Secondary Fluid Network (SFN)
Secondary Fluid Network (SFN) for Liquid-Cooled Data Centers
RexEdge designs, manufactures and commissions the Secondary Fluid Network (SFN) — the stainless steel piping, row manifolds and rack drops that carry coolant from your CDU to every liquid-cooled rack. We make the tube ourselves, fabricate and passivate the assemblies in an ISO 8 cleanroom, and deliver a clean, leak-tested network ready for cold plates.
What Is a Secondary Fluid Network?
A Secondary Fluid Network is the coolant loop between the Coolant Distribution Unit (CDU) and the IT racks. ASHRAE calls it the Technology Cooling System (TCS). It is the “clean side” of a liquid cooling system, because its fluid flows straight into the cold plates on GPUs and CPUs.
The SFN sits between two other layers:
- Primary Fluid Network (PFN) — facility water from chillers, dry coolers or cooling towers to the CDU.
- Secondary Fluid Network (SFN) — conditioned coolant from the CDU to the racks, through row manifolds and rack drops.
- In-rack manifolds — vertical manifolds at the back of each rack that feed individual servers.
Air cooling reaches its limit at roughly 30–50 kW per rack. AI training racks now run far above that, so the SFN has become as critical to uptime as the power busway.
Engineered for Clean, Leak-Free Coolant
Cold plates have micro-channels that clog with weld scale, oxides or particles. Our SFN process is built around fluid cleanliness from the first cut:
- Material: SS316L (low carbon, molybdenum-bearing) as standard; SS304L where the spec allows.
- Welding: orbital GTAW welding with full purge for smooth, oxide-free internal welds.
- Cleaning and passivation: chemical cleaning and passivation in an ISO 8 cleanroom, then capped and bagged.
- Fittings: sanitary tri-clamp, flanged or welded joints to your specification.
- Fluids: compatible with treated water, propylene glycol blends (such as PG25) and other approved coolants.
- Design inputs: sized to your rack density, flow rate, pressure drop and redundancy (N, N+1 or 2N loops).
Quality Control and Testing
Every Secondary Fluid Network assembly passes the same checks before dispatch:
- Material test certificates traced to heat number for every pipe and fitting.
- Weld inspection, including visual and borescope checks of internal weld beads.
- Hydrostatic pressure testing to specification.
- Helium or pressure-decay leak testing.
- Particle-count flush and cleanliness verification.
- Dimensional check, labeling, end-capping and nitrogen-purged packing.
Why Choose RexEdge for Your SFN
- Tube mill to rack drop: we manufacture seamless and ERW stainless pipe and fittings in-house, so material, lead time and traceability stay under our control.
- Capacity at scale: our SFN plant is built for 10 km of process piping per month.
- Cleanroom fabrication: ISO 8 cleanroom for passivation and final assembly.
- Approved-equal ready: we build to your engineering specification and submittal format.
- Install and commission: our team installs, flushes, fills and commissions the network on site, including in the US.
- One cooling partner: PFN, SFN and CDU engineering from one team, backed by our CDU Design & Engineering Lab in Noida.
Plan Your Secondary Fluid Network with RexEdge
Share your rack layout, target density and CDU details. Our engineers will send a technical proposal and budget estimate.
Click HereFREQUENTLY ASKED QUESTIONS (FAQ)
The primary fluid network carries facility water from chillers or dry coolers to the CDU. The secondary fluid network carries clean, conditioned coolant from the CDU to the racks. A heat exchanger in the CDU keeps the two fluids separate.
Yes. SFN is the common industry term; ASHRAE calls the same loop the Technology Cooling System. Both describe the piping between the CDU and the IT equipment.
? SS316L contains molybdenum for higher corrosion resistance and low carbon for clean welds. That suits treated-water and glycol coolants that flow directly into server cold plates.
Very clean. Cold-plate micro-channels can be blocked by weld scale or particles. RexEdge cleans and passivates every assembly in an ISO 8 cleanroom and verifies cleanliness with a particle-count flush.
Yes. We work from your drawings, specification and submittal requirements and can be listed as an approved-equal supplier.
Yes. Our team installs, flushes, fills and commissions the network, including for customers in the United States.
Registered Office:
REXEDGE PVT. LTD.
INDIA :-
105, Tower B, Noida One,
Sector 62, Noida (UP), India – 201301
SEATTLE, US :-
WA, Bellevue – Redmond Center
2018, 156th Avenue, N.E., Building F, Suite 100, Bellevue, Washington 98007