What should be avoided when bending a pipe as per NFPA 13 guidelines?

When bending a pipe in accordance with NFPA 13 guidelines, it is crucial to avoid kinks and distortions. Kinks can significantly weaken the structural integrity of the pipe, leading to potential failure when the system is pressurized. Distortions of the pipe can also alter its internal diameter, which affects water flow and pressure throughout the fire sprinkler system. Maintaining the pipe's integrity and ensuring a smooth curvature during the bending process is essential for optimal performance and reliability of the fire protection system.

The other choices suggest practices that may not directly adhere to the intent of maintaining pipe quality as outlined in the guidelines. For instance, bending pipes over 45 degrees is not inherently problematic if done appropriately, and bending pipes at all is often necessary within fire sprinkler installations as long as it is executed correctly to prevent damage. Certain materials might also have specific guidelines for bending, but focusing on kinks and distortions ensures that the essential structural integrity of the piping is preserved.