Note 5 - Revenue Recognition (Tables)
 12 Months Ended
Jan. 31, 2020
Notes Tables  
Disaggregation of Revenue [Table Text Block]
   
2019
    
2018
  
   
Sales
    
% to Total
    
Sales
    
% to Total
  
Products
   $
15,991
      
12
 %   $
13,576
      
11
 %
                                 
Specialty Piping Systems and Coating
      
 
      
 
      
 
      
 
Revenue recognized under input method
    
48,415
      
38
 %    
40,525
      
31
 %
Revenue recognized under output method
    
63,257
      
50
 %    
74,864
      
58
 %
Total
   $
127,663
      
100
 %   $
128,965
      
100
 %
Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block]
   
Contract Assets
  
Balance January 31, 2018
   $
1,502
  
Costs and gross profit recognized during the period for uncompleted contracts from the prior period
    
(6,458
 )
Costs and deferred gross profit incurred on uncompleted contracts not billed at the end of the current period
    
6,609
  
Balance January 31, 2019
   $
1,653
  
Costs and gross profit recognized during the period for uncompleted contracts from the prior period    
(6,697
 )
Costs and deferred gross profit incurred on uncompleted contracts not billed at the end of the current period    
7,210
  
Closing Balance at January 31, 2020
   $
2,166
  
         
   
Contract Liabilities
  
Balance January 31, 2018
   $
1,967
  
Revenue recognized during the period for uncompleted contracts from the prior period
    
(3,222
 )
New contracts entered into that are uncompleted at the end of the current period
    
2,824
  
Balance January 31, 2019
   $
1,569
  
Revenue recognized during the period for uncompleted contracts from the prior period    
(3,276
 )
New contracts entered into that are uncompleted at the end of the current period    
2,880
  
Closing Balance at January 31, 2020
   $
1,173
  
Schedule of Assumptions for Long-Duration Contracts by Product and Guarantee [Table Text Block]
(In thousands)
  
2019
    
2018
  
Costs incurred on uncompleted contracts
   $
15,553
     $
12,348
  
Estimated earnings
    
8,641
      
7,430
  
Earned revenue
    
24,194
      
19,778
  
Less billings to date
    
23,201
      
19,694
  
Costs in excess of billings, net
   $
993
     $
84
  
Balance sheet classification
      
 
      
 
Contract assets: Costs and estimated earnings in excess of billings on uncompleted contracts
   $
2,166
     $
1,653
  
Contract liabilities: Billings in excess of costs and estimated earnings on uncompleted contracts
    
(1,173
 )    
(1,569
 )
Costs in excess of billings, net
   $
993
     $
84