Note 4 - Revenue Recognition - Revenues by Revenue Class (Details) - USD ($) $ in Thousands	12 Months Ended
Jan. 31, 2021	Jan. 31, 2020
Sales by product	$ 84,694	$ 127,663
Sales by product, percent	100.00%	100.00%
Product [Member] \| Transferred at Point in Time [Member]
Sales by product	$ 11,496	$ 15,991
Sales by product, percent	14.00%	12.00%
Specialty Piping Systems And Coating [Member] \| Transferred at Point in Time Using Input Method [Member]
Sales by product	$ 35,041	$ 48,415
Sales by product, percent	41.00%	38.00%
Specialty Piping Systems And Coating [Member] \| Transferred at Point in Time Using Output Method [Member]
Sales by product	$ 38,157	$ 63,257
Sales by product, percent	45.00%	50.00%

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