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MetalKeen manufactures custom stainless steel welded pipes for vacuum piping systems and industrial water cooling loops. Produced from 304 and 316L stainless steel, our welded tubes feature internally electropolished surfaces, orbital TIG welding, and helium leak testing to ensure ultra-clean, leak-free performance in semiconductor process equipment, laboratory UHV systems, and precision liquid cooling applications.
A stainless welded pipe for vacuum and water cooling is a custom-fabricated tubular component that serves two distinct but equally demanding roles:
Vacuum Piping: Transports process gases, maintains vacuum integrity, and connects chamber components in semiconductor, coating, and analytical instruments. Requires ultra-low outgassing, smooth internal surfaces, and leak-tight welds.
Water Cooling Piping: Circulates deionized (DI) water or coolant to thermal management systems in lasers, RF generators, power electronics, and vacuum pumps. Requires corrosion resistance, clean welds without internal protrusions, and pressure-rated construction.
MetalKeen produces both straight lengths and prefabricated spool assemblies with flanges, fittings, and elbows to your exact system layout.
Table
Material | Grade | Vacuum Application | Water Cooling Application | Surface Finish |
|---|---|---|---|---|
304 SS | ASTM A312 TP304 / 1.4301 | Roughing lines, forelines, general vacuum | Non-corrosive cooling water, ambient loops | Mill finish; internally ground |
316L SS | ASTM A312 TP316L / 1.4404 | High vacuum (HV) and UHV process lines; corrosive gas handling | DI water, aggressive coolant, high-purity loops | Internal EP Ra ≤ 0.4 μm; external MF |
316LN SS | ASTM A312 TP316LN | UHV systems; low magnetic permeability requirements | High-pressure cryogenic cooling | Internal EP Ra ≤ 0.25 μm |
304L SS | ASTM A312 TP304L | Low-cost vacuum lines; welded assemblies without sensitization risk | General industrial cooling | Pickled and passivated |
Why 316L for Vacuum & Water Cooling?
Ultra-low carbon prevents chromium carbide precipitation at welds
Excellent corrosion resistance withstands DI water, halogens, and process chemistries
Smooth EP surface minimizes virtual leaks and microbial adhesion in cooling loops
Non-magnetic for ion beam and e-beam vacuum systems
Table
Specification | Range / Options |
|---|---|
Outside Diameter (OD) | 6 mm (1/4") – 406 mm (16"); custom sizes available |
Wall Thickness | 0.5 mm – 10 mm (SCH 5S, 10S, 40S, 80S) |
Length | Straight lengths up to 6 m; custom spools up to 12 m assembled |
Manufacturing Standard | ASTM A312, ASTM A269, ASTM A270, EN 10217-7, GB/T 12771 |
Welding Process — Longitudinal seam | TIG (GTAW) or plasma (PAW) welded strip; 100% RT or ET tested |
Welding Process — Circumferential joints | Orbital TIG autogenous welding; no filler for same-diameter joints |
Internal Surface — Vacuum service | Electropolished (EP) Ra ≤ 0.4 μm; optional Ra ≤ 0.25 μm for UHV |
Internal Surface — Water cooling | Mechanically polished Ra ≤ 0.8 μm; or EP for DI water purity |
External Surface | Mill finish, mechanically polished, or passivated |
End Connections | Plain ends, beveled for BW, flanged, Tri-Clamp, VCR, Swagelok, NPT/BSP |
Table
Feature | Description | Benefit |
|---|---|---|
Internally Electropolished (EP) | Electrolytic removal of surface layer; chromium enrichment | Reduces outgassing rate 10×; eliminates virtual leaks from surface pores |
Orbital Welding — Autogenous | Automated 360° TIG weld without filler wire | Smooth internal bead; no crevices for gas trapping; consistent quality |
100% Helium Leak Tested | Mass spectrometer testing of welds and joints | Guarantees ≤ 10⁻⁹ Pa·m³/s leak rate for HV; ≤ 10⁻¹⁰ for UHV |
Nitrogen Purged & Capped | Internal nitrogen fill with sealed end caps | Prevents oxidation and contamination during storage/shipment |
Bellows Flex Sections — Optional | Hydroformed or welded bellows integrated into spool | Absorbs thermal expansion and alignment tolerance |
Custom Manifolds — Multi-port headers | CNC machined distribution blocks welded to pipe | Simplifies chamber gas distribution |
Table
Feature | Description | Benefit |
|---|---|---|
Clean Internal Welds — Orbital TIG | Controlled penetration with flush internal bead | No flow restriction; no turbulence; no particle generation |
