Question 85General Subjects - 1st Asst/Chief

The correct answer is A) prevent leakage past the floating end tube sheet. The packing ring in a shell-and-tube type cooler is used to form a seal between the floating end tube sheet and the shell, preventing leakage of the cooling medium (typically water) past the tube sheet. This is necessary to ensure the cooling medium flows through the tubes as intended, maximizing the heat transfer efficiency of the cooler. The other answer choices are incorrect because they do not accurately describe the purpose of the packing ring in this type of cooler. Option B is irrelevant, option C is too general, and option D describes a different function of the cooler design.