Container Weight System™ seamlessly integrates SOLAS compliant load monitoring technology onto existing container handling equipment to redefine the VGM weighing process.

Adopted by the world’s leading ports and terminals, CWS™ replaces time-consuming weighbridges to provide a new, faster method of container weighing. With its real-time data output, our system automatically weighs containers during your routine stacking cycles to generate precise VGM certificates without the hassle.

CWS™ utilises our proven, highly-accurate load monitoring pins and diaphragm load cells to provide an efficient, SOLAS compliant method for VGM processing. These are installed into the spreader, headblock, or sheaves of container stacking equipment and deliver container weighing speed increases of up to 300% when compared with weighbridges and other alternative solutions.

On this page you will find everything you need to know about CWS™:


CWS™ significantly improves port efficiency by providing an integrated system that provides VGM certification as part of the container stacking cycle.


CWS™ provides a more efficient solution to VGM certification that enables terminals to charge a processing fee for the VGM verification of all containers handled without compromising output.


CWS™ has been specifically developed to achieve full compliance with the International Maritime Organisation’s latest amendments to its SOLAS safety guidelines.

Why do I need a Container Weighing System on stacking equipment?

Weighing Review Listed


    Weighing and validating the VGM of every laden container bound for export using a weighbridge as a means to increase revenue is just not feasible. With the timely process required to weigh the container and then re-weigh once the container is removed to offer a tare weight – any increases in revenue gained from charging for this service are quickly offset by the inefficiency caused in this lengthy process.

    With its turnkey design, this faster, automated method of VGM verification Container Weighing Systems for container handling equipment unlock new revenue streams that ensure swift ROI.

    By using a container weighing system like CWS™ installed on Straddle Carriers, Reach Stackers, RTGs etc allows terminals to completely eliminate this inefficient process and instead obtain VGM data during when lifting and stacking containers in the stacking yard.

    This means that terminals determine VGMs instantly, with zero compromise to efficiency and can therefore benefit from being efficient enough to weigh every container without detriment to overall output and therefore benefit from the added revenue from a chargeable VGM verification service.

    By verifying the weight as a chargeable service, it then also offers the opportunity for terminals to charge a larger fee for any VGM discrepancies that will require a new VGM.

    Why CWS™?

    True weigh-in-motion capability – Unlike other solutions available, CWS™  can capture dynamic loads using our tried and tested in-house software. This accelerates container weighing speed by enabling the system to weigh containers while they are still in motion. This means that operators no longer need to slow down or stop their work in order to take load measurements.

    Automatic operation – With its automated weighing capability, CWS™ requires no input from the crane operator during its typical use. Integrating with your existing TOS (terminal operating system), this allows VGM verification to be completed for every container without interrupting your routine lifting/stacking operations.

    Increased productivity – CWS™ enables ports to significantly increase the number of containers that they can process. By integrating onto existing stacking equipment, weighing can be completed on multiple machines simultaneously, whereas weighbridges can only handle one container at a time. The system also reduces VGM weighing time to less than 30 seconds – down from the lengthy 10-minute processing time offered by weighbridges.

    Proven track record – Having supported the world’s leading ports and OEMs, CWS™ has a proven track record in raising the bar for container weighing operations on a global scale, with over 500 systems being sold to date.

    Why choose CWS™ over a weighbridge?


    • Enables terminals to implement a chargeable VGM verification on all export containers without compromise to TEU output
    • Fully automates the VGM process
    • VGM obtained during normal stacking operations, removing the need for a separate VGM weighing process
    • CWS™ improves VGM speed by up to 300% allowing you to weigh more containers in the same time
    • CWS™ enables all stacking cranes to generate VGMs, mitigating the risk of downtime as opposed to a single point of failure with a weighbridge


    • VGM verification is slow and inefficient –vehicles need to be weighed twice (with and without the container) to determine the tare weight
    • Creates a bottleneck in operations and single point of failure if the weighbridge is down the terminal cannot process containers
    • Weighbridges are too inefficient to introduce a chargeable VGM verification service – any gains in revenue are offset by inefficiency
    • Significant capital investment that has no other application

    What machine types is CWS™ available for?

    The system is available as a ‘factory fit’ option for new machines and can also be easily retrofitted into a wide range of port and terminal equipment such as reach stackers, straddle carriers, RTGs, ERTGs, rail gantry cranes (RMGs), automated stacking cranes (ASCs) and sidelifters.

    Developed in partnership with the world’s leading original equipment manufacturers (OEMs), CWS™ is fully adaptable to suit all the major crane and spreader manufacturers’ equipment types. The flexible system also provides different outputs to enable integration into any existing TOS, delivering a simple, efficient, and automated method of VGM certification.

