Seamless steel pipe for low and medium pressure boiler

Pressure seamless steel pipe because of its special purpose, a series of tests must be made before using. If not, it is likely to leave hidden problem for future safety production. Because of the working pressure of low and medium pressure boiler seamless steel pipe is less than 5.88Mpa, operating temperature is below 450 ℃; this is a rough range, as long as the low and medium pressure boiler seamless steel pipe is produced according to the standards, there is no problem to use it normally. Of course, it has no problem also for the medium pressure boiler seamless steel pipe to be pressurized to about 7,8MPA, but if it is long-term work under this pressure, seamless steel amounted to less than its normal life. Leakage may occur and cause accidents in advance.
(1) flattening test
For outside diameter D> 22 mm, wall thickness S≤10 mm pipe, flattening test should be carried out, flat pitch h following formula
h = (1 + α) S / (α + S / D) where S --- pipe wall thickness, mm;
D --- pipe diameter, mm;
α --- unit length deformation coefficient, 0.08; when the S / D≥0.125 0.07.
(2) Bending test
D≤22mm outer diameter pipe bending test should be carried out. Bending angle is 90 °, the apex radius of 6 times the pipe diameter. Not bend cracks and cracks.
(3) hydraulic test
Should be carried out by the root test, the test pressure P (MPa) is calculated as follows, but 10 steel maximum pressure 7 MPa; 20 steel maximum pressure 10 MPa, the regulator for not less than 5 s.
P = 2SR / D where S --- nominal pipe wall thickness, mm;
D --- nominal diameter pipe, mm;
R --- allowable stress, provides 60% of the yield point, MPa.
Supplier eddy current testing can be used instead of hydraulic tests.