Self-Pressurizing Liquid Nitrogen Dispensing Dewar

What is the Self-Pressurizing Liquid Nitrogen Dispensing Dewar?

A self-pressurizing liquid nitrogen dispensing dewar holds 25–230 L and builds 0.3–1.5 bar of pressure internally, so liquid can be drawn off through a valve without pouring. It is the right choice for laboratories that need to fill smaller dewars, cold traps or instruments from a safe, controlled source.

Overview

This dewar is built as a pressure vessel with a stainless steel inner tank, a vacuum jacket, a safety valve and a burst disc. A pressure-building valve diverts liquid through a vaporizing coil back to the headspace, raising pressure to the working level, typically 0.35–1.5 bar, which pushes liquid out through the withdrawal valve and hose. A pressure gauge and a liquid level gauge give the operator visibility, and a vent valve controls depressurizing. Models from 25 to 230 L are mounted on casters and have a fill port for refilling from a bulk tank. A phase separator can be fitted at the outlet to deliver liquid without gas, which stabilizes filling of narrow-neck dewars and cold traps. Because the vessel works under pressure, inspection, safety valve testing and operator training are essential.

How does it work?

A liquid nitrogen tank consists of an inner vessel, usually aluminum alloy or stainless steel, suspended inside an outer shell by low-conductivity neck tubes and supports. The annular space is evacuated to a high vacuum and filled with multilayer aluminized film and adsorbent, which suppresses convection, conduction and radiative heat transfer. The remaining heat leak, mostly through the neck, boils nitrogen off slowly as a vapor that exits through the vent. Because no power is needed, the vessel works as a passive store, and holding time depends on volume, neck diameter and insulation quality. Samples sit in canisters, racks or goblets, either submerged in liquid or held in the cold vapor above it. Pressurized dispensing tanks add a relief valve and a pressure-building coil that drives liquid out through a withdrawal valve.

What are the key features?

• Built-in pressure-building circuit allows pour-free liquid withdrawal without external pumps.
• Safety valve and burst disc protect against overpressure.
• Pressure gauge and level gauge allow quick verification before dispensing.
• Casters and fill port simplify movement and refilling from bulk tanks.
• Optional phase separator gives gas-free liquid at the outlet.
• Stainless steel inner tank resists cycling between cryogenic and ambient temperatures.

What are the technical specifications?

A typical self-pressurizing liquid nitrogen dispensing dewar configuration offers capacity (liquid) of 25–230 L, working pressure of 0.35–1.5 bar, maximum allowable working pressure of 1.4–2.4 bar, static evaporation rate of 0.8–2.5 L/day, safety devices of Safety valve and burst disc and inner vessel material of Stainless steel. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Self-Pressurizing Liquid Nitrogen Dispensing Dewar is used in laboratory liquid nitrogen distribution, filling storage dewars and cold traps, cryo-grinding and sample preparation and material testing at low temperature. Across the wider Liquid Nitrogen Tanks class, laboratories also deploy it for fertility clinic gamete and embryo storage, biobank sample storage and cell line and hybridoma banking.

Which standards and certifications apply?

Relevant standards and methods include ISO 21009-1, ISO 21010, GB/T 18442, EU Pressure Equipment Directive 2014/68/EU, ISO 20387 and IATA Packing Instruction 202. Certification candidates for this model are CE, ISO 9001 manufacturing, PED 2014/68/EU conformity and GB/T 18442 conformity; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Install tanks in a ventilated room with an oxygen sensor, away from drains and enclosed spaces, and on a level floor rated for the filled weight. Never seal a storage tank airtight, because boil-off gas must be able to escape. Inspect the vessel regularly for frost on the outer shell or a rising evaporation rate, which suggests vacuum loss. Measure liquid level with a dipstick or sensor on a fixed schedule and record it. Clean with mild detergent and dry completely before refilling, and keep canisters and lids free of ice. Users should wear cryogenic gloves, a face shield and closed footwear. Recertify transportable vessels according to local pressure-equipment rules.

How do I select the right Self-Pressurizing Liquid Nitrogen Dispensing Dewar?

Select a self-pressurizing dewar for regular dispensing into instruments and smaller dewars, and a transport dewar for occasional manual pouring, since it avoids lifting and pouring heavy vessels by hand. In an RFQ, specify capacity, working pressure, withdrawal rate, phase separator, connection thread, pressure-equipment certification requirements and the local inspection regime.

How does it compare with other Liquid Nitrogen Tanks variants?

The first decision is function: storage, transport or dispensing. For storage, choose the neck diameter and capacity to suit the vial format, since wide-mouth tanks hold more vials and allow easier access but lose liquid faster. Compare static evaporation rate and holding time at the stated fill level, and ask for the test method. For transport, prioritize vibration and tilt resistance, a lockable lid and a rated holding time during shipping, and confirm airline and IATA rules for dry shippers. For dispensing, check working pressure, withdrawal valve type and whether a pressure relief device is fitted. Consider construction material: aluminum is light, stainless steel is stronger. Also specify a level indicator or gauge, casters, and a lockable lid for material that requires audit control.