How to design the technical gas supply to a laser machine ART-159

Start with a process matrix, not a pipe

One fiber laser may cut carbon steel with oxygen, stainless steel or aluminum with nitrogen, and—in OEM-permitted scenarios—with treated compressed air. Linde describes oxygen as an active assist gas and nitrogen as an inert gas for clean cutting. These are different technological processes, so a “universal supply line” without separate requirements creates a risk of inconsistent quality and incorrect switching.

For each representative group of parts, record:

• material, thickness, and surface type;
• the gas permitted by the process sheet;
• purity, pressure, and permitted range at the machine inlet according to the OEM;
• operating and short-term peak flow;
• piercing, cutting, pause, and purge durations;
• the number of simultaneously active machines;
• edge-quality criteria and whether an oxide layer is acceptable;
• the consequence of a brief pressure drop or purity change;
• the need for backup while changing the supply source.

The starting document is a time profile, not an average “cubic meters per month.” An average helps estimate gas purchasing, but does not prove that the vaporizer, regulator, and supply line can handle simultaneous piercing or several machines switching to a high-flow mode.

Separate gas requirements from network requirements

Purity affects the process but does not replace the required pressure. Pressure at the source does not guarantee pressure at the machine. A large pipe diameter does not compensate for insufficient vaporizer capacity. The specification therefore has four independent groups.

| Group | What to confirm | Where to measure | |---|---|---| | composition and purity | gas specification, moisture, impurities | batch certificate and agreed monitoring point | | pressure | minimum, operating range, permitted maximum | machine connection point under flow | | flow | steady, peak, peak duration, simultaneity | actual operating cycle | | availability | reserve, changeover, low-level signal | source, manifold, and supervisory system |

Linde publishes its own recommended LASERLINE specifications and emphasizes alignment with laser manufacturers' requirements. This usefully confirms the importance of purity, but is not a universal recipe for every machine. The current manual for the ordered configuration and OEM approval take priority in the design.

Select the supply source by profile, not fashion

### Individual cylinders

Suitable for small or infrequent consumption, backup, or testing. Their weaknesses are frequent changes, limited simultaneous flow, pressure decline as they empty, and many manual operations. A cylinder cannot be assessed by its geometric volume alone; the supplier must determine the available gas quantity and withdrawal rate in the required mode.

### Cylinder manifold or bundles

A manifold increases the available reserve and may provide automatic bank changeover. It also adds headers, check valves, regulators, safety devices, and a safe replacement procedure. Determine whether the machine will experience a dip during changeover and how the system reports the transition to backup.

### Microbulk or cryogenic tank

This solution reduces manual cylinder replacement and may better suit steady, substantial demand. However, the installation includes storage, a vaporizer, regulation, a filling area, protection from vehicles, telemetry, and permitting requirements. Capacity is not determined by storage volume alone: at peak withdrawal, vaporization, ambient temperature, and operating pressure may be critical.

### On-site generation

PSA or another technology may be economical for steady consumption if it actually achieves the required purity, pressure, and flow. A generator needs treated air, electrical power, maintenance, and buffer storage. If it covers average flow but not a brief peak, a receiver, booster, or another agreed circuit is required. Linde describes on-site plants with backup as a distinct reliability requirement, not an optional embellishment.

Calculate simultaneity through scenarios

Build a cycle for each machine: standby, pre-purge, piercing, cutting, transition, and final purge. Then overlay machine cycles in several scenarios:

1. a normal mixed schedule; 2. the most demanding verified mode of one machine; 3. a permitted simultaneous peak of two or more machines; 4. manifold changeover or tank refilling during production; 5. degradation of one source or compressor; 6. future expansion already approved in the layout.

Do not reduce design flow with an arbitrary “they never all cut at once” factor. If scheduling genuinely prohibits certain overlap, this must be a controlled restriction with a responsible person, not a verbal promise. Conversely, there is no need to design the entire network for an imaginary overlap that is technologically impossible. The largest credible combination is required.

