Backside Welding

In principle it is repairable with welding from the back. To make a safe weld, release stress from gravity or pressure by supporting your workpiece.

Prepare your welding space with a disk grinder and build up a new root from bottom to top if want maximal strength.

Weld through well and let it cool down in a natural way. Use welding material of same composition and hardness.

You should have best results with MIG /or preheat evenly between 300 and 600 degrees Fahrenheit.

Consider a multi pass weld when your material is thick. (grind in again) More info can be supplied if you give an idea of mass and dimensions of your workpiece, the place and type of crack and the size.

How long is repair.

Dear Nizamudeen ,

if you look at the welding techinque of GTAW - in which welding is permitted with backing of gases where as in SMAW technique welding is permitted withbacking of GTAW deposited weld metal ( in a case of GTAW+SMA WPS).

in your case weld defect repair is permitted by only SMAW because GTAW+SMAW WPS is approved the SMAW techinque with backing of deposited weld metal which is applicable in case of back welding.

with regards

it is true that more information regarding the size of the repair is required but you should follow some basic steps during repair welding as under:

1) assess the defect and grind the same to sound metal so as to make a V-groove.

2) after grinding Die peneterant test shall follow to chack the if there are any cracks/inclusion etc. left in the groove. if cracks/inclusions found then repeat the grinding process.

3) repeat the steps 1 and 2 till you get sound metal. this will help in getting a good welding quality for the repairs.

4) this will require further PWHT (depending upon your material) after the rectification is carried out. follow the procedures that are earlier followed for PWHT.

It depends on what you are welding. Is it a pressure vessel or something that will cause injury or damage if the weld fails. If yes, then a back weld cannot be used to repair a bad weld. You will have to grind the weld down to solid metal, reweld and then backweld if needed. This backweld is called a reinforced weld.

If this is for ASME Section 1, paragraph PW-40 governs the repair of defects. P-40.3 lists the P-No. groups that may be repaired without subsequent PWHT, but must be repaired prior to to the final hydro. If the work is under other sections of the ASME Code, those sections must be consulted before any repair work is performed to make sure that the repair work is in accordance with that particular Section (III, IV, VIII, XI), and B31.X must also be consulted.