Pickling & Passivation | Post-weld chemical treatment | Removes heat tint; restores corrosion resistance in HAZ |
Internal Polishing — Ra ≤ 0.8 μm | Mechanical or electropolish of water wetted surface | Prevents biofilm adhesion; maintains DI water resistivity |
Pressure Tested — Hydrostatic | 1.5× operating pressure held for 30 minutes | Validates weld integrity for pressurized cooling loops |
Flanged or Grooved Ends | ANSI, DIN, or Victaulic-compatible | Easy field assembly and maintenance disconnection |
Insulation Jackets — Optional | Foam or mineral wool with SS cladding | Prevents condensation on chilled water lines |
Table
Step | Process | Quality Control |
|---|---|---|
Material Verification — PMI + MTR | Spectrometer check of coil or plate chemistry | Reject if non-conforming |
Strip Forming — For welded pipe | Roll forming of SS strip into cylindrical shape | Dimensional check of OD and wall |
Longitudinal Welding — TIG or PAW | Automated seam weld with argon backing | 100% RT (radiographic) or ET (eddy current) inspection |
Sizing & Straightening — Cold drawing or roller | Achieve final OD/ID tolerance and straightness | Laser micrometer; straightness gauge |
Internal Surface Treatment — Grinding, polishing, or EP | Belt grinding → mechanical polish → electropolish (if specified) | Ra profilometer; borescope inspection |
End Preparation — Cutting, beveling, facing | CNC pipe end prep machine | Angle and land dimension verification |
Prefabrication — Elbows, tees, flanges, manifolds | TIG welding of fittings to pipe spools | 100% VT; PT/RT on critical joints |
Cleaning — Degreasing, DI rinse, drying | Ultrasonic cleaning with semiconductor-grade solvents | Residue testing; particle count |
Leak / Pressure Testing — He leak test or hydrostatic | Mass spectrometer or water pressurization | Certificate per test |
Packaging — Nitrogen purge, end caps, sealed bag | Cleanroom or clean workshop packaging | Visual final inspection |
Table
Test | Method | Standard | Purpose |
|---|---|---|---|
PMI (Positive Material Identification) | XRF or OES spectrometer | ASTM E415 | Verify 304/316L chemistry |
Dimensional Inspection — OD, ID, wall, length | Ultrasonic thickness gauge; laser micrometer | ASTM A312 / EN 10217 | Confirm tolerance compliance |
Surface Roughness — Internal | Contact profilometer on sample coupon | ISO 4287 | Verify EP or polish Ra value |
Non-Destructive Test — Seam Weld | Radiographic (RT) or Eddy Current (ET) | ASTM E94 / ASTM E309 | Detect lack of penetration, porosity, cracks |
Non-Destructive Test — Circumferential Weld | Dye Penetrant (PT) or Radiographic (RT) | ASTM E165 / ASTM E94 | Detect surface and volumetric weld defects |
Helium Leak Test — Vacuum piping | Mass spectrometer with vacuum or sniff method | ASTM E498 / ISO 20485 | Verify ≤ 10⁻⁹ Pa·m³/s leak rate |
Hydrostatic Pressure Test — Water cooling | Water pressurization to 1.5× design pressure | ASME B31.3 / PED | Validate pressure integrity |
Cleanliness Verification — Particle / residue | Optical inspection; solvent extraction | SEMI F104 / Customer spec | Ensure particle-free for vacuum/DI water service |
Our custom stainless welded pipes serve critical systems across industries:
Table
Industry | System | Pipe Specification |
|---|---|---|
Semiconductor — Etch, CVD, PVD, ALD chambers | Process gas lines; vacuum forelines; chamber cooling loops | 316L EP; orbital welded; He leak tested |
Flat Panel Display (FPD) — OLED, LCD vacuum coating | Large-diameter vacuum manifolds; cooling distribution | 304 or 316L; DN100–DN400; internal polish |
Solar / Photovoltaic — PECVD, sputtering | Vacuum process piping; module cooling | 316L; flanged spools |
Laboratory & Research — UHV chambers, mass spectrometers | UHV transfer lines; cryogenic cooling | 316LN EP; Ra ≤ 0.25 μm; bellows integrated |
Medical Equipment — MRI, proton therapy, electron accelerators | Magnet cooling; vacuum beam lines | 316L; high purity DI water; pressure tested |
Laser Systems — Fiber lasers, CO₂ lasers | Resonator cooling; optics cooling manifolds | 316L EP; small OD precision tubing |
Power Electronics — RF generators, IGBT modules | Liquid cold plates connected by welded pipe | 304/316L; flanged or quick-connect |
Vacuum Pumps & Compressors — Dry pump, cryopump | Pump cooling jackets; exhaust lines | 304; water cooling spools |
