Assist Gas Cost & Selection Guide
Choose a machine-approved gas recipe that meets the job’s edge requirement, then calculate its delivered gas cost from measured flow, gas-on time, and current supply terms.
Cost Comparison by Application
| Job condition | Candidate process | Confirm before use | Quote inputs |
|---|---|---|---|
| Carbon steel; oxidation acceptable only if drawing/customer permits | Use the approved oxygen recipe if available | Material/thickness chart, edge acceptance, and sample result | Measured flow, active time, delivered price, and finishing |
| Carbon steel; oxide-controlled edge required | Use the approved nitrogen recipe if available | Customer finish, coating/weld route, machine support, and sample result | Measured flow, active time, delivered price, and avoided/rework finish |
| Stainless steel; specified edge/finish | Use the material-specific approved recipe | Grade, thickness, gas specification, pressure basis, and sample result | Measured flow, active time, delivered price, and quality route |
| Aluminum or another reflective alloy | Use only a recipe approved for the machine/material | Exact alloy/thickness, machine limits, edge acceptance, and sample | Measured flow, active time, delivered price, and quality route |
| Compressed-air process | Use only where the machine and compressor instructions allow | Required filtration/drying, flow, pressure, material, and sample result | Electricity, treatment, maintenance, leakage, and measured flow |
This table does not prescribe a gas for a material. Machine/OEM recipe and the accepted part control the choice; copy the approved recipe and measured use into the quote.
Gas Volume and Cost Calculation
| Quantity | Unit / basis | Calculation | Record before quoting |
|---|---|---|---|
| Job gas volume | m³ | Flow (m³/h) × gas-on minutes ÷ 60 | Separate cut, pierce, and purge minutes when their flow differs |
| Volume from metric flow | L/min to m³ | Flow (L/min) × gas-on minutes ÷ 1,000 | Keep the meter’s actual/reference-state label and measurement point |
| Delivered unit price | Currency / m³ | Cylinder or bundle delivered cost ÷ supplier-stated usable gas volume | Keep rental, delivery, and service fees separate; match the gas and volume reference conditions |
| Variable gas cost | Currency | Job volume (m³) × delivered price (currency/m³) | Use a quote or invoice for the same gas and reference-volume basis |
| Cost per accepted part | Currency / part | (Variable gas cost + allocated delivery/rental or air-system cost) ÷ accepted quantity | Allocate fixed charges by the shop’s documented method |
| Generator electricity cost | Currency / m³ | Measured system electricity (kWh) ÷ usable gas produced (m³) × tariff (currency/kWh) | Measure the full required system boundary, including feed compression and drying where applicable |
Worked volume example
Illustrative arithmetic only: 30 L/min × 10 gas-on minutes ÷ 1,000 = 0.300 m³. At your delivered unit price P per m³, variable gas cost = 0.300 × P. This flow value is not a recommended machine setting.
Actual and standard flow
Do not compare actual L/min with SCFH or standard L/min until the meter’s reference temperature and absolute pressure are known. Keep pressure as process context; pressure alone does not determine flow through a nozzle.
Reference data governance
Last reviewed: 2026-04-27 (reference-governance baseline). Page content reviewed: 2026-11-05. Gas cost and flow inputs come from supplier quotes and shop measurements; replace every placeholder with delivered gas contract terms, generator proposal data, and measured flow before quoting.
Oxygen (O2)
Use when:
Only a material/thickness recipe approved for the machine and job
Advantages:
- Can be appropriate where the qualified process and accepted edge permit oxygen use
- Use delivered cost and measured flow for the quote
- Record oxidation and downstream finishing requirements
Disadvantages:
- Oxidized edges may fail a finish or weld requirement
- Material compatibility and feed are machine-recipe specific
Nitrogen (N2)
Use when:
Only a material/thickness recipe approved for the machine and job
Advantages:
- Can support an oxide-controlled edge where a qualified recipe confirms it
- Compare finish and downstream work on an accepted sample
Disadvantages:
- Delivered cost depends on cylinder, bulk, or generator terms
- Flow, purity, and pressure must match the machine recipe and acceptance requirement
Air (Compressed)
Use when:
Only where the machine, compressor, and material recipe explicitly allow it
Advantages:
- Can use an on-site supply; cost still includes compression and air treatment
Disadvantages:
- Air quality and process suitability are equipment-specific
- Include electricity, drying, filtration, maintenance, and leakage in cost
On-Site Nitrogen Generation Review
Build the purchase case from supplier-backed and measured inputs.
