Understanding the Four Critical Boundaries

Arc flash protection is built upon a system of four distinct boundaries, each serving a specific protective function.

Limited Approach Boundary

The Limited Approach Boundary represents the distance from an energized component where
unqualified persons (those without proper electrical safety training) must not cross without escort. This
boundary serves as the outermost protective perimeter and is determined based on nominal system
voltage.
Unqualified individuals may only cross this boundary when they demonstrate a valid need and receive
continuous escort by qualified personnel. This first line of defense ensures that individuals without
proper training remain at a safe distance from potential electrical hazards.

Restricted Approach Boundary

The Restricted Approach Boundary establishes a more stringent protective zone that only qualified
electrical workers may enter. Within this boundary, specific PPE and insulated tools become
mandatory, and inadvertent movement must be prevented through proper work positioning. The risk of
electrical shock increases significantly due to proximity, and documented work permits are required
for any repair work inside this limit.

Arc Flash Boundary

Unlike the previous boundaries based on shock protection, the Arc Flash Boundary specifically
addresses thermal energy exposure. This critical boundary marks the distance at which
second-degree burns could occur during an arc flash incident. It requires determination through
incident energy calculations specific to each piece of equipment.
The Arc Flash Boundary may extend significantly farther than shock protection boundaries in certain
systems, sometimes reaching 20 feet or more for high-energy equipment. Anyone crossing this
threshold must wear appropriate arc-rated clothing and PPE matched to the estimated incident energy
levels.

Calculation Methodologies: Beyond the Simplified Tables

While NFPA 70E offers tables for estimating boundaries, comprehensive protection requires more
detailed calculation approaches.

Incident Energy Analysis Method

The incident energy analysis method applies IEEE 1584 calculation methodologies to determine
equipment-specific boundaries rather than relying on general categories. This engineering-based
approach accounts for system-specific factors including available fault current, protective device
clearing time, gap between conductors, working distance, system grounding configuration, and
enclosure type and size.
This method typically provides more precise PPE requirements and often reduces excessive PPE
compared to table methods. The calculations produce specific incident energy values measured in
calories per square centimeter (cal/cm²) at defined working distances, which directly correlate to PPE
arc ratings.
Organizations implementing this approach must maintain regular updates when system changes occur.
Modifications to electrical distribution systems, changes in protective device settings, or even routine
maintenance on circuit breakers can significantly alter arc flash boundaries, requiring recalculation and
relabeling.

Practical Implementation Strategies

Translating calculated boundaries into workplace practice requires systematic implementation
approaches that make abstract mathematical concepts visible and understandable in the field.

Equipment Labeling Systems

Effective labeling forms the cornerstone of boundary implementation. Equipment labels should clearly
display all relevant boundaries, indicate required PPE categories, and include incident energy values at
working distance. Consistency across the facility helps workers quickly recognize and interpret
boundary information regardless of which area they’re working in.
Advanced labeling systems incorporate color-coding for rapid recognition and may include QR codes
linking to detailed procedures for that specific equipment. Labels must include calculation dates for
verification and be constructed from materials capable of withstanding the environmental conditions
present in the installation location.

Temporary Boundary Marking

Maintenance and project work often require temporary boundary marking systems to create visible
reminders of invisible boundaries. Facilities typically deploy portable boundary tape stands at
calculated distances, with distinct colors representing different boundaries. Some organizations
implement digital projection systems for complex environments where traditional boundary marking
proves difficult.
Effective programs train workers on proper placement verification and create standardized boundary kit
contents available at job sites. Work permits should document actual boundary placement, particularly
in areas with overlapping boundaries from multiple energy sources.

Digital Boundary Management

Advanced organizations increasingly implement digital boundary tracking systems to enhance
traditional approaches. Mobile applications can display real-time boundary information specific to
equipment being serviced, while wearable technology can alert workers to boundary encroachment
before violations occur.
Some facilities utilize augmented reality displays showing boundaries in complex environments,
particularly useful in congested industrial settings. These systems often integrate with work order
management systems to ensure appropriate precautions appear automatically when work is scheduled
on specific equipment.

