Liquid Cooling Data Center Flanges: Material & Connection Selection Guide

Introduction: Cleanliness & Leak-Proof Requirements for Liquid Cooling Data Centers

Data center liquid cooling is no longer a niche solution. As AI workloads and high-density servers continue to grow, reliable cooling has become one of the most critical factors for stable data center operation.

In liquid cooling systems, piping connections are under constant thermal cycling, pressure changes, and long-term fluid contact. A small leak, corrosion point, or contaminated inner surface can lead to serious consequences:

• Server room downtime

• Equipment damage

• Increased maintenance cost

• Risk of biological growth or fluid contamination

• Higher total cost of ownership

For this reason, flanges for data center liquid cooling are not just standard pipe fittings. They must be selected based on three core requirements: corrosion resistance, cleanability, and connection reliability.

In this guide, we explain how to choose materials, connection types, and surface treatment solutions for IDC liquid cooling projects.

Operating Conditions & Key Performance Requirements

Liquid cooling systems usually operate under moderate pressure and temperature, but they place higher demands on long-term stability and cleanliness.

Typical Conditions

• Working pressure: often 6 barg to 16 barg

• Working temperature: 20°C to 60°C, sometimes higher for waste heat recovery

• Media: water, glycol-water mixtures, dielectric fluids, or treated cooling water

• Thermal cycling: repeated temperature changes during system start-stop and load adjustment

Key Flange Performance Requirements

1. Corrosion resistance The flange must resist water-induced corrosion, pitting, and long-term scaling.

2. Low leakage risk Connections must remain stable under thermal cycling and pressure fluctuations.

3. Clean inner surface Smooth, controlled surface finish helps reduce particle adhesion and biofilm formation.

4. Good sealability Gasket compatibility and flange face quality are as important as the base material.

5. Easy maintenance Modular data center projects often require flexible assembly and reliable disconnection.

Material Selection: 304 / 316L / Carbon Steel

Material selection is the first and most important step. Different cooling media, water quality, operating temperature, and project cleanliness levels will affect the final choice.

1. Carbon Steel

Carbon steel is more common in conventional industrial cooling systems, but it is not always the best choice for high-density IDC liquid cooling.

Advantages:

• Lower material cost

• Good mechanical strength

• Suitable for some large industrial cooling loops

Disadvantages:

• Lower corrosion resistance

• Risk of rust and scaling

• Requires more careful coating or passivation control

• Less suitable for high-purity or closed-loop cooling water systems

Recommendation: Carbon steel can be considered for non-critical auxiliary cooling circuits, but stainless steel is strongly preferred for the main liquid cooling piping close to IT equipment.

2. 304 Stainless Steel

304 is a common choice for general cooling water systems and less demanding IDC cooling projects.

Advantages:

• Good general corrosion resistance

• Lower cost than 316L

• Easy to process and weld

• Suitable for many water and glycol mixture systems

Disadvantages:

• Lower pitting resistance in chloride-containing water

• Not ideal for highly aggressive or high-purity cooling loops

• Long-term performance depends on water quality control

Recommendation: 304 stainless steel flanges can be used in standard IDC cooling systems with good water treatment. However, if the system involves higher chloride levels, stricter cleanliness, or longer design life, 316L is a better option.

3. 316L Stainless Steel

316L is the most recommended material for high-reliability data center liquid cooling flanges.

Advantages:

• Excellent corrosion resistance in cooling water and glycol mixtures

• Good pitting and crevice corrosion resistance

• Better stability under thermal cycling

• Suitable for high-purity closed-loop systems

• Easy to achieve clean inner surface finish

Disadvantages:

• Higher material cost than 304 and carbon steel

• Slightly higher manufacturing cost

Recommendation: 316L stainless steel flanges are the first choice for main liquid cooling piping, close-loop cooling, CRAH/CDU connections, and high-density AI data center cooling systems.

Connection Type Selection: Welded / Slip-On / Clamp

Different connection types affect installation speed, reliability, maintainability, and leakage risk.

1. Welded Flange

Welded flanges, especially weld neck flanges, provide high structural integrity and are commonly used in industrial piping.

Advantages:

• High structural strength

• Excellent seal reliability

• Suitable for higher pressure and thermal cycling

• Low long-term leakage risk

Disadvantages:

• Installation requires welding and NDT

• Higher installation cost

• Less flexible for frequent disassembly

Recommendation: Welded flanges are suitable for main supply and return piping in large IDC liquid cooling systems, especially for permanent underground or fixed piping runs.