Bottled Nitrogen Costs
Generator Investment
Compare on the same basis: Purchased-gas annual cost = measured annual volume × delivered price per m³ + annual rental and delivery charges. Generated-gas annual cost = measured system electricity cost + maintenance/service + equipment financing or an accounting allocation over the same comparison period.
For unit cost, divide each total by usable gas delivered at the same reference conditions and meeting the required purity and delivery pressure. Include required feed compression and drying in the generator system boundary; do not use a generator nameplate flow as measured output.
Purchase review: Treat generator decisions as a shop-specific model. Collect nitrogen cutting hours, delivered gas contract terms, electricity tariff, maintenance plan, financing terms, floor-space constraints, and a vendor proposal before comparing bottled supply with on-site generation.
Flow & Pressure Reference
Keep conversion factors handy when translating supplier data.
Common conversions
- 1 bar = 100 kPa ≈ 14.5038 psi; retain gauge or absolute basis.
- 1 m³ = 35.3147 ft³. Convert only when both flows use the same stated reference conditions.
- SCFH/standard L/min include specified reference temperature and pressure; record those conditions.
Volume and flow conversions do not change the gas reference temperature/pressure. Keep the supplier’s standard-state definition with any price comparison.
NIST SP 811: unit conversionsSetup checklist
- Record gas purity and dew point required by the machine recipe or supplier specification; no universal threshold is assumed here.
- Confirm regulator Cv and hose ID match the required flow rate.
- Record nozzle size/focus inside your processing parameter sheet for repeatability.
Gas cost and process notes
1. Compare gas choices by job requirement
Compare the delivered gas contract, edge requirement, post-processing route, and sample-cut record before choosing oxygen, nitrogen, or air. A lower unit gas price does not decide the route when the customer or drawing requires a different edge condition.
2. Review gas pressure
Use the current machine recipe for pressure and retain its gauge/absolute basis. Do not infer flow from pressure or change a setting outside the machine/OEM-approved range; use an approved process test and measured flow when conditions need review.
3. Fix Leaks Promptly
Even small leaks in your gas system can accumulate into meaningful annual cost. Check connections regularly with leak detection spray and use your own gas pricing to estimate the financial impact. Common leak points include quick disconnects, regulators, and nozzle seals.
4. Consider Bulk Gas Delivery
Compare bulk liquid and cylinder supply using your actual annual demand, delivered volume price, rental, delivery, tank/site requirements, and contract term. Ask suppliers for quotes on the same volume and reference-condition basis.
5. Evaluate compressed air only where approved
Compressed-air suitability, quality, pressure, and flow are machine and material specific. Follow the machine and compressor instructions for filtration and drying, and include measured compressor energy, treatment, maintenance, and leakage in the cost basis.
Cost Workflow Checklist
Tie gas pricing to the calculators so every quote reflects real consumption.
- 1. Capture contract pricing. Store cylinder rental, delivery fees, purity, and pressure requirements inside your sourcing log so operators and estimators share the same assumptions.
- 2. Calculate gas consumption. Feed flow (m³/h), active cutting time, pierce time, and price per m3 into the Gas Consumption calculator before rolling the result into shop-rate or quote math.
- 3. Push per-part cost downstream. Apply the hourly gas cost inside the Laser Cutting calculator or Price per Meter tool so final quotes show true margin impact.
The gas choice is part of the process
This reference is most useful when a shop is deciding whether a gas change improves the finished part enough to justify its time, consumption, or downstream work.
Gas belongs in the quote as both a consumable and a process choice. The right comparison is the cost of an accepted part, including edge condition and any finishing the selected gas creates or avoids.
A gas row cannot approve pressure, speed, nozzle, or material compatibility for a machine it has not seen. Keep the cut chart, flow evidence, and customer finish requirement with the decision.