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Container top safety frames

SIM 05/2008/05


This SIM updates and replaces SIM 05/2003/56 and offers inspectors guidance on the issues to consider during the inspection of container top safety (CTS) frames and the associated training and systems of work. Much of the guidance will also be applicable to other types of frame such as "Torpedo" and "Stinis" frames.

The guidance was written specifically for gantry cranes. Although many of the principles will apply to the use of CTS frames with slewing cranes, inspectors may wish to seek further advice from the sector on specific issues arising in these instructions.


1 Loading and unloading containers from ships usually involves access to the tops of container stacks to remove and place the securing devices holding the stacks together (known as twist locks).

2 Containers are normally around 3m tall and stacks can be up to 5 containers high above the deck of a ship. Despite the obvious risk of falling container operations were, traditionally, carried out by stevedores walking across container tops. This work was often carried out with no fall prevention methods. When fall prevention was provided it was in the form of a harness. This method sometimes had significant problems as access to suitable anchor points was difficult.

3 There are a number of methods for reducing the risk of falls when working on containers. Information on these systems and their relative merits can be found in international guidance (see 'Further information' below). The use of one of these methods, namely CTS frames, is increasing and this SIM deals with the specific issues arising out of the use of these frames.

4 CTS frames are cages suspended from a container crane in which workers are carried to and from the container stack and from which work on the stack can take place. They are usually the size of a container, with an enclosed roof and open sides with hand rails. Contact with the crane driver is by radio and/or hand signal. Many operations which previously required personnel to walk on container tops can be carried out from within the frame.

5 CTS frames usually operate above containers and access to twist locks is gained through flaps in the floor. The frame is designed for continuous motion over the container stacks usually working from sea to quay across the ship. Operators will stoop or kneel on the floor of the frame for these operations. Such operations are carried out over stacks of containers which are all the same height.

6 There are times, however, when the frame will be adjacent to rather than above containers and other fixed objects. If the frame is in motion, under these circumstances, there is the potential for any part of the body which is outside the frame to be trapped or crushed. One worker has been killed in this way.

7 In particular, there are times when the frame will be used beside other stacks of containers to undo twist locks etc. Examples include occasions when an adjacent stack is to stay on the vessel and go to another port (such containers are known as "remain on boards") or when adjacent container stacks have "over height" containers in them (containers which are taller than the standard version). There may also be the need to work beside container stacks to free jammed twist locks. These types of operation must only be attempted with the frame stationary.

8 To reduce any trapping risk to a minimum the use of CTS frames must be subject to an adequate risk assessment which should consider both the frame and the tasks that will be carried out from it. This will include consideration of the frame design, an adequate safe system of work and the training required by staff. The results of the assessment should be implemented, monitored and reviewed.

9 A good design together with a safe system of work and adequate training will help reduce the risk from container operations eg by minimising the need to work outside the frame.

Design of frames

10 The following issues should be considered for during a risk assessment for a CTS frame:

System of work

11 There must be a written safe system of work in place covering the operation of these frames. It will usually need to cover (but not be limited to):


12 Training is an essential part of CTS frame safety. Prior to any training employees must be assessed as being physically fit, as this is a heavy manual job. They must also have an ability to work comfortably at height.

13 Training must include a significant practical element which is carried out under close supervision preferably on a training rig to begin with. Following training, a competence test should be undertake by all trainees. Both training and competence assessment must cover the full range of operations carried out using the frame.

14 Training must include full details of the safe system of work and measures in place to protect employees using the frame.

15. It is good practice for trainees to be identified (eg by wearing different coloured safety helmets).

Relevant legislation

16 The legislation which applies is:


17 The likelihood of a serious or fatal accident in a well-designed and operated CTS frame should be remote. Significant shortcomings in the frame design, systems of work and training when assessed against the criteria in this SIM will quickly increase the risk gap. Where inspectors find frames that are not being operated in accordance with a written SOW, where staff are untrained or where the design or condition of the frame has significant inadequacies a prohibition notice should be considered.

Further information

18 For further information on the issues raised in this SIM contact the STSU Transportation Section in East Grinstead on 01342 334261.

19 Further information can also be found in PSS's Health and Safety in Ports Guidance Sheet SIP003 - Guidance on container handling and in the International Cargo Handling Co-ordination Association (ICHCA) document "Guidelines for lifting persons at work for cargo handling purposes in the port industry".

Action by inspectors

20 Inspectors are asked to:

Cancellation of instructions

21 Cancel and destroy SIM 05/2003/56.
Updated 2020-12-15