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10 déc. 2013 (il y a 5 années et 2 mois)

233 vue(s)

xpsOES : A New Tool for
Improving Safety at

Yasar Kucukefe, Ph.D.,

National Power Energy



Accidents at Workplace

Swiss Cheese Model of Accidents

What is xpsOES ?

Implementation of xpsOES



Most of the time, human errors are caused by
momentary lapse of attention, lack of training, poor
instructions or bad design. Pressing

wrong button
or overhauling a wrong valve can result in serious
consequences at an industrial plant.

Even though people can be encouraged to consider
all possible risks before any action, slips and lapses
might still occur, especially under stress. Eliminating
momentary lapses of attention completely by further
training or punishment is not possible.

Preparation for Maintenance Work

Preparation of plant equipment for maintenance
work involves proper isolation, correct identification,
removal of hazards and following safety procedures.

Working on the correct equipment and performing
the correct operation is important to achieve safety
at a workplace. Failing to do so can cause serious
accidents and put lives at risk.

What went wrong?

Transformer explosion in a UK power plant in 2001
caused death of 3 workmen. They were adjusting
taps of the transformer when the explosion occured.
The transformer was off
load but was not off
(i.e. it was still energized ).

Tap adjustments other than on
load tap changers
must be done only when a transformer is off

What went wrong?

Generator terminal short circuit occured prior to unit
synchronization when a plant operator gave close
command to the generator earth switch by mistake.

Investigation revealed that hard
wired interlocks
preventing such a wrong operation were by
without any record.

The incident resulted in several months of loss
generation and huge repair costs.

What went wrong?

A pump was being dismantled for repair. When the
cover was removed, hot oil above its auto
temperature, came out and caught fire. Three men
were killed, and the plant was destroyed.

Examination of the wreckage after the fire showed
the pump suction valve was open and the drain valve
was shut, indicating clearly that the safety isolation
was made wrongly.

What went wrong?

An electrical technician was injured from an arc
flashover whilst opening the rear of a live electrical

Safety from the system was correctly provided for the
panel on which the maintenance work was planned.
But the adjacent equipment was in normal
operational service and the injured party mistakenly
opened the rear of this live panel.

Swiss Cheese Model of Accidents

xpsOES | Safety Layer


helps prevent human errors by warning operators and
maintenance staff before a wrong operation is performed or
an unsafe work is carried out.

xpsOES | Description

xpsOES in action

xpsOES in action

xpsOES | Knowledge Transfer

xpsOES | User Interface

PHP code runs on Apache Server. User Interface uses
jQuery and Ajax. Database: Oracle or mySql

xpsOES | Setup

Initial setup involves creating categories for plant
equipment, operational actions, engineering units

Plant equipment on which maintenance work can be
carried out are created in the database. Then the
preconditions for performing work on plant
equipment are defined in the form of tables.

xpsOES | Setup

xpsOES | Setup

xpsOES | Safeguards

No evaluation result is displayed if real time value of a tag
used in decision table is not known.

Only decision tables with final stamp are used in the
evaluations. Every plant equipment is in ‘edit mode’ by

No complex logical operations are used in preconditions
table. Only AND logical operation is available.

Only warning messages are displayed. No green light
indication for any intended work or operation.

xpsOES | Mobile Application

Any mobile device with barcode or NFC code reading
capability can be used.

Identification tag stored in barcode or NFC code
contains data required for evaluation wirelessly. The
mobile device receives the evaluation result from the
xpsOES Server.

Android and iOS mobile applications for xpsOES are
also available.

xpsOES | Mobile Application

All responses from the xpsOES server is stored for
further evaluation if required.

Additional traning requirements for employees can
be identified by reviewing the response log.

xpsOES Server requires actual status of tags used by
decision tables. Communication setup with plant real
time data server is site specific.


helps prevent human errors by warning
operators and maintenance staff before a wrong
operation is performed or an unsafe work is carried

Identification tag on the site equipment is read by a
mobile device and transmitted to the xpsOES server
for evaluation using decision tables. If the intented
operation is dangerous, warning message is sent to
the mobile device screen.

xpsOES is not a black box system. It is a PHP code
running on an Apache Server. Setup and interlock
configuration are made using a standard browser.