How do plastic cable trays reduce total installation cost compared to galvanized steel alternatives?
If you’ve had experience managing large electrical installations, you’re familiar with using a cable tray for the project specification and using galvanized steel as your primary choice for the tray for several decades, because it has proven strong and effective at performing the task at hand. Project Managers and Procurement Personnel are now frequently asking whether using galvanized steel remains the most economical option.
The competition for galvanized steel trays comes from fibreglass-reinforced plastic (FRP/GRP) cable trays.
At first glance, the steel tray’s initial quote may seem less expensive; however, many cost factors come into play concerning the total installed costs of both trays (compression labour, movement, safety equipment, and time required to install), and these additional costs can often bring the total costs of the FRP tray below that of the galvanized steel tray.
Let’s break down where and how the total costs for installing FRP trays are lower than those for installing galvanized steel trays.
1. The “Weight Tax” on Steel
When you pick up a part of plastic versus a piece of metal, you can feel the difference immediately. The most immediate difference between plastic and steel is in the weight of each material.
Galvanized steel is heavy and requires multiple workers to lift long pieces. Most of the time, cranes or hydraulic lifts are needed on high-rise construction jobs.
FRP/plastic is about 70% to 75% lighter than steel.
Why does this save money?
- The biggest variable in construction costs is labour. The faster a material can be picked up and moved from one location to another, the less time and money it will cost.
- A job that takes four men to lift and install a heavy steel channel can be done by two men when using FRP.
- The added speed of logistics will also save on how fast materials can move from the loading dock to the installation location, so that workers aren’t exhausted before their task begins.
- Less heavy lifting equipment, such as cranes and scissor lifts, is typically required for elevated runs of FRP as compared to steel.
In summary, if you are using lighter-weight components, this will have a direct correlation to lower labour hours and lower insurance rates (less potential for back injuries).
2. No Grounding, No Bonding, No Headaches
The unforeseen costs of steel construction can be significant. Due to steel’s conductivity and ability to conduct electricity, there is a requirement for Metallic Trays to be grounded and bonded based on the NEC and the requirements of international standards.
By using the current workflow for Steel Trays, the labour and material spent on grounding and bonding are as follows:
- Install the tray
- Install bonding jumpers across the joints of the trays
- Create an uninterrupted grounding path for the trays
- Test for ground continuity
The material used includes Copper Wire, Copper Lugs, etc. The Labor costs include the time it takes for the electricians to install the wiring and lugs, continuity testing, etc.
In contrast, the workflow for using Fibreglass Reinforced Plastic (FRP) Trays is as follows:
- Install the tray
- There is no other processing required
Since FRP is inherently non-conductive, it acts as an electrical insulator. FRP does not require grounding and bonding because stray voltage and/or fault current cannot be carried through it.
The money saved using FRP compared to using a steel tray is:
- No use of copper grounding wire or lugs
- No time spent by installers/electricians checking continuity
- The risk of stray voltage causing an electric shock or other damage to equipment through the tray is eliminated.
3. The “Toolbox” Factor: Cutting and Fabrication
Time equals money on job sites. When modifying a tray to fit around an object, how much time does the modification take?
Galvanized Steel: Cutting a galvanized steel tray requires a chop saw (with a metal cutting blade that generates sparks), drills for holes, and a deburring tool to smooth out any sharp edges. Cutting galvanized steel can also be quite noisy (due to the metal blades generating noise and sparks). Furthermore, cutting galvanized steel is very hot and will take considerable amounts of time compared to the two other materials being discussed. In addition, the sparks produced from cutting the iron and steel trays may present serious safety risks in an existing commercial facility or chemical plant.
Plastic (Fibreglass Reinforced Plastic): You can cut a fibreglass reinforced plastic tray using an ordinary carbide-tipped circular saw blade or by using a heavy-handed hand saw. If you need a hole in the tray for a rod hanger or a custom angled cut in the tray, many manufacturers produce modular FRP systems that can flex or fit together with a simple snap fit.
