Designing a Safe Reefer Connection: Part 2

Designing a Safe Reefer Connection

Increasing safety

While little has changed in the construction of the receptacles themselves over the years, ESL is constantly challenged to find new solutions that meet unique customer safety and operational requirements. Usually terminal operators have limited or no control over the maintenance and standards associated with male plugs on reefer container cables, the quality of which varies considerably. A male plug with water and salt ingress can “flash” outwards into the operator when the interlock actuator is engaged. In order to energize a receptacle from a safe distance, ESL designed a rear-actuated receptacle that removes this safety risk by requiring the operator to engage the actuator rod from behind the assembly enclosure, out of the way in case of a flashover. Since the development of our rear-actuated receptacle, ESL has installed systems at terminals in Philadelphia, Nairobi and Vancouver. In Philadelphia, ESL added LED lights on the rear of the enclosures so operators can see they have energized the correct receptacle.

Damage control

Properly treated and maintained, a safety-interlocked reefer receptacle is designed to last many years. The reality, however, is that equipment is often damaged through misuse. In our experience, the number one cause of receptacle damage is “drive-offs”, where the reefer is moved without first being disconnected. This will destroy a nylon or plastic ROA, but not a stainless steel one. Stainless steel ROA’s can be repaired by just replacing the receptacle or swapping out a safety-interlocked outlet from another ROA. In North America, the incidence of drive-offs is such that stainless steel ROAs should be considered as an industry standard. ESL also offers microswitches in the receptacle that signals whether a container is connected, regardless of whether the reefer is energized or not. This information could be sent to the terminal operating system (TOS) and an instruction to move a reefer could be blocked if it is still connected.

If you missed part  of our series  focusing on operating reefers at terminals efficiently click here.

Designing a Safe Reefer Connection: Part 1

Safe reefer operations require a receptacle system that exceeds minimum standards in electrical codes.

Designing a safe connection - part 1

Safely connecting and disconnecting reefer containers operating on 3 Phase 440-480v power represents one of the largest safety risks from an electrical hazard at the majority of container terminals. Reefer receptacles are designed and listed to electrical safety standards of UL and CE self-certification, but these only “certify” that the receptacle can carry the required electrical load. Other standards, such as IEC 60309-1 and 60309-2 cover configurations of the plug and receptacle and ensure compatibility. It is widely accepted that dealing with 480v, 32A supply presents a safety (and liability) risk and that the standard is to have interlocked connections. A safety interlock is a mechanical or electrical device that prevents a receptacle from being energized unless the male plug is properly engaged and disconnects the power supply automatically as the plug is removed. Although the safety interlock design prevents operators from “making” or “breaking” under load, it is not required under electrical codes and in some cases, terminal construction contractors look to install non-interlocked receptacles, which pose a higher safety risk to operators, but offer cost savings. Some situations arise where contractors facing strict budgets try to install non-interlocked receptacles. The objective is to make sure interlocked receptacles rather than “complying” receptacles are specified when projects are tendered. As far as the design of the interlock is concerned, there are several options. ESL’s standard system detects the ground pin of the male plug before allowing the unit to be energized, whereas other designs interlock off the key on the side of the plug. ESL believes the ground pin is the safer option. Additionally, in some markets, plug keys are frequently “shaved off” to allow a 32A plug to mate with a 30A (non-interlocking) receptacle, meaning the 32A male plug must be replaced elsewhere in the supply chain in order to safely connect to a receptacle that interlocks at the key.

Operating Efficiently

Another important aspect of reefer power supply is designing the receptacle system so the terminal can perform reefer operations efficiently. In considering the layout of the reefer area(s), terminal management has to weigh the initial costs of installing more reefer outlet assemblies (ROAs) against the labor costs of managing cabling from fewer centralized ROAs. A reefer rack structure is typically six or seven containers wide and some operators opt for an ROA with six or seven receptacles mounted centrally. This configuration is more prone to tangled reefer cables, which present tripping hazards and the chance of disconnecting the wrong cable. Terminals with wider reefer racks may even require extension cables to reach the outer containers. Installing more receptacles per ROA is ultimately a cheaper solution, but a trend towards two and three-gang ROAs due to operational efficiencies is growing. Demand is also increasing for two LED lights, one to indicate line power is available to the ROA and a second to show that the receptacle is energized and power is flowing. If the first LED is not showing, the operator will know immediately that there is an upstream power supply problem. An available option is the incorporation of an equipment ground fault protection (GFP) device on an outlet module to isolate the effect of a phase to ground short. ESL has frequently been asked to incorporate a simple ground fault protection device that can isolate a fault at the receptacle and prevent upstream switch gear from being tripped by a short. Terminal design engineers need to take into account that reefers generate ground currents during the defrost cycle, so the GFP devices should be selected and set at a value above the defrost cycle ground currents to avoid nuisance tripping.

Read part 2 of our series  focusing on reefer receptacle safety and damage control.

Positive Expectations for Reefer Shipping

reefer shipping

As projected at the beginning of 2016, this year is proving to be one of the worst for global container shipping, with one exception – reefer shipping.

