Question

what two methods are used to start a plasma arc cutting arc?

hf arc and contact
hf and scratch
contact and scratch

Explanation:

Identify the core question

The question asks for the two primary methods used to start a plasma arc cutting (PAC) arc.

Analyze the options

• HF Arc and Contact: High-Frequency (HF) start uses a high-frequency, high-voltage spark to ionize the gas path and initiate the pilot arc without touching the workpiece. Contact start (often using a blowback start mechanism where the electrode moves away from the nozzle) initiates the arc through physical contact and separation inside the torch.
• HF and Scratch: Scratch starting is commonly used in TIG welding, but not standard for starting a plasma cutting arc.
• Contact and Scratch: Scratch starting is not a standard plasma arc starting method.

Determine the correct method

The two standard, widely recognized methods for initiating a plasma cutting arc are High-Frequency (HF) starting and Contact (or blowback) starting. Therefore, "HF Arc and Contact" is the correct choice.

Answer:

• (A) HF Arc and Contact (Correct answer)
• (B) HF and Scratch
• (C) Contact and Scratch