    • RTGs, ERTGs, ARTGs and ASCs
    • Straddle and Shuttle Carriers
    • RMGs, ERMGs and CRMGs
    • Reach stackers
    • Sidelifters
    • Portable


    • Accuracy exceeds industry expectations and is a fully certified system
    • Weight obtained during the normal lifting cycle
    • Retrofit solutions for all existing spreader based container handling systems
    • Simple to install – minimal modification required to existing equipment
    • Full TOS integration, with data output in various analogue / digital formats
    • Dynamic “in-motion” weighing – VGM obtained during the normal lifting and stacking cycle
    • Identifies eccentrically loaded and overloaded containers
    • Simple to install – no modification required to existing equipment
    • 1% accuracy exceeds industry expectations for load cell based systems
    • Wireless system options
    • No driver intervention required – fully automatic system
    • Rugged proven technology – vibration and shock resistant
    • On-board data logging


    • Full compliance to SOLAS regulations
    • No delay to port or terminal operations or compromises to efficiency
    • Flexible integrated solution
    • Seamless process for producing VGM
    • Improved safety
    • Reduced installation costs resulting in minimal downtime
    • Eliminates potential for human error, no training required
    • Highly reliable for long life and low maintenance
    • Historical data available for analysis and a backup to TOS system
    • Quick installation and eliminates the risk of cable damage
    • High accurate VGM that meets type-approval criteria

    How is CWS™ installed, commissioned, and calibrated?

    InstallationCWS installation

    CWS™ is designed to be retrofitted to existing container handling equipment with minimal modification required. This ensures a quick and easy installation process. Typically, two systems can be installed and commissioned per day – our engineers will install the first system and will usually supervise subsequent installations.

    The system can be retrofitted into the spreader headblock or at the twistlock making it a permanent feature of the container handling equipment. This minimises wear by replacing existing load bearing pins with our strain gauged load monitoring pins, which can be integrated without our CWS™  interface, display and software algorithms if required.

    Working closely with the world’s leading ports and terminals, CWS™ is fully adaptable to any pre-existing set-up.

    “We assessed a number of different options to be able to offer a container weighing service to our customers and selected the system because it doesn’t require any changes to our port operating procedures and is quick to install. The trials demonstrated an accuracy above our expectations.”
    Nick Loader, chief executive officer, DP World Southampton

    Calibration and Commissioning CWS installation

    For type-approved systems: In line with our accreditations, our expert commissioning engineers are on-hand to install, commission, and calibrate type-approved systems. Systems can also be installed by third-parties, however, these will need to be commissioned by us if they are to be EU type-approved.

    For non type-approved systems: we are able to offer full installation, commissioning, and calibration training packages to enable you to install CWS™ yourself. CWS™  can also be installed by end-users or qualified technicians.

    Container weighing FAQs:

    We have compiled a list of the key frequently asked questions relating to the implementation of the new SOLAS container weighing regulations.

    The international convention for the Safety of Life at Sea (SOLAS) is an international maritime treaty to ensure the safety of the ship, the safety of workers both aboard ships and ashore, the safety of cargo and overall safety at sea. The treaty has been recently amended (chapter VI, part A, regulation 2) to require (by law) that packed containers’ gross mass are verified prior to stowage aboard ship. This legislation covers all SOLAS regulated vessels, which is 98.6% of the world’s tonnage.

    The IMO’s SOLAS amendments provide two approved methods in determining the container weight:

    • Method 1 – weighing the loaded container
    • Method 2 – weighing the contents of the container and adding those weights to the containers tare weight

    If the new regulation is clear, at least in principle, on what needs to be done to achieve compliance, it is also unambiguous on who is ultimately responsible: Container VGM determination can be subcontracted to a third party by the shipper, but the shipper remains responsible for regulatory compliance.

    Under the SOLAS requirements, the shipper named on the ocean bill of lading is the party responsible for providing the maritime (ocean) carrier (master) and the terminal operator (terminal representative) with the verified gross mass of a packed container. The carrier and the terminal operator must not load a packed container aboard a ship unless they have the verified gross mass for that container.

    Due to the complexity of the international supply chain, the entity identified as the shipper on the bill of lading may not have direct or physical control over key elements of the process by which verified gross mass is determined. A shipper in such circumstances should be aware of their responsibilities and ensure that arrangements are in place to obtain and provide a verified gross mass in compliance with these international and national regulations.

    SOLAS does not instruct any particular form for communicating the verified gross mass of a container. The VGM information must be signed and dated by the shipper or a person duly authorised by the shipper. Signatures may consist of the last name of the responsible person in capital letters and can be exchanged electronically.

