xpsOES : A New Tool for Improving Safety at Workplace Yasar Kucukefe, Ph.D., National Power Energy

Agenda Introduction Accidents at Workplace Swiss Cheese Model of Accidents What is xpsOES ? Implementation of xpsOES Conclusion

Introduction Most of the time, human errors are caused by momentary lapse of attention, lack of training, poor instructions or bad design. Pressing a 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-circuit (i.e. it was still energized ). Tap adjustments other than on-load tap changers must be done only when a transformer is off-circuit.

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-passed 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-ignition 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 cubicle. 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 xpsOES 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 | 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 etc. 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 | 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 default. 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.

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