OSHA (Occupation Health and Safety Administration) has mentioned minimum protective shade number of welding glass for different welding processes and respectively for different current range.

What is Shade number???

Electromagnetic energy given off by an arc or flame can injure eyes and is commonly referred to as radiant energy or light radiation. A shade number indicates the intensity of light radiation that is allowed to pass through a filter lens to one’s eyes. Therefore, the higher the shade number, the darker the filter and the less light radiation that will pass through the lens.

The tables below list the minimum protective lens shade numbers for commonly used welding and cutting processes.

* As a rule of thumb, start with a shade that is too dark to see the weld zone. Then, go to a lighter shade which gives a sufficient view of the weld zone without going below the minimum.

** Values apply where the actual arc is clearly seen. Lighter filters may be used when the arc is hidden by the workpiece.

 

Reference: OSHA fact sheet

Keep reading, Happy welding

Thank you,

KP Bhatt

There are certainly many answers for what exactly does HOT PASS means in welding terminology and from where it actually evolved. Different people had different opinion and they are as below mentioned.

• It is to fill the weld bevel.
• It is to Melt and float out the wagon tracks left after the root pass.
• To release trapped gases.
• A significant other is that a large majority of pipeline welds are done in a clamp and under some sort of stress. A root bead and hot pass are generally the minimum amount of weld that must be done before the crane / side boom etc can be released and the weld can then be left to completely cool and be filled and capped at a later time / date.

But actually it’s a kind of a misnomer that second pass after root pass for example TIG joints is hot pass, even though its sometimes run colder than the root.

Then what exactly it is?

A hot pass is a term used in stove-pipe welding, when the bead is complete it is given a quick clean up with a grinder then the hot pass follows, it burns out the slag that is trapped at the junction between the bead and the pipe wall, the slag is often called wagon tracks.

The hot pass got the name from 6010 pipe joints where the second pass had to be “hot” enough to burn out any leftover slag from the root. The one thing you can probably count on is that the term “hot pass” is always referring to the pass after the root pass usually on pipe welds.

Keep reading, Happy welding

Thank you,

KP Bhatt