    As an international issue, SOLAS regulations state that VGM weighing equipment, for both method one and two solutions, must meet national certification and calibration requirements. There is no provision in SOLAS for any margin of error.

    Shippers using compliant weighing equipment and procedures will obtain VGM values that are well within any national tolerances adopted for enforcement purposes.

    The new ruling will be officially enforced by the maritime authorities of individual nations, whose implementing regulations will vary depending on country and region. The real-world enforcement seems most likely to be carried out directly by the container lines and terminal operators, who are obligated not to load a container without the certified VGM document accompanying it. National enforcement agencies may implement measures to satisfy themselves that compliance is achieved, which could include documentation checks, auditing or random weight checks.

    Compliance with this obligation by the carrier and terminal operator may result in commercial and operational penalties, such as delayed shipment and additional costs if the shipper has not provided the verified gross mass for the packed container. As a commercial issue, penalties may involve repacking costs, administration fees for amending documents, delayed or cancelled shipments.

    Although the shipper is ultimately responsible for declaring the verified weight of a container, the new amendments will affect and therefore apply to everyone within the supply chain. Shippers, freight forwarders, vessel operators and terminal operators will all need to establish procedures to ensure the implementation of the SOLAS regulatory change.

    The SOLAS rules require the shipper to communicate the verified gross mass as part of an official shipping document. It must be signed by a person duly authorised by the shipper, with a first and last name, not just a company name. The signature may be an electronic signature or may be replaced by the name in capitals of the person authorised to sign it.

    The VGM and signature can be part of the shipping instructions communicated via electronic data interchange (EDI), or be contained within a separate communication including a hard copy document. In either case, the document should clearly highlight that the gross mass provided is the verified gross mass.

    While the onus is upon the shipper to fulfil the container weight verification obligation, the most practical location at which weighing can take place is at the ports and terminals, where lifting is a part of the existing cargo handling process.

    Our Container Weight System™ enables the weight of a container to be determined without the need to do anything different to what ports and terminals do today, the weight is obtained during the course of existing lifting operations. Spreader based weighing solutions are the only solution that have zero time and operational impact on existing terminal operations.

    There is no need to implement separate lift and drop or more complex weighbridge based processes. This gives ports and terminals the opportunity to obtain a VGM for each container without any additional operational cost If a container turns up to a terminal without a verified weight it cannot be loaded onto the vessel. By installing a container weighing system on site, any potential issues of containers being stranded at the terminal need not be a worry.

    The SOLAS regulations provide that verified gross mass shall be obtained under both method 1 and 2 by using weighing equipment that meets the applicable accuracy standards and requirements in the State in which the equipment is being used. Those national standards and requirements will determine the acceptable level of accuracy of the weighing equipment used.

    There is no single international approval for weighing equipment to provide accurate VGM, however, all equipment used (whether for method 1or method 2) will need to meet the applicable accuracy standards and requirements of the state in which the equipment is being used.

    NOTE: CWS™ has successfully achieved EU-type approval, ensuring full SOLAS compliance.

    The requirement for Type Approval weighing systems generally only affects countries within the European Union (EU). However, each country is responsible for how weight verification systems for commercial use are regulated, therefore you should check with your own relevant governing bodies to determine if Type Approval is required.

    Type Approved systems have been introduced as a requirement for container weighing systems used for commercial purposes operating inside of the EU.

    The legislation was interceded to provide greater regulation of the performance of systems that are used for commercial weighing applications to ensure the accuracy of container weights, prior to being loaded on board container vessels.

    There are several key differences between the way a non-Type Approved and Type Approved VGM system operates and is maintained.

    Description Type Approved Non-Type Approved
    Displayed total value 1 decimal place – to the nearest 200kg (0.2t) 3 decimal places
    Display zeroing (rest of offset back to zero) using the F1 button Restricted by Type Approval requirements Unlimited
    Certified performance Yes No
    Calibration Verification procedure – to be undertaken by qualified personnel (Module D) only, or the local authority Can be undertaken by the end user
    In-service Inspection Mandatory Optional, but recommended

    CWS™ has been certified to the most stringent standards and offers full OIML certification (R51) issued by the NMO, as well as EU Type Approval offering compliance for use in EU countries.

    Our CWS™ system for RTGs , Straddle Carriers, RMGs and ASCs using our advanced proprietary software algorithms to capture the VGM in real-time as the containers are lifted. There is no requirement to stop the lift.

    Our CWS™ for Reachstackers differs in that it requires the operator to pause once the containers are lifted to capture the VGM in order for the forces from the hydraulics to subside. The process is still very efficient however, and takes less than five seconds in most cases to capture the VGM once the container lift has stabilised.

