What can cause nozzle after-drip?

Nozzle after-drip is primarily caused by conditions that prevent the complete shutoff of fuel when the burner stops operating. A defective pump shutoff valve may not close properly, allowing oil to continue flowing into the nozzle even when the burner should be off. Additionally, if air becomes entrapped in the nozzle line, it can disrupt the fuel flow and create a situation where excess oil accumulates, leading to dripping after shutdown.

Oil expansion in the nozzle due to excessive radiant heat is another critical factor. When the oil is heated, it expands, which can lead to residual fuel remaining in the nozzle after the burner has stopped. This combination of factors results in the after-drip phenomenon, where fuel drips from the nozzle following a heating cycle.

Understanding the specific mechanical and physical issues that lead to nozzle after-drip can help in diagnosing and preventing this issue from occurring, ensuring more efficient operation and less unnecessary oil spillage. Other options, while they may lead to different operational problems, do not directly relate to the common causes of nozzle after-drip.