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Pepperl+Fuchs Blog

What Makes an Inductive Sensor Weld-Immune?

Posted by Zach Steck on Tue, Nov 12, 2013

Weld-immune inductive sensors are designed for use in weld-sensing applications. Inductive sensors installed in harsh welding environments are exposed to strong magnetic fields as well as sparks and weld slag. So what exactly is a weld-immune inductive sensor?

Inductive sensors for welding
There are three main features that make a sensor weld-immune:

  1. Magnetic-field-immune electronics
  2. Weld slag-resistant coatings
  3. High-temperature sensing face materials

Let’s take a look at these three features individually:

Magnetic-Field-Immune Electronics

The strong electromagnetic fields common to the welding process can cause an inductive sensor to provide false triggers or lock on the output. The use of magnetic-field-immune electronics allows the sensor to function without false signals in these environments, ensuring accurate detection of metal targets.

Weld-Slag-Resistant Coatings

During the welding process, molten fragments are expelled and can resolidify on surrounding metal surfaces. This is called weld slag. Weld-immune sensors feature a high-temperature coating to prevent weld slag from accumulating on their housings. Weld slag build-up on the face of the sensor can cause the sensor to lock on indefinitely. Slag can also be a problem for the body of the sensor if it accumulates on the threads, making removal of the sensor extremely difficult. The image below shows the effect of weld slag on an uncoated sensor:

Weld Slag on an Inductive Sensor

High-Temperature Sensing Face Materials

High-temperature-resistant plastics are used to protect the sensor face from the extreme temperatures common to welding applications. Some models feature a ceramic-coated sensor face for better protection against weld slag. It is very important to protect the sensing face from melting or eroding in these harsh environments.

Weld-immune sensing options are not limited to standard cylindrical inductive sensors. Pepperl+Fuchs also offers weld-immune products in the following inductive families:

Surface mounts

Weld-immune surface mount sensors are available in various housing options including flat pack, limit switch, Rhino (cube), and some low-profile designs. The surface mount sensors have a longer sensing range than the cylindrical styles.

Pile Driver

Pepperl+Fuchs’ metal-face inductive sensors are also available in weld-immune options. This is our most durable inductive sensor design and used in the most demanding applications. The weld-immune version is an all stainless steel housing coated with BlackArmor™. BlackArmor is an extremely tough, slag-resistant coating that ensures survivability in very aggressive welding applications.

Reduction Factor 1

Reduction Factor 1 weld-immune sensors detect both ferrous and nonferrous targets without any reduction in the sensing range. These are available in cylindrical, Rhino (cube), and flat pack housing styles.

Gripdicator

Gripdicator sensors are used in power clamps to confirm gripper extension and retraction. These are designed to be universally compatible with products from a variety of manufacturers. The Gripdicator sensors are weld-field-immune and offer extremely accurate gripper position indication.

Inductive Cylindrical Position Sensors

Weld-field-immune inductive cylindrical position sensors provide reliable end-of-stroke sensing in hydraulic or pneumatic cylinders. These sensors are rated for pressures up to 3,000 PSI and can be ordered in a variety of probe lengths ranging from 0.835 to 4.562 inches. They are available in two different probe diameters and with multiple connectivity options.

Designed to perform consistently in the demanding environments common to welding applications, our sensors provide a durable, resilient, and reliable option for metal detection within the welding process.

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Topics: Inductive Sensors

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