    CWS™ is designed to require minimal modifications. A display needs to be mounted within the driver’s cabin, and an interface unit fitted to the spreader. The load cells are designed to replace existing pins or collars, so require a simple swap from a non-instrumented pin/collar to a load monitoring pin/collar.

    Developed in partnership with the world’s leading original equipment manufacturers (OEMs), CWS™ is fully adaptable to suit all the major crane and spreader manufacturers’ equipment types.

    CWS™ provides a range of streaming outputs (Ethernet, RS232, RS422 and RS485) allowing CWSTM to have the ability to be integrated into all major TOS systems.

    Within +/-1% of full scale, in line with type approval regulations. CWS™ is more accurate than traditional load cell-based systems currently available.

    CWS™ is designed to retrofit onto existing container handling equipment with minimal modification required. CWS™ offers a quick and easy installation process, allowing two systems to be calibrated and commissioned in one day.

    CWS™ sensors (load cells) can be easily retrofitted into the spreader headblock or at the twistlock (replacing existing pins/collars) making installation simple with like-for-like replacement as each load cell are designed bespoke for your machine. The interface unit is mounted on the spreader either using bolts or welding the mounting brackets. The cabling is then routed from the load cells to the spreader mounted interface unit. The interface unit then transmits the weight data via a wireless connection to an in-cab display.

    Whilst the preference is for our fully qualified and experienced engineers to supervise installation and commission the system, we do also allow terminals to install and commission the systems themselves once they have received training from our commissioning team.

    CWS™ does not come with an in-cab printer as standard. However, this can be purchased as an optional extra.

    We recommend outputting the data directly to the TOS, which fully automates the process.

    No. A key advantage of the CWS™ system for RTGs, Straddle Carriers and RMGs is that CWS™ is able to weigh in motion.

    Using our advance in-house developed proprietary software, CWS™ is able to define the VGM (to +/-1% accuracy) in real-time as containers are lifted in-motion without any need to interrupt existing lifting and stacking operations by stopping the lift to take a stable weight.

    Our CWS™ system for Reachstackers differs in that it requires the operator to stabilise lift and forces from the hydraulics in order to obtain an accurate VGM reading. The process is still very efficient, the system will identify once a stable holding weight can be taken and in most cases captures with VGM in less than five seconds.

    CWS™ is fully adaptable to suit all the major crane and spreader manufacturers’ equipment types.  Contact us for confirmation regarding compatibility with your existing equipment.

    We will review your machine configuration and will design a bespoke load cell that offers the best performance for your machine and spreader. In most cases, a load bearing pin that replaces the existing pin in the hoisting sheaves is appropriate however, we can also supply a diaphragm (annular) compression load cell that replaces the existing collar around the twist lock.

    CWSTM can be supplied for both new machines and retrofit for most crane makes/models available.

    CWS™ requires minimal maintenance for typical use. Once installed the load cells need to be regularly greased – we recommended that the systems are calibrated at least once yearly to ensure accuracy is maintained.

    For EU-type approved systems, the system requires calibration once per year by technicians with the required certification. Our engineers are able to offer certified calibration in order to maintain type approval.

    For non-type approved systems, terminals are able to calibrate their own systems once trained.

    If you are considering using VGM certification as a commercial opportunity, please Contact Us for more information [link to CWS enquiry page]

    Yes, CWSTM is fully automatic in operation when integrated with the terminals TOS. Weights are captured with no operator intervention required, or change in operation as the stable weight is captured in real-time during normal stacking operations and automatically output into the TOS.

    CWSTM has been specifically designed to comply with SOLAS regulations and also offers further compliance with EU-type approval for terminals operating inside the EU.

    Yes. The system is able to identify eccentrically loaded containers – in addition to the stable holding weight, all four load cells weights are displayed (and can be output to the TOS) making the identification simple and automated if required.

    CWSTM is a wireless system as standard. Whilst the load cells themselves are cabled in either option to the spreader-mounted unit, we can provide either a wired or wireless communication between the spreader mounted interface box and the in-cab display. If a cable option is preferred, you will need to find suitable cable routing between the spreader and cab display.

    Yes, the system offers two types of data logging. We offer a short data-logging application within the CWS™ configurator software to aid in troubleshooting as well as live data streaming output to log the data via an external system – i.e. TOS.

    Our Container Weighing Solutions

    Container Weight System™

    Container Weight System™

    CWS™ for RTGs

    CWS™ for RTGs

    CWS™ for Straddle Carriers

    CWS™ for Straddle Carriers

    CWS™ for Reachstackers

    CWS™ for Reachstackers

    CWS™ Sidelifter Configuration

    CWS™ Sidelifter Configuration


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