04.12.2008

Skyjack warns on SJ8841 inspections

Skyjack has issued a service advisory following a recent incident with a nine year old SJ8841 scissor lift. The advisory warns owners and users to ensure that they check pins and bushes for any signs of seizing.

The advisory follows an incident on a scissor lift rented by Kier plant for a job on an Asda supermarket in the UK. Two men were about to lift the platform to the work area when a noise was heard, loud and disturbing enough to cause them to stop lifting. Those on board and a third man on the ground checked for any obstruction in the scissor mechanism.
Please register to see all images

The scissor lift after the incident

Having found nothing obvious, they attempted to continue to raise the platform until a loud bang was heard, at the same time the front end of the platform tilted forward into the position shown in the photograph.

The platform had just lifted from the closed position and was under two metres high when the incident happened. The two men were pitched forward but were unharmed and were able to climb to the ground.

It appears that one of the bottom set of pivot pins had seized in their bushings, causing the noise and then extreme stress on the bearing retainer loops/end caps on the scissor arms, effectively tearing them allowing the arms to come free from the pivot pins.
Please register to see all images

The lower arm end caps/pivot bush retainers failed

Please register to see all images

The end caps were cracked and stretched by the extreme stresses of the siezed joints

We understand that the lift had several owners during its life and may not have always been as well serviced and maintained to the same standards as its current owners, The Platform Company, (now Nationwide Platforms) are known for, The advisory from Skyjack is published in full below and warns on the need to fully inspect such stress points, especially on older machines. Tell-tell signs include noisy pins/bushes and localised rust, where paint may have flaked due to the heat generated by semi seized pins.
Please register to see all images

A close up suggests that one of the cracks may have been older than the other?

SkyJack Service Advisory

It is important that operators and maintenance personnel carry out
inspections as outlined in the applicable Skyjack operator and service
manuals.

It is important that inspections are carried out on a regular basis, and
adhered to as required by local regulations, (i.e. LOLER etc) and in
accordance with the correct periods of inspection, which may be daily /weekly / monthly.

For example; all pins, weldments and pivot points are subject to high
stress, and special consideration should be given to these particular
areas as with any load bearing points.

Older machines in particular may have seized pins or joints, and if there is any doubt regarding the integrity of particular assemblies, they should be stripped and inspected further. Cracked paint, rust or loose retaining bolts can often indicate a problem which otherwise may not appear immediately obvious.

Our manuals are accessible online – www.skyjack.com

Vertikal Comment

Scissor pins and bushes can be subject to corrosion and eventual seizing, particularly in hostile environments where moisture and dust are frequently present, excessive overloading can also exasperate the condition, adding fatigue to the equation. If the situation is allowed to persist, especially on the lower pivot points, a failure such as this can occur, no matter the make of the machine.

If in doubt there are several ways to double check that pins are not beginning to seize, from listening closely to checking for heat generation.

While this is a serious situation, the failure is most likely to occur during times of maximum stress - during lift off as in this case or just before reaching the fully closed position if stopped.

Skyjack has been contacting owners of similar machines to the one involved in this incident and has taken a laudable and professional approach to the issue. The failure should serve to remind all owners and users of all scissor lifts to maintain and properly inspect pivot points and stress areas on scissor arms.