Skid Design & Pre-Fabrication for Georgia Power Plant

VALVE MANIFOLD SKID – Galvanized Steel Frame, Fiberglass Reinforced Plastic (FRP) Pipe, Valves, Instruments, Control Panels, Control Air Tubing, Conduit & Wiring, Ready for Shipment on Conestoga Step Deck Trailer.

Wm.T. Spaeder was contracted by a water treatment and industrial firm to design and fabricate thirteen (13) unique equipment skids for a large power plant in Georgia. This power plant was in the process of decommissioning their settling ponds and replacing them with a new wastewater treatment system to treat flue gas desulfurization (FGD) waste as mandated by new EPA regulations and these skids will become part of that complex treatment process. Spaeder designed, fabricated, and shipped the skids from our shop in Erie, Pennsylvania to our customer’s job-site in Georgia.

Wm. T. Spaeder was asked to create skids of to serve a variety of functional and process requirements. From pipe manifolds to sample stations and pump skids to chemical dilution skids, Spaeder created unique design solutions that met our client’s needs. These designs covered a range of space limitations, accessibility requirements, pump types, and materials of construction.

Wm. T. Spaeder regularly fabricates piping systems from carbon steel, stainless steel, and CPVC materials.  All three of these materials were required to be used on this project plus fiberglass reinforced plastic (FRP) pipe.  FRP pipe is a specialty pipe material with high corrosion and abrasion resistance, perfect for FGD wastewater applications.  Incorporating the FRP pipe specialty material shows the adaptability of Spaeder’s design and fabrication teams in being able to address the additional challenges inherent to this type of material.  The challenges that Spaeder overcame included: an iterative design process to account for pipe stress on an unforgiving material of construction combined with equipment support requirements/limitations -and- imprecise dimensional tolerances on fittings and spools due to the hand lay up process of manufacturing the FRP pipe, fittings, and spool joints.

The Advantages and Challenges of Skid Work

Skids are a packaged system (or part of a system) that are preassembled in a fabrication shop or off-site location and shipped complete to a jobsite for a drop-in place installation with minimal field connections. Any combination of major equipment, pumps, valves, instruments, control panels, heat tracing and insulation, insulation lighting, etc. can be installed, piped, and wired on one or more structural frames to create a skid. Some skids, including many of the skids that we fabricated for this project, were of a size that required them to be split into multiple smaller skid sections to allow for interstate shipping.

MULTI-SECTION PUMP SKID – Pipe Section (left), Pipe/Pump Section Fit-up (center), Pump Section (right)

Prefabricated equipment skids present many advantages for our customers.  The value that Wm. T. Spaeder provides to our customer includes:

• Fewer safety hazards by working in a fabrication shop with a controlled environment for workers instead of a field construction site.
• Higher quality control with shop testing and equipment functional tests performed prior to shipment
• Lower total installed cost.
• Onsite VDC/Engineering staff to resolve fabrication issues as they arise.
• Minimized field installation time and effort.
• Smaller footprints

The very things that make skids valuable to customers can present challenges to design teams and fabrication facilities.  Additional structural steel is required to mount and support all equipment on a frame that is sufficiently robust to withstand the stresses and vibrations of over-the-road or overseas shipments for equipment that might be otherwise bolted directly to a concrete foundation.  Design teams must incorporate operational and maintenance functionality into an already complex design, but also consider factors such as shipping costs/limitations, lifting requirements, etc. that might not regularly be a factor when stick building onsite.  Piping between components is regularly fitting-bound to minimize footprint of the overall skid leaving little to no room for adjustments due to design inaccuracies.

3-SECTION PUMP SKID MODEL – Pipe Section (left), Pipe/Pump Section Fit-up (center), Pump Section (right)

Effective skid design and fabrication requires detailed organization, coordination, and scheduling.  Often, customers will supply equipment as free-issue items to a skid fabricator.  This means that the customer purchases equipment (pumps, valves, instruments) directly and the skid manufacturer installs them.  Significant coordination is required between the customer and skid fabricator to not only ensure timely delivery of the free-issue, but also to obtain detailed engineering information on those components necessary for an accurate design.  Customers regularly require extensive submittals and review processes which take time as well as witnessing functional tests of completed skids before shipment.  Coordination with our’s subcontractors doing work in our fabrication facilities is essential as skids require multiple trades for completion.  Successful execution requires that a detailed schedule be developed prior to contract award and followed throughout completion.  Critical path tasks must be regularly identified and monitored throughout the project.

DUPLEX CENTRIFUGAL PUMP SKID – Model (left), Finished Skid (Right) – Galvanized Steel Frame, Duplex Centrifugal Pumps, Painted Carbon Steel Pipe, Valves, Instruments, Junction Box, Control Air Tubing, Conduit & Wiring, Ready for Shipment on Trailer

Spaeder’s ability to do prefabrication directly in our shop has been advantageous for ourselves and our customers.  Not only does it allow us to work effectively with out of state clients — some over a thousand miles away — but it affords us a level of quality control and safety not possible on most job sites.  We have access to a complete arsenal of tools, better rigging, immediate overhead cranes, and a full staff of technicians ready to successfully tackle any challenges that come our way.

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