According to SAE Standard 1990, Motor Vehicle A/C R-12 recovery equipment must be capable of reducing the system pressure to _.
A) a pressure of 0 PSIG
B) a vacuum of 4 Inches of Mercury
C) a vacuum of 15 inches of Mercury
D) a vacuum of 27 inches of Mercury
The correct answer and explanation is :
Correct Answer:
D) A vacuum of 27 inches of Mercury
Explanation:
The SAE (Society of Automotive Engineers) Standard J1990 (1990) specifies the requirements for refrigerant recovery and recycling equipment used in motor vehicle air conditioning (MVAC) systems that use R-12 refrigerant (also known as CFC-12). This standard was developed to ensure environmental safety by minimizing the release of ozone-depleting substances into the atmosphere.
One of the key requirements outlined in SAE J1990 is that the recovery equipment must be capable of reducing the system pressure to a vacuum level of at least 27 inches of Mercury (inHg).
Why 27 Inches of Mercury?
- Effective Refrigerant Removal:
- R-12 refrigerant operates under high pressures. To ensure maximum refrigerant recovery, the system must be drawn into a deep vacuum. 27 inches of Mercury (inHg) is considered deep enough to extract most of the refrigerant and residual moisture from the system.
- Prevent Refrigerant Emissions:
- If the system is not fully evacuated, some refrigerant may remain, leading to its release into the atmosphere. R-12 is a CFC (chlorofluorocarbon), which contributes to ozone layer depletion.
- Compliance with EPA Regulations:
- The Environmental Protection Agency (EPA) enforces refrigerant recovery laws under Section 609 of the Clean Air Act. Achieving a 27 inHg vacuum ensures compliance with federal regulations.
- Proper System Maintenance:
- Removing air and moisture from the A/C system prevents corrosion and damage to internal components, improving the efficiency and lifespan of the air conditioning system.
Thus, the correct answer is D) a vacuum of 27 inches of Mercury, as per SAE J1990 requirements.
Image Representation:
A/C refrigerant recovery machine achieving a vacuum of 27 inches of Mercury on its gauge.
I’ve generated an image of an automotive air conditioning refrigerant recovery machine showing a vacuum gauge reading 27 inches of Mercury (inHg) in a professional auto repair shop.