Why should an acetylene regulator on a cutting rig not be adjusted over 15 PSI?

• A. Acetylene has a tendency to combust unpredictably at high settings
• B. It causes excessive heat in the cut
• C. It wears out the regulator faster
• D. Acetylene is unstable above this pressure

Answer: (D)

Acetylene becomes unstable when the pressure gets too high, so the safe working limit is set at about 15 psi. This instability means the gas can decompose violently if pushed past that point, which can lead to a dangerous explosion or flare in the line. In practice, acetylene is stored under pressure in cylinders in a stabilized form, and the regulator is there to keep the outlet pressure within a safe range. When you raise the regulator above roughly 15 psi, you increase the chance of an unintended, dangerous decomposition of the gas, not just changes in flame color or heat, which is why this limit exists. The other reasons—excess heat in the cut, faster wear on the regulator, or acetylene combusting unpredictably at high settings—do not pinpoint the fundamental safety concern as precisely as the instability of acetylene above that pressure. Keep acetylene regulated well below that threshold to maintain safe cutting operations.