CSA Class E4 vs. Class E6 Personal Energy Absorber (PEA)
Comparison between class E4 and E6 personal energy absorbers (PEA).
There is a misconception, and for good reason, that the CSA Z259.11 Class E6 personal energy absorber (PEA) requires more clearance to arrest a fall than the Class E4 PEA. Also, most users steer away from the Class E6 PEA as it deploys at a higher arrest force. However, the benefits to the worker using the Class E6 PEA in a Personal Fall Arrest System (PFAS) greatly outweigh these two reasons for not using the Class E6 PEA.
I will explain the benefits by examining the two concerns noted above. First, let’s consider the higher deployment force. The Class E6 PEA is designed to deploy at a force no greater than 6 kN (kilonewtons) (or 1,350 lbs.), in accordance with the CSA Z259.11 standard. However, due to variations in the manufacturing process of the tear-away webbing mechanism that creates the energy absorbing device, there will always be some variation in the deployment force of the device. Unfortunately, the only way to determine what the deployment force of an energy absorber will be is to deploy the energy absorber, destroying it in the process, and measuring the average deployment force. Now, there is empirical data regarding the average deployment force of the energy absorber and with some statistical analysis the manufacturers, with confidence, can ensure the device meets the requirements of the CSA Z259.11 standard. The average deployment force will always be less than the rated or Class deployment force. The big question now is, what is the average statistical deployment force of a CSA Class E6 personal energy absorber? In my experience, most energy absorbers sold on the market by the major manufacturers will have an average deployment force from 65% to 85% of the rated value. This goes for either CSA Class personal energy absorber, E4 or E6. Therefore, the actual arrest force for the CSA Class E6 PEA is between 3.9 kN (877 lbs.) and 5.1 kN (1,147 lbs.). This force isn’t much higher than the rated deployment force of the Class E4 PEA. And by comparison, the actual arrest force for the CSA Class E4 PEA is between 2.6 kN (584 lbs.) and 3.4 kN (764 lbs.). I will come back to the forces towards the end of this discussion.
|Free Download: Construction Fall Safety Checklist|
Now let's address the concern that the CSA Z259.11 Class E6 energy absorber requires more clearance for fall arrest. Let me explain why I commented earlier that this was for good reason. Most end users are taught to assume full deployment of an energy absorber when calculating required clearance. The Class E6 PEA has a maximum deployment length (elongation) of 1.75m (5.74 ft), in accordance with the CSA Z259.11 standard. If we compare this to the Class E4 PEA, which has a maximum deployment length of 1.2m (3.94 ft), in accordance with the CSA Z259.11 standard, we see that the E6 will require 0.55m (1.8 ft) more clearance to arrest the fall of a worker. Assuming full deployment of the PEA, the worker will always calculate a more conservative required clearance for the Class E6 PEA. Unfortunately, it would appear that more clearance is required for the Class E6 PEA than for the Class E4 PEA.
Now, let’s review both of these factors together, force and distance. When multiplied together, these values calculate the capacity of the energy absorber. If we think of the capacity as the total amount of fall energy the device can absorb, all other factors being equal, we can make a practical comparison between the two CSA Classes of personal energy absorber.
First, let’s calculate the capacity of the Class E4 PEA, using the minimum average arrest force and maximum elongation. 2.6 kN x 1.2m = 3.12 kN.m (584 lbs x 3.94 ft = 2,300 ft.lbs) energy absorption capacity.
Second, let’s calculate the capacity of the Class E6 PEA, using the minimum average arrest force and maximum elongation. 3.9 kN x 1.75m = 6.83 kN.m (877 lbs x 5.74 ft = 5,033 ft.lbs) energy absorption capacity.
By examination it can be seen that the Class E6 PEA has more than twice the capacity of the Class E4 PEA, all other factors being equal. This will always be true as the Class E6 PEA deploys at a higher force than the Class E4 PEA.
E4 capacity kN.m (ft.lbs)
E6 capacity kN.m (ft.lbs)
@ 65% rated arrest force
@ 85% rated arrest force
@ Rated arrest force
Now, let’s look at a real fall scenario. A worker weighs 100 kg (220 lbs.), including tools, clothing and other PPE. Let’s assume the worker has a fall using each of the Classes of energy absorber examined above. Let’s also assume that the worker has his fall arrest system configured that he has exactly a 1.8m (6 ft) free fall (FF), before the fall arrest system begins to arrest the fall of the worker.
The total amount of fall energy the worker will generate during the fall, regardless of Class of personal energy absorber, will be 100 kg x 9.81 m/s2 x 1.8m = 1.77 kN.m (220 lbs x 6 ft = 1,320 ft.lbs). But, since the worker will continue to fall as the fall arrest system arrests the fall (deceleration phase), the actual distance required to stop the worker falling, (i.e. arrest the fall), is dependent on the Class of personal energy absorber used.
