Note 4 - Revenue Recognition - Revenues by Revenue Class (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jul. 31, 2022	Jul. 31, 2021	Jul. 31, 2022	Jul. 31, 2021
Sales by product	$ 37,003	$ 39,804	$ 68,225	$ 64,227
Sales by product, percent	100.00%	100.00%	100.00%	100.00%
Product [Member] \| Transferred at Point in Time [Member]
Sales by product	$ 3,868	$ 4,548	$ 6,780	$ 7,135
Sales by product, percent	11.00%	11.00%	10.00%	11.00%
Specialty Piping Systems And Coating [Member] \| Transferred at Point in Time Using Input Method [Member]
Sales by product	$ 12,707	$ 13,999	$ 23,325	$ 23,952
Sales by product, percent	34.00%	35.00%	34.00%	37.00%
Specialty Piping Systems And Coating [Member] \| Transferred at Point in Time Using Output Method [Member]
Sales by product	$ 20,428	$ 21,257	$ 38,120	$ 33,140
Sales by product, percent	55.00%	54.00%	56.00%	52.00%

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

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+ Details