MIL-STD-1330D(SH)
w/ Change 1
5.11 Piping repairs.
5.11.1 Applicability. For repairs of piping, the following procedure may be employed to eliminate the need to hydrostatically test and clean the piping. Local engineering approval is required to employ this procedure.
5.11.2 System preparation. The area where cutting or grinding will occur and the adjacent piping or equipment shall be externally cleaned to remove loose scale, dust, dirt, oil, grease, and other foreign materials as specified in
5.10.1.1. That portion of the system where cutting or grinding will occur shall be depressurized and purged of dangerous gases (such as, oxygen, hydrogen) using helium or nitrogen. The affected portion of the system where
cutting or grinding will occur shall be isolated by shutting the boundary isolation valve. A convenient bleed point within the affected boundary shall be allowed. After the affected portion has been depressurized, systems containing
oxygen at levels greater than 22 percent or hydrogen at levels greater than 3 percent shall be purged with helium or
nitrogen to eliminate fire or explosion hazards as specified in 5.10.1.4.
5.11.3 Maintenance of purge. During cutting or grinding and when the system is open to the atmosphere, maintain a slight positive helium or nitrogen purge of about 2 lb/in2 to prevent possible entry of airborne contamination or contamination from cutting or grinding.
5.11.4 Cutting or grinding of system. When cutting, cut to the blue line and carefully break the pipe or remove the fitting minimizing the entry of contaminants. When grinding, grind carefully to prevent the entry of contaminants. Exercise extreme caution when performing cuts in vertical pipe runs to prevent introducing contamination. A cut in a horizontal pipe run should precede any vertical cut. Increase purge pressure as necessary during cutting or grinding to prevent the entry of contaminants.
5.11.5 Cleaning. While maintaining the purge, locally clean the pipe internally and externally where the cutting or grinding occurred as specified in 5.12.4. If there are any significant delays during fit up and welding, the system shall be packaged as specified in 5.16.1.3. The purge shall be maintained during joint fitup. Depending on the welded joint design, the purge pressure established to maintain cleanliness may need to be reduced or the purge stopped to allow satisfactory completion of the weld. In this case, once the cleanliness boundary is secured, such as when the weld joint is tacked to positively prevent separation, and verified by a Certified Oxygen Clean Worker qualified in accordance with 5.14, the welder can adjust the purge as necessary provided this does not otherwise conflict with the requirements of NAVSEA S9074-AR-GIB-010/278. Work shall be planned to minimize the time the system is open to the atmosphere or temporarily packaged. If cleanliness is maintained properly and no contamination is detected, flushing of the piping system is not required. If contamination is detected, the extent and source of the contamination shall be determined and the system shall be cleaned as required to remove the contamination as specified herein.
5.11.6 Inspection and testing. Hydrostatic testing is not required if the operating test option authorized in NSTM S9086-RK-STM-010/CH-505 is used. The operating test option of NSTM S9086-RK-STM-010/CH-505 specifies that the weld root shall be inspected by liquid penetrant (PT). The option to inspect the weld root with 5X visual per NAVSEA S9074-AR-GIB-010/278 is deleted. After welding, perform a joint tightness test as specified in
5.9.
5.12 Loss of system cleanliness.
5.12.1 Definition. Contamination of a system which has previously been cleaned as specified by this standard due to other than normal system use is considered a loss of system cleanliness. Examples include loss of a purge, system degradation causing pieces of material to deposit in the system, and inadvertent exposure of a cleaned surface to an uncontrolled atmosphere.
5.12.2 Method for determination of extent of contamination. Whenever loss or suspected loss of cleanliness occurs, the extent of the contamination shall be determined by performing a visual inspection as specified in 5.13.1. The boundary of the contamination is determined based on the inspection results. The following would be considered as unacceptable requiring corrective action as specified in 5.12.3. This list is for guidance only and does not include all items that may be encountered requiring corrective action.
a. Any fluorescence under ultraviolet light or observable coatings attributed to other than approved lubricants. The procedure specified in 5.13.6 for detecting hydrocarbon contamination by swipe is useful in differentiating an approved lubricant from a hydrocarbon contaminant.
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