Voltage Reduction Device (VRD) in Welding: Beginner’s Guide

ByAndrew Valsamis Updated on Guides

As technology and safety awareness grow, more welding safety measures such as voltage reduction devices (VRD) are introduced. After reading this article, you will learn the basics of a VRD and if you need one.

Table of Contents

What is a welding voltage reduction device (VRD)?

A voltage reduction device (VRD) is a hazard reduction device that lowers the welder’s open-circuit voltage (OCV) to prevent electric shock. A VRD is often combined with stick welding machines used in damp environments.

The OCV is the voltage between the electrode holder (or stinger) and the working (or grounding) clamp when the power supply is on, but you are not welding. If you have a welding rod in the stinger and the working clamp is connected, the OCV is between the rod and the base metal.

Heavy-duty stick welding (SMAW) machines use a high OCV of up to 85V, for even more demanding work they can reach up to 110V. Affordable ones for light welding have a 50V OCV. A VRD reduces these voltages below 15V.

In many high-risk situations, VRDs are mandatory and specific laws control VRD’s specifications and usage. For high-risk welding, it is illegal to deactivate them.

What are the types of voltage reduction devices?

There are three VDR types:

1. External VRDs for heavy-duty work

External VRDs are stand-alone units. You connect them to the welding cable connectors. Then, you connect the stinger and the working clamp to the VRD.

This type is heavy-duty that can operate under demanding environments with safety:

  • They are impact and corrosion resistant.
  • Fully waterproof.
  • Can handle a wide range of welding voltage and amperage with a 100% duty cycle.
  • They also have built-in warning systems in case of failure.

As expected, external VRDs are very expensive.

2.VRD kits to add the function internally

VRD kits are small components that you can install permanently into welders. This way you can add a VDR to an existing welder.

The problem here is that each kit is compatible only with a specific heavy-duty welding machine.

3. Embedded VRDs

Finally, many modern stick welders, or TIG welders that can also stick weld, already embedded a VRD. Some machines allow you to choose whether or not to use it. You can also set the delay time before the OCV drops after stopping the arc. This helps when you want to reignite the arc for tacking.

Why is a voltage reduction device useful?

A voltage reduction device (VRD) is useful because it reduces the electric shock hazard under high-risk conditions. At the same time, it manages to provide the proper OCV when necessary.

Most stick welders use a high OCV to burn all available stick welding rods, especially basic or low-hydrogen rods such as the E7018.

An OCV value of 75V and higher will start the arc on the first try and prevents the rod from sticking to the base metal.

But the higher the OCV is, the higher the risk for an electric shock. When welding, the most probable point to get an electric shock is when changing the electrode.

If you use the correct safety practices, a shock from the welding current is minimal. Under typical conditions, a voltage of 75V or even 85V is not high enough to bypass the resistance of dry skin.

However, many jobs are performed under conditions that are not ideal:

  • Especially in summer, you sweat, and your gloves and clothes can absorb the sweat to dangerous levels before you realize it.
  • If you weld very early in the morning or close to water.
  • The welding leads might not be in good condition with exposed wire.
  • Many times, welders use gloves that are not in good condition and leave the skin exposed.
  • You might weld on or around metallic surfaces.

If your skin comes into contact with water, the natural resistance to electricity drops many times. Furthermore, if your skin is cut or burned, it’s even worse.

Under such conditions, even a low OCV of 30V can force the current to pass through your skin. Even a short electric shock can through you off balance. You might fall from a height, on hard surfaces, or on an extremely hot joint.

How does a VRD work?

The VRD monitors the resistance level of the welding terminals. When the resistance is high, for example, the air, your welding gloves, or even your skin, the VRD keeps a reduced OCV of 15V or even less.

An image of the voltage reduction device effect on open-circuit voltage during welding
VRD effect on open-circuit voltage before and after welding.

When you try to start the arc by touching the electrode on the base metal, the resistance drops to a very low level, and the VRD detects that. To be able to start the arc, the VRD allows the normal OCV value.

When you finish welding, the VRD detects the new high resistance levels and, after a short delay, reduces the OCV to 15V.

What are the disadvantages of a VRD?

The main disadvantage of a VRD is giving you trouble when you want to work with hard-to-start electrodes:

  • Basic or low-hydrogen rods such as the E7016 and the E7018.
  • Cellulosic rods such as the E6010 and the E6011.
  • Rods for high-alloy steel, for example, stainless steel.
  • Rods for nonferrous metals.

These rods need a high OCV of at least 75V for good results. If the VRD does not have a swift response time when the electrode touches the base metal, you will end up with arc strikes and a rod stuck to the base metal.

Arc strikes are considered a defect when welding hardenable metals because they can result in cracking.

Furthermore, a VRD that drops the voltage immediately after you stop the arc makes tack welding very troublesome or even impossible.

For these reasons, many welders avoid using a VRD or deactivating it, even illegally.

Modern VRDs, try to fight this problem by providing a rapid response time and a programmable time delay, making it easier to start and restart the rod.

Also, when VRDs were introduced, they were big and heavy reducing portability, and were prone to failure. However, these days technology offers compact VRDs often embedded into the welder and are very reliable.

How do you test a welder’s VRD?

The simplest way to test the VRD’s promised lower voltage is to check the electrode holder and the working clamp with a voltmeter or a multimeter (Wikipedia).

After that, there are dedicated VRD testers. These can range from simple testers that act like specialized voltmeters to heavy-duty testers that connect to the lead connectors and monitor the voltage in real time.

Do you need a VRD to weld?

If you are welding fabrications or doing repair work in dry environments and your PPE is always dry, you do not need a VRD. However, if you weld outdoors, in a wet or damp environment, or in conductive confined spaces, VRDs are necessary.

Conclusion

A voltage reduction device is vital when welding in wet or damp environments to minimize the risk of electric shock and serious injuries.

Existing welding machines can combine with an external or internal VRD. Some may come with an embedded one.

While VRDs are very useful, many welders find it troublesome to weld with low-hydrogen rods when a VRD is active.

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