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Gas Generators – Part 2B – Nitrogen Generators

19 May 2023

In my previous installment titled Gas Generators – Part 2A – Nitrogen Generators, I explained that Restek sells two types of nitrogen generators, those for LC-MS and one for GC.  I provided a summary of how a nitrogen generator takes compressed air and turns it into high-purity nitrogen.  I then provided part numbers and descriptions for the nitrogen generator and maintenance kit which Restek offers for our gas chromatography customers.

In this installment, I will provide the models and maintenance kits offered by Restek for LC-MS.  These models have a wide range of flow rate capabilities.   Restek offers four Parker models: N2-04, N2-14, N2-22 and N2-35.  These generators use membrane separation/filtration technology (described in my previous post).  As a result, no electricity is needed.

N2-04

The Restek part number for model N2-04 is 22130.  The Parker Installation, Operation and Maintenance Manual can be found here.  TI_N2_04K_NitrogenGenerator.pdf (parker.com).    As with all nitrogen gas generators Restek sells, a source of clean compressed air is required.  Pasted below are the specifications which are suggested on page 3 of the manual.

Compressed Air - The N2-04 Nitrogen Generator requires a source of clean, dry compressed air for operation. The incoming air should be between 60°F and 110°F (15°C and 43°C) and be relatively free of water, compressor oil, hydrocarbons, and particulate matter. An oil content <0.01 mg/m3 is recommended. The compressed air dewpoint is recommended to be 40°F (5°C) at 145 psi. The inlet pressure of the compressed air supply should be regulated to 60 psig to 145 psig (4.1 barg to 10 barg).  Note: Do not use high temperature air directly from the compressor!

Please review the table titled “Nitrogen Flow and Inlet Air Consumption at Various Purities and Pressures” on page 6 of the manual.  It will provide information on operating pressure, flow rates and nitrogen purity.   A few things to keep in mind.
  1. The higher the inlet air pressure, the higher the nitrogen flow rates.
  2. The lower the nitrogen flow rates, the higher the nitrogen purity.
 
The maintenance kit for the N2-04 generator is Restek 21647.  This kit contains the following filters, which will need replaced on an annual basis.
  1. 1st stage filter (Parker 100-12-DX)
  2. 2nd stage filter (Parker 100-12-DX)
  3. Final filter (Parker GS-050-05-95)

N2-14

The N2-14 model is Restek part number 26077.  The Parker Installation, Operation and Maintenance Manual can be found here.  TI_N214H_NitrogenGenerators.pdf (parker.com).  Compressed air specifications are shown below.  These specifications are similar to the generator listed above but the maximum incoming air temperature should not exceed 95°F.

Compressed Air - The Parker Balston Nitrogen Generator requires a source of clean, dry compressed air between 60 psig and 145 psig for operation. The incoming air should also be between 60°F and 95°F (15°C and 35°C), and relatively free of water, compressor oil, hydrocarbons, and particulate matter. An oil content of <0.01 mg/m3 is recommended. The compressed air dewpoint is recommended to be less than or equal to 40°F (5°C) at 145 psi. The compressed air consumption varies with inlet pressure and nitrogen purity. Consult chart in System Specification Section to ensure an adequate supply of compressed air is available for the generator.

Please review the tables shown on page 12 of the manual for pressures, flow rates and nitrogen purity.  As with most generators, higher pressures = higher flows, higher flows = lower purity.

Restek sells two different maintenance kits for the N2-14 model.  One is part number 21648 (Parker # MK7572), which contains the items listed below.  Each filter should be replaced every 6-months.  Since two filters are included with each kit, you will have enough filters for a full year.
  1. Two 1st stage filter (Parker 100-12-DX)
  2. Two 2nd stage filters (Parker 100-12-BX)
  3. Two final filters (Parker GS-100-12-95)
 

The second kit available from Restek is 22135.  This kit contains the same filters as 21648, but it also contains two carbon filters (sometimes referred to as hydrocarbon scrubbers).  This kit is Parker MK7572C.  As with the other filters, each hydrocarbon filter should be replaced every 6-months.

N2-22

The N2-22 model is Restek 22131.  The Parker Installation, Operation and Maintenance Manual can be found here.  TI_N214H_NitrogenGenerators.pdf (parker.com)  You will notice that it is the same manual as for the N2-14 generator.  They use the same maintenance kits as for the N2-14 generator.

N2-35

The N2-35 model is Restek is 22133.  Just as with the N2-22 and N2-14 generators, the manual is the same, and so are the maintenance kits.

You may be asking yourself, if the manual and maintenance kits are the same for these three generators, how are the generators different?  The answer is capacity.  Below are the maximum nitrogen flow rates for each generator if the inlet air pressure is 100psi and the output nitrogen purity is 95% and 99.5%.  If your inlet pressure is different, additional flow rate values can be found on page 12 of the manual.
Model 95% purity 99.5% purity
N2-14 42.0 L/min 8.1 L/min
N2-22 61.2 L/min 13.3 L/min
N2-35 90.9 L/min 20.5 L/min
 

I hope you have found these two posts on the nitrogen gas generators informative.  In my next installment, I will discuss Zero Air Generators.