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Medal Group
HL Cryogenics delivers advanced Vacuum Jacketed Pipe (VJP), also designated Vacuum Insulated Pipe (VIP), designed to solve the critical thermal management, thermodynamic equilibrium, and phase stability challenges in cryogenic liquid handling.
Heat transfer within a vacuum jacket is dominated by three mechanisms: conduction, convection, and radiation. By drawing the annular space to high vacuum (<1×10⁻³ mbar), gas conduction and convective currents are practically eliminated.
Cryogens like LN2, LOX, and LH2 have extremely narrow enthalpy margins between saturated liquid and vapor. Uninsulated or conventionally insulated pipes induce flash boiling, excessive Boil-Off Gas (BOG), and disruptive two-phase slug flow.
In humid cleanrooms, semiconductor fabs, and biobanks, polyurethane or aerogel insulation inevitably degrades, allowing water vapor ingress, mold proliferation, pipe corrosion, and icy hazardous condensation dripping onto equipment.
HL Cryogenics manufactures rigid and flexible VIP systems customized according to fluid dynamics, internal operating pressures, and piping thermal contraction loads.
| Nominal Size (DN / NPS) | Inner Tube OD × Thk (mm) | Outer Jacket OD (mm) | Design Pressure (Bar) | Heat Leak Rate - LN2 (W/m) | Heat Leak Rate - LH2 (W/m) | Standard Connection Type |
|---|---|---|---|---|---|---|
| DN15 (1/2") | 21.3 × 2.0 | 63.5 | 16 / 25 / 40 | ≤ 0.28 | ≤ 0.42 | Bayonet / Butt-Weld |
| DN25 (1") | 33.7 × 2.5 | 76.2 | 16 / 25 / 40 | ≤ 0.45 | ≤ 0.65 | Bayonet / Flange / Weld |
| DN40 (1-1/2") | 48.3 × 2.77 | 88.9 | 16 / 25 / 40 | ≤ 0.68 | ≤ 0.98 | Bayonet / Butt-Weld |
| DN50 (2") | 60.3 × 2.77 | 114.3 | 16 / 25 / 40 | ≤ 0.85 | ≤ 1.25 | Bayonet / Butt-Weld Sleeve |
| DN80 (3") | 88.9 × 3.05 | 168.3 | 16 / 25 / 40 | ≤ 1.30 | ≤ 1.95 | Field Welded Sleeve / Bayonet |
| DN100 (4") | 114.3 × 3.05 | 219.1 | 16 / 25 / 40 | ≤ 1.75 | ≤ 2.60 | Field Welded Evacuated Sleeve |
| DN150 (6") | 168.3 × 4.0 | 273.0 | 16 / 25 / 50 | ≤ 2.65 | ≤ 3.90 | Field Welded Evacuated Sleeve |
| DN200 (8") | 219.1 × 4.5 | 323.9 | 16 / 25 / 50 | ≤ 3.60 | ≤ 5.40 | Field Welded Evacuated Sleeve |
Choosing between factory-sealed static vacuum piping and continuously pumped dynamic systems dictates capital expense, maintenance regimens, and operational reliability.
Each pipe spool is evacuated to high vacuum in the factory, baked out under thermal desorption protocols, sealed with dedicated evacuation valves, and sustained with chemical getters.
The annular vacuum spaces of multiple piping sections are interconnected through vacuum jumper hoses and continuously or intermittently evacuated using high-vacuum turbomolecular pumping units.
