Labor contracts covering 13,000 Twin Cities hospital nurses expired Friday without new agreements as their union negotiators continued to press for new deals with pay increases, safeguards against workplace violence and other benefits.

The expiration was something of a formality, as the old contracts remain in effect and nurses remain on the job while talks continue between the Minnesota Nurses Association (MNA) and 14 hospitals.

However, it also marks a sense of futility in the citywide negotiations not seen since summer 2010, when a prolonged contract showdown over staffing led to a one-day strike by 12,000 nurses.

"It's very disappointing that we're here again," said Angela Becchetti, a registered nurse at Abbott Northwestern Hospital and part of the MNA's bargaining team with Allina Health.

Nurses in red shirts have been conducting informational picketing over the past two weeks outside hospitals operated by Allina Health, Children's, Fairview Health Services and HealthEast, as well as Methodist Hospital in St. Louis Park and North Memorial in Robbinsdale.

The demonstrations evoked memories of 2016, when Allina nurses went on two strikes for a combined 44 days in a dispute centered on health insurance. But that was a relatively calm negotiating year for the other hospitals, which quickly reached agreements that focused just on wages.

Leaders on both sides expressed optimism Friday that three-year deals could be reached this summer without the kinds of labor stoppages that cost Allina $149 million in temporary staffing and other expenses in 2016.

"The hospitals continue to strive toward contracts that are fair for the nurses, other employees, patients and their families, and the community," said Andrea Mokros, a spokeswoman for all the hospitals in negotiations except Allina. "We are hopeful and optimistic that agreements can be reached soon."

Strikes can't occur unless the nurses vote to authorize them and the union then gives notice to the hospitals. No such steps are being considered by MNA negotiators at the moment.

This year, the union's most public negotiating issue has been workplace violence prevention, sparked by numerous reports of nurses being seriously injured by aggressive, confused or panicked patients. Workers' compensation payouts have increased over the past five years, data show, because of assaults that seriously injured nurses.

While hospitals have been working to improve safety, the union wants to hold them accountable by contractually obliging them to certain standards. Union proposals include policies that would allow nurses to rotate off caring for patients who have assaulted them and to take time off to heal even before workers' compensation coverage decisions are made.

"I would think the public would understand our need to be protected," Becchetti said.

Nurses have also requested clearer lockdown policies in the event of violent incidents at Unity Hospital in Fridley, which has seen an uptick in "code green" safety alerts and staff injuries since Allina began steering more inpatient mental-health services there.

North Memorial and Allina on Friday joined the other hospital systems in tentatively agreeing to the union's workplace safety requests.

Talks between the union and Allina continued Friday with federal mediation. Allina initially made its agreement on safety issues contingent on the union dropping other contract revisions. But an MNA spokesman said late Friday that this condition had been dropped.

A joint letter from the chief nursing officers of five Allina hospitals said they hope to hasten an agreement by dropping many of their own proposals and focusing on wages and safety: "In conversations with nurses and other staff, we hear loud and clear that employees want these negotiations behind us. We do, too."

Jeremy Olson • 612-673-7744