In written clarifications by The Journal of Commerce, Container News, World Cargo News and Cleanleap, studies show cold chain has proved to be growing strong with frozen food shipments up 4% and chilled products up by 7%. The expectation being that the global refrigerated ocean transportation market will grow steadily from 2016 through 20201.

According to the latest edition of the Reefer Shipping Market Review and Forecast 2016/17, by 2020 seaborne reefer cargo will reach a staggering 120 million tonnes – increasing by an average of 2.5% per annum2. Such increases will have a direct effect on both container lines with reefer capacity and specialized reefer operators.

So where are these predictions coming from? One strong theme in reefer shipping performance is being attributed to the growing demand for food throughout Asia and rapid growth in meat imports into China3. China’s cold chain is now reported to be growing at 25% per year and projected to be worth $75 billion by 20174. In addition to the Asian market, Indian cold chain is also forecast to grow at 25% per year to 2017. This prediction is being accredited to popular fast food supply exports to India tripling over the last six years. Evidence shows the reefer shipping sector is also betting on growth in new and emerging economies, including Cuba. Trade organizations and industry groups have already conducted trade missions to Cuba in anticipation of the lifting of the U.S. trade embargo5.

…having reliable equipment when and where it’s needed is mandatory.

Emerging economies are not the only impact being taken into account, new business segments such as floriculture and pharmaceuticals are anticipated to continue to contribute greatly to the reefer shipping sector. Floriculture, or flower farming, is a $32 billion industry. It ranks as the third-largest U.S. crop, and growers in California make up 75% of the market. Pharmaceutical shippers are also looking more closely at ocean freight for their temperature-controlled shipments. The seasonal nature of floricultural and agricultural products combined with their short shelf lives mean having reliable equipment when and where it’s needed is mandatory. Despite the many current difficulties for the maritime sector, the predicted growth of reefer shipping has an encouraging outlook.



3””Reefer Cargo is Hot” World Cargo News Magazine, September 2016, pp. 17



Be Proactive: Help Prevent Container Drive-offs

Many key factors play a role in getting cargo in & out of ports and on the road to their final destination. In the process of getting reefer containers from one destination to the next, it is important that precautionary measures are taken to mitigate the occurrence and impact of accidents and safety hazards.

Drive-offs in a port terminal happen when an operator moves refrigerated cargo containers while they are still connected to an electrical source such as a rack mount reefer outlet assembly (Fig. 1 & 2). When a drive-off occurs, the plug or receptacle are in danger of breaking away. This breakaway can result in damage to equipment and infrastructure. In addition, and more importantly, it could also create hazardous conditions.

Aside from being dangerous, damage to refrigerated cargo containers can also be costly. In addition to repair or replacement cost, disruption to operations due to the unavailability of the reefer container slot corresponding to the damaged reefer outlet should be considered. Drive-offs are especially disruptive in automated container terminals. For safety reasons the automated operation must be stopped in the all or part of the stacking row while repairs are performed. Units must be repaired quickly in order to allow operation to continue and reduce financial loss.

Port Drive-off

In order to minimize drive-offs, ESL recommends plug sensing devices which can be added to Reefer Outlet assemblies. This solution contains a dry contact micro switch powered by a secondary source which can be used to help trigger a warning system (visual or integrated to TOS). This proactive option helps limit damage caused by human error which in turn, reduces operational costs and the need for replacement receptacles.

When it comes to breakaways, ESL offers receptacles made from polyamide, a non-metallic material designed to break easier under stress, preventing further damage to other components of the Reefer Outlet Assembly. This allows for easy replacement of broken receptacles and less operational time lost.

With increased education about the dangers of port drive-offs, and implementing precautions such as Safety-interlocked cord connected devices, injury and cost can be minimized. Learn more about ESL and how we can help keep your port safe by visiting our Intermodal page or contact us!

ESL’s Power Metering & Reefer Monitoring Assembly

Power metering and reefer monitoring assembly

ESL Power Systems, Inc. and Refrigerated Transport Electronics have teamed up to offer an integrated solution encompassing Reefer Outlets, Revenue-grade Power Metering and Reefer Monitoring. This system provides a single source of information for reefers while reporting energy consumption per reefer with revenue-grade accuracy.

The monitoring system uses power meters that can be integrated with RTE’s GRASP software. ESL’s assembly can be designed for multi-gang configurations in multiple mounting options.

Terminals can gain significant value from real data on reefer power consumption. With reefer containers accounting for up to 50% of a terminals total electric consumption, improving reefer management can deliver significant savings by providing necessary data. Power parameters measured with this new system include total power consumption, RMS current and voltage, frequency and power factor. This system also measures reefer parameters including Container ID, Sensor Valves; temperature, air, moisture, etc., Reefer operations; fan speeds, controller modes and Pre-trip state & alarms.

The potential impact for terminals and reefer service providers worldwide will be significant for understanding actual consumption, the baseline carbon footprint and improving terminal energy efficiency.

View ESL’s Power Metering & Reefer Monitoring capabilities sheet for additional information.