Fed up with an impasse in contract talks, union crane operators staged a protest Friday at the new Comcast tower being built in Center City. Construction halted as the other building trades walked away from the job.

Hundreds of workers clogged the corner of 19th and Arch Streets, the northwest corner of the building site, at 6:30 a.m., the start of their shifts, waiting for instructions on whether to enter.

Local 542 of the International Union of Operating Engineers has not put up picket lines at other sites so that construction can continue and the other building-trades unions can keep working. Ordinarily, union members do not cross another union's picket lines.

As a practical matter, however, construction will slow further if the impasse continues, because union members operate the construction elevators that move workers and materials to higher floors and the cranes that lift heavy material.

Union negotiators met Thursday with representatives from the General Building Contractors Association (GBCA), which negotiates on behalf of the subcontractors that hire crane operators. That meeting ended without an agreement.

The contract expired April 30.

Core compensation is not an issue. The two sides agree on a $2-an-hour raise for the length of the contract. At issue are the job titles of oiler and oiler apprentice, with the GBCA saying oilers are not as necessary with today's machines, and the union saying all of its workers begin as oiler apprentices to learn the mechanics of the machinery and to act as a second set of eyes signaling operators to avoid hazards. Other issues include how overtime is paid on the weekend and how the GBCA should collect dues from its subcontractor members.

"Contractors are ready to get back to work and hash out our differences without sacrificing other trades and our industry. At this point we're just waiting for the operating engineers to feel the same way," said Benjamin Connors, president of the GBCA.

Said Tom Danese, recording secretary of the union: "We met again yesterday, it was the same-old same-old, they can't make a decision." The union had offered to give contractors more flexibility in how they use the oiler apprentices, similar to how they are used on highway projects, Danese said.

Construction is continuing, albeit slowly, around the city. At the Hotel W on Chestnut Street, workers could be seen lugging materials up four flights of stairs built into scaffolding. At the former Gallery at Market East, laborers are breaking up loads of heavy material that might have been moved using equipment operated by Local 542 members. Instead, they are either carrying the loads themselves or using smaller equipment they are permitted to operate under their contracts.

"I'm running 500 people a day up and down my hoist," Local 542 member Kevin Staten, 47, said of his normal work while holding a sign outside the construction site. "I'm moving material from the loading dock to the 62nd floor. There was lots of activity on the 62nd floor."

The union's lead supervisor on the site, Shawntee Willis, said that typically there would be 15 members of Local 542 working on the Comcast site, part of a crew of 1,300 carpenters, ironworkers, glaziers, and others, with 1,000 on the job during the day and the rest working at night.