In addition to straight pipe, MetalKeen supplies ready-to-install spool assemblies:
Table
Assembly Type | Components Included | Benefit |
|---|---|---|
Vacuum Spool with Flanges — ISO-K, CF, or KF | Straight pipe + welded flanges + bellows (optional) | Eliminates field welding; guaranteed leak rate |
Water Cooling Loop Spool — For tool or chamber | Pipe + elbows + tees + flanges/grooved ends + vents/drains | Reduces installation time; pressure tested at factory |
Manifold Distribution Header — Multi-port | Main pipe + CNC machined header + multiple outlet nozzles | Simplified gas/coolant distribution |
Jacketed Pipe Spool — Process + heating/cooling jacket | Inner process pipe + outer jacket pipe + baffles | Maintains process temperature; prevents condensation |
✅ Dual Service Expertise — Vacuum piping and liquid cooling from one supplier
✅ 316L EP Capability — Internal electropolishing to Ra ≤ 0.4 μm for UHV compatibility
✅ Orbital Welding — Automated autogenous TIG for flawless internal weld beads
✅ Helium Leak Tested — Every vacuum spool certified to 10⁻⁹ Pa·m³/s or better
✅ Pressure Verified — Hydrostatic testing for all water cooling assemblies
✅ Custom Prefabrication — Spools with flanges, fittings, and manifolds ready to install
✅ Clean Packaging — Nitrogen-purged, capped, and sealed for cleanroom entry
Q1: What is the difference between a vacuum pipe and a water cooling pipe in stainless steel? While both are made from stainless steel, vacuum pipes prioritize internal surface smoothness (low Ra), low outgassing, and extreme leak tightness (helium leak tested) to maintain vacuum integrity. Water cooling pipes prioritize corrosion resistance, clean internal welds without flow restriction, and pressure-rated construction to handle pressurized coolant circulation. MetalKeen manufactures both types with processes tailored to each service.
Q2: Why is internal electropolishing important for vacuum stainless steel pipe? Electropolishing removes a thin surface layer, creating a microscopically smooth, chromium-enriched surface with Ra ≤ 0.4 μm. This dramatically reduces outgassing rates (critical for achieving high vacuum), eliminates virtual leaks from surface pores and crevices, and improves corrosion resistance. For UHV systems, EP is essential; for roughing lines, mechanical polishing may suffice.
Q3: What stainless steel grade should I choose for my vacuum or cooling system? For high vacuum and corrosive process gas lines, 316L is the industry standard due to its weld corrosion resistance and low outgassing. For general water cooling with non-corrosive fluid, 304 is cost-effective. For UHV or low-magnetic applications (ion beam, e-beam), 316LN is recommended. For DI water high-purity cooling, 316L EP prevents metallic ion contamination.
Q4: Do you provide orbital welding for vacuum pipe joints? Yes. We use orbital TIG welding for circumferential joints, producing autogenous (no filler) welds with smooth internal beads and full penetration. This is the preferred method for vacuum piping as it eliminates internal crevices where gas can trap, and delivers consistent, repeatable weld quality that manual welding cannot match.
Q5: What leak rate can you guarantee for vacuum welded pipe? Our standard vacuum pipe and spool assemblies are helium leak tested to ≤ 1×10⁻⁹ Pa·m³/s, suitable for high vacuum (HV) applications. For ultra-high vacuum (UHV) service, we can achieve ≤ 1×10⁻¹⁰ Pa·m³/s through enhanced EP, electron beam welding, and meticulous cleaning protocols.
Q6: Can you prefabricate pipe spools with flanges and fittings to my isometric drawing? Yes. We manufacture complete spool assemblies from your P&IDs or isometric drawings, including straight pipe, elbows, tees, flanges (ISO-K, CF, KF, ANSI, DIN), Tri-Clamp fittings, and bellows flex sections. Every spool is leak tested or pressure tested before shipment, reducing field installation time and ensuring system integrity.
Q7: What pressure rating do your stainless water cooling pipes have? Pressure rating depends on OD, wall thickness, and material. Typical SCH 10S 316L pipe (e.g., DN50) is rated for ~20 bar at ambient temperature. We design and test each cooling loop to 1.5× operating pressure per ASME B31.3. Higher pressure ratings up to 100+ bar are achievable with thicker walls and 316LN material.
