VRD stands for voltage reduction device. When a VRD is fitted to a welding machine it reduces the maximum unloaded open circuit voltage across the output terminals of the welder to a safe voltage normally this reduced voltage is about 12 volts (Australian Standards 1674.2 2003 state this voltage must be less than 35 Volts DC and 25 Volts AC). When a load of less than 200 ohms resistance is applied to the output of the welding machine the VRD will sense this and turn the welder to full output then welding will commence.

When the resistance across the output rises above 200 ohms or the electrode is removed from the workpiece then the VRD will turn the output of the welder back to a reduced output state.

The rules pertaining to voltage reduction can be obtained from website www.standards.com.au "Type in Standard no 3195".

Why is this necessary?

A lot of new welders and some older units have an open circuit voltage in excess of 105 volts D.C. or 85 volts a.c. This voltage is currently legal and in normal (dry) conditions may be quite safe.

The only trouble is 95% of sites do not have these normal conditions e.g. (damp or wet, caustic, salty, working at height or in a confined space) an electric shock in these conditions can and has proven fatal. (Ventricular fibrillation, falling from heights and inability to escape the power source when in confined spaces) not to mention the serious physical injuries sustained as a secondary result of an electric shock.
Electric shock from a welder power source can also cause serious internal injuries to the human body. These injuries are not always immediately noticeable.

Another safe work practice is to have a Dead Man (Isolation)switch in the electrode circuit, this switch will isolate the power from the electrode should the need arise. This system requires a trained observer to operate the Dead Man switch should the welding operator get into any life threatening situations.

It is also recommended all the above devices be tested regularly. SafeTac manufactures the VRD, Dead man switch and test unit mentioned above. Other VRD and safety devices can be designed to suit special operator and company requirements.

• Welding machine insulation levels should be checked regularly.
• Voltage Reduction Devices are used as an aid in operator safety.

SAFE WORKING PRACTICES MUST ALWAYS BE OBSERVED!

WELDER FIT CHART 

welderfit.pdf

The new products can now be fitted internally.

There is now VRD technology that is reduced to the size of two matchboxes.

A test unit is available that can be used to test the correct operation of the V.R.D.

All Safetac VRD units have flashing Red lights to indicate Danger the electrode is live and constant Green to indicate the output voltage is reduced and the electrode is safe to change.

If the site allows you can use an external DM1(200 Amp) or DM2 (400 Amp) Deadman isolation switch.

If you have the new VRD workshop fitted internally, it becomes part of the normal operating system.

No, the inverter model will not effect the equipment manufacturers duty cycle. The engine drive model has a duty cycle of 400 Amps @ 100%. This can be upgraded to 600 amps adding an extra contactor.

Yes. This method will function and offer an improved degree of safety over no protection at all but there is still a possibility of the operator coming into contact with full OCV 110 Volts during the weld iniation cycle. This is because of the welder design allows full OCV to be present when the trigger is pressed and welder is in an unloaded condition. With a VRD the welder is turned only in a loaded condition causing the output voltage to be around 20 to 40 volts rather than 110 or full OCV . Most welding shocks are caused by contact with the electrode or becoming the path for a poor work return circuit during the weld iniation or rod changing cycle. With a trigger operated activation either intentional or not it is possible for the operator to come into contact for longer than 2 sec with full OCV during the iniation stage. Also with a trigger operated welder if the work return circuit is incomplete and the operator presses the trigger to begin welding and at the same time is in contact with the work return circuit they would receive a full ocv shock. With a VRD welder the welder is not turned to full output until there is a metal to metal contact of less than 200 ohms which also pulls the output of the welding machine to a voltage of less than ½ of the normall ocv Also with a VRD if the work leads return circuit is incomplete (Bad Earth) the welder will not activate as the resistance is above 200 ohms offering a high degree of protection to the operator.

The only cables required for this VRD operation are your normal handpiece and work lead.

You no longer have to do this for the V.R.D. although you still need to reverse the welding leads.

The new range of VRD units available meets both of these requirements.

You can get the external model which comes in 304L or 316L stainless steel.

This V.R.D. has a very quick response time.

Yes the equipment has been tested by Western Power, Metering Division N.A.T.A.
Lab Accreditation No 47 for compliance to Australian Standards Ruling No 3195 Section 17,AS 1674.2 2003 WTIA Tech note 22-02.

Yes a full N.A.T.A. test report is available upon request.

All SafeTac VRD units have a .3 second post weld delay to enable tacking operations, this is the maximum time allowed under Australian Standards.