Written by Eamonn Ryan
Cold chain warehousing has experienced notable technological advancements over time.
Two elements that have become increasingly important are dock levellers, essential for unloading and loading trailers and trucks, and curtains.
As more businesses load containers or trucks, the demand for efficient loading and unloading systems has increased. Dock levellers create a secure and convenient link between the loading bay and the truck.
Loading bays, along with guides, shelters, seals, levellers, doors, curtains, supports, and rails, all influence the functionality of the cold chain, spanning from farm packhouses to retail outlets and transportation in between. Today, there are numerous designs and technologies available to choose from. In this feature, we explore these solutions, examining their functionalities, how they enhance value, mitigate risks, and improve overall operational efficiency. Additionally, we consider their impact and integration with refrigeration and storage systems within facilities.
Dock levellers and curtains are pivotal in maintaining temperature control during loading and unloading operations. Sustaining an uninterrupted cold chain requires meticulous attention to sealing and insulating dock levellers and curtains to reduce air leakage and minimise heat transfer.
Kobus Pretorius, an application engineer at DDL Equipment, elaborates: “To reduce heat transfer, DDL offers three types of dock sealing systems: CCS (Contact Curtain Seals), DCS (Dock Cushion Seals), and Combo shelters. These systems are designed to accommodate vehicles of varying sizes and their specific applications. The choice of system depends on the type and dimensions of the vehicles being loaded and the building’s exterior mounting surface. Additionally, sectional and high-speed doors are included to help manage the environment. Different models are available to suit various environments and can be operated through various methods, such as push buttons, radar sensors for detecting pedestrian traffic, remote controls mounted on forklifts, loop detectors embedded in the floor, or even biometric systems.”
Dock levellers and curtains play a crucial role in preventing airborne contaminants like dust, pests, or pollutants from infiltrating cold storage areas. Effective sealing mechanisms, including inflatable or brush seals, are essential for maintaining the cold chain by creating a barrier between indoor and outdoor environments.
Pretorius further explains: “DDL employs brush seals and PVC skirts, which can be installed at the front of a dock leveller to create an additional barrier that reduces the entry of contaminants. This setup also inadvertently helps to reduce theft. The seals cover the entire vehicle to block pollutants and dust. High-speed doors are increasingly used to manage temperature control, prevent cross-contamination between areas, and keep pests out of the building. These doors operate by opening and closing rapidly, incorporating numerous safety features. For instance, some models can automatically realign themselves if they are bumped and will resume normal operation. These high-speed doors are specifically designed for various environments.”
He emphasises that safety is a major priority in dock operations. Manufacturers prioritise incorporating safety features into dock levellers and curtains to prevent accidents and injuries. These features include safety edges, photoelectric sensors, and emergency stop systems. “Safety is a crucial element in the design and production of docking systems. Ongoing research and development continually enhance our offerings, which may range from simple handrails and walkways to advanced signaling systems. For example, our designs allow for the integration of additional safety sensors as needed.”
Dock levellers and curtains endure substantial wear and tear from frequent use and harsh conditions. To ensure durability and long-term performance, manufacturers use high-quality materials and robust construction techniques. Regular maintenance and inspections are vital to detect and resolve any issues promptly, thereby reducing downtime and extending the equipment’s operational life.
“For example, DDL seals are crafted from a double layer of durable canvas, which makes them repairable in most cases, thus extending their service life,” notes Pretorius. “Canvas is also washable and withstands cleaning with chemicals and disinfectants used to maintain dock hygiene. For dock hardware installations, aluminium is preferred due to its lightweight nature and resistance to rust when exposed to the elements. It is recommended to service dock levellers quarterly, and customers might also consider a Service Level Agreement (SLA) for added peace of mind, ensuring their dock equipment remains in optimal condition and any potential issues are addressed promptly. In coastal or corrosive environments, fully galvanised dock levellers and pit frames are often chosen.”
Manufacturers must comply with relevant regulations and standards for dock levellers and curtains. These regulations may include safety codes, building standards, fire safety measures, and energy efficiency requirements. Adhering to these standards ensures the safe and efficient operation of dock facilities and helps avoid potential penalties or legal issues.
Pretorius details that dock levellers are built to the BS-EN-1398 standards, which adhere to both British and European regulations and align with local food safety requirements. “At DDL, our dock levellers are engineered by our in-house team, with third-party engineering firms conducting Finite Element Analysis to scrutinise every component and ensure long-term durability. Additionally, we perform strength tests to assess the dock leveller’s lifecycle.”
Automation and technology are becoming more prevalent in the cold chain and logistics sectors. Engineers are integrating dock levellers and curtains with automated systems, such as dock management systems, to enhance operational efficiency. This integration may involve automated levelling, remote control functionalities, or connections with warehouse management systems for improved inventory tracking and logistics planning.
DDL has developed a comprehensive docking bay communication system that connects all docking equipment, including dock levellers, sectional doors, traffic light systems, and sealing systems. “The PLC (programmable logic controllers) system can be connected wirelessly if required. Sensors installed along the floor monitor the vehicle’s position in the docking stage, typically used alongside truck wheel guides. These guides help direct the truck into the docking bay, ensuring it aligns perfectly with the seal for optimal contact between the truck and the building.”
