No 170

170/1
Our Most Frequent Accidents
170/2
A Runaway FLT
170/3
An Unexpected Fall
170/4
Crash Barriers
170/5
A Leak Leads to a Fire
170/6
Another Unexpected Fall
170/7
Temporary Obstructions
170/8
Unusual Accident No. 118,
Flames in a Confined Space
An Engineer’s Casebook No. 70 In this Issue:-
Glandless Pumps UPLIFT
170/1 Many of the accidents involve lift trucks. When used for
Our Most Frequent ancillary work in chemical manufacturing units, these trucks
are often in continuous use under rough conditions. Wear
Accidents and tear is much more severe than that experienced in a
commercial warehouse. Consequently, more care is needed
Materials handling,
to select the correct type for the work to be done, to use it
whether literally by hand
carefully, inspect it frequently and maintain it properly. ICI
or using machines, Is our
readers may like to consult.
greatest single cause of
personal injuries. “Code of Practice for the Procurement, Examination and
Inspection of Purchased and Hired Fork Trucks”. February,
1980, issued by the Company’s Materials Handling Panel.
All readers will find two other booklets useful:-

“Safety in the Stacking of Materials” Health and Safety at

Work Booklet No 47 published by Her Majesty’s Stationery
Office.

and

“Safety in Working with Lift Trucks” a booklet in the HS(G)

series also published by HMSO.

This Safety Newsletter records some incidents which have

occurred because the good advice so readily available has
not been followed.

170/2 A much more usual cause of trouble is the failure simply to

A Runaway FLT put on the handbrake when the truck is not in use. In a
recent accident a truck was parked on a slope with the
In an earlier Safety brake off. The truck subsequently rolled down the slope and
Newsletter (160/4) I rammed a closed door at the entrance to a warehouse.
described an incident in Trucks should not be parked on sloping ground and the
which a Fork Lift Truck handbrake should be carefully maintained and used
ran away when Its battery whenever a truck is parked
was reconnected because
it had been left in gear
with its ignition switch in
the ‘on’ position.

170/3 A Fork Lift Truck was being used to load a trailer parked
An Unexpected Fall next to a loading platform. The driver drove his truck, loaded
with a pallet on to the trailer platform and deposited his load
Failure to use a safely. He then tried to reverse his truck onto the loading
handbrake caused platform. However, when he reached the rear edge of the
another incident which trailer the whole trailer moved forward and the truck fell into
could have had much the gap created between the trailer and the loading
more serious platform. Fortunately the truck landed in the upright position
consequences. and the driver was not hurt. The brakes of the trailer had not
 been properly applied.

170/4 Collisions with doors or with door jambs frequently occur.

Crash Barriers Pedestrians are often injured as they emerge from a
doorway and appear unexpectedly in the path of a fork lift
Pathways for trucks and truck being driven in the opposite direction.
pedestrians are best kept
completely separate and Pathways should be arranged so that as much chance as
free from obstructions. possible is given to drivers to see any obstructions in good
time. It will help if a separate door can be provided for
pedestrians.

So will crash barriers designed to prevent people from

‘sliding round’ the corner of a doorway. Additionally, the
reduction in maintenance costs for damage to the doorways
will often more than pay for the cost of installing a barrier.

170/5 There are, however, other causes of fires. In a recent

A Leak Leads To a incident a fork lift truck caught fire when oil from a failed
hydraulic hose was sprayed onto the truck’s exhaust pipe.
Fire
The fire extinguisher on the truck was empty and so did not
Neglected electrical work. As a result extinguishers on the trucks are now
equipment sometimes inspected by the supervisor once a month and replaced
causes a short circuit and every six months. In addition the drivers are reminded that
a fire. the ICI Code of Practice requires that drivers check the
hydraulic system for obvious leaks or cracks at the start of
every shift.

Many incidents in chemical plant operation are similar to this

one and the preventative measures are also similar.

