The Federal Home Loan Bank Board, concerned that too rapid growth and risky investments have contributed to failures in the industry, yesterday voted generally to limit both the growth of savings institutions and the range of their investments.

The board unanimously approved restrictions on both inordinate growth and direct investments by thrifts in real estate, securities and other activities unrelated to housing finance. The rules take effect in a month.

The long-debated regulations, intended to curb abuses resulting from deregulation, introduce a new concept to the industry: the supervisory agent with discretionary power over savings institutions' business judgments involving growth and investments above approved minimums.

William B. O'Connell of the U.S. League of Savings Institutions praised the final version of the rules, which was modified to allow more flexibility. However, George Hanc of the National Council of Savings Institutions expressed reservations that the growth limits would prove "unrealistic in many market areas."

As for investments, he said, "Well-managed institutions should be allowed to do whatever is permitted under state law without federal intervention."

One regulation will change the way net worth is calculated by eliminating five-year averaging, with certain exceptions, and by increasing the capital required to back new deposits in excess of 15 percent annual growth. In effect, it says that institutions may grow by no more than a 25 percent annual rate for more than one quarter, according to economist Dennis Jacobe of the U.S. League. "Above that, you would have to make a heck of a good case to a supervisor," he said.

The new regulations will necessitate more net worth for perhaps 10 percent of the industry in which institutions have been rapidly increasing deposits. One unidentified S&L grew 950 percent in two years, a board economist said yesterday. It had a net worth ratio of .076, or just $91,000 capital to back $119 million in deposits.

The rule sets a limit of 10 percent of assets (or twice regulatory net worth) for direct or equity investment without prior approval. Above that, permission will be required from the supervisor, usually a Federal Home Loan Bank. The brunt of this will be borne by Sun Belt states, which have greatly expanded the investment powers of thrifts they charter. Citing deregulation as the cause, one FHLBB official said some large institutions currently have up to 40 percent of their assets in direct investments, including such things as boxing matches, restaurants and aircraft parts.