Note 5 - Revenue Recognition - Revenues by Revenue Class (Details) - USD ($) $ in Thousands	12 Months Ended
Jan. 31, 2020	Jan. 31, 2019
Sales by product	$ 127,663	$ 128,965
Sales by product	100.00%	100.00%
Product [Member] \| Transferred at Point in Time [Member]
Sales by product	$ 15,991	$ 13,576
Sales by product	12.00%	11.00%
Specialty Piping Systems And Coating [Member] \| Transferred at Point in Time Using Input Method [Member]
Sales by product	$ 48,415	$ 40,525
Sales by product	38.00%	31.00%
Specialty Piping Systems And Coating [Member] \| Transferred at Point in Time Using Output Method [Member]
Sales by product	$ 63,257	$ 74,864
Sales by product	50.00%	58.00%

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