Training Methodologies for Boundary Awareness

Effective boundary training goes beyond concept explanation to develop practical application skills that
workers can implement in diverse field conditions.

Boundary Decision-Making Scenarios

Training should incorporate decision-making elements that reflect real-world complexity. Scenariobased exercises should present multiple boundaries requiring assessment, dynamic situations with
changing requirements, and emergency response protocols when boundaries are compromised.
Workers need clear understanding of authorization processes for boundary crossing and communication
protocols when working near boundaries. Documentation requirements for various boundary zones
should be practiced until they become second nature rather than burdensome administrative tasks.

Special Applications and Considerations

Certain situations require modified approaches to boundary management due to their unique challenges
or heightened risk profiles.

Complex Multi-Feed Equipment

Equipment with multiple power sources presents unique boundary management challenges. Safety
professionals must determine worst-case boundary scenarios accounting for all potential energy sources
and establish clear procedures for boundary hierarchy during partial de-energization.
Documentation systems must account for the complexity of these situations, with special labeling
requirements indicating multiple sources. Workers require specialized training on verification
procedures for all potential energy sources before boundaries can be modified or reduced.

Outdoor and Extreme Environments

Outdoor installations and extreme environments necessitate adaptations to standard boundary practices.
High-wind environments may require enhanced boundary marking methods, while wet or corrosive
atmospheres demand more durable marking solutions.
Extreme temperature environments affect both boundary implementation and PPE utilization. Cold
weather may require additional protective layers beneath arc-rated clothing, potentially affecting
movement and dexterity within restricted boundaries. Limited visibility conditions in outdoor settings
during night work or adverse weather require enhanced marking strategies to maintain boundary
awareness.

Continuous Process Environments

Facilities where shutdown is exceptionally costly require specialized boundary management
approaches. These organizations often implement remote monitoring and operation strategies to
minimize the need for boundary crossing during normal operations.
When boundaries must be crossed in these environments, enhanced PPE protocols and specialized
work practices help reduce risk while maintaining operational continuity. Many such facilities invest in
engineering controls specifically designed to reduce boundary zones, such as remote racking systems,
infrared viewing windows, and robotic inspection technologies.

Measuring Program Effectiveness

Evaluating boundary program effectiveness requires both leading and lagging indicators. Organizations
should track boundary procedure compliance rates, authorized versus unauthorized boundary crossings,
and worker competency assessment scores as leading indicators of program health.
Near-miss reporting related to boundary violations provides valuable insights for program
improvement, while PPE compliance verification at various boundaries helps identify potential training
gaps. Regular review of boundary documentation in work permits reveals how well theoretical
knowledge translates to field application.
Effective programs establish feedback mechanisms allowing qualified workers to suggest
improvements to boundary management systems based on field experience. This continuous
improvement approach recognizes that those working within the boundaries daily often develop the
most practical insights for enhancement.

Beyond Compliance to Culture

Effective arc flash boundary management extends beyond mere regulatory compliance, becoming
ingrained in organizational safety culture. By implementing comprehensive assessment protocols,
practical field applications, and engaging training methodologies, organizations transform abstract
calculations into tangible protection systems.
The most successful electrical safety programs recognize that boundaries represent more than
mathematical formulas or floor markings—they serve as critical decision points where worker
behavior, engineering controls, and administrative systems intersect to prevent catastrophic injuries.
Through proper implementation of these concepts, electrical workers can navigate hazardous
environments with the protection afforded by invisible but life-saving perimeters.

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Critical Electrical Safety Targets

Make sure these get done!

• De-energize. Unless the employer can justify live work, it is not permitted. Live testing and troubleshooting are allowed, but altering the circuit live is difficult to justify.
• Workers must be qualified for each electrical task they perform, and the electrical hazard they are exposed to.
• Workers must know how to perform a risk assessment, and how to reduce the associated risk.
• A worker must have access to and utilize the appropriate PPE for the electrical hazard.
• Employers need to ensure the worker has access to arc-rated PPE throughout the range of incident energy indicated by their incident energy analysis.
• Test-Before-Touch. A qualified worker must verify zero energy before contacting de-energized parts by performing the Live-Dead-Live test.
• While verifying zero energy, the qualified worker must utilize appropriate PPE and insulated tools.
• All PPE, as well as all tools and equipment with electrical insulation, must be inspected daily before each use.
• The owner of the electrical equipment is responsible for providing labels that include nominal voltage, arc flash boundary, and a method of determining the appropriate arc flash  PPE to be worn.
• Rubber insulated gloves must be electrically tested every six months.
• Arc-rated clothing and insulated gloves must fit the user, and provide full coverage.

