Hi Vasu,
The main function of a hot pass is to provide feed to the shrinking root pass weld metal lest it shrink-cracks. The root pass has to penetrate and fill the root gap and initiate the joint. Once it gets a proper metal feed by way of a hot pass, it will do its job well. That is why HP is conducted immediately after the root cleaning operation is over and the root pass is still hot, hence maintaining the same welding set up as used for root pass (and welders) is highly recommended.
It can be seen then why: The hot pass generally uses a higher than normal amperage setting (approx. 10% higher than root amps setting) and a fast travel speed. The latter to reach all shrinking areas in time. No welding will stop before RP+HP are complete as a minimum.
Shashank Vagal
--- On Sun, 28/11/10, M.Shankar <mails_shankar@yahoo.co.in> wrote:
From: M.Shankar <mails_shankar@yahoo.co.in>
Subject: Re: [MW:8419] HOT PASS
To: materials-welding@googlegroups.com
Date: Sunday, 28 November, 2010, 6:19 PM
Hi Mr. Rao
About & Purpose "HOT PASS" The surface of a root pass may be irregular, have undercut, overlap, slag incl., or other defects, depending upon the type of weld and the condition of the root pass. The surface of a root can be cleaned by grinding or hot pass.
A hot pass can be used to correct some of the problems caused by a poor root pass. The hot pass may be a hotter than normal filler pass or it may be made without adding extra filler.
A hot pass can be used to correct incomplete root fusion or excessive concavity of the root surface, and improper penetration also. Eg.1: Improper fusion generally is caused by insufficient heat and temperature for the joint. To correct this condition, a hot pass is used without adding more filler metal. Eg.2: Concave root surface are generally caused by insufficient filler metal for the joint. To correct this condition, a " hot filler pass" is used to add both the needed metal and heat.
The hot pass should be conducted the same as the first welding process, but depends on your situation. Eg. In piping if you use GTAW for root pass, then hot pass should be GTAW-it is preferable. If the welder grind the root to remove defects as stated above, he may remove root completely at any point (accidently), so in this case same welding process is preferred to cover root & your WPS.
The hot pass generally uses a higher than normal amperage setting (approx. 10% higher than root amps setting) and a fast travel speed.
From: srinivas rao <ksrvasu@gmail.com>
To: materials-welding@googlegroups.com
Sent: Thu, 25 November, 2010 12:46:43 AM
Subject: [MW:8366] HOT PASS
Hi Gents, I have doubt reg HOT PASS. 1. what is the purpose of doing HOT PASS with more speed and high current? 2. Should the Welding Process used for Root be the same for HOT PASS? If not necessarily then how should we decide? Thank you All Regards, Vasu -- To post to this group, send email to materials-welding@googlegroups.com To unsubscribe from this group, send email to materials-welding+unsubscribe@googlegroups.com For more options, visit this group's bolg at http://materials-welding.blogspot.com/ The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents. -- To post to this group, send email to materials-welding@googlegroups.com To unsubscribe from this group, send email to materials-welding+unsubscribe@googlegroups.com For more options, visit this group's bolg at http://materials-welding.blogspot.com/ The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.
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For more options, visit this group's bolg at
http://materials-welding.blogspot.com/ The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.
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