There is a pressure-drop budget from source to machine

Pressure in the tank or after the first regulator is progressively consumed by the pipeline, fittings, valves, filters, drying, meter, flexible connection, and local fittings. The designer prepares a hydraulic calculation for the specific gas, pressure, temperature, and flow. A general-purpose air table cannot be used as a completed oxygen or nitrogen calculation.

A pressure budget is useful:

| Section | Inputs | Criterion | |---|---|---| | source and vaporizer | minimum available pressure, peak flow | covers the worst permitted state | | primary regulation | range and flow capacity | stability without freezing or hunting | | main line | length, diameter, material, fittings | permitted drop at peak flow | | local assembly | shutoff, filter, gauge, hose | compatibility and service access | | machine inlet | OEM pressure/flow envelope | verified by a dynamic test |

A gauge without flow may show a normal value even though pressure drops during cutting. Commissioning therefore includes measurement at the critical point during actual withdrawal, preferably with rapid-change logging.

Materials and components must be compatible with the gas

Oxygen service requires particular cleanliness and compatibility. OSHA 1910.253(b)(5)(i) explicitly prohibits oil or grease on oxygen valves and fittings and handling them with oily hands or gloves. Components, seals, piping, regulators, valves, and cleaning must be specified by the design for the particular gas, pressure, and temperature. A “for air” label does not establish suitability for oxygen. This reference is a US jurisdictional requirement and does not replace current Ukrainian regulations or an oxygen-system design.

Each line needs:

• unambiguous gas and direction marking;
• protection against incorrect connection;
• compatible materials, seals, and lubricants, or their absence;
• protection of fittings and pipes against forklift impact;
• access to normal shutoffs without entering a hazardous area;
• controlled depressurization for service;
• technical documentation and an as-built diagram;
• a cylinder-change and leak-check procedure.

Field pipeline testing is performed under an agreed procedure. EIGA Doc 254 emphasizes a safe means of depressurizing sections and specific requirements for test media in oxygen systems. This is work for a competent organization, not an instruction for DIY “pressure testing” or increasing pressure.

Provide gas-quality control

A supplier certificate confirms the product at a defined point, but there is a network between the source and nozzle. Moisture, particles, or the wrong material may remain inside after installation. Contamination may occur after repairs. Compressed air also introduces oil, water, and particles from the compressor system.

The control plan defines:

• where the gas certificate is accepted;
• how the cleanliness of a new or repaired line is confirmed;
• which parameters are monitored continuously and which periodically;
• how a process defect is distinguished from a gas-supply problem;
• who may return the line to service;
• where pressure, flow, and alarm trends are stored.

Do not install a random filter “for improvement.” It may introduce a pressure drop, an incompatible material, or a new contamination point. Every element must be included in the calculation and replacement schedule.

Backup is a controlled transition

A stock of cylinders beside the machine is not a complete backup. You need to know how long it supports the critical mode, who initiates changeover, whether cutting is interrupted, how backflow is blocked, and when an order is sent to the supplier.

A practical failure matrix:

| Event | Automatic response | Production decision | Evidence | |---|---|---|---| | low primary stock level | early notification | finish the schedule or switch to backup | threshold test | | pressure drop at peak flow | controlled stop according to OEM | do not mask it with the regulator | inlet trend | | noncompliant purity | prohibit the affected process | isolate the batch/line | analysis and record | | generator failure | switch only to approved backup | reduced list of modes | test | | leak or damage | isolation without hazardous approach | emergency procedure | training and inspection |

Backup may have different economics and even a different permitted production profile. For example, it may support finishing the current sheet but not the entire overnight queue. This is a valid limit if the scheduler knows it.

Source location and routing

Gas infrastructure competes for space with sheet deliveries, service zones, extraction, and evacuation routes. Protect the source and fittings from impacts; do not place them in a random recess or block them with a future rack. Store and use cylinders according to local regulations and supplier rules; the general requirements of OSHA 1910.101 refer to compressed-gas handling rules and serviceable relief devices.