2. Slip-On Flange

Slip-on flanges are widely used in moderate-pressure cooling water systems.

Advantages:

• Easy to align and install

• Lower machining cost

• Good for straight piping runs

• Suitable for many secondary cooling loops

Disadvantages:

• Lower structural strength than weld neck flanges

• Double welding is required for full reliability

• Not the first choice for highly cyclic or critical connections

Recommendation: Slip-on flanges can be used in auxiliary cooling water systems and non-critical piping, but they should be carefully specified for IDC main cooling loops.

3. Clamp Connection

Clamp-style connections are increasingly used in modular data center liquid cooling because of their fast assembly and disassembly.

Advantages:

• Fast installation and maintenance

• Easy to disconnect and reconnect

• Ideal for modular CDU/CDU connections

• Good seal performance when matched with proper gaskets

Disadvantages:

• Lower pressure rating than heavy welded flanges

• Requires careful gasket selection

• Not suitable for extremely high pressure or large pipe sizes in all cases

Recommendation: Clamp connections are highly recommended for skid-mounted units, modular cooling units, quick-connect piping, and areas that require regular maintenance.

Cleanliness & Inner Surface Treatment Requirements

Cleanliness is one of the most overlooked but critical requirements in data center liquid cooling. Poor internal surface quality can lead to particle shedding, biofilm growth, corrosion, and reduced heat exchange efficiency.

Recommended Cleanliness Levels

While specific project requirements may vary, IDC liquid cooling flanges should generally meet:

• Low residual oil and grease

• No loose scale or oxide layers

• Controlled inner surface roughness

• Proper sealing surface quality

• Clean packaging before installation

Common Surface Treatment Options

1. Pickling & Passivation Removes scale and free iron from the stainless steel surface, improving corrosion resistance.

2. Electropolishing Provides a very smooth inner surface, reducing particle adhesion and making the piping easier to clean.

3. Mechanical Polishing Suitable for visible surfaces and external finishes, improving appearance and basic cleanliness.

4. Passivated Inner Surface Recommended for closed-loop cooling water systems where long-term cleanliness is important.

Face Finish Considerations

The flange face must be compatible with the gasket. For liquid cooling applications, a smooth, defect-free face helps maintain seal reliability.

Common face types include:

• Raised Face (RF)

• Flat Face (FF)

• Ring Type Joint (RTJ) — less common in standard IDC cooling, but applicable in some high-pressure systems

Application Cases in Liquid Cooling Projects

Case 1: AI Data Center Closed-Loop Cooling

A high-density AI data center requires stable cooling for GPU clusters. The main cooling loop uses 316L stainless steel flanges with welded connections and pickled-passivated inner surfaces.

Solution:

• Material: 316L stainless steel

• Connection: Weld neck flange

• Surface treatment: Pickling and passivation

• Benefit: High corrosion resistance and low leakage risk

Case 2: Modular Data Center CDU Piping

A modular data center project requires fast assembly and easy maintenance for CDU connections. Clamp-style stainless steel connections are selected for the interface skids.

Solution:

• Material: 316L or 304 stainless steel

• Connection: Clamp connection

• Benefit: Quick installation, simplified maintenance, good sealing reliability

Case 3: Large-Scale IDC Secondary Cooling Water Loop

A large IDC campus uses a central cooling system with multiple secondary loops. Some auxiliary circuits use slip-on flanges in carbon steel or 304 stainless steel, depending on water quality and pressure class.

Solution:

• Material: Carbon steel / 304 / 316L, depending on loop importance

• Connection: Slip-on flange or welded flange

• Benefit: Balanced cost and performance

Liquid Cooling Flanges & Piping Components | Project Inquiry

As an experienced stainless steel flange and pipe fitting manufacturer, we provide flanges and piping components for data center liquid cooling projects.

Product Scope

• Stainless steel flanges: 304, 316L

• Connection types: Weld neck, slip-on, clamp, threaded

• Fittings: elbows, tees, reducers, couplings

• Surface treatment: pickling, passivation, mechanical polishing

Project Support

• Material selection based on cooling medium and operating conditions

• Connection type recommendation

• Cleanliness and surface treatment consultation

• Custom dimensions and drawings

• Project quotation for IDC liquid cooling loops

Inquiry Information

To provide an accurate quotation, please send us:

1. Nominal size and pressure class

2. Material grade

3. Connection type

4. Cooling medium and operating temperature

5. Cleanliness or surface treatment requirements

6. Quantity and delivery schedule