater than 400	Inspect and test every 3 months

Example 1: Consider a Class 1 desktop PC used in an office environment where usually there have been hardly any failures. A Class 1 appliance has a RW of 4, a desktop PC is a piece of IT equipment and has a RW of 2 and an office environment is low risk and has an RW of 1. Previously the failure rate has been low at less than 1 in a hundred appliances failing so we can assign an RW of 1 to this.

 

Multiplied together (4x2x1x1) this gives a risk factor (RF) of 8. Using the guidance above we would mark this appliance down as needing an inspection every 2 years and test every 4 years.

 

Example 2: In the example above if the PC was a laptop, then as this is considered to be movable the RW for this would be 4 and the overall risk factor would be 16 – still requiring inspecting every 2 years and testing every 4 years. However, if the failure rate increased to more than 1% this would double the risk factor to 32, requiring inspection every year and testing every 2 years.

 

Example 3: A Class 1 (RW of 4) kettle (RW of 4) in a shop (RW of 1) with previous failure rate of less than 1% (RW of 1). Multiplied together this gives a risk factor of 16 - inspect every year and test every 2 years.

 

Example 4: A Class 2 (RW of 2) drill (RW of 4) is used in a school workshop and there is no information from previous years. In this case we use a risk weighting of 2 for previous failure rate. Although the environment is a school, as it is used by students a higher risk weighting of 8 is assigned here (as students should be regarded as customers). Overall risk factor is 128 (2 x 4 x 2 x 8) and this drill would have to be inspected and tested every year. 

 

Example 5: The same as example 4, but experience suggests that the failure rate is more than 10%. That is on average out of the 20 items, 2 or more fail every time inspection and testing is carried out. In this case the RW changes from 2 to 4, resulting in an overall risk factor of 256. This drill will now have to be inspected and tested every 6 months.