Deep Technical Chapters · Pressure Testing & Leak Diagnosis
Supermarket Rack Pressure-Testing & Ball Valves
On racks and distributed systems, isolation valves can separate sections — but a closed ball valve is an assumption, not proof of a pressure boundary.
Supermarket racks and distributed refrigeration systems use isolation valves to separate rack sections, liquid lines, suction lines, individual cases, evaporators, condensing equipment, service sections, controls and pressure-sensing lines. That makes pressure testing more powerful — and more dangerous — because a closed valve is not a guaranteed boundary.
What isolation valves can separate
- Rack sections
- Liquid lines and suction lines
- Individual cases and evaporators
- Condensing equipment
- Service sections
- Controls and pressure-sensing lines
A closed ball valve is not a guaranteed boundary
A valve may pass internally because of damaged sealing surfaces, debris, contamination, seat damage, wear, incorrect operation, or general valve condition. If a valve passes, nitrogen can migrate into a section believed to be isolated.
- It can produce a misleading pressure result.
- It can pressurise equipment that was not intended to receive the test pressure.
- It can contaminate or alter the condition of a section that should have remained under its existing service condition.
- It can create a ghost leak or a misleading pressure decay.
Before introducing nitrogen
- Trace the system.
- Identify the isolation points.
- Identify what is on each side of each valve.
- Establish the intended test boundary.
- Confirm component pressure limitations on both sides.
- Then test.
Field Rules
- 01
"Know your test boundary before you introduce nitrogen."
- 02
"A closed valve is an isolation point — not proof that everything beyond it is protected."
- 03
"A closed ball valve is an assumption. A proven isolation is evidence."
Diagnosis at a glance
Common mistakes & callbacks
- •Assuming every closed ball valve holds.
- •Pressurising a section without confirming what is on the other side of every valve.
- •Over-pressurising a control or sensing line that was meant to stay isolated.
