An interesting article about a seemingly easy and innocuous activity like opening a door.. But when you relate it to a freight container, you can see the importance that it holds..
Car manufacturers may advertise the reassuring ‘clunk’ when a car door is shut and we would generally expect to open a car door with ease. On a particularly frosty morning, when ice has seized them shut, we would never consider using a crow bar. Conditions may be more extreme in container operations, but is it reasonable to use mechanical force to open or close container doors? Experience suggests that it is not – and often ends with someone being hurt.
Injuries to personnel involved with opening and closing container doors are increasing, and often it is as a result of an inappropriate technique that is being employed. We might expect container doors to open and close as if they were car doors, without understanding why this might not be the case.
Starting with the structure of container doors, most will have four or five hinges per door. The mechanics at the point of manufacture is that the hinge pins must be all aligned on the same plane (vertical and horizontal) and in line. Offset hinge pins will result in the blade binding when it is rotated about the pin – the more the misalignment, the greater resistance will be encountered during operation. At the time of manufacture, therefore, it might be expected that the hinge pins on every door are aligned and free to fully open (270º of operation).
Let’s assume that the container is presented in pristine or well-maintained condition; why might the door not open with ease? Containers are generally either on a trailer / chassis or on the ground, and in both cases the position of the locking gear handles are at an inconvenient height. For best results, the handles should be directly in front of you and at a height that is above the waist and below the shoulders.
Technique is all-important. Start with the two lock rods on the right hand door, lift the handles out of the retainers and rotate them together as far as they will go. This should be more than 90º and rotation beyond 90º often initiates the door opening process by forcing the cams out of their keepers. Then grasp the vertical locking bars, one in each hand, so that your hands are just below shoulder height and pull back with your body, using your leg muscles rather than you back.
If the door is still stuck, unless specifically advised against doing so (ie. the container is carrying a flexitank or bulk cargo), open the locking bars on the left hand door and then grasp the inner locking rod of both doors and pull back, again using your body not your back. If the door still will not open, ask a colleague to pull on one door while you pull on the other.
Injuries almost always occur at the point frustration takes over and mechanical means are employed – the crow bar or a fork truck. So why will the door not open? Generally, this can be attributed to one of four reasons:
- The container frame is racked so that the door gear will not operate correctly. This may be caused by cargo shifting during transit. Look at the container to make sure that the doors are aligned and level, both top and bottom.
- The hinge pins and blade are seized due to corrosion.
- The door gasket has been damaged and is preventing opening. Door gaskets are designed to present two or more fins against the structure or adjacent door. These are generally flexible but when the gasket is damaged, they may become hard or blocked thus jamming the door closed, or preventing it being closed.
- Water has become trapped between the doors and frozen, particularly relevant to refrigerated cargoes, or containers with moisture releasing cargoes in cold weather.
Doors that open but are stiff to operate may suffer from the first two reasons above, as well as misaligned hinge pins. Pins can become misaligned by damage to the ‘J-bar’ which has twisted one or more pins or a repair to the hinge blade or pin that has incorrectly aligned the blade with the remainder of the hinges on the door. For example, adding a backing plate under a single hinge blade will immediately take the blades out of alignment. Therefore, when a hinge blade needs to be refitted because of damage or corrosion and a doubler plate is required, plates should be inserted under all the blades on that door.
The safe operation of doors requires that some attention be given to them. Many hinges have coatings to the inner surface of the hinge blade, others use plastic liners, both of which are designed to protect against corrosion. Some designs are fitted with greasing apertures. Fundamental to success is the examination and maintenance processes.
Typically, doors will be opened for in-service inspections and off-hires. Where oil does not free the hinges, repair work is necessary. These inspections include a visual check that the hinges and hinge pin welds are not broken or cracked. Opening doors could valuably be done when a depot releases a unit for packing, since it may have been in the stack for a prolonged period.
If the doors cannot be opened to pack a container, send the unit back! If it is already packed and you need to open the doors, but they will not open by hand, try to pull both doors open at the same time with increasing power. If you need more than two people, ensure you tell the container operator, especially if, as a result of opening the door, the locking gear or doors are or become damaged.
And, when you are opening a packed container, remember to watch out for those packages that are just about to fall out. In all these matters, be alert that the doors are big and heavy – treat them with respect and report anything unusual.
Source : http://www.ttclub.com