Cell guideson container ships.

Cell guides are the vertical guides in the hold of a container ship. They lead each container into its slot during loading and keep the stack in place at sea. Class rules also call them guide bars or guide rails.

This article is for shipyards, owners and superintendents who need to assess a damaged guide or plan a repair. Where a figure applies to one classification society only, we say so.

01What are cell guides on a container ship?

A rigid securing system of vertical steel angles. ABS defines cell guides as angles spaced with some margin on container length and width, which align the container stacks and restrain them horizontally¹. ClassNK puts it more briefly: the angle bars fix the four corners of the containers. During cargo handling they guide, during the voyage they hold².

A hold fitted with cell guides is divided into cells, and each cell takes one stack of containers. Most container ship holds are designed for 40 ft containers⁵. To carry 20 ft containers in 40 ft cells, the Lloyd's Register rules, for example, allow provision for temporary intermediate guides³.

At the top of the guides sit entry guides. They open like a funnel in both directions and pre-centre the container before it slides into the cell^2,3. Lloyd's Register lists fixed even peaks, fixed high and low peaks and "flip-flop" systems as typical designs³.

02How are cell guides built?

Generally from steel plate and rolled sections, attached firmly enough to the supporting structure that container loading cannot trip or distort them³. The main parts:

The widths and thicknesses are guide values, not fixed standard sizes. What counts are the approved drawings of the ship.

One point matters for any repair: cell guides are not part of the hull girder. Lloyd's Register states that they are not to form an integral part of the ship's structure and should be kept free of the main hull stresses. At the same time they must transmit the loads from cargo handling and ship motions into the hull structure³. That makes the connections the sensitive spots.

03How much clearance does a container have in the cell?

Very little. Under the Lloyd's Register rules the total clearance between container and guide bars must not exceed 25 mm in the transverse and 40 mm in the longitudinal direction. The deviation of a guide bar from its intended line is generally not to exceed 4 mm transverse and 5 mm longitudinal³.

"Total clearance" means both sides together. If the container touches one side, at most 25 mm are left on the other. For comparison: an ISO container is 2,438 mm wide, a 40 ft container 12,192 mm long². The Standard Club, a P&I club, sums it up: the clearances, and hence the construction tolerances, are very tight⁵.

These figures come from the July 2022 edition of the Lloyd's Register rules. Other societies set their own requirements; the Indian Register of Shipping, for example, refers to ISO 3874⁴. For your ship, the values of its classification society and the approved drawings apply.

04What damage do cell guides suffer?

The best documented damage is deformation from impacts. IACS, the International Association of Classification Societies, writes in its recommendation for container ships that cell guides and their connections to the side structure can be found deformed or distorted due to mishandling during container stowage⁶. The hold side structure is also prone to damage from cargo and cargo handling equipment during loading and discharge⁶.

A research group described the problem in the journal Sensors in 2022. Containers sway while the crane moves them through the cell and hit the guides. This can mean serious downtime while damaged sections are replaced. If the impacts keep hitting the same places over a long time, the ship's structure itself can be damaged⁷.

An example in the IACS recommendation shows that the damage need not stay in the guide. It describes a fracture at a main hatch corner that started at the welded joint of a cell guide. The repair advice: crop and renew the fractured deck plating, avoid welding the cell guide to the deck plating at the hatch corner, and connect it to the structure below deck level, or integrate it into the hatch corner⁶.

05How do you spot a damaged guide?

Usually by eye, reliably only by measuring. The Standard Club advises checking before loading that guides are not bent or deformed, are clear of obstacles, straight and not buckled⁵. Under the Lloyd's Register rules for annual surveys, the surveyor examines the fixed cargo securing fittings as far as necessary and practicable, to be satisfied as to their general condition¹³.

Visible signs are dents and kinks in the angles, bent entry guides and cracks at brackets or connections. Whether a guide is still within tolerance only a measurement along its intended line will show. We recommend measuring before and after a repair and recording the values.

06Does class need to attend the repair?

That depends on the damage and on the society. Under Lloyd's Register, fixed fittings which are part of the container lashing equipment or which may affect hull strength are subject to approval. Drawings showing materials, design and scantlings of the cell guide structure are to be submitted⁸. The initial survey of fixed fittings, including cell guides, is mandatory on all ships⁹.

Repairs needed for a ship to retain her class are to be carried out to the satisfaction of the surveyors, and damage which could affect the conditions of class is to be reported without delay¹⁰. This does not mean every small repair to a guide has to be witnessed. Whether a surveyor attends is agreed case by case between owner and classification society.

IMO also has the topic covered. Its guidelines for the Cargo Securing Manual apply explicitly to container stowage within or without cell guides, and the manual should contain procedures for accepting, maintaining and repairing or rejecting cargo securing devices¹¹. It is worth checking it before the repair.

07How does a cell guide repair work?

This is how we approach it at Nauticon. The sequence is the same on every ship; the scope is not.

1. Record the damage. Photos, position of the cell in the hold, affected height, visible cracks at brackets and connections.
2. Agree the scope. With the owner and, where needed, with class: will a surveyor attend, which drawings and materials apply, is a poor connection changed?
3. Prepare. Hot work only with a fire watch, the hot work permit as required by owner or yard. Hold clear, access and lighting arranged.
4. Repair. Cut out and replace damaged sections or bring them back into line. Welding by welders qualified to EN ISO 9606, under welding coordination to EN ISO 14731.
5. Measure. Check the guide against its intended line and the class tolerances, record the values.
6. Accept. Together with the client and, if agreed, the surveyor, with feedback to you.

08What should you prepare as a client?

The better the first enquiry, the more precise the planning. Helpful:

• vessel name, IMO number and the port or yard where the ship is
• hold and cell, in practice with bay and row
• photos of the damage, ideally with a tape measure in the picture
• the drawings of the cell guide structure, if available on board
• whether class has already been informed
• the time window: port stay or yard period

09Summary

Cell guides are simple parts with tight tolerances. Deformation from impacts is the best documented damage, and a badly detailed connection can crack into the deck structure. Whoever repairs them should think about the cause, agree the scope with owner and class early, and measure the result.

Research is working on the subject too. From 2019 to 2022, Hamburg University of Technology ran the "CellGuide" project, aiming at improved cell guide designs, including retrofit solutions, that secure cargo without lashing¹².