What cooling and power supply does a laser cleaning machine need?

The figures quoted come from manufacturer documentation for individual laser sources, machines and cooling units and indicate orders of magnitude — the details for the specific machine are binding.

Where electrical safety and inspections are concerned, this article replaces neither the risk assessment nor advice from a qualified electrician or legal advice.

Why clarification starts before delivery

Under the German Industrial Safety Regulation, the employer assesses the hazards arising before work equipment is used. According to § 3 (3), this risk assessment should already begin before selection and procurement.

Obstacles on the day of delivery can also lie in the peripherals:

• the socket does not match the machine plug
• the circuit is not designed for the power consumption
• the prescribed coolant is missing
• a required compressed air connection is not available

Air cooling: few peripherals, clear limits

With air-cooled machines, the waste heat from the laser source is released directly into the room air. There is no cooling circuit, cooling water or frost protection.

Manufacturer documentation shows this design mainly for lasers of lower power. JPT, for example, offers an air-cooled pulsed fibre laser source with 200 and 300 watts for cleaning that does not need an external cooling unit, and states an operating temperature range of 0 to 40 °C. At Clean-Lasersysteme, the low-power systems with 12 to 100 watts are described as air-cooled. For the mid-power systems from 150 to 600 watts, the product overview names air or water cooling, with a lower permissible ambient temperature for air cooling (36 instead of 40 °C). So there is no fixed wattage limit between the two designs.

The waste heat does, however, remain in the room, and a permissible temperature range applies here too.

At Beamlux, the portable BL Portable Pulse is air-cooled and can be operated on battery power. For work without a mains connection, the question of the socket therefore does not arise — operating time and charging times should then be matched against the machine data in advance.

Water cooling with a cooling unit

In the documents consulted on hand-held continuous wave machines and laser sources in the kilowatt range, water cooling is provided. A cooling unit — also called a chiller or recooler — pumps water in a closed circuit through the laser source and, depending on the design, through other components, and releases the heat into the room air.

How much cooling capacity is needed depends on the laser power. For its continuous wave fibre laser sources, Raycus specifies more than 5,000 watts of cooling capacity at 2,000 watts laser power and more than 15,000 watts at 6,000 watts; the cooling water temperature is specified as 22 ± 1 °C. The unit must therefore remove considerably more heat than the laser emits as radiation.

At Beamlux, the BL CW 2000 and the BL Welding Machine are water-cooled. For these, coolant, frost protection and dew point are added as planning points.

Cooling water, frost and longer breaks

Which fluid belongs in the circuit is specified by the manufacturer. The manuals consulted name purified, distilled or deionised water. The manual of the TEYU CW-5000/5200 cooling unit excludes fluids containing solids or corrosive constituents and suggests changing the water roughly every three months.

If the filled cooling unit is stored below 2 °C, the same manual requires an antifreeze additive; an agent based on ethylene or propylene glycol at no more than 30 per cent is recommended. For ambient temperatures between −10 and 0 °C, Raycus prescribes an ethanol solution at 30 per cent by volume and, below that, a cooling unit with a heating function in uninterrupted operation. The specifications differ considerably — the manual of the installed cooling unit and of the laser source is decisive.

According to the Raycus manual, the cooling water must also be drained if the machine is not used for a longer period, as permanent damage may otherwise occur.

Dew point and condensation

If the cooling water is colder than the dew point of the room air, moisture condenses on lines and cooled components. Raycus warns that condensation in the laser or on the output cable can cause irreversible damage, and prohibits operation below the dew point.

The manual contains a dew point table with a cooling water temperature of 22 °C as the reference. Two values from it:

• at 30 °C room temperature and 60 per cent relative humidity, the dew point is 21.5 °C — just below the water temperature
• at 30 °C and 70 per cent it is 24 °C — in that case the manufacturer requires countermeasures before operation

The measures named are feeding in clean, dry air via a connection provided for this purpose or lowering the room temperature, for example with a control cabinet air conditioner. In the event of condensation, TEYU recommends a higher water temperature or insulating lines and cooled parts.

Ambient temperature and installation site

For the Raycus continuous wave fibre laser sources, an ambient temperature of 10 to 40 °C, 30 to 70 per cent relative humidity and a level, vibration-free installation site are specified.

The cooling unit needs space for air intake and exhaust. For the TEYU CW-5000/5200, the manufacturer requires a clearance of at least 30 cm at the rear air outlet and at least 8 cm at the side air inlet; the dust filter gauze must be cleaned regularly. Larger units may require different clearances.

In addition, the following applies:

• For the fibre optic cable, Raycus specifies minimum bending diameters for transport and operation.
• The laser manuals consulted require a properly connected protective earth conductor.
• The DGUV publication FBHM-139 points out that laser equipment is always an effective ignition source. Combustible materials in the surroundings belong in the risk assessment.

Single-phase or three-phase connection

In the German low-voltage grid, there are 230 V between a line conductor and the neutral conductor, and 400 V between two line conductors. With laser machines, the connection type depends on the power class.

The manual of one manufacturer of hand-held fibre laser machines gives an example of this, with the nominal values 220 and 380 V, which correspond to 230 and 400 V in Germany:

• 1,000 and 1,500 watts laser power: single-phase, power consumption below 6 and below 8 kW respectively
• 2,000 and 3,000 watts: three-phase, power consumption below 10 and below 12 kW respectively

The Raycus laser sources from 2,000 to 6,000 watts are designed for 360 to 510 V AC and a connected load of 7.5 to 22 kVA.

