The hazard
A lot of the safety on a job depends on messages getting through: the morning plan, a shouted warning, a hand signal to an operator, a tag on a switch, a label on a drum. On a crew that speaks more than one language, any of those messages can get lost without anyone noticing. A nod does not always mean someone understood. Clear communication is a safety control, just like a guard or a harness.
The action
Hand signals and radio calls only work if everyone means the same thing. On crane work, the operator, signal person and lift director (if there is one) must be able to effectively communicate in the language used. For any equipment, agree on the signals with the operator before work starts, and do not switch to new ones partway through the job. (29 CFR 1926.1421(c))
ASK THE CREW
What is our stop word and stop signal, and does everyone here know it in English and Spanish?
From the talk: Safety communication on mixed-language crews. Read it in full, free, with the questions and the sign-in sheet.