Changes in piping during the construction phase
- Posted by: Bonnie Baker
- Category: Piping
When a change is identified during construction, a lot of effort is put into identifying the impact of the change for cost, schedule, engineering/design and materials, and then having the change order approved.
Change is always disruptive during construction. The crew has to stop what they are working on, make the existing area safe, and then be moved to another area. Subsequent crews scheduled to be in the area may need to be diverted to other work. The work schedule will need to be reassessed. Equipment, tools and materials for the new area have to be arranged. Getting back into the original area to complete the disrupted work depends on the delivery of engineering drawings, revised materials, and available manpower.
As noted in a previous blog, in many engineering companies, each individual discipline is usually challenged to work within the lowest possible budget – both for workhours and for material costs. Unless the designers are astute, there can be some unintended consequences.
Although a change can impact many disciplines, this post will only deal briefly with steel and pipe. Materials for changes need to be selected and sourced with the schedule (as well as the cost) in mind. Steel structures should be easy to fabricate in the shop, and/or assemble on site. It may be worth discussing with the steel fabricator what sections are available, or are easy to obtain. If the change involves an unusual size of type of pipe, it is worth discussing with the materials management department to see if there is anything currently available that could be diverted to the change, or if they could make a few calls to see if any of their suppliers have any (properly documented) spare materials. Any materials that are diverted will likely need to be reordered, so the time and cost for this needs to be taken into account.
Once the steel and/or pipe has been fabricated, it needs to be delivered to the site. It can be worth discussing with transportation whether the additional cost of an LTL (less than truck load) or a hot shot is warranted. If either is warranted, there will already be an existing system in place to notify the site that the material is coming. If neither is warranted, and the site is not advised that the materials are coming, it may take additional time for the materials to be directed to the correct area.
The true cost of the change can be difficult to ascertain, particularly for duration related indirect costs. It is difficult to tell if the cumulative effect of several smaller changes (however meticulously documented) or some other situation causes the project to finish later than scheduled. It is usually a combination of events, and ascertaining the proportion of the time and costs to be applied to each of the events can be very challenging. The impact of a change can increase the later it is identified.
Experienced engineers/designers understand the importance of understanding all aspects of a change, and take the overall impact to the job into account when they make recommendations on how to deal with a change.
If you want to know more:
ASME VIII | Design of Pressure Vessels
TEMA | Design of Shell & Tube Heat Exchangers