Time for welding

[arcpro]

I have to estimate the time required to weld 25 weld joints in 8" Sch. 80 piping for an upcoming short shutdown of one facility.
Please share how can I correctly estimate in addition to get an estimate from welders and their supervisors.

[mechcolor]

Which welding processes are you planning to use?

[arcpro]

GTAW for root and hot pass and SMAW from remaining passes.

[mechcolor]

Time of welding can be calculated by using the following formula:
T = W / (D x K)
where,
T = welding time
W = total weight of weld metal (for 8" NPS Sch. 80 welds with V-groove, take weight as 1.5 kg/m length for steel)*
D = deposition rate (depends upon the welding current with SMAW, for 120 A take 2 kg/hr max.)
K = Operating factor (take 25-30% for GTAW / SMAW)

W can be calculated as:
W = S x N x C
where,
S = Cross sectional area of weld joint
N = length of the weld joint
C = specific gravity of weld metal

Calculations for your case assuming welding of steel:
Total length to be welded (m) = 25 (no. of welds) x 0.6882 (length of each weld) = 17.21
W (kg) = 1.5 (* see above) x 17.21 = 25.82

Welding time (hrs) = 25.82 / (2 * 0.25) = 51.64

Hope this would give you some idea.

[arcpro]

Thank you very much mechcolor.
It is indeed very useful.
Can you share the reference for values like weight/length for welds with double V-groove, J-groove and deposition rates.

[ashfaqanwer]

Very useful formula.

[mechcolor]

arcpro
These and many other very helpful calculations have been given in "AWS Handbook - Economics of Welding & Cutting".

[Nabeel Ahmed Qureshi]

Mechalor,

Thanx for sharing. Really useful
NAQ