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Introduction

This control panel is like thousands of control panels out in facilities today, and maybe even many in your facility. It controls a machine on the factory floor. It has four motor starters, individual circuit breakers for those motor circuits, ice cube relays, small fuses, and a control transformer. And on the door there are pushbuttons, indicating lights, rotary switches. In the lower right

corner of the panel is the main circuit breaker. With the door closed, we can still operate the breaker through the hole in the door. Pretty typical of many control panels. The question is how do we de-energize this panel to establish an electrically safe work condition.

Circuit Breakers

Circuit breakers have a line and load side. The line side is where the incoming power is connected. The load side is where the downstream loads are connected. In this case, the downstream loads are everything else in this panel and all of the motors and other components in the control circuit outside the panel. Everything downstream from this main breaker is being protected from over-currents by this breaker.

The question is, does this circuit breaker de-energize this panel? The answer is no. Opening this breaker de-energizes everything in this panel as well as the downstream loads, everything except for the line side of the breaker itself. When this circuit breaker is opened, turned off, the line side of the breaker is still hot. With the line side still energized by the incoming power, the panel has to be considered energized because the main breaker still has a shock and arc flash hazard. You could not use this breaker to establish an electrically safe work condition for this panel.

Electrically Safe Work Condition

To properly de-energize this panel to establish an electrically safe work condition, you would need to locate the circuit breaker or disconnect that feeds power to your control panel. Your lockout tagout procedures should indicate the location of this breaker or disconnect. Once that is found you would open that disconnect or circuit breaker and apply your locks and tag. Return to the control panel and follow through with all of the required lockout tagout procedures. The most important of which is the live-dead-live test to verify zero voltage. Always Test-Before-Touch. And of course, always wear the required PPE while verifying zero volts. Every circuit has to be considered energized until you’ve proven it’s not.

Troubleshooting Example 1

As a troubleshooting example, let us use a situation in which the operator of this machine reports that one of its four conveyors stopped running. You show up and ask the operator what led up to this problem, and they state that that conveyor has been making a lot more noise than usual. A squealing sound. You suspect a mechanical problem, and on an inspection of the conveyor pulleys, it is evident that a bearing has failed thus causing too much load on the motor. Next, we go to the control panel and see that it has an arc flash label that states an arc flash rating of 11 cal/cm2 and a voltage of 480. We must don the appropriate PPE to protect you from such an arc flash and voltage. Because we are only going to do a visual inspection and we are wearing the proper PPE we can proceed. We do an orderly shutdown of everything the panel controls then open the main breaker. We then open the control panel door and see that the motor starter has tripped for that motor. Everything else in the panel appears fine, we reset the motor starter, and close the door. We place our lock and tag on the main breaker, and we perform all other procedures required by our lockout tagout procedures and proceed to repair the bearing.

Troubleshooting Example 2

In the next example, the operator reported the conveyor wouldn’t turn on. There was no mention of a squealing noise. During our initial troubleshooting, we attempt to turn on that conveyor manually and we hear the motor starter turn on, or pull-in as we say,  inside the cabinet. But, the conveyor is still not moving. We don the appropriate PPE, open the control panel door and begin our visual inspection of the panel. We immediately notice the motor starter for conveyor four is showing signs of heat damage. A  dark smoke-like film is on the area covering the motor starter contacts. This, we know from experience, is an indication of poor contact being made by the starter contacts. The other starters don’t show this damage. Now we know we are going to have to remove and replace the starter or at least disassemble it for inspection and repair. In either case, we’ll need to completely de-energize the panel. At this time we’ll need to close the control panel door and open the main breaker. We then must go to the upstream circuit breaker for this panel, turn it off and apply our lock and tag. Upon returning to the control panel, wearing the appropriate PPE we open the control panel door. Using an appropriate volt-meter, we test that meter on a known live circuit, then measure incoming line leads phase-to-phase and phase-to-ground and do verify that we indeed have zero volts. We then retest the meter on a known live circuit to confirm the meter is still working. That is the Live-Dead-Live test. Now we can remove the PPE and begin our repair work. We find the contacts badly damaged from not making proper contact and the carbon buildup inside the starter is preventing the contact assembly from moving freely. We replace the motor starter, and now all conveyors are working fine.

