An escape clause in the federal health program could let thousands of U.S. workers switch their insurance coverage for 1982 even though the government has frozen most workers into their present insurance package.

The Office of Personnel Management, as reported here yesterday, has announced that it will not hold an open season enrollment period this year as scheduled, and has said that it may be late 1982 before U.S. workers get a chance to shop for better, or lower-cost health insurance.

That position was upheld yesterday by U.S. District Court Judge Aubrey Robinson Jr. who denied a motion filed by the National Treasury Employees Union that would have forced OPM to hold the open season soon so that the 9.2 million feds, family members and retirees could get out of their present plans if they wanted and pick new coverage for 1982.

Many of the health plans will raise rates dramatically next year (the increases range from 5 percent to 50 percent). Some of the plans will make significant cuts in benefit levels. Most will raise deductibles to the $200 range. That means higher premiums, and greater out-of-pocket costs next year for many workers. OPM's decision not to have an open season has cheered a number of plans that, because of premium increases and benefit cuts, feared they might lose thousands of enrollees (who pay premiums ranging from $200 to $800 a year) to less-costly plans.

Although the open season door is closed for most people in the program, there may be a way out for union members who are enrolled in plans sponsored by their union, or for nonmembers who pay an associate fee to belong to a union health plan. This is it:

Under federal regulations union-backed health plans have the option of dropping people who quit the union and associates who stop paying fees. The language originally was written to protect unions from being forced to carry "free riders" in their health plans, but it could be turned around to give unhappy enrollees an out. If they quit the union or stop paying associate fees, some unions might well oust them from their plans.

Union health plans have been very popular. The American Postal Workers Union has more people covered by its health plan (580,214) than it has members. The National Association of Letter Carriers plan covers 551,312 members, associates and their families. The Mail Handlers plan covers 395,107 people. Although there are fewer than 70,000 postmasters and rural letter carriers, health plans sponsored by the two organizations cover nearly 300,000 people ranging from postal workers to foreign service personnel.