How do FRP cable trays improve safety in chemical industries?

The chemical sector has one of the most rigorous infrastructures on the planet. Everyday occurrences of corrosive acids, flammable vapors, volatile solvents, extreme temperatures, and humid conditions make for an environment full of everyday hazards rather than isolated events. Therefore, Cabling materials to manage electrical/instrumentation systems within this type of facility are not just a procurement issue but are also important from a safety-critical perspective. Historically, steel/aluminum cable trays were used in these environments because they were well known, readily available, & considered standard. However, they are also well known to be susceptible due to rusting, chemical corrosion, electrical conductivity, and weight fatigue due to the installation of overhead systems. The advent of Fiber Reinforced Polymer (FRP) cable trays represents a materials innovation that has changed the way users of chemical plants/refineries/process industries view safety in relation to infrastructure construction.

Why Industrial Environments Demand Better Ladder Solutions?

What Are FRP Cable Trays?

Fiber Reinforced Polymer (FRP) Composite Material consists of reinforcing glass fibers in a matrix of a polymer resin (most commonly polyester, vinyl ester, or epoxy). The resulting composite material is lightweight with a high degree of structural integrity and is also chemically inert to most industrial chemical substances. There are four styles of FRP cable trays manufactured, including ladder, perforated, solid bottom, and channel, with each type providing an equivalent configuration to a comparable conventional metal tray; however, the performance characteristics of FRP cable trays outperform the performance characteristics of conventional cable trays in an extremely hazardous chemical environment.

The following are some primary characteristics of FRP Cable Trays:

The composite composition of FRP cable trays utilizes glass fibers in the polymer resin.
FRP cable trays are manufactured in four respective styles: ladder, perforated, solid bottom, and channel.
FRP cable trays are naturally chemically inert, non-conductive, and lightweight.
FRP Cable Trays should provide substantial service for 25 to 40 years when utilized in very aggressive industrial environments.

1.Superior Corrosion Resistance: The First Line of Chemical Defence.

The primary benefit of FRP cable trays is their ability to resist chemical corrosion, providing immediate safety benefits. Cable trays in chemical plants and refineries are continuously exposed to harsh chemicals that will eventually corrode the metal infrastructure.

Cable trays in chemical plants can be exposed to the following damaging chemicals:

Strong Acids (Hydrochloric, Sulfuric, Nitric)
Alkalis (Sodium Hydroxide, Ammonia Solutions)
Chlorinated Solvents/Process Chemicals
Salt Spray (Coastal/Offshore Installation)
High-Pressure Cleaning Agents and Washdown Fluids

Steel cable trays (including galvanized and epoxy-coated) will corrode in any of these chemical exposures. Once they corrode, the structural integrity will be compromised; A corroded bracket will break, a rusty rung will warp, and the section of cable tray will drop down; this will take down electrical power supply cables to the pumps, control systems, and emergency equipment.

The following features of FRP material distinguish it from steel material:

It does not rust or oxidize under any environmental conditions.
Resin properties can be specified at the time of design to provide resistance to the specific chemicals that will be present on the job site.
There will be no loss of structural load-carrying capability over the service life of the FRP material.

2.Non-Conductive Properties: Eliminating Electrical Hazards.

FRP cable trays provide a safety benefit not often recognized: they do not conduct electricity. On the other hand, metal cable trays can conduct electricity if the insulation on a wire fails or if they touch an energized part, which is especially dangerous around wet and humid chemical processes.

FRP’s dielectric characteristics eliminate the following risks:

Electrical shock to workers who touch the tray structure
Fires caused by short circuits from insulation failure
Stray currents that damage sensitive instruments and control circuits
Electrocorrosion of structures in contact with metal trays

There are also some practical installation benefits to consider:

No grounding continuity bonds (required for metal trays and a continuing maintenance issue) are required
Safe for use when located near high-voltage power runs and/or sensitive signal cables
Less complex to install in electrically sensitive process areas than metal trays

3.Flame Retardancy: Containing Fire in High-Risk Zones.

Chemical facilities work with flammable (solid, gas, and liquid) substances every day. When fires occur, the unprotected cable tray systems can be a significant vector for flame propagation, causing the spread of fire across zones and creating a nearly impossible situation for fire containment. However, FRP cable trays constructed to current industrial standards are made with flame-retardant resin systems, resulting in a very different risk proposition.

Some of the ways FRP helps improve fire safety are as follows:

Will self-extinguish when the ignition source is removed
Will not allow flames to spread down the tray surface
Comply with ASTM E84, IEC 61537, and NFPA 70 Article 392 for flame performance
Will maintain low thermal conductivity, limiting the heat transfer to cables, and extending circuit integrity during a fire

When comparing steel to FRP in a fire situation, the way the materials react is very different:

Steel will conduct heat very quickly and add to the damage of the cables in adjacent areas.
FRP will act as a thermal insulator, allowing emergency systems to work longer.
The ability of cables to survive longer during a fire can change the outcome of what may be a controlled fire into a catastrophic fire situation.

4.Structural Reliability Under Thermal Stress.

Thermal stability is rare for chemical environments. Thermal cycling – repeating expansion and contraction over years on steam lines, exothermic reactions, furnaces, and extreme temperatures can cause fatigue of metal systems in cable management systems.