170/6 An investigation of the dock leveller showed that a fulcrum

Another pin had dropped out of the lip operating mechanism,
allowing the lip to collapse sufficiently to become detached
Unexpected Fall from the container.
A fork lift truck was being The fulcrum pins were each secured by a grub screw. Split
used to stuff an ISO pins would have been better and modifications were made.
container. As the truck It was noted that the lip of the dock leveller tended to lift by
reversed out the driver a couple of inches. It therefore received a shock each time a
heard a clattering noise
which he assumed was truck was reversed over it. The correct counter balance is
caused by the truck difficult because the leveller can easily be made too heavy
hitting the raised lip of the to handle if insufficient is used. Requirements for different
dock leveller. He purposes are clearly in conflict. An ideal solution may be
continued to reverse. As impossible and regular careful inspection for possible
the truck moved on to the damage will still be needed.
leveller it fell about one
foot.

170/7 Two of the most common obstructions are packages left in

Temporary thoroughfares and scaffolding obstructing or partially
obstructing the usual path. Many people do not realise how
Obstructions manoeuverable fork lift trucks are and they do not realise
that they are causing serious obstruction by their own
People get used to doing
actions.
things as a matter of
habit, and this applies to On one plant some scaffolding was erected to support an
fork lift truck drivers as to overhead steam pipe and provide access for maintenance
everyone else. They are work. Overhead clearance was carefully attended to but
not always prepared for half-way down the structure one scaffold pole was left
avoiding unexpected protruding into a thoroughfare. Some packages on a pallet
temporary obstructions. being carried by a lift truck struck the scaffold pole and were
damaged. Fortunately no person was hurt and the load on
the truck did not collapse. An obvious hazard had been
taken care of but the small obstruction had not been noticed
or had been thought to be negligible

170/8 Four young people were sitting in a car gazing out to sea
Unusual Accident near the beach at a local resort. One decided to light a
cigarette. First he had to refill his cigarette lighter and to do
No 118: Flames In a so he used a canister of lighter fuel which he had in the car.
Confined Space When he struck a light there was a flash and a bang and
four shocked people jumped out of the car. Two were
To retain the interest of sufficiently badly burned to need attention at a local
those readers who are hospital.
bored by fork lift trucks,
here is an account of a Fumes of lighter fuel had created a flammable atmosphere
totally different sort of in the confined space in the car and a source of ignition,
accident. when used, produced the inevitable consequences!

An Engineer’s Case Book Glandless or “canned” pumps are used when any leakage
No 70 GLANDLESS of process fluid cannot be tolerated because of toxic,
PUMPS flammable or smell hazards. These pumps have no gland or
mechanical seal on the rotating shaft to retain the process
fluid within the pump casing, but have the complete rotating
assembly including the electric motor rotor and stator
enclosed within thin walled cans of Nimonic 75 material.
The electrical energy to rotate the pump passes through the
 cans from the stator windings.

Several of these pumps were installed in 1974, running at

2,900 rpm on duties where the problem of smell from
leakage had to be eliminated, and gave very little
mechanical trouble for a number of years.

Gradually, the frequency of major failures increased, until a

fundamental investigation into overhaul procedures had to
take place. The type of failure was mainly worn journal
bearings resulting in the rotor and stator cans touching
causing either puncture of the stator can and ingress of
liquid into the electric motor or seizure of the motor. Both
types of failure resulted in expensive and time-consuming
pump and motor overhauls.

Initial attempts were made to predict the point at which

failure occurred by using a hand held vibration monitor but
no correlation appeared to exist between pump failure and
vibration amplitude. Close examination of the wear rings,
and shaft spacer sleeves from a failed pump revealed wear
on only one side suggesting there were out-of-balance
forces acting. These forces would produce much greater
loads on the carbon journal bearing bushes, causing
excessive wear and premature failure. At the first
opportunity, a multi-stage rotor and a full set of impellers
were sent for balancing and, as predicted, the out-of-
balance forces were substantial.

Generally, at pump overhauls, the impellers were re-used,

usually after the wear rings had been replaced, and were
not re-balanced before re-fitting. The rotor, if undamaged,
was refitted to the pump after new journals had been fitted
and again this item was generally not re-balanced. If the
rotor required a new can, it was sent back to the
manufacturers for fitting and, unless specified in the order,
was not re-balanced. It was therefore not surprising that the
frequency of pump failures increased as the pumps became
older and the rotating elements became worn and out of
balance.

Since then, all rotors and impellers have been balanced at

overhauls and pump outage has dramatically reduced.

J N Aitchinson

August 1983