Hi All Welding Experts
I am putting together a baseline programme for a large industrial plant where the pipeline contractor is telling me that his planned sequence of work for each section of piperack was:
Start loading out prefab pipes - biggest / heaviiest on high racks then smaller / lighter on the low racks.
Welding then starts on the high rack pipes while loading out is going on below.
I have my doubts about this sequence on two of fronts:
1. Health and Safety Rules with welding overhead of loading out.
2. Practicality of welding round a small pipe with a large pipe above it - on average there is 100mm lagging so max 300 gap.
Please give me the benefit of your experience on these matters.
Best regards
Mike Testro
Hi Mike
I regret that i do not recognize the material types. The most piping materials are covered under the following terminologies
For offshore fabrication work
For Oil and chemical plant
Fabrication norms are more difficult to detail because there are so many possibilities. I use Spon's Fabrication norms for offshore structures and OCPCA Data Bank of Estimating Norms for Oil and chemical plant constructors association. Page and Nations is the other estimating norm .
However some guide lines. Handle pipe though all stages of erection ( taking from store, transporting to site, trail erection and erection in the final position,and all the work associated with the permanent fixing to the main structure, ranging from 1.55 hrs for 2"pipe to 11..35 hrs for 18" pipe. Note that these norms may be adjusted depending on labor relations, job conditions, equipment and weather conditions. Suggest that norms as described are for maximum for Western Europe. All for 1 meter length. For this handling norm use no materials factor.
Regards
Johannes
Hi Johannes
No I do not have any industry standard productivity rates.
I do have the company tender hours per metre of pipe which is related to Diameter and Metal type CBC BBC CBA etc of which I have no understanding whatever.
I tried to investigate weld inches for each pipe length but could get no correlation for that and hours per pipe length.
Any help to assist my understanding will be gratefully accepted.
Best regards
Mike Testro
Hallo Mike
I guess you may have the appropriate productivity norms for welding and pipe fitting. If not, let me know i may be able to assist.
Johannes
Mike,
You can define shifts for your crews within the allowable working hours. You can define shifts for multiple crews working on a single activity or it can be a single crew working on different activities. It all depends on your modeling needs.
If you are allowed to work some specific hours a day, say 8 hours I do not see why you cannot set your model to assign welding during certain hours of the week, say 30 hours [8am-12noon; 2pm-4pm five days a week] while 10 hours [12noon-2pm five days a week]will be for loading the pipes into the pipe rack. Say 12 noon to 1pm is meal break for the welding team while from 1pm to 2pm the welding team will be doing other related work.
Of course with the limitation on time hours some efficiency will be lost anyway but setting specific shifts might prevent some chaos.
In this particular case I believe it shall be modeled using separate activities with different calendars. I do not believe using a single activity is a good option because welding and pipe loading are different operations and require different teams. You have shift work on different activities that cannot be performed at the same time, it is easy to model. It is up to you and your particular needs to decide on how to balance your work flow.
Best regards,
Rafael
Hi Rafael
I am putting together the baseline to represent completed work.
Shift work was not allowed for environmental reasons.
Best regards
Mike Testro
Consider shift work as to keep welding and installation crews working on different shifts. Maybe the second shift shall be scheduled to work 3 days a week while the first shift work 5 days a week, it is just a matter of balancing the work flow.
Hi Johannes
Thanks for your response.
Your advice about welding integrity affected by vibration is something new to me.
I will have to reconsider my position.
Best regards
Mike Testro
Hi Mike
I concur with you first observation that it is not good practice to start welding on pipes on a higher level while loading the smaller pipes at a lower level. Health and safety issues is the first item but the next item is that you start pipe welding while you are installing other pipes because of vibrations in the pipe rack that may impair welding.
300 mm gap shall be sufficient for welding , provided that you have 300 mm on all sides of the joint.
May be consider the following the approach for the installation of the pipes in the racks. I would make up pre-installation pipe lengths of twice the double random lengths and assemble these and weld, x-ray, paint and lag all the joints prior to loading into the pipe rack.
Make as many pre-assembled lengths as required and install these all at in one go. Do not fix the lagging over the last 300 mm of the joints and make sure that all the welds are accessibly. Weld all the joints in the rack all at ones while the other members of the team are continuing in the pre-assembling work.
Hi Mike
With vibrations i mean vibrations from manipulating, rigging and installing the pipes in the pipe racks at the same time as the welding process.
Regards
Johannes