Electric Arc Welding Onboard: Essential Safety Checks and Precautions
Leif Andersen , Technical Product Manager Welding
Ships at sea depend for their safety upon the knowledge, skill and self-reliance of the crew when carrying out maintenance and repair work during the voyage and between dry-docking. To their owners, ships also depend on a healthy and competent crew to keep work-related injury, unexpected costs and vessel offhire to a minimum.
Performing in-voyage maintenance is part and parcel of the crewman’s job and tasks such as welding onboard are commonplace. Even so, it is essential that crew performing onboard welding do so in accordance with strict safety principles. The consequences of failing to adhere to the correct safety procedures or in failing to maintain the equipment can be very serious. For the crew, there is a risk of personal injury and long term health hazards.
For the vessel, the risks to safety and equipment integrity are just as serious and ultimately if the ship is damaged or diverted because of health or hardware problems, the impact can be financial too. It is crucial that welding equipment and gases are handled in a safe and secure way - safety in operation must always be a priority. Here are the safety checks and precautions that crew should adhere to before and during electric arc welding onboard.
Alternating Current (AC) will always be available onboard from the ship’s mains supply but crew should take note of the equipment they are asked to operate and make decisions accordingly.
There are two types of welding machines available; a transformer which takes in AC and supplies AC but at a lower voltage and rectifier/inverter machines which convert AC to Direct Current (DC) output at lower voltage.
Our advice is that crew should avoid using AC current when performing welding onboard ship. This is because in the case of accidental electrocution, AC current is transmitted through the human body, potentially causing seizures which can result in cardiac arrest. By contrast, a DC current will flow on the surface of the welder should he accidently become part of the electric circuit.
Voltage & Frequency
The main purpose of all welding machines is to bring high voltage down to suitable safe working voltage. The working voltage of a welding machine is referred to as Open Circuit Voltage (OCV) or sometime referred to as Non load Voltage. The definition of OCV is the voltage between the terminals of a welding machine that is switched on but not in use.
The UK Maritime and Coastguard Agency’s Code of Safe Working Practices for Merchant Seamen states that the maximum voltages should be as follows:
For rectifiers and inverters delivering DC: Max 70 V DC
For transformers delivering AC Max 25 V AC
Therefore the first thing that any crewman should check before they start working is whether the welding machine onboard is in compliant with these values. On most welding machines this is stated on the machinery plate.
WSS also recommends that crew should avoid using welding machines which use High Frequencies (HF) for starting the Tungsten Inert Gas (TIG) process. HF may cause interference with radio communications equipment and can also interfere with the start/stop controls of electronically operated equipment such as pumps. Low voltage TIG starting systems using the ‘lift arc’ process are available and make it unnecessary to use HF for starting the welding process.
Within the European Union and on ships flagged to EU member states, crew should also check if the machine is in conformance to the Conformity European (CE) mark. This is a form of ‘passport’ that allows goods to pass freely into and throughout Europe and also guarantees that the machine conforms to EU electrical directives & standards.
The standards that welding equipment should conform to in EU member states are as follows:
EN 60974-10 European Norm for electromagnetic compatibility.
EN 60974-1/5 European Norm for arc welding appliance: current sources for welding.
Operators should also look for the ‘S’ mark, indicating that the equipment is suitable for use in areas with increased electric shock hazard. This is of particular importance whenworking in potentially wet, humid and cramped locations such as the double bottom or in ballast tanks.
The Return Cable
Another area that requires certainty is the use of terms such as ‘earth’ and ‘ground’. The welding machine return cable is often referred to as earth or ground but it is neither.
The terms ‘ground’ and ‘grounding’ are used in US electrical engineering to represent electrical equipment that is securely bonded to the ground for safety reasons. In the UK the equivalent terms are ‘earth’ and ‘earthing’.
The return cable on an arc welding machine carries just as much current as the welding cable itself. Both the welding and return cables are part of the electric circuit. As a result, for safe welding the crewman must use a return clamp and cable, which must be placed as near to where the welding is taking place as possible.
Placing the return clamp to the nearest bulb iron will make the ship’s hull live in that area, creating the risk of electrocution. The welder will be actually standing on the return, possibly in poor quality footwear, using soiled gloves, in wet conditions, perhaps in salt water (an excellent conductor of electricity).
If lying flat on his stomach or his back in a sweaty boiler suit he is exposing large parts of the body to a live deck. If the welding cable is not well insulated then using the hull as a return can also cause a short circuit, creating sparks and an explosion risk. This kind of operation, combined with the use of a transformer delivering AC with high OCV can be fatal to the welder.
It should also be remembered that connecting the return cable direct to the ship’s hull can also cause the current to pass through ball bearings and pistons, causing damage. When welding on engine equipment the crewman should always run the return cable and clamp to where the welding is taking place and fasten it as close as possible to the welding area.
Make yourself safe for welding
To avoid electric shocks and the risk of electrocution and to ensure they are working safely, ships’ personnel should take the following precautions:
- Only use DC power sources with an OCV below 70 volts;
- Place the return clamp and cable as close to where welding takes place as possible;
- Remember that there is as much current running through the return cable as through the welding cable;
- Use of the hull as return conductor is against flag state regulations;
- Wear dry, insulated protective clothing and gloves in good condition, changing as necessary to keep dry;
- Insulate yourself from the work piece and return cable by wearing rubber-soled shoes or stand on a dry, insulated mat. Do not touch the return with any other part of your body;
- Use fully insulated electrode holders;
- Do not use worn, damaged, undersized or poorly spliced cables;
- Do not wrap cables carrying current around your body;
- Do not touch an energized electrode with bare hands;
- Turn off all equipment when not in use;
- Use only well-maintained equipment. Repair or replace damaged parts before further use;
- Wet working conditions should be avoided. Even a person's perspiration can lower the body's resistance to electrical shock.
These points may seem obvious but in our experience, there are often occasions when crew are not working safely. The results can be serious – and are most serious for the crew involved.
Case Study 1
A ship fitter was setting up his welding equipment and as he installed the whip to the feeder, one hand came in contact with the metal nozzle of the whip while his other hand was touching the wire from the feeder. This completed the electrical circuit which allowed 80 volts of electricity to run across his chest. The employee sustained burns to his hands and was transported to the hospital for treatment.
Case Study 2
A ship fitter arrived onboard the ship at the start of a shift, discovering water on the deck from an overnight rainstorm. He knew of the risk of shock, so he stood on the coaming around the door opening before reaching for the welding machine. Unfortunately, both his boots and work gloves were already wet. When the employee touched the welding machine, he completed the circuit and current ran through him, sustaining injuries that required hospital treatment.
Case Study 3
A crewman came back out on the ship’s deck after a rain storm. He was in a hurry to move the welding machine and complete a job before lunch. The fitter knew not to stand in the water while working with electrical equipment, but he failed to notice that the thin plywood on which he stood became submerged the moment he stepped on it. His clothes and boots were already wet from the storm. When he touched the equipment, the circuit was completed and current ran through his body. He too had to be taken to the hospital for treatment.