ATPV - Arc Thermal Performance Value
ATPV, or Arc Thermal Performance Value, measures the amount of incident energy that flame-resistant (FR) fabric can absorb before it allows enough heat to cause second-degree burns. Expressed in cal/cm², this value helps determine the level of protection offered by clothing during an arc flash. It is a crucial metric for ensuring safety in high-risk environments where electrical hazards are present. The higher the ATPV, the greater the protection it offers against burns.
The thermal performance value ATPV is a key measurement used to determine arc ratings ATPV, which indicate the level of protection provided by FR clothing. ATPV is based on the Stoll Curve and considers only the onset of second-degree burns when determining a fabric's ability to withstand arc flash energy. The rating is noted as the onset of second-degree burns, providing a 50 chance that the wearer will avoid burns in the event of an arc flash. Some materials are more insulative than they are strong, while others are stronger than they are insulative, influencing how ATPV and EBT values are assigned.
How is ATPV measured, and what does the rating indicate?
ATPV is measured using a standard test method for determining the arc rating of materials for clothing. In this test, the FR fabric is exposed to varying incident energy levels until the point when heat transfer causes the onset of second-degree burns. This value is reported as the arc rating on the clothing label. The ATPV tells you how much energy the fabric can withstand without causing burns, and only the onset of burns is considered. The rating ensures that workers know the degree of protection offered by their protective gear.
What is the difference between ATPV and EBT (Energy Breakopen Threshold)?
The key difference between ATPV and EBT lies in how they measure fabric performance. ATPV measures the fabric’s thermal resistance before it transmits enough heat to cause burns. EBT, on the other hand, measures the point at which the fabric breaks open due to the arc flash energy. Some fabrics are stronger than they are insulative, while others are more insulative than they are strong. If a fabric breaks open before it transfers enough heat to cause burns, the EBT is noted as the arc rating on the clothing. The lower of the two values, ATPV or EBT, is used as the arc rating for clothing.
Selecting the Right ATPV-Rated Clothing
When selecting arc-rated clothing, it's essential to consider the specific arc flash hazard level in your workplace. This information is typically determined through an arc flash risk assessment. The higher the incident energy level, the higher the required ATPV rating for the clothing.
Factors that can influence the selection of arc-rated clothing include:
- Job duties: The type of electrical work performed will impact the level of protection required.
- Exposure time: The duration of exposure to an arc flash can affect the severity of burns.
- Environmental conditions: Extreme weather conditions can impact the performance of arc-rated clothing.
Factors Affecting ATPV Over Time
The ATPV rating of a material can be affected by several factors over time:
Wear and Tear: Normal wear and tear, such as abrasion or exposure to chemicals, can degrade the fabric's performance.
- Cleaning and Maintenance: Improper cleaning or storage can damage the fabric's protective properties.
- Exposure to Light and Heat: Prolonged exposure to sunlight and high temperatures can degrade the fabric's fibers.
Therefore, it is essential to inspect arc-rated clothing regularly for signs of damage and to replace it as needed to maintain its effectiveness.
ATPV is essential for determining the level of protection provided by FR clothing against arc flash hazards. It helps workers assess how much energy their protective gear can withstand before causing burns. By understanding the difference between ATPV and EBT, and selecting clothing appropriate for the specific energy levels in the workplace, workers can ensure their safety in environments with electrical hazards.