“The HMI (human-machine interface) screen inside the building directs the operator through each step of the process. Sensors are activated as the truck’s wheels pass through the beams, triggering different colored lights to indicate various stages of the docking procedure. The final sensor is positioned on the dock sealing system, illuminating a red light once the truck has achieved the optimal seal, just before it contacts the building or docking structure. This setup protects both the building and the seals by ensuring that the vehicle makes contact without overly compressing the seals, thus preventing damage. Additionally, trip switches on the doors are linked to the dock leveller to ensure that the dock leveller cannot be operated unless the door is fully open, and vice versa, to prevent closing the door before the dock leveller has returned to its resting position,” he explains.
Dock operations often demand flexibility to accommodate a variety of vehicles, container sizes, and load configurations. Dock levellers and curtains are designed with this adaptability in mind, featuring adjustable or modular systems that can handle different dock heights, door sizes, and specialised loading equipment.
At DDL, Pretorius notes that the company provides a design service tailored to meet specific client requirements. “This service includes custom seals designed to accommodate various vehicle types or to address spatial limitations in loading areas. Mini-dock levellers are available, though they are most effective with uniform vehicles. For situations where traditional loading docks aren’t feasible, elevating dock levellers or scissor lifts offer a compact solution, which is advantageous in space-constrained environments. Additionally, freestanding dock levellers can be paired with ISO panel enclosures, allowing for the installation of seals to ensure effective sealing.”
The advances of strip- curtains
Strip curtains have been in use for over forty years, and during this time, there has been significant advancement in the flexible PVC materials used to manufacture them. Today, there are various grades of these materials available, but for high quality, it is recommended to choose materials made with non-phthalate plasticisers, which are more environmentally friendly compared to some of the cheaper alternatives.
Maxiflex provides a range of materials tailored for different environments and applications. For freezer environments, the Polar material is suitable, handling temperatures from -25°C to +30°C, while the Super Polar material is designed for blast freezers and can endure temperatures as low as -60°C. These materials are specifically engineered for cold conditions, preventing them from becoming hard and brittle, which can lead to cracking and breaking. Thus, selecting the correct material for your specific needs is crucial.
Additionally, Maxiflex offers specialised materials such as the anti-insect variant, which includes citronella to repel flying insects, and the stop bac, which possesses antibacterial properties. Flexible PVC is available in standard clear, transparent, or opaque colored options.
Strip curtains have become a widely adopted solution for managing various factors in different settings. They are effective in controlling temperature, dust, pests, and wind, making them ideal for spaces that need to be enclosed, such as food manufacturing areas. In these environments, strip curtains offer a cost-effective alternative to high-speed doors or can be used alongside freezer doors to prevent cold air from escaping when the door is opened. By adding an extra layer of protection, strip curtains enhance energy efficiency.
During audits conducted by national retailers of their food suppliers, the presence of strip curtains is typically a minimum requirement. They are also frequently utilised in conjunction with freezer doors in hospitals or cold storage facilities. In these settings, strip curtains serve as barriers to minimise the loss of cold air when doors are opened, thus playing a crucial role in maintaining the desired temperature and hygiene standards.
In modern loading bays, goods are often moved directly from cold room facilities onto trucks. Loading bays can be designed as part of the building or situated outside on a loading platform or mounted on a freestanding frame. Opting for external loading bays offers several advantages, such as freeing up valuable space within the warehouse and enhancing energy efficiency. This setup allows for the integration of features like dock levellers, dock shelters, and load houses, which contribute to a more efficient loading process.
There are primarily two types of dock levellers: air-powered and hydraulic. When constructing a new facility, incorporating a loading dock is a crucial consideration, especially when handling heavy items with equipment like lift trolleys and forklifts. Dock levellers play a vital role in ensuring worker safety by bridging the gap between the loading bay and the truck floor. For effective operation, docks should have a minimum height of 1.2 meters, whether loading with a forklift or pallet jack.
Ideally, loading docks should be part of the initial design and construction of a warehouse. However, many older facilities may lack these features but can be retrofitted to meet modern requirements. Retrofitting involves assessing the existing layout and functionality to determine the best placement for equipment. This process may require constructing ramps or modifying existing structures to meet the 1.2m height requirement for docks.
Several accessories complement dock levellers to enhance their functionality and efficiency. These include bumpers that protect the dock and door from damage, dock shelters that help prevent cold air from escaping, thereby improving energy savings and working conditions, and other supportive features.
A notable advancement in dock leveller design is the telescopic dock levellers. This innovation allows the doors to open within the sheltered area by extending outward, providing greater reach and flexibility. Telescopic dock levellers facilitate access to trucks or containers that are positioned farther from the dock, thus streamlining the loading and unloading process. This technology is especially beneficial in cold climates where maintaining sheltered access and precise temperature control is essential, effectively preventing any temperature loss.
Another significant development is the introduction of insulated dock levellers. These levellers feature a fully sealed underside and incorporate insulation materials to minimise temperature gaps, reduce energy loss, and prevent the influx of cold air. Insulated dock levellers are particularly favoured in European countries with stringent energy efficiency regulations. By maintaining better temperature control, they help businesses lower energy consumption and operational costs. While these insulated dock levellers are relatively new to South Africa, they have a well-established history in Europe.