Note 4 - Revenue Recognition - Revenues by Revenue Class (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Oct. 31, 2022	Oct. 31, 2021	Oct. 31, 2022	Oct. 31, 2021
Sales by product	$ 37,903	$ 35,199	$ 106,128	$ 99,426
Sales by product, percent	100.00%	100.00%	100.00%	100.00%
Product [Member] \| Transferred at Point in Time [Member]
Sales by product	$ 4,363	$ 3,340	$ 11,144	$ 10,475
Sales by product, percent	12.00%	10.00%	10.00%	11.00%
Specialty Piping Systems And Coating [Member] \| Transferred at Point in Time Using Input Method [Member]
Sales by product	$ 12,593	$ 9,166	$ 35,918	$ 33,118
Sales by product, percent	33.00%	26.00%	34.00%	33.00%
Specialty Piping Systems And Coating [Member] \| Transferred at Point in Time Using Output Method [Member]
Sales by product	$ 20,947	$ 22,693	$ 59,066	$ 55,833
Sales by product, percent	55.00%	64.00%	56.00%	56.00%

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