THE PENNSYLVANIA Convention Center Authority board this week did what no one thought could happen in Philadelphia: It faced down a powerful union boss and demanded change.

In a way, the board had no choice. Business at the $1.3 billion center has been sinking ever since a huge extension opened up in 2011. The new supersized hall was supposed to draw 25 to 30 major conventions a year. This year, it will host 14; numbers trail off to single digits going forward.

The loss of those conventions will ripple through the rest of the city's economy - to the tune of $1 billion in spending lost by hotels, restaurants and other services that cater to conventioneers.

Something had to be done to overcome the major obstacle to new and repeat business: the labor hassles that drove customers to give up on Philadelphia and go elsewhere.

Ed Coryell, head of Carpenters Local 8, said "no" at every turn to new work rules that would let exhibitors do more of their own setup and take-down work, which is now common in the convention business.

He wanted those jobs for his members and refused to budge from that position, despite management's argument that any hours lost would be made up by attracting more conventions.

In fact, Coryell pulled his members off the job last week and set up picket lines while one convention was inside the building waiting for a take down, and other events were lining up to use it over the weekend.

That was the final straw for the board. It meant another black eye for Philly in the world of convention bookers, many of whom had already soured on the city.

The board called Coryell's bluff. Instead of caving to the carpenters, it reached new agreements with the four other unions that work at the center that included the work-rule changes - and also guaranteed a 3 percent annual raise for union members over the next 10 years.

Two unions - Carpenters Local 8 and Teamsters Local 107 - refused to make a deal, so the board showed them the door. It said the work those unions did will be picked up by the four unions signing the agreement.

Coryell was furious. At a board meeting, he accused Heather Steinmiller, the city's representative on the board, of being a "bully." Steinmiller has been a longtime advocate of the work-rule changes, although often a lonely voice on the board.

If Coryell wants to see a real bully, he should try a mirror.

He was willing to take the center down in exchange for jobs that represent just a sliver - about 2 percent - of the total wages earned by carpenters in this region.

Ed Coryell is a powerful man. His union has been a generous giver to Gov. Corbett and has made substantial campaign contributions to the politicians who appointed the center's board.

The board, chaired by Josh Shapiro, of Montgomery County, deserves credit for taking a united stand on this issue. Let's hope they remain united in the coming days as Coryell and his allies apply pressure to reverse this decision and get their way.

Their way spells disaster for the center and for a vital segment of the city's economy.