A technician has to leave refrigerant and nitrogen cylinders on a roof for several hours during a long change-out. How should those cylinders be handled while they sit there?
- ALaid down flat on the roof deck so that wind and foot traffic cannot tip them over
On its side a cylinder's relief device may sit in liquid instead of vapor, which changes how it behaves in an overpressure event. Cylinders are stored and used standing upright and secured.
- BSet close against the unit's hot condenser coil so they stay warm and hold enough pressure to charge with
Deliberately warming a cylinder raises the pressure inside it, which is the hazard being guarded against. Heat is what overfilled cylinders fail from, and a running condenser is a heat source.
- CLeft with the valve cracked slightly open so internal pressure cannot build while they sit
An open valve is a deliberate release, which is prohibited, and it empties the cylinder besides. Pressure is managed by keeping the cylinder cool and correctly filled, not by venting it.
- Stood upright and secured against tipping, out of direct sun so heat does not drive the pressure up
Why D is correct
Upright placement keeps the pressure relief device in contact with vapor rather than liquid, securing prevents a fall that can break off a valve, and keeping cylinders out of the sun holds the liquid temperature down so the internal pressure stays within the range the cylinder and its relief device were designed around.
What this question is testing
This item checks knowledge of correct cylinder handling and the reasoning behind it, including the relationship between temperature and cylinder pressure and the function of the relief device.
On the job
Roof work adds hazards that ground-level work does not have: no shade, hot membrane surfaces that can exceed air temperature by a wide margin, wind, and a long carry back to the truck. Crews stage cylinders against a curb or a rail with a strap, throw a light cover over them, and keep the number of cylinders on the roof to what the job actually needs. Fall protection near the edge and a secured ladder belong on the same checklist.
Memory technique
Stand them up, strap them down, keep them cool, keep them shut.
Exam tip
Upright, secured, shaded, valve closed. Any option that heats a cylinder or opens its valve is wrong on both safety and regulatory grounds.
Where to look it up
Cylinders are stored and used upright and secured; heat raises internal pressure. Venting refrigerant to atmosphere is prohibited.