After more than a decade of pleas, talks, threats, and work stoppages, the Convention Center board on Tuesday unanimously approved work rules supporters say will attract more big shows to the underused, taxpayer-built showplace.

The substantially altered rules are meant to make it easier to fill hotels and restaurants with free-spending conventioneers. That is a vision, heretofore unmet, on which a generation of Philadelphia's leaders have bet Center City's economic future.

The board's action created a rift - noteworthy in a town that has long considered itself rock-ribbed union - among the six unions that represent the 500 or so workers at the Convention Center on any given day.

Four unions have signed on to the altered work rules. Two others, Teamsters Local 107 and Carpenters Local 8, have not, claiming they would lose up to half their working hours.

The center's chief executive, John McNichol, said he expected members of the four unions that agreed to the changes to work even if the two other unions set up picket lines.

One union leader expressed full-throated agreement with that expectation. The Carpenters and Teamsters have contracts to remain working at the center only until Saturday.

Lost hours should be more than offset by new shows requiring more workers, Bob McClintock, senior vice president of SMG, the West Conshohocken firm hired to manage the center last fall, told the board before the vote. The board also agreed to 3 percent annual pay increases for the next 10 years for workers covered by the new rules.

The center's $780 million expansion, finished in 2011, was supposed to draw up to 30 major conventions a year, but fewer than half that many have been scheduled per year through 2017.

The new rules would:

Allow exhibitors to set up booths (up to 600 square feet, double the present limit) with their own full-time employees instead of the center's union workers.

Let exhibitors use stepladders and power screwdrivers to build booths, and plug in their own computers.

Allow management to choose workers and foremen from a core staff of experienced union workers.

Hasten dispute resolution between Convention Center executives and union workers, instead of waiting for long-term grievance and arbitration procedures.

Submit workers to a standard drug-testing program.

The four unions that approved the work rules are Laborers' Local 332, Electrical Workers Local 98, Stagehands Local 8, and Iron Workers Local 405.

McNichol had reason to be optimistic that members of the four unions would do the work of the Teamsters and Carpenters if necessary, and cross picket lines. "We'll do whatever it takes to make the center more effective. We stand united with John McNichol," said Ryan N. Boyer, business manager for the Laborers District Council, the largest of the unions that agreed to the work rules.

"We need the business. We need this building packed," Boyer added.

Asked if Laborers would be willing to cross picket lines, Boyer repeated: "Whatever it takes."

"This won't be the end of things," said Edward C. Coryell Sr., secretary/treasurer of the Carpenters district council. "We won't be run out of this building and go away. That's not going to happen.

"I will do whatever's necessary to keep our members in this building."

Coryell spoke during the meeting, interrupting a review of the rules, to protest the way the board plans to implement them.

Asked about the prospect for labor strife, Mayor Nutter said, "Negative reaction will only further damage the reputation of the center."

Those in the hospitality trade have been impatient for the new work rules. Jonathan Tisch, cochairman of the Loews hotel chain, on a visit to Philadelphia in April, said his firm invested $20 million last winter in an upgrade of its Market Street hotel, which faces the Convention Center's front door, because he expected SMG to come through with long-awaited "new labor contracts."

Jack Ferguson, president and chief executive of the Philadelphia Convention and Visitors Bureau, says the city lost more than $1 billion in convention, hotel, restaurant, and services spending for 2014 through 2017 when groups "canceled or were lost to antiquated work rules" at the center. He cited the True Value hardware cooperative and the National Association of Fire Chiefs among groups that canceled.

The Carpenters, largest of the six unions working at the center, staged a brief strike May 1 that center board members said gave them more reason to act quickly on the new rules, before labor tensions became further reason for meeting planners to pull shows from Philadelphia.

"The Carpenters were surprised by this ultimatum at the last minute, when they were in the middle of negotiations," said Martin O'Rourke, a spokesman for the union.

After picketing last week, the Carpenters returned to work, agreeing to extend their contract until Saturday.

"Now they aren't returning our phone calls," O'Rourke said of the center's managers.

Heather Steinmiller, the board member (representing Nutter) whose committee drafted the rules, said they were based on an 11-year-old proposal.

Similar changes were recommended by board members and managers under former chief executive Ahmeenah Young. Boyer, the Laborers' leader, said previous managers were hampered by "political favors and appointments."

"Politics plays a part in the building," Boyer said. "SMG doesn't have that cross to bear, so to speak."

The move to a private manager gained momentum after Gov. Corbett took office in 2011 and promised to privatize state-run industries. Separately, private management has been backed by at least one union leader, Local 98's John "Johnny Doc" Dougherty, who is active in Democratic politics, and some of the board's minority Democrats, including Montgomery County Commissioners Chairman Josh Shapiro.

"It's a great day for us," said Ed Grose, executive director of the Greater Philadelphia Hotel Association. "It is so important to our industry that we make radical changes. Meeting planners have been hearing things are going to improve here for 20 years."

Contributing to this article were Inquirer staff writers Jane M. Von Bergen, Chris Hepp, Claudia Vargas, Troy Graham, and John Duchneskie.

215-854-5194 @PhillyJoeD