Why must the relief piping downstream of a chiller's rupture disc never be plugged, valved shut or blocked?
Correct Answer
D) The vessel could be over-pressured with no path to relieve, and the shell itself could fail
A rupture disc protects the vessel by giving pressure a controlled way out. Block the path behind it and the disc cannot do its job, so a pressure rise from fire, an overcharge or a loss of cooling has nowhere to go but into the shell. Vessel failure is violent and releases the entire charge at once, along with fragments. That is why relief piping is run without valves, kept clear of debris and blockages, and routed so nothing can obstruct it.
Why This Is the Correct Answer
A blocked relief path defeats the entire pressure protection scheme. The disc may burst as designed, but with no route out, pressure keeps building against the vessel until something gives, and the failure of a large chiller shell is far more dangerous than a controlled relief discharge.
Why the Other Options Are Wrong
Option A: The purge unit shares the same line to discharge non-condensable gas to the outside
The purge discharge is a separate connection routed on its own. Relief piping is dedicated to the relief device, so blocking it would not affect how the purge unit vents non-condensables.
Option B: The disc would begin to weep refrigerant continuously into the machine room once it is blocked
A rupture disc either holds or bursts; it is not a device that seeps when the line behind it is plugged. Blocking the piping changes what happens after it bursts, not before.
Option C: The machine could not be evacuated for service or repair with the line blocked
Evacuation for service happens through the machine's service valves, not through the relief line, so a blocked relief path would not stop the work. It only removes the pressure protection.
Memory Technique
A relief valve with nowhere to go is just decoration. Keep the path open all the way outside.
Reference Hint
Relief piping from a rupture disc must remain unobstructed so the vessel always has a path to relieve pressure.
More epa-608-type-3 Questions
Some jobs on a chiller count as a major repair under the refrigerant rules, which changes what a technician is allowed to do with a badly leaking machine. Which job falls into that category?
An owner asks how many pounds of refrigerant the rules allow to be left inside a chiller once the recovery has been signed off. What is the correct answer to give him?
The motor of a hermetic centrifugal chiller sits inside the pressure boundary rather than outside it on a shaft. What follows from that construction?
An oxygen monitor is used to decide whether a chiller machine room is safe to enter after a refrigerant release. Below what oxygen reading is the atmosphere treated as oxygen deficient?
A low-pressure chiller's rupture disc has a discharge line running from it. Where does that line have to terminate?
A refrigerant vapor detector in a chiller machine room reaches its alarm level. Besides sounding, what is that alarm expected to do?
Which piece of equipment requires a technician to hold Type III certification before it may be serviced?
What property of the refrigerant is what actually places an appliance into the low-pressure category?
During normal operation, what condition exists inside the evaporator of a running low-pressure centrifugal chiller?
In what unit is the required final recovery vacuum for a low-pressure appliance normally expressed?
People Also Study
Business & Financial Management
120 questions · 70% to pass
Contract Administration
60 questions · 70% to pass
Project Management
60 questions · 70% to pass
Related Study Resources
Previous Question
A leak has been found on a large low-pressure chiller that falls under the leak repair provisions. Within what period does the rule expect that leak to be repaired?
Next Question
What hose arrangement keeps the vapor phase of a low-pressure recovery from dragging on longer than necessary?