BY BRANDON SAWYER

Oregon Business’ Private 150 turns 30 this year. The list continues to evolve from being dominated by forest products and other heavy industries to one with more service-sector companies. Construction giant Hoffman Corp. jumped from No. 10 to No. 2 this year, passing up Knowledge Universe, No. 3, but otherwise the top 10 remain largely the same as in 2011.

Portland’s Erickson Air-Crane (No. 51 last year) is no longer on the list because its long-anticipated IPO took place in April, when it became Oregon’s fist new public company in several years.

Two companies fell off the list because of bankruptcy: Tualatin-based Lumber Products Co. (No. 32 last year) filed Chapter 11 reorganization, and Portland-based United Pipe & Supply Co. (No. 71 last year) is liquidating assets after 60 years in business.

Twenty-one companies were not on the list last year, and most of them have never been listed, including Albany-based Oregon Freeze Dry (No. 62), Portland’s Rodda Paint Co. (No. 84), TraneOregon (No. 105) of Tigard, Directors Mortgage (No. 108) in Lake Oswego, Bend Research (No. 116) and all of the final eight companies that are listed.

As always, a number of privately held companies that should be on our list declined to reveal their annual revenue this year. Eighteen companies from last year’s list chose not to participate, including Prineville’s Les Schwab Tire Centers, which ranked No. 3 in 2011.