Safety checks before welding on board

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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 common place. 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 injuryand 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. This article examines the safety checks and precautions that crew should adhere to before and during electric arc welding onboard.

Alternating Current

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.

WSS’ 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 compliance 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 forstarting the welding process.

Compliance

Within the European Union and on ships flagged to EU member states, crew should also check if the machine is in conformance with 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 when working 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 throughthe 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 asnecessary 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 yourbody;
• 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 furtheruse;
• Wet working conditions should be avoided. Even a person’s perspiration can lowerthe 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.

Leif Andersen

Technical Product Manager Welding, Marine Products, Wilhelmsen Ships Service

Above article has been initially published atWilhelmsen Ships Service webiste and it is reproduce here with kind permissions. Further information about welding may be found at http://wssproducts.wilhelmsen.com/welding/