Equipment operator was manually stiff lancing vertical tubes positioned on a scaffold using an overhead lance pulley and a 20K pump. The initial setup included a 1/8" stiff lance rod and a nozzle with an O.D. of approximately 1/2" run through an articulating arm equipped with a 3/8" horseshoe or "half-moon" lance stop for anti-withdrawal. An in-line dump valve was in place and being operated by the equipment operator. At some point during the job the supervisor changed the nozzle to a nozzle/tip with a smaller O.D. Shortly after the nozzle/tip change, the stiff lance hydraulicked back out through the anti-withdrawal device and the nozzle water jet came in contact with the equipment operator's right hand resulting in three small puncture wounds.
A "donut" or full circle/moon lance stop is typically used when stiff lancing. Horseshoe or "half-moon" lance stops are used when flex lancing. Also, before starting stiff lance operations the lance should be pulled back against the lance stop/insert to verify that it will prevent the stiff lance from being withdrawn. Finally, always identify and address any hazards associated with changes in a job/task to include setup or tooling changes