OKLAHOMA CITY (AP) â¿¿ LSB Industries Inc. said Wednesday that it shut down its main ammonia plant for six to eight weeks because of unexpected maintenance work, and the company will lose $2 million a week during the outage. LSB shares fell $1.90, or 5.6 percent, to $31.80 in afternoon trading. The company said it had planned to install a new ammonia converter to boost capacity in January, "but this outage began earlier and is likely to be longer" than expected because of a problem with a compressor at the plant in Pryor, Okla. The company said operating income will fall until production resumes. Last year the company's operating income was $84 million on revenue of $805.3 million. LSB makes heating and air conditioning products for homes and commercial buildings, including geothermal and water-source heat pumps, fan coils and chillers. It also makes chemicals for agricultural, mining and industry.