SAFETY BULLETIN: Precaution measures before refiner maintenance

At Valmet, safety comes first. From new innovations, to product management and continuous improvement, safety is at the forefront of all we do. Within our own workspaces – both company buildings and home offices – and our customer sites, we lead by example. We make it our mission to always keep each other safe.

Case: Event description

Valmet recently learned of a faulty maintenance procedure that could have resulted in serious injury. Mill personnel attempted to unplug a refiner inlet pipe using a 2000 PSI pressure hose, while the refiner was offline and with its outlet shutoff valve closed. The refiner was rated for 100 PSI. No one was hurt, but the damage was extensive. The missing door on this unit weighed over 7,000 lbs. Obviously such an explosion could have been fatal to anyone in the vicinity of the door.

Shared learnings

Incidents of this nature can be avoided. Safety measures are put in place to keep people safe, even when human error or other unknown factors have the potential to put human life at risk. Mistakes are part of human nature, thus equipment protections must go beyond the human reach.

In order to prevent such situations from occuring in the future, it is important that we share our observations and issue the following recommendations:

• Always ensure that machine operators, including temporary workers, are properly trained and equipped with specific knowledge of best safety practices before beginning work on the unit.
• Valmet requires numerous safety interlocks prior to starting any new refiner for the protection of the equipment and all those around it.
• We strive to ensure these interlocks are both functional and kept in place during every refiner inspection we conduct.
• These interlocks, however, only protect the refiner when its main motor is in operation.
• Every refiner should be equipped with further protection from overpressurization issues outside of the normal operation. Rupture disks or electronic pressure relief valves linked to refiner pressure controls are strongly recommended.
• Had the refiner mentioned in the case above been equipped with one of these, the high pressure water/pulp would have safely discharged away from the refiner and potentially into a chest without damaging the refiner, and minimizing the risk to those working nearby.

CAUTION: Before performing maintenance or service on any refiner, the following safety measures should be checked and double-checked to avoid accidents. Identify the refiner’s Maximum Allowable Working Pressure (MAWP.) Confirm that all equipment, including hoses, involved in the maintenance procedure have a MAWP less than the MAWP of the refiner. Confirm that all over-pressurization and pressure-release safety devices are operational. Confirm that all safety interlocks are operational even when the main motor is deactivated. Monitor refiner pressure throughout and avoid approaching the refiner’s MAWP.

Please contact the refiner team via your Valmet representative if you would like more information on Valmet’s customer focused approach to refiner service or would like a set of refiner pressure labels. Owners of Valmet refiners may also request an electronic copy of Valmet’s Operation & Maintenance Manual.