Nitrogen generators require significant capital expenditure regardless of the required gas volume. Companies investing in onsite generators will continue to pay for their new equipment even if their gas use decreases in the future. Conversely, there is no flexibility in volume should demand increase rapidly, unlike conventional gas supply. Consider whether it's worth the investment just to switch from external gas supply to internal supply – often the money could be better spent on capital that directly increases productivity and/or profitability.
An often-cited benefit of onsite nitrogen generators for laser cutting applications is avoiding the need to shut down equipment to refill the gas supply. However, with modern nitrogen supply modes, such as the CryoEase® service from Air Products, high pressure nitrogen can be refilled with no interruption to production. In fact, our gas delivery drivers can refill tanks independently, with no need for you to be involved in the delivery at all.
However, what is often omitted is the significant energy required to power the air compressor for a gas generator. As utility prices escalate year on year, this is a substantial cost to be considered.
Nitrogen generators are not the "set and forget" devices that many adopters expect them to be. As complex machines, they require ongoing maintenance to ensure that breakdown is avoided. As well as cost, this maintenance requires regular periods of shut-down which means either a loss in production time, or the necessity for a back-up nitrogen supply, often in the form of a cylinder pack with its associated costs. In addition, gas generator filters need to be replaced at least every 5 years, and can equate to as much as 75% of the original generator purchase cost.
Labour is always an expensive resource. Running an onsite gas generator requires continual input. Could your time and resources be better spent elsewhere in production? Often, the additional effort required to use an onsite generator means that conventional nitrogen gas supply is a far more efficient option.
Though there are applications where onsite nitrogen generation is beneficial, this is often not the case for laser cutting. In our experience, customers who move to gas generation often move back to cryogenic liquid gas supply as the more cost-effective and hassle-free option.
Production floor space can be calculated in revenue per m3. Gas generators are typically supplied on a skid which needs to be located close to the point of use in the workshop. By comparison, a cryogenic supply can be stored in an outdoor tank and piped to the point(s) of use, freeing up valuable production floor space.
Cryogenic nitrogen tanks come in a range of sizes to suit medium to high volume requirements. For laser cutting applications, often a mini-tank is sufficient – these require no special foundations and can be sited on a static or non-static plinth.
Alternatively, smaller volume applications typically use cylinder packs. Usually located close to the laser machine, these offer a significantly smaller footprint than the equivalent onsite gas generator.
In laser cutting, a clean unoxidised edge can only be achieved when using high purity nitrogen. Often operating at lower levels of purity are a false economy as increased preparation costs are incurred prior to the next stage of the process, such as painting or powder coating. Nitrogen sourced from large-scale air separation plants – such as those operated by Air Products – will be guaranteed at 99.998% purity. With continuous purity checks throughout the production process, large-scale producers can better ensure the required purity levels for the most demanding applications. The standard purity levels produced by gas generators is much lower and any increase in purity will involve a significant increase in running costs.
Therefore, for laser applications, it is always important to bear in mind the above considerations when assessing the best gas supply mode for your business.