The plan must show:

• the source area and filling route;
• physical protection and access control;
• ventilation and hazardous zones, if identified by the assessment;
• main lines with elevations and crossings;
• isolation and monitoring points;
• vaporizer, booster, buffer, and manifold locations;
• each machine connection;
• access for inspection, replacement, and emergency response;
• future expansion zones.

Exact distances, cylinder quantities, and site requirements are determined by Ukrainian regulations, the gas supplier, and a competent designer. Numbers from a foreign rule must not be transferred automatically to a local site.

Commissioning must take place under actual withdrawal

A static leak test is necessary but does not prove production capability. The acceptance program must include correct marking, cleaning documentation, pipe tests, regulator settings, stock-level signals, backup changeover, and a dynamic peak.

During test cutting, record pressure and, where available, flow at the source and near the machine. Run the most demanding agreed scenario, not just a thin demonstration sheet. For multiple machines, test permitted simultaneity. Assess part quality together with process parameters so that a nozzle, focus, or material defect is not attributed to the gas network.

Acceptance criteria should be numerical only where they come from the OEM and design. Replace “there is enough pressure” with a record of the minimum under actual peak flow, stability throughout the cycle, and the absence of unapproved switching.

Close acceptance with an evidence package

A signature on a general acceptance report does not show which party checked each requirement. An acceptance matrix is useful: requirement, responsible party, verification method, expected record, actual result, deviation, and the role authorized to close it. The gas supplier confirms the product and supply conditions; the designer confirms the agreed architecture; the installer provides the as-built diagram and test reports; the OEM confirms permitted machine-inlet parameters; and the site owner confirms operating roles, training, and response.

A separate open-item register prevents unresolved requirements from being hidden behind “the system works.” Each item receives a risk description, temporary restriction, owner, deadline, and retest criterion. If dynamic operation, purity at the point of use, or backup functionality is unproven, restrict production release to verified materials and modes or keep it on hold.

After a deviation is resolved, retain not just correspondence but the specific report, current diagram revision, and link to the retest result. A source replacement, addition of a second machine, or section repair then triggers a controlled review of precisely the assumptions that changed, rather than a new acceptance “from memory.”

The handover package should also include monitoring points and data owners so that a shift change does not lose the context of accepted restrictions.

Common mistakes

• calculating the system from the monthly bill rather than the peak cycle;
• taking purity from an advertising page instead of the machine manual;
• measuring pressure only without flow;
• selecting a tank without checking the vaporizer and regulator;
• using one pipe or component for incompatible services;
• failing to account for purges, leaks, and bank changes;
• installing a generator without a buffer or backup;
• leaving fittings in the forklift traffic area;
• omitting filters and valves from the pressure budget;
• not defining the procedure after a line repair;
• treating compressed air as an unconditional substitute for nitrogen;
• not checking simultaneity after adding a second machine.

Final checklist

• OEM requirements have been obtained for each permitted gas and process;
• a steady and peak time profile has been built;
• the largest credible simultaneity has been defined;
• source, vaporizer, regulation, and backup have been considered as a system;
• pressure drop to the connection point has been calculated;
• materials and components are approved for the specific gas;
• the oxygen circuit has verified cleanliness;
• piping is marked and protected against mechanical damage;
• pressure is monitored under flow and an early stock-level signal is available;
• the backup changeover procedure has been tested;
• documented pressure/leak tests have been performed by a competent party;
• commissioning includes the actual most demanding production profile;
• the as-built diagram, responsibilities, and maintenance schedule have been handed over to production.

A well-designed gas system is unobtrusive in operation: it does not force the operator to adjust the regulator, does not change quality between the beginning and end of a bank, and gives early warning of low stock. Its quality is proven by data at the machine connection point, not just source specifications.

Safety boundaries

• No universal pressures, flows, diameters, purity levels, or reserve quantities are given.
• No instructions for installing, testing, or repairing gas pipelines are provided.
• Foreign-source requirements are not declared to be Ukrainian regulations.
• Compressed air is not presented as an unconditional substitute for nitrogen.
• The topic does not duplicate electrical supply ART-152, compressor ART-155, or extraction ART-157/158.
• Status is DRAFT; integration, sitemap, robots, and publication have not been touched.

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