Liquid-Cooling Systems

Overview 

The SN6600-LD, SN6810-LD and SN6800-LD liquid-cooling systems feature parallel cooling loops operating concurrently. The below curves apply to PG25 at 45°C (see (1.0) Specifications). As the systems have two parallel inlet/outlet ports, the flow rate at the operating condition is half the total switch liquid flow rate.

Liquid Cooling Systems P-Q Curve
SN6600-LD:	SN6810-LD:	SN6800-LD:

Deployment

Inserting the Switch Module (Liquid System Related)

The switch modules are pre-filled with nitrogen in the cooling system, pressurized to at least 1 psi. If the pressure is below 1 psi, perform a "Pressure Hold": refill to 50 psi with N2, wait 12 hours, and verify that the pressure remains above 48 psi to pass. Positive nitrogen pressure prevents humidity or dust ingress.

• Before insertion, release the gas using the open-ended hose from the maintenance kit. 
  

  

• Connect the hose to either of the two FRU hoses to automatically expel the gas. 

• Disconnect the hose once the gas is fully released, then proceed with module insertion.  

Liquid-Cooling System Related Actions 

Pressure Check of Nitrogen-Filled Components

Purpose:

• Confirm that cold plate assemblies, switch trays, and manifolds retain supplier-filled N2 pressure, ensuring no leaks during transit.

Required Hardware:

• Digital pressure gauge (0–2.1 bar or 0–3.4 bar), data logging.

Process

• Scan the QR code, log pressure

• Release the internal pressure

• Cycle time: <1 minute

Pass/Fail Criteria

• Must retain ≥1 psi.

• If the pressure is lower than 1 psi, please perform a "Pressure Hold" test as follows:

  • Refill to 50 psi with N2

  • Wait 12 hours

  • Recheck the pressure. If the pressure is above 48 psi, the unit has passed the test.

• Failures are returned to the supplier.

PG25 Fill

Purpose:

• To fill assemblies (both individual components and full racks) with 25% propylene glycol, and 75% water solution, ensuring complete fluid coverage and air removal for optimal thermal performance.

Required Hardware:

• For vacuum fill: Vacuum pump, liquid trap

• For positive pressure fill: Fill pump

• 25-micron filter on the supply side (for both the component and the rack)

Process

• Vacuum Fill:

  • Pull vacuum on the assembly from the outlet quick disconnect (QD).

  • Fill the fluid from the inlet QD.

  • Stop filling when the fluid enters the liquid trap.

  • Vacuum specification: 5 kPa or less.

• Positive Pressure Fill:

  • Use a fill pump to introduce coolant.

  • Circulate the fluid back into the reservoir briefly to ensure no bubbles remain.

Pass/Fail Criteria

•  Fluid reservoir weight can optionally be measured before and after filling as a quality check.

Caveats: 

• If using a positive pressure pump with circulation, ensure a 25-micron filter is installed on the supply side.

• If the assembly is complex with multiple fluidic elevations or high points, vacuum filling is preferred.

• Expected Cycle Time: 2–3 minutes.

Last updated: June 07, 2026