For commercial use, there are CEE plugs and sockets to DIN EN 60309. According to MENNEKES, blue indicates the 200 to 250 V range and red 380 to 440 V; single-phase versions have two poles and an earth contact, three-phase versions three poles with an earth contact, possibly with a neutral conductor. Rated currents are, for example, 16 A or 32 A. The colour, number of poles and rated current of the machine plug should be known before delivery.

Power consumption and fusing

The laser power on the data sheet is not the power consumption from the mains. In the example above, a power consumption of below 10 kW is stated for a machine with 2,000 watts laser power.

What counts for the power supply:

• the power consumption of the complete machine, including any separate cooling unit
• short-term current peaks: with the TEYU CW-5000/5200, according to the manufacturer, the current can at times reach 6 to 10 A despite low average consumption
• other loads on the same circuit, such as the extraction
• a stable voltage: Raycus requires checking before switching on that the supply voltage is stable and the protective earth conductor is in order; an incorrect supply voltage can damage the machine

A suitable fuse rating cannot be derived from this across the board. If a socket has to be installed or a circuit changed, the employer must ensure under § 3 of DGUV Vorschrift 3 that this is done only by a qualified electrician or under their direction and supervision.

Compressed air and air quality

Some hand-held lasers need a compressed air connection. The manual of one manufacturer of hand-held fibre laser machines requires compressed air or nitrogen to be connected during laser operation; the compressed air should be clean and dry, at around 0.2 to 0.3 MPa, i.e. 2 to 3 bar. According to the manual, a burnt-in protective window must be replaced, as the focusing lens may otherwise be damaged.

Air can also play a role at the laser source: Raycus provides a connection for clean, dry air to prevent condensation — with a dew point of no more than 0 °C and particle and oil mist filters down to 0.1 µm.

Whether a machine needs compressed air, and of what quality, is stated in its manual. Where it is required, it should be checked in advance whether the pressure and treatment of the workshop supply are suitable.

Electrical safety and inspections

DGUV Information 203-071 describes portable electrical equipment as equipment that can be moved during operation or easily taken from one place to another while connected; transportable equipment is treated in the same way as portable equipment. How a mobile laser cleaning machine is to be classified is determined in the risk assessment.

Among other things, the following applies:

• According to DGUV Information 203-071, ready-to-connect portable equipment must at least undergo an inspection for visible defects such as transport damage.
• If the safety of work equipment depends on the installation conditions, it must be inspected by a person qualified to carry out inspections before it is used for the first time, in accordance with § 14 (1) BetrSichV.
• Work equipment exposed to damaging influences that can lead to hazards for employees must be inspected at recurring intervals. The employer determines and sets the intervals; according to DGUV Information 203-071, reference values from the implementation instructions for § 5 of DGUV Vorschrift 3 are intended as guidance.
• For testing electrical safety, FBHM-139 refers to the operating instructions and, for emergencies, names switching off the laser equipment, de-energised if possible. Where the machine is disconnected from the mains should therefore be established before it is first used.

Which inspections are required in your own company is clarified by the risk assessment, with expert advice where necessary.

Checklist for the installation site

Before delivery, these details should be available and matched against the place of use:

1. Connection type according to the data sheet: single-phase or three-phase, voltage and frequency
2. Power consumption as well as colour, number of poles and rated current of the plug
3. existing circuit and fusing, with a qualified electrician in the event of changes
4. Type of cooling and, with water cooling, coolant, change interval and frost protection
5. Room temperature and humidity over the course of the year
6. Clearances for air intake and exhaust of the machine and cooling unit
7. Compressed air: whether required, at what pressure and of what quality
8. Visual inspection after delivery and integration into the inspection organisation

Laser area, protective equipment and extraction are added as separate topics of the risk assessment.

Sources

• Raycus — Continuous-Wave Fiber Laser User Guide RFL-C2000S-HP to RFL-C6000S-HP — Operating environment, connected load, supply voltage, cooling water, dew point table, air connection.
• TEYU S&A — CW-5000/5200 Industrial Chiller User Manual — Current peaks, ventilation clearances, cooling water, frost protection, condensation.
• STYLECNC — Handheld 3 in 1 Laser Machine User Manual — Connection type and power consumption by power class, compressed air, protective window.
• JPT — CL3 air-cooled pulsed fibre laser, product data — Air cooling without an external cooling unit, operating temperature range.
• Clean-Lasersysteme — Product overview cleanPRODUKTE — Air-cooled low-power systems, mid-power systems with air or water cooling, and permissible ambient temperature.
• MENNEKES — CEE plugs: pin assignment, colours and clock-hour position — Identification colours, numbers of poles and rated currents to DIN EN 60309.
• Energie-Lexikon — Niederspannungsnetz — 230 V phase-to-neutral voltage and 400 V line-to-line voltage.
• BetrSichV — German Industrial Safety Regulation, § 3 and § 14 — Risk assessment before procurement, inspection of work equipment, inspection intervals.
• DGUV Vorschrift 3 “Electrical installations and equipment”, § 3 — Work on electrical installations by or under the supervision of a qualified electrician.
• DGUV Information 203-071 “Recurring inspections of electrical installations and equipment” — Edition January 2020; definitions, inspection before initial commissioning, inspection intervals.
• DGUV — FBHM-139 “Blasting work – cleaning and decoating with laser radiation” — As of 20.06.2024; ignition sources, testing of electrical safety, emergencies.

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