The article presents the results of the stability of the microstructure and properties of catalytic cast pipes in steam reforming conditions. The growing prices of catalytic pipes have resulted in the attempts to prolong of the pipe work above 100,000 h stability. Increasing the time and temperature of operating causes coalescence and coagulation of secondary carbides reducing thus the creep resistance of the alloy. Currently there is no definite and commonly used method to assess the degree of degradation of the microstructure and properties of catalytic pipes. The destructive test methods of catalytic pipes are usually reduced to the assessment of the effects of metallographic creeping process, ie. relative volume and distribution of mikrovoids on the pipe wall section, as well as evaluating the mechanical properties of steel. These methods generally give a clear assessment but require disassembly for testing pipes and replace ment with new ones. The author developed the regression which show a significant dependence of mechanical properties (Rm A5, KCU 2) on the operating parameters of the reformer (PLM, σ) and hardness HB cast IN 519. The equations have been applied to assess the possibility of using non-destructive testing for the assessment of the degree of degradation of the catalyst steel pipe.