Note 4 - Revenue Recognition - Revenues by Revenue Class (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
Sales by product	$ 32,806	$ 27,498	$ 94,020	$ 77,851
Sales by product (percent of total)	100.00%	100.00%	100.00%	100.00%
Product [Member] | Transferred at Point in Time [Member]
Sales by product	$ 4,440	$ 2,504	$ 9,447	$ 5,830
Sales by product (percent of total)	14.00%	9.00%	10.00%	7.00%
Specialty Piping Systems And Coating [Member]
Sales by product (percent of total)			90.00%
Specialty Piping Systems And Coating [Member] | Transferred at Point in Time Using Input Method [Member]
Sales by product	$ 11,869	$ 10,986	$ 32,778	$ 34,240
Sales by product (percent of total)	36.00%	40.00%	35.00%	44.00%
Specialty Piping Systems And Coating [Member] | Transferred at Point in Time Using Output Method [Member]
Sales by product	$ 16,497	$ 14,008	$ 51,795	$ 37,781
Sales by product (percent of total)	50.00%	51.00%	55.00%	49.00%