An ambulance ramping ban at Royal Perth, Fiona Stanley and Sir Charles Gairdner hospitals has gone well on its first day, the WA health minister says.

Emergency departments have not descended into chaos on the first day of an ambulance ramping ban at three of Perth's hospitals, the state health minister says.

Ramping refers to the length of time paramedics must wait around busy hospitals before they can transfer responsibility for patients to staff.

From July 1, this will have to be done within 30 minutes of arrival at Royal Perth, Fiona Stanley and Sir Charles Gairdner hospitals.

Medical unions claimed the ban would cause chaos in the hospitals and bring back "corridor care" for patients.

But Kim Hames said he'd been told it was all going well and the unions' claims were quite silly.

If hospital staff were unable to cope with the extra handful of patients, then the paramedics would stay in the emergency departments, Dr Hames said.

"If I have egg on my face because for a time paramedics are having to stay there for longer than the 30 minutes, then so be it as long as patients are safe," he said.

"We're not trying to change the world here - all we're doing is stopping the paramedics from being stuck in our emergency departments."

Over the past seven days, ambulances spent 56.6 hours ramped at Fiona Stanley Hospital, 31.3 hours at Sir Charles Gairdner, and 19.8 hours at Royal Perth.