A Shield May Not Work

Some people have suggested that if you add a plastic or metal shield to the main breaker that covers the energized line leads that should solve the problem. It actually can create a whole new problem. OSHA requires electrical equipment to be “accepted, or certified, or listed, or labeled, or otherwise determined to be safe by a nationally recognized testing laboratory.” Underwriters Laboratory is such a lab. If you add a plastic or metal shield to your breaker, it is no-longer UL Listed because it didn’t have your shield when tested. The shield could cause the breaker to operate differently than when it was manufactured and tested, resulting in an unsafe situation.

Control Panel Design

This next piece of advice doesn’t help you with existing control panels but could make your future panels safer and easier to work with where 70E is concerned. That advice is to ask the OEM of your new panels to put this main breaker in a separate box on the side of the panel. Putting the main circuit breaker in a separate enclosure is becoming quite common now, and manufacturers of these boxes are offering this option. Hoffman’s SEQUESTR line of enclosures is one such offering.

Circuit Breaker Panel Boards

I used a control panel as an example here, but all of this applies to circuit breaker panel boards as well, not just control panels. Opening the main breaker of a circuit breaker panel does not establish an electrically safe work condition. If you’re going to add a circuit breaker, for example, turning off the main breaker for the panel board is not sufficient. You will need to open the circuit breaker that feeds this panel to establish an electrically safe work condition.

Conclusion

In conclusion, it is essential that we know what does and what does not make an electrical panel electrically safe. It must be spelled out in your lockout/tagout procedures which disconnect, or circuit breaker removes power from the equipment that will enable us to create the electrically safe work condition. We will wear the appropriate PPE any time the equipment has an energized circuit component above 50V.

Relevant courses

The post The Main Circuit Breaker For This Control Panel Doesn’t De-energize The Panel appeared first on ElectricalTrainingPro.com.

Watch for next years conference February 26-28, 2019.

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In this video I talk about the importance of verification of isolation in establishing an electrically safe work condition. Verifying the absence of voltage. A strong lockout tagout program has to be the key element of your electrical safety program. Establishing an electrically safe work condition is where you must begin. Appropriate shock and arc rated PPE must be worn while verifying an absence of voltage. Every circuit must be considered live until verified it is not.

OSHA will cite you for not wearing PPE during verification of zero energy.

You may also like this video: Using OSHA Citations As Electrical Safety Training Tools

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Energized Electrical Work Permit

Exemptions

A permit is not required for testing, troubleshooting, measuring voltage, thermography and visual inspections. Access to and egress from an area with energized electrical equipment if no electrical work is performed and the restricted boundary is not crossed. An exemption also exists for general housekeeping as long as the restricted boundary is not crossed.

“Working On”

There are two kinds of “Working On” as defined by NFPA 70E. Diagnostics and repair. Diagnostics does not require a permit, repair does. Repair means any physical alteration of the circuit. Replacing or removing of components.

When Are Required

A worker crossing the restricted boundary with the intent to alter the circuit would require a permit. If the worker was to interact with a circuit, even if the conductors were not exposed, but where there existed an increased likelihood of an arc flash occurring, a permit would be required. Such as racking in a breaker, or performing switching of a large breaker.

Elements Of A Permit

An energized electrical work permit must include, among other things, justification to why the work has to be done live. A lot of live work is stopped right here, because your justification written down on paper somehow doesn’t sound as good. And it might be hard to sign your name to it. For a complete list of what needs included see NFPA 70E 130.2(B)

Samples

There is a sample permit along with an energized electrical work permit flow chart that takes you through the decision making process.

