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What are the typical repair rates for welded products and what are the main factors affecting them?

 

Frequently Asked Questions

An industry survey on ‘repair rates’ was carried out by TWI in 2011 with the following conclusions:

  1. Repair rates for specific sectors and material grades are reported in the table below.
  2. Average repair rates for the Oil & Gas and Power sectors range from 1 to 3%. With peak rates up to 25% in specific locations and exceptional values up to 55%.
  3. Peak repair rates are typically observed in root runs, fillet welds and areas with limited access.
  4. The major factors perceived to affecting repair rates are welder’s skills, location or accessibility of welds and poor fit-up prior to welding (see figure below).

Average repair rates for different welded products and materials, according to TWI’s industry survey.

Type of product

Average repair rate, any material grades, %

Average repair rate per material grade, %

Mild steel

Stainless steel

Low-alloy steel

Ni-alloy

Low-temperature steel (eg Ni steel)

High strength steel

All products

-

2.0

2.2

3.1

3.4

2.2

-

Offshore structures (3)

2.0

2.1(1)

1.1

-

2.0(1)

2.2

-

Other welded structures (3)

1.0

1.5(1)

0.7

-

-

-

-

Piping systems (4)

3.0

1.7

3.5

4.2(1)

-

-

-

Pressure vessels (4)

2.0

2.8

1.1

0.5(2)

-

1.7

-

Offshore pipelines (4)

2.0

0.9

7.5

-

-

1.8

-

Onshore pipelines (4)

3.0

2.5(1)

-

2-5(2)

-

2-5(1)

-

Cryogenic storage tanks (4)

0.5(2)

-

0.5(2)

-

-

-

-

Hydroelectric turbines (3)

1-2(2)

1-2(2)

-

-

-

-

-

Notes:

  1. Based on less than 5 entries.
  2. Based on one entry.
  3. Average repair rate data provided as fraction of the length of repaired weld versus the total weld length.
  4. Average repair rate data provided as number of repaired welds versus the total number of welds.
Distribution of factors affecting repair rates in weld
Distribution of factors affecting repair rates in weld

For more information please email:


contactus@twi.co.uk