How Thermal Cycling Damages Metal Trays:

Steel expands and contracts with every temperature change.
Repetitive thermal cycling causes fasteners to loosen and creates stress on mounting brackets.
Long lengths of tray can bow or deform from sustained thermal loads.
While aluminium is lighter than steel, it actually expands more than steel with increased temperature.

The thermal Advantages of using FRP:

FRP has a lower thermal coefficient of expansion than steel or aluminium.
Due to reduced movement of FRP, there is reduced mechanical fatigue on mounting points and support brackets throughout the life of the tray.
Reduced stress on the mounting points and support brackets throughout the life of the tray creates a lower chance of dropped spans, wires getting pulled out of the termination, and/or damage to the cable jacket due to structural movement.

5.Lightweight Design: Reducing Installation and Structural Risk.

Compared to equivalent steel cable trays, FRP cable trays are approximately 25 – 40 % lighter, which provides multiple cascading benefits starting with the installation and moving to safety throughout the life of the installation.

Benefits During Installation

Lightweight cable trays result in fewer strains on the workers during the manual handling of the trays
Reduce potential dropped-load accidents during overhead construction at heights.
More rapid installation with smaller installation crews results in less time-at-risk from working-at-heights.
More easily reposition and adjust on complex plant structures

Benefits Post-Installation

Reduced static and dynamic loads on pipe racks, structural steelwork, and building frames.
Allows for expansion of capacity without the need for structural enhancement of existing support systems.
Reduces the risk of latent overloading of old facilities when they are modified and upgraded.

Benefits for Seismic Areas

Lighter trays would have a much lower level of inertial forces generated by an earthquake.
Reduced risk of tray collapse during seismic events.
Increased likelihood that the integrity of cable circuits would be preserved; therefore, emergency systems will be fully operational following the earthquake.

6.Low Maintenance, High Reliability Over Time.

Safety at a chemical facility concerns performance, not just at the time of installation, but also how that performance is maintained throughout the life of the facility. Elevated cable tray installation requires an inherently hazardous maintenance activity.

The hazards associated with maintaining metallic cable trays are as follows:

Use of scaffolding, aerial lifts, or access towers to access overhead cable tray runs
Dropped tools/equipment in the live process area below
Working from heights is a leading cause of worker fatalities
Accidental contact with live cables during maintenance and/or inspection

How does FRP Reduce Maintenance Risks?

7.Chemical-Specific Formulation: Engineered for Your Hazard Profile.

Another significant advantage of FRP as a material is that it is possible to design the material according to the particular chemical hazards of each site during the resin selection stage, which steel cannot possibly do.

Types of resins and corresponding uses:

Polyester resin – used for general applications, with reasonable acid/alkali resistance
Vinyl ester resin – has great resistance to strong acids, solvents, and oxidizing agents, especially recommended for harsh conditions
Epoxy resin – has good mechanical strength, alkali resistance, and some solvent resistance

Some implications of the above:

The chlorine plant uses a different resin than the sulfuric acid plant does
Aggressive solvent conditions in a petrochemical cracker dictate a different kind of resin formulation than that of an ammonia plant
Proper performance of the resin system under real conditions can be verified before installation, rather than being found out after a failure
Safety measures become proactive rather than reactive (corroded trays replacement)

FRP’s corrosion resistance means maintenance will not need periodic repainting or section changes
Routine inspections of FRP cable trays show little to no deterioration requiring intervention.
Over the life of a facility, there will be fewer entries into hazardous elevated locations.
There will be no galvanic corrosion between dissimilar metals at the points of support.

An average of twenty to thirty years in the life of a facility, reduced maintenance will lead to reduced exposure to hazardous, elevated, energized, and chemically dangerous work environments for employees. This safety benefit is often overlooked when procuring new products for facilities. This benefit is significant compared to the vast amount of time that employees will spend in this type of environment.

8.Compliance with International Safety Standards.

Industrial FRP cable trays are produced and tested according to internationally recognized standards in order to provide facilities with the documentation that they require for their safety cases and regulatory compliance purposes.

Relevant industry standards for FRP cable trays include:

IEC 61537 – Cable Management: Cable Tray Systems and Cable Ladder Systems
NEMA VE 2 – Installation Guidelines for Cable Tray System (North American Standard)
BS EN 61537 – European Equivalent to IEC Standard
ASTM E84 – Surface Burning Characteristics (Flame Spread Index)
NFPA 70 (NEC) Article 392 – Requirements in the United States National Electrical Code

The reasons why adhering to standards is important from a safety perspective:

Provides independent verification of load bearing, flame behavior, and corrosion resistance
Provides documentation for Process Safety Management regulatory submittals
Helps in HAZOP and Risk Assessment through tested performance data
Allows specification of like-for-like on a global basis throughout multi-site chemical facilities

Conclusion

When considering all of the safety concerns facing chemical industries, such as corrosion, electrocution, fire spread, thermal fatigue, and maintenance accidents, there is no other product available that covers so many of these issues as effectively as FRP cable trays. They won’t corrode, don’t conduct electricity, can resist flames, and can even be formulated in such a way to accommodate the unique dangers of each factory. Their lightweight decreases installation dangers, their lack of need for maintenance reduces the number of times personnel have to venture into dangerous areas, and their conformance to international regulations allows the kind of documentation required in today’s process safety management systems. For an industry where any accident can spell death and environmental disaster, safety is achieved through a long string of small choices, and choosing FRP cable trays is one of those choices.