What pressure limit should CNG cylinders not exceed during operation?

CNG cylinders have specific pressure limits to ensure safety and integrity during operation. The correct answer indicates that the pressure within CNG cylinders should not exceed 125 percent of the marked service pressure. This guideline is crucial because operating above this threshold could compromise the structural integrity of the cylinder, making it susceptible to failure or rupture under high-pressure conditions.

Marked service pressure is the maximum pressure that the cylinder is designed to handle safely during normal operations, and exceeding this amount could lead to catastrophic results, including leaks or explosions. Adhering to the 125 percent limit provides an additional safety buffer, ensuring that the cylinder operates well below the threshold at which damage or failure might occur.

In contrast, the other options suggest pressure levels that either exceed safe operational limits or do not provide a sufficient margin of safety. Understanding and adhering to these pressure limits is essential for the safe handling and delivery of CNG.