Furthermore, many of the newer modular plastic systems use quick-connect fittings and don’t require any tools to connect. Modular plastic tray systems can save contractors up to 40% in installation time as compared to bolted metal tray systems, according to various manufacturers.
4. The Corrosion Tax: Coatings vs. Composition
Galvanised steel is a form of steel that has a layer of zinc coating. This process generally works very well until the zinc is scratched. Once zinc is scratched, the steel is exposed at that location by a cut edge, an object dropped onto it, or a cable dragged across it. The scratched area becomes a rust-generating area in a chemical plant, wastewater treatment facility or in coastal areas.
To protect from this corrosion, the steel is frequently in need of:
- Repair paint (labour and material) for touch-up zinc coating.
- A thicker coating of zinc through Hot-Dip Galvanising vs Pre-Galvanising, which will add cost.
- Replacement after 5 to 10 years in a harsh, corrosive environment.
Plastic will not experience corrosion. FRP will not corrode when it is exposed to salt water, acid or chemicals. In the harsh environment of the Middle East, as well as chemical plants in the United States, FRP is the standard material of choice. This material eliminates the maintenance costs associated with repainting steel or replacing corroded steel.
While the up-front costs of FRP may be greater than steel, because you only have to install it one time and can expect 20 years of service life from it, the lifetime cost of ownership will be significantly lower than with steel.
5. The Freight Factor
When you buy cable trays from 10,000-foot sections, then when shipping is invoice will also include the weight.
Steel will cost more because you are shipping heavy metal. This will also increase the shipping costs associated with the amount of fuel used to ship heavy metals.
Plastic trays will typically be made from a combination of resin & glass fibers; therefore, they require more linear feet per pound, which means that you can deliver more material on one truck, resulting in a reduced overall carbon footprint for your project.
The “But Steel is Stronger” Argument
Let’s talk about the elephant that everyone is avoiding! On paper, steel does have higher tensile strength than FRP; however, FRP’s strength is still very strong. The strength-to-weight ratio of FRP is fantastic. FRP handles any standard cable loads very well (such as control cables, power cables, and fiber optics). Unless you are trying to suspend heavy, large-amount transmission lines (or using a concrete/steel ladder tray), FRP will be able to handle the loads with ease.
The Verdict: When should you choose Plastic?
Plastic-Raised Floor is an indistinguishable champion in terms of Total Installed Cost in four different venues:
In chemical and industrial plants, it saves both application and maintenance costs by eliminating the need for heavy equipment and grounding. Additionally, it eliminates all risk of corrosion, which equates to a tremendous reduction in ongoing maintenance expense.
In offshore/marine applications, the corrosive nature of saltwater greatly reduces the life expectancy of steel. Consequently, the use of FRP guarantees long life for the cable tray, equal to that of the platform.
In data centers, plastic’s non-conductive and non-ferrous properties make it the ideal medium to contain sensitive data cabling.
In remote locations, when access is difficult, utilizing lightweight shipping and installing quickly (and without the need for tools) results in enormous savings associated with logistics.
Conclusion
Although quoting a galvanized steel cable tray may be a lower price initially, the total cost to install an FRP/GRP cable tray will remain less than that of a galvanized steel cable tray. Its significant weight reduction (70-75%) minimizes labor and shipping costs (as well as reducing the need for heavy lift equipment), and eliminating any requirement for bonding or grounding reduces both the material costs and the time spent by the electrician. Using simple hand tools and snap-fit connectors to install the trays will result in considerably reduced labor hours as well.
Steel’s advantage in regard to initial material cost is lost when cost factors such as labor, logistics, grounding materials, and long-term maintenance (especially in corrosive applications, such as chemical manufacturing plants, offshore oil platforms, etc.) are considered. Project managers who place an emphasis on reducing total project costs should specify plastic cable trays due to their faster ROI from quicker installation times, reduced labor to install, and no ongoing maintenance over many decades.