Introduction
Search for PSA nitrogen generator manufacturers in India and you will find dozens of names, from small fabricators to international brands. Their quotes for the “same” plant can differ by lakhs, and the cheapest quote is often the most expensive plant to own. Every PSA generator works on the same principle, so the differences that matter are in efficiency, build quality, the molecular sieve, service and the contract terms (1).
This guide gives you a practical scorecard to compare suppliers, the questions to ask, and the red flags to watch for.
Start With Lifecycle Cost, Not Price
A PSA nitrogen generator typically runs for about 10 years, and over that time the electricity bill is several times the purchase price (1)(2). In our analysis of two real quotes for 100 Nm³/hr of 99.99% nitrogen, the plant that cost ₹10 lakh more to buy saved ₹1.2 crore over ten years, because it needed a 55 kW compressor instead of 75 kW (2).
Figure 1: 10-year cost of two quotes for the same 100 Nm³/hr, 99.99% duty (₹8/kWh, 24 hrs/day) (2)
| Vendor 1 | Vendor 2 | |
|---|---|---|
| Plant cost | ₹20,00,000 | ₹30,00,000 |
| Compressor power | 75 kW | 55 kW |
| Electricity per year | ₹52,56,000 | ₹38,54,400 |
| Maintenance over 10 years | ₹20,00,000 | ₹30,00,000 |
| 10-year cost | ₹5,65,60,000 | ₹4,45,44,000 |
Table 1: Lifecycle cost of two PSA nitrogen quotes (Absstem analysis) (2)
The Supplier Scorecard
Score each supplier from 1 to 5 on each line, multiply by the weight, and add up.
| # | What to evaluate | What to ask for | Red flag | Suggested weight |
|---|---|---|---|---|
| 1 | Energy efficiency | Guaranteed flow and compressor kW at your purity; kWh per Nm³ | Flow quoted only at 99% or 99.9%; kW not stated | 25% |
| 2 | Air-to-nitrogen ratio | Air consumed per Nm³ of nitrogen at your purity | Unwilling to state it | (part of 1) |
| 3 | Molecular sieve | Sieve make and grade, fill method, warranty period | Warranty under 5 years, or “topping up” listed as routine | 15% |
| 4 | Start-up time | Time to reach your purity from cold | More than about 15 minutes | 5% |
| 5 | Turndown / power saving | How power falls when demand falls | Compressor runs at full load whatever the demand | 10% |
| 6 | Air treatment and controls | Dryer, filters, oxygen analyser range, off-spec vent, remote monitoring | Analyser optional or not ppm-capable for high purity | 10% |
| 7 | Service and maintenance | CMC price and scope, response time, spares stock, engineers near your site | No CMC offered, or CMC excludes consumables | 15% |
| 8 | References | Running plants in your industry and purity, contactable | Only brochure photos | 10% |
| 9 | Documentation and compliance | Performance test, manuals, pressure vessel documents; PESO paperwork if filling cylinders | No written performance guarantee | 10% |
Table 2: PSA nitrogen supplier scorecard
The Points That Separate Good Suppliers
1. Energy per Nm³ at your purity
The running cost of a PSA generator is mostly electricity for the air compressor, so efficiency is decided by how much air the generator needs per Nm³ of nitrogen (1). A generator with an air-to-gas ratio of 4:1 uses less power than one at 5:1 for the same output, and the gap is paid every hour for ten years (1). Ask for both the flow and the compressor kW at your purity, because a plant that makes 100 Nm³/hr at 99% may make far less at 99.999%.
Cost per Nm³ = Electricity used per hour (kWh) ÷ Nitrogen produced per hour (Nm³) (1)
2. Molecular sieve and its warranty
In a well-designed plant, the sieve lasts the full life of the generator. Replacing it typically costs 30–40% of the generator price, so the warranty matters (1). Absstem offers molecular sieve warranties of up to 10 years (3).
3. Start-up time
Modern PSA generators reach purity in about 5–12 minutes, depending on purity; older designs can take 1–3 hours, wasting energy every start (1).
4. Power-saving mode
If your demand varies through the day, a generator that reduces power when demand drops can cut energy use roughly in proportion; for example, about 50% less power at half load (1). Ask about the turndown range.
5. Maintenance contract
Total maintenance over 10 years without a contract is the annual maintenance cost times 10, plus consumables, plus breakdown repairs (1). A Comprehensive Maintenance Contract (CMC) fixes that cost at a known annual fee, typically 7–10% of the plant cost per year (2), and makes sure maintenance is actually done.
6. Service on the ground
For an Indian plant, a supplier with engineers and spares in India shortens downtime. Ask where the nearest service engineer is based, what response time the CMC guarantees, and which spares are stocked locally.
Questions to Ask Every Supplier
- What flow do you guarantee at my purity and pressure, and what is the compressor kW?
- What is the kWh per Nm³ at my purity?
- What is the warranty on molecular sieves?
- How long does the plant take to reach my purity from start?
- What happens to power consumption at 50% demand?
- What air treatment and oxygen analyser are included?
- What does your CMC cost, and what does it include?
- Can I speak to two customers running similar plants?
- What performance test will you run at handover?
Red Flags in a Quote
- Flow stated without purity, or purity stated without flow.
- No compressor kW, or a compressor supplied “by customer” with no air requirement stated.
- Sieve warranty of one or two years, or routine sieve topping up.
- No written performance guarantee.
- Maintenance “as required” with no fixed CMC option.
Internal Resources – Next Steps
- Absstem’s proprietary ROI and Savings Calculator – compare two suppliers’ quotes
- nGEN – PSA Industrial Nitrogen Generator
- Absstem Shield – AMC and CMC for PSA plants
Consult Us
For PSA oxygen and nitrogen generators sized to your plant, contact us:
- Email: info@absstem.com
- Phone: 1800 547 0506 (toll-free)
- Website: absstem.com
References
- Absstem Technologies. (2024). How to Choose a Good PSA Oxygen or Nitrogen Generator.
- Absstem Technologies. (2025). Operational Cost Versus Capital Cost of a PSA Oxygen or Nitrogen Plant.
- Absstem Technologies. (2025). Myth vs Reality: Grade 5 Nitrogen.