Thermal continuity across field joints is critical. HL Cryogenics offers three connection technologies engineered for zero frost, high mechanical rigidity, and low pressure drop.
| Joint Technology | Thermal Efficiency | Installation Speed | Reusability & Maintenance | Recommended Fluid Services |
|---|---|---|---|---|
| Bayonet Coupling (Johnston Type) | High (Gas-Lock Seal) | Very Fast (Bolt-clamp connection in <15 mins) | 100% Demountable, seals can be replaced easily | LN2, LOX, LAR, LCO2 (Industrial & Cleanrooms) |
| Vacuum Insulated Flange | Moderate (Minor Flange Heat Gain) | Standard Flange Bolting Routine | High (Facilitates valve and component removal) | Utility battery limit transitions, plant skid skids |
| Field-Welded Evacuated Sleeve | Maximum (Continuous MLI Insulation) | Requires field butt welding, NDT, and pump-down | Permanent installation (Non-demountable) | LNG Bunkering, Liquid Hydrogen (LH2), Subsea/Buried lines |
Deep insertion profile creates an elongated heat conduction path along the thin stainless steel walls.
Boiling cryogen forms a captive warm vapor seal at the closed apex, preventing liquid contact with warm seals.
Silicone or Viton O-rings reside at warm ambient temperature, preventing brittleness and seal blowout.
Precision bolted outer clamp locks mechanical axial loading while dampening structural vibrational stress.
Austenitic stainless steel (SS304/316L) contracts by roughly 3 mm per linear meter when cooled from ambient (+20°C) to Liquid Nitrogen temperature (-196°C). In Liquid Hydrogen (-253°C), contraction reaches 3.3 mm/m.
Hydroformed multi-ply stainless steel bellows are integrated into the inner liquid transfer pipe. They absorb cyclical axial shrink-stretch fatigue without transmitting destructive bending loads to outer structural welds.
Radial support spiders engineered from high-strength G-10 glass-epoxy or proprietary ceramic polymers separate the internal cryogenic pipe from the outer jacket, maintaining exact concentricity with fractional conduction heat ingress.
Every spool incorporates an ASME-compliant vacuum pump-out port integrated with an internal rupture disk and spring-loaded relief plate to prevent catastrophic over-pressurization if inner pipe leakage ever occurs.
A truly efficient cryogenic network requires seamless integration between the VJP piping run and specialized peripheral hardware to manage pressure transients, degasification, and safety pressure relief.
Globe, check, and proportional control valves built inside an extended vacuum jacket. Extended bonnets ensure the stem packing seal stays at ambient temperature, completely stopping cryogenic freeze-up and stem seizure.
Installed at high elevation loop crests, these float-actuated mechanical vapor traps automatically vent accumulative BOG bubbles without permitting liquid cryogenic fluid loss, preserving pure liquid phase delivery.
Atmospheric or pressurized phase separation reservoirs supply low-pressure, bubble-free, subcooled cryogenic liquid on demand directly to high-precision test stations, MBE chambers, and freezing machinery.
Decades of field audits reveal critical recurring mistakes during piping system engineering and field erection. HL Cryogenics assists engineering teams in avoiding costly redesigns.
Whenever cryogenic liquid is trapped between two shut-off valves, ambient heat causes pressure to spike exponentially (up to 400 bar). Failing to incorporate dual thermal safety relief valves will cause catastrophic pipe burst.
Engineers accustomed to conventional water systems often oversize cryogenic piping. Oversized pipe dramatically increases surface area, wetted steel cooldown mass, and subsequent BOG boil-off consumption during chill-down cycles.
Clamping outer jackets with rigid unyielding steel brackets blocks the natural contraction cycles of the internal piping core, leading to premature bellow shear fatigue and internal vacuum rupture.
Positioning take-off lines on top of the main headers allows warm gas to accumulate in branch lines, creating gaseous vapor locks that starve downstream point-of-use equipment of saturated liquid.
Piping evacuated at room temperature without high-temperature vacuum baking outgasses volatile water vapor and hydrocarbons from the inner steel walls within months, ruining vacuum insulation levels.
Bending flexible vacuum hoses beyond manufacturer minimum bend radius crushes internal MLI foil layers together, creating hard thermal cold shorts and rapid vacuum failure.
Key technical answers for procurement directors, pipeline design engineers, and cryogenic system specifiers.
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