Business Segment Information - Net Sales and Operating Income (Loss) by Business Segment (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Net sales	$ 197,317	$ 135,052
Income from operations	6,972	16,683
Engineered Equipment Technology and Parts [Member]
Segment Reporting Information [Line Items]
Net sales	125,248	88,679
Met-Pro [Member]
Segment Reporting Information [Line Items]
Net sales	30,526
Contracting / Services [Member]
Segment Reporting Information [Line Items]
Net sales	19,500	25,527
Component Parts [Member]
Segment Reporting Information [Line Items]
Net sales	21,908	20,771
Corporate and other [Member]
Segment Reporting Information [Line Items]
Net sales	135	75
United States [Member] | Engineered Equipment Technology and Parts [Member]
Segment Reporting Information [Line Items]
Net sales	88,170	75,824
Netherlands [Member] | Engineered Equipment Technology and Parts [Member]
Segment Reporting Information [Line Items]
Net sales	25,588
China [Member] | Engineered Equipment Technology and Parts [Member]
Segment Reporting Information [Line Items]
Net sales	7,763	4,905
Canada [Member] | Engineered Equipment Technology and Parts [Member]
Segment Reporting Information [Line Items]
Net sales	3,557	7,611
Brazil [Member] | Engineered Equipment Technology and Parts [Member]
Segment Reporting Information [Line Items]
Net sales	170	121
India [Member] | Engineered Equipment Technology and Parts [Member]
Segment Reporting Information [Line Items]
Net sales		218
Operating Segments [Member] | Engineered Equipment Technology and Parts [Member]
Segment Reporting Information [Line Items]
Income from operations	18,652	15,562
Operating Segments [Member] | Met-Pro [Member]
Segment Reporting Information [Line Items]
Income from operations	1,383
Operating Segments [Member] | Contracting / Services [Member]
Segment Reporting Information [Line Items]
Income from operations	2,008	3,461
Operating Segments [Member] | Component Parts [Member]
Segment Reporting Information [Line Items]
Income from operations	4,172	4,198
Operating Segments [Member] | Corporate and other [Member]
Segment Reporting Information [Line Items]
Income from operations	(17,754)	(6,474)
Inter-segment Elimination [Member]
Segment Reporting Information [Line Items]
Income from operations	$ (1,473)	$ (64)