Is a second hydrostatic test required?
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There is a new issue: the equipment has been heat-treated (using 14Cr1MoR material) and has passed the hydrostatic test. It was found that the external pre-welded parts were not welded (they are quite thin); after welding, overall heat treatment was carried out again. Is it necessary to conduct another hydrostatic test?
This post was last edited by zjq1962 on 2018-1-27 at 16:22. Although it is said that no welding work should be carried out after a voltage tolerance test, this rule should be applied flexibly; in your case, I think it is not necessary to conduct another voltage tolerance test. Paragraph 6 of Clause 4.1.9.2 of the Fixed Volume Specification states that after the pressure test, if the repair depth exceeds one-half of the thickness, the pressure test must be conducted again. Conversely, even in the case of repair, as long as the depth does not exceed the specified limit, it is not necessary to conduct a voltage resistance test; therefore, in your case, there is no need to carry out such a test at all. The purpose of the voltage withstand test is to check the overall strength of the equipment. Since its strength has already been verified as being satisfactory, welding prefabricated parts to the main body should not affect the equipment’s strength. Of course, it’s best to avoid such a situation if possible. In your case, according to Article 4 of Specification 4.2.1.4, heat treatment is not required. The above is my personal understanding
After heat treatment, the strength of the material may decrease. Therefore, the previous water pressure tests were, in strict terms, invalid. I think it should be suppressed again.
Originally, very thin pre-welded parts could do without heat treatment (according to Clause 4.7 of NB/T47015-2011, surface inspection was sufficient), but since heat treatment has been carried out, the properties of the material may have changed and the internal stresses in the equipment may have been redistributed; therefore, another hydrostatic test is necessary to verify its integrity.
This post was last edited by *AOL_1 on 2018-1-30 at 13:31. According to HG20584, a pressure test is required. (Exemption for 2mm or less) However, in my opinion: a hydrostatic test is not necessary, but full surface magnetic particle testing is required. Furthermore, individuals tend to opt for only local heat treatment after patch welding. Heat treating CrMo steel materials is not necessarily a good thing.
No need for hydraulic pressure for heat treatment, right?
After heat treatment, a hydrostatic test should theoretically be conducted again. On the one hand, the properties of the material change after heat treatment; on the other hand, the geometric tolerances of some sealing surfaces also change as a result of heat treatment. All of these require verification through rehydrostatic testing.
Local heat treatment is preferred; there are no mandatory requirements regarding water pressure, which depends on the client’s requirements.
In my opinion, it is not necessary to carry out overall heat treatment or pressure testing; instead, only local heat treatment of this area is required, and magnetic particle inspection should be performed on this area after the heat treatment