Conclusion

An energized electrical work permit will help eliminate live work at your facility. It requires us to justify and document live electrical work. Exposure to energized conductors can lead to injuries from arc flash and shock hazards. And finally, it will help keep you in compliance and maybe prevent a tragedy.

www.osha.gov

www.nfpa.org

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Arc Flash Incident Energy Analysis Hidden Benefits

Single Line Drawings

Whoever does the assessment of your electrical distribution system will have to find out, in simple terms, what is connected to what. They will follow conductors as they connect to panelboards, circuit breakers, disconnects, control panels, etc. They will follow it all the way from your utility connection point, or points, and continue down to your equipment on the plant floor. Using software they will build a single-line or one-line diagram of your electrical distribution system. A sort of road map of your facility’s electrical system.

Regulations

Chapter 2 of NFPA 70E, Article 205.1 states: A single-line diagram, where provided for the electrical system, shall be maintained in a legible condition and shall be kept current. An incident energy analysis will gill give you a set of single-line drawings. Keep them up-to-date. They will assist maintenance, engineering and contractors in doing their jobs more efficiently and safer. Insist these drawings be updated when changes are made.

Inventory Of Equipment

At the completion of the arc flash risk assessment you should have an inventory of most of your fuses. I say most of your fuses because it depends on how much of your plant is actually surveyed. It is possible that some of your equipment will not be looked at. Certainly fuses inside control panels will not all be recorded. But you should have a good look at most of them in disconnects, motor control centers, combination starters and switchgear. Ask the people doing the arc flash risk assessment specific questions concerning your study.

How To Use The Inventory

If after looking at this inventory you discover you have several fuses that are exactly the same, yet you have none of those in your store room, you might want to order some to have on hand. If a fuse blows and you don’t have one in stock this could create excessive downtime while one is brought in. Or, it could tempt someone to use a fuse that is not an exact replacement. This can cause many problems depending on what they put in. A fuse can only be replaced by a fuse that has all the same specifications as the one it is replacing.

Improper Wiring Conditions

Another unintended benefit of an arc flash risk assessment is that a knowledgable person is going to open all of your panels to collect data. In the process of data collection it is not uncommon that wiring problems become apparent. It isn’t necessarily what the data collector is there to do, and not exactly what they’re looking for but sometimes the issues are just too obvious to miss. You should ask your data collectors to inform you when they find anything like this.

Crazy Things

Some of the crazy things they find are funny, but some could be deadly if not corrected. One I remember was a Tuna can used as a junction box. I don’t remember Tuna cans being allowed by the National Electrical Code. Another is copper tubing or copper bars being used to replace fuses. Granted, a 1/2 inch piece of copper tubbing will last much longer than a fuse, but the building might burn down because of it. Sometimes an electrical panel is opened and it is discovered that the panel is completely full of wood dust, flour, sugar, metal dust, metal shavings, or just what ever it is that the plant processes. I remember shaken data collectors calling the office to report panels full of rat nests, tarantulas, a dead squirrel and snakes. These last problems would indicate unused opening not properly covered. It shouldn’t be hard to keep a squirrel out of your electrical enclosures. They are apparently good conductors. Tarantulas might be a bit harder.

Infrared Survey

Thermal imaging cameras have advanced in the last several years to the point where Flir can turn your iPhone or Android phone into a thermal imaging camera for a couple hundred dollars. Because you are going to open all of your electrical enclosures it makes sense to incorporate as much of an infrared study into your arc flash risk assessment as you can. The data collection will be done while the facility is in operation with equipment running. It makes sense to shoot the cabinet to see if you have issues.

In Conclusion

It is great you are having an arc flash risk assessment done to improve the general electrical safety of your facility. The arc flash incident energy analysis hidden benefits are substantial and can impact electrical safety. To get the best value out of your study take advantage of these hidden benefits to the best of your ability.

You may also like “Properly Labeled Panels”

http://flir.com/flirone/android/?pi_ad_id=%7Bcreative%7D&gclid=CMnOqoaYldQCFdm6wAodalMN6g
http://www.osha.gov
http://www.nfpa.org

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Electrical Safety Hazard Caused By Unused Openings In Electrical Equipment

Electrical Safety Hazard Caused By Unused Openings In Electrical Equipment

Missing Circuit Breaker

Unused openings are created when a circuit breaker has been removed. Unused & Uncovered Openings In Electrical Equipment Can Pose An Electrical Safety Hazard. This might happen when a particular piece of equipment is no longer in use or has been moved to another location in the plant. The area vacated by the circuit breaker has to be covered
and made safe.

