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NORHOF LN2 Freezer backup system  model #607

Do you want only ONE backup system, suitable for all your mechanical freezers?

• Always ready to use
• Every freezer will be prepared with extra cold exchanger.
• One portable backup pumpsystem, for use with up to 20 freezers.
• Connection of pumpsystem to broken freezer in just two minutes.
• No opening of the freezer needed.
• Start of cooling after switched ON in just one minute
• Cooling temperature to exact -85, also on the top shelf of the freezer.
• Pressure-less flow of LN2, without spilling, noise, vibrations etc. 
• Reservoir dewar of 50 Liters sufficient for holding the freezer for 24 hours on -85 (depending on brand and model of the freezer) 

picture shows pump mounted on a 35 Liter dewar, possible dewars are 25, 35 or 50 Liter       total system height 79 cm	Cold exchanger inside freezer, in the top
		connecting box on rear side of the freezer

Norhof manufactures cooling systems in which Liquid Nitrogen (LN2) is used as the cooling medium. LN2 is supplied without any pressure and filling an application is like a teapot filling a teacup.

You may compare our liquid nitrogen dispenser system with a water tap , but instead of giving water, it gives LN2, starting  with some drops, up to 1 Liter/minute.

Liquid Nitrogen (LN2)

The pump will gently fill the cold exchanger with LN2, depending of the temperature in the top of the freezer. The cold exchanger will become –196 degrees Celsius, creating a falling cold flow. The warmer gas from the top will be exhausted, thus cooling the interior of the freezer from the bottom to the top. The level in the cold exchanger is controlled, and the temperature in de top is controlled, so the pump stops automatically when the temperature of -85 is reached.

Usage

The majority of this system find use in the field of laboratories, research centers etc. where a backup system should be stand-by in case of incidents with freezers, or during maintenance of a freezer.

• Backup of freezers during maintenance
• Backup of freezers during failure
• Extra cooling when a lot of warm samples is placed in a freezer.

* For automatic filling of other small applications we have the #900 serie of microdosing pumps, see the left column

WORKING PRINCIPLE The pressure above the liquid level inside the dewar is built by heating a small amount of liquid in the bottom of the dewar.  With only 100 mBar of overpressure, the liquid will gentle rise out of the rise pipe and fill the cold exchanger in the freezer. Because we evaporate some LN2 to build pressure, there is no adding of ice inside the dewar, such as with manual systems which use air from the environment.

In the Norhof LN2 cooling systems Liquid Nitrogen is stored in pressure less Dewars. When LN2 is required, a small overpressure is generated by a small heater element in the LN2, and liquid flows out of the system like water from a tap, without spilling, noise, vibrations etc.

The advantages are numerous:

• the system is extremely safe

the operator comes not in contact with LN2.

• the system is time saving, and thus sample saving

any operator can install the system on a freezer in just minutes.

• the system can cool the freezer just with a press on the start button

this means that the system is ready for use 24 hours a day, and starts cooling in 3 minutes.

• the system delivers LN2 without any pressure

this means without noise, vibration, excessive waste, etc.

• there is no external LN2 valve used

that implies no unnecessary heat input which spoils a lot of LN2

• there is no internal LN2 valve in the pump

LN2 comes out of insulated tubing without making contact to warm metallic parts, so very fast

• there is a very low thermal masse to cool down in the pump

Filling efficiency is better than 90%, due to very less loss for cooling down pump parts.

• there is a very low thermal connection to the ambient temperature

This means that the system is extremely economic in stand-by. Typical usage less than 0,5 Liter / day

• P.E.D. 99/36/EC (Pressure European Directive) for pressurized vessels does not apply for this system

The maximum possible pressure is lower than 300mBar.Therefore this system is allowed to be used inside the lab, near your working place, without danger.

Technical Specifications

Static evaporation rate	< 0,5 liters per day
Flow rate	Dripping up to 1 Liter/minute
Maximum working pressure	< 300 mBar
Reaction time	40-80 seconds (depending on level in dewar)
Power connection	115V / 230V AC with supplied power supply or 12 Volt AC/DC
Power consumption	average 10 Watts, during pumping 50 watts
Storage container volume	25 Liter(on request)	35 Liter(on request)	50 Liter (standard)
Outside dimensions (round)	395	480	500 mm
Height dimensions	736	643	727 mm
Weight (empty,full)	10 / 31	13 / 41,5	17 / 51,5 kg
System includes	Dewar, pump, flexible fill hose 1.00 m, power supply
Alarms/warning                 acoustical/ visual / mechanical	Dewar empty, 5 liters left, broken sensor, overpressure protection
per freezer, backup kit	Cold exchanger, including level sensor and temperature sensor, exhaust tube. Connection box, including cryo connector for pomp hose
included	Transport trolley 5 wheels (12 cm height)
Options	Clamp for pump to hang on rear side of a freezer

for more models use links in left column