The actual formula used to calculate the deployment distance (elongation) of a personal energy absorber to arrest a fall is called the Personal Energy Absorber Equation and can be found in section 188.8.131.52 of the CSA standard Z259.16-04 Design of Active Fall-Protection Systems. Without getting too technical, below is a comparison of the elongation of the Class E4 and the Class E6 PEAs for the above scenario. Using the minimum average arrest force will result in the greatest PEA deployment (elongation or Deceleration Distance, DD).
Energy Absorber Equation: Xpea = mgh/(Favg – mg)
PEA elongation (DD)
Arrest distance (FF + DD)
E4 @ 65% rated arrest force,
2.6 kN (584 lbs)
1.09m (3.58 ft)
2.89m (9.48 ft)
E6 @ 65% rated arrest force,
3.9 kN (877 lbs)
0.60m (1.97 ft)
2.40m (7.87 ft)
The Class E4 PEA actually deploys more, and requires 0.49m (1.60 ft) more clearance than the Class E6 PEA due to the lower average arrest force.
In conclusion, because the Class E6 Personal Energy Absorber has a greater capacity to absorb fall energy, it is the better device to use for any worker weighing above 90 kg (200 lbs) using a Personal Fall Arrest System (PFAS).
Check out the rest of our content about Personal Protective Equipment here.
More from AD Safety Network
- When should you consider using custom molded earplugs?
- At what height do falls become deadly?
- Who should be responsible for rescuing fallen workers?
- What kind of training do loading dock workers need?
- How often should I inspect a loading dock?
- How is wind chill calculated?
- What is the difference between occupational safety and process safety?
- Why should rubber insulating gloves be tested?
- What happens if I tie off at the foot level with a personal SRL?
- Why is testing with a NAIL4PET accredited lab important?
- What kind of face protection do I need when using a chainsaw?
- What is the permissible exposure limit (PEL) for silica?
- What is silica and why is it hazardous?
- Video Q&A - What is a safety policy?
- What kind of fire extinguisher is best for your work site?
- How do I choose the right respirator and mask for working with silica?
- Can I wear fall protection equipment over my rainwear or winter gear?
- When do I need a cage ladder?
- What types of gloves protect your hands from hazardous chemicals?
- How come I still got hurt while wearing flame-resistant clothing?
- How do I win over my most reluctant employees?
- What kinds of jobs should use disposable safety gloves?
- Is it true that safety shouldn't be a top priority?
- When are employers allowed to conduct drug and alcohol tests on their employees?
- How can I get employees more involved in the risk assessment plan?
- What are some of the indirect costs of workplace accidents?
- How often do fire extinguishers need to be inspected?
- What is the best way to store rubber safety gloves?
- How much voltage protection is needed for safety gloves used in electrical work?
- What is the difference between a safety valve and a release valve?
- When do workers have the right to refuse to work?
- What is the most overlooked item when designing Lockout/Tagout (LOTO) procedures?
- What are some of the misconceptions about heat stress and what should we do to address them?
- What tools should I tether when working at heights?
- What types of gas should I watch out for when working in a confined space?
- How do you create a culture of safety in your workplace?
- What is the difference between industrial safety and industrial hygiene?
- Is it important to get PPE assessments by trained professionals?
- What is a fault tree analysis?
- What kind of respirator cartridge should I use?
- What are the safety benefits of a whistleblower program?
- What type of safety record-keeping and recording should we be doing?
- What makes a hi-vis safety vest ANSI compliant?
- Why is it important to have air sampling done to determine my PELs?
- What is the life expectancy of fall protection equipment?
- What are some basic fall protection rules that each of my workers need to understand?
- How much clearance do I need to safely use a Leading Edge SRL?
- What is the difference between an acute hazard and a chronic hazard?
- What’s the difference between a bump test, a calibration check, and a full calibration?
- Is there any legislation regulating lone worker safety I should know about before hiring?
- What kind of fire extinguisher and accessories should be kept on hand on a factory floor?
- What can companies do to reduce their lost time injury frequency rates?
- Video Q&A - What's your safety network like?
- Video Q&A - What are the 3 levels of safety?
- Video Q&A - How do you treat a near miss?
- Does body weight affect falls differently?
- What ages are most affected by falls?
- Why do workers take risks?
- What Is the Difference Between OHSAS 18001 and 18002?
- What is the difference between lost time injury and medical treatment case?
- What is the difference between occupational health and safety and workplace health and safety?
- What is the difference between occupational health and occupational safety?
- What is the difference between a lost time injury and a disabling injury?