OSHA

OSHA addresses these hazards in 1910.303(b)(7)(i).
“Unused openings in boxes, raceways, auxiliary gutters, cabinets, equipment cases, or housings shall be effectively closed to afford protection substantially equivalent to the wall of the equipment.”

Visual Inspection

A safety manager can easily spot these hazards with a visual inspection. Open the hinged door on circuit breaker panel boards, this should expose only the face of the circuit breakers, and observe if there are any breakers missing. If you see an unused opening close the door and notify maintenance for repair.

Filler Plates

When a circuit breaker is removed from a breaker panelboard it leaves an unused opening. Every manufacturer of panelboards makes what is called a filler plate to cover this opening. These filler plates are important; without them workers are exposed to live conductors anytime the door is opened. Depending on what kind of panelboard it is and what type of breaker the hole left could be large enough to stick your hand in.

Wrong Solution

I have been witness over the years to some very imaginative methods of covering these holes. These have included electrical tape, duct tape, cardboard and combinations of each. None of these are remotely acceptable. You need an appropriate, inexpensive, filler plate specifically made for that panel.

Knock Outs

Look for other unused openings on the sides, top and bottom of all electrical panels as well. Sometime unused round holes, called knockouts, are not covered. You can also purchase what are known as knock out plugs or knock out seals to easily cover these
holes. Again, duct tape is not the answer.

Keep Panels Clean

Another reason you need to cover unused openings is that it keeps the interior of the electrical equipment from being exposed to the dirt, dust and other contaminates you may have at your facility. Allowing the interior of a circuit breaker panel to become dirty could cause additional safety issues.

Conclusion

Unused and uncovered openings expose your employees and contractor employees to unnecessary electrical hazards. This hazard can be identified with a little effort and help from your maintenance staff. Finally, these can be resolved very easily and with little cost. I encourage you to take the steps to survey your facility, and if you find these exposures get them corrected as soon as possible.

Link To Related OSHA Regulation

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Only Qualified Persons May Work On Live Electrical Equipment

Intro

OSHA states in 1910.333(c)(2) “Work on energized equipment.” Only qualified persons may work on electric circuit parts or equipment that have not been deenergized…. OSHA is serious about only qualified persons may work on live electrical equipment.

Training

The qualified employees must be trained in electrical safety to be considered qualified. This training, both NFPA 70E and OSHA work practices, includes electrical shock and arc flash. An unqualified person would not have had that training and must be kept out of electrical cabinets.

Unqualified Access

It has become common in some facilities for unqualified operations staff be allowed to access control panels. This must be stopped.

Qualified

All qualified employees must have received electrical safety training in order for you to consider them qualified. It doesn’t matter if you have an employee that for 25 years has been considered capable of working in electrical cabinets, if they have not received electrical safety training, OSHA will not consider them qualified.

Conclusion

Sadly, too often this doesn’t get discovered until someone is injured or killed. In summary, we have to keep unqualified employees out of electrical cabinets and we have to train our maintenance staff before we can say they’re qualified.

Link to related OSHA regulations.

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This video covers the issue of improper labeling of circuit breakers, disconnects & over-current devices.

Not labeling a circuit breaker may seem like a small thing, but it can cause electrical safety issues and can cost the facility money in unseen ways. Problems occur when maintenance personnel attempt to isolate a piece of equipment when overcurrent protection devices and disconnects are not properly labeled. If they can’t find the circuit break to isolate a piece of equipment they have to begin a costly search for the missing breaker. It is incredibly easy to label the breaker when installed but it can be very hard to find it later. Especially if you have many not labeled or mislabeled. Sometimes it might require the removal of covers to trace wires to the proper breaker. OSHA will also fine your facility for not correctly labeling overcurrent devices and disconnects.

You may also like this related article: Proper Labeling Of Circuit Breakers & Covering Unused Openings

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