Outboard Loading arm LNG (Liquified Natural Gas) Inspection use DPT (Dye Penetrant Test)

Bontang, Desember 7th 2013 16:22

di kamar PC6 115D

Good evening sob? how are you today? today I will explain you about loading arm LNG inspection in dock #1 use DPT (Dye Penetrant Test). I am Pendekar and I am Student of LNG Academy second generation.

okay I  will start...

what is outboard loading arm? outboard is part of loading arm that has function to connect with LNG Carrier at the time LNG is transferd.

      In practice this time, we will perform an inspection on the outboard surface of the loading arm to determine the condition of the surface. The outboard loading arms inspections performed in 7 process they are pre-clean process, penetrant application, remove excess penetrant, developer application, interpretation, and report post-cleaning.

     The first thing that must be considered before the inspection process is a pre-cleaning process. Because it will affect the results.  Pre-cleaning is one of the important stages for the purpose of pre-cleaning is ensuring Parts must be free of dirt, rust, scale, oil, grease, etc to perform a reliable inspection. The cleaning process must remove contaminants from the surfaces of the parts and defects, and must not plug any of the defects. For outboard inspection, pre-cleaning is done with sandblasting then cleaned with a cleaner. Sandblasting is a process of cleaning the surface with fire particles (sand) to the surface of the material causing friction collision. The material surface will be clean and rough. Sandblasting is done in the "workshop" and then outbourd be carried to “IKPT” for inspection.

     The next process is clean the surface outboard with use cleaner. Surface that cleaned is part of welding. Cleaner is applied to the  HAZ area 2 cm in side on welding.

      Then penetrant is applied on surface of outboard, focused on welding joint, due to a potentially defective part. Penetrant can applied in 3 methods, they are : spraying, brushing and immersing. For this case using "brushing or spraying" because more efficient and simple. then wait a few minutes to penetrate on the surface. Time that use penetrant to enter on the surface of outboard is called "dwell time". There are some explanation about dwell time :

§  The penetrant dwell time is the total time the penetrant is in contact with the part surface.

§  Dwell time is important as it gives the penetrant sufficient time to seep or be drawn into the flaw / defect.  

§  The dwell time vary according to penetrant type, temperature, material type and surface finish.

§  The ideal dwell time is often determined by experimentation and very specific to a particular application.

§  Reference : penetrant manufacturer or applicable code / standards (ASME, ASTM etc.).

(me)

(dwell time)

      After that, penetrant removal process. Devide 3 methods they are :

Water Washable, Post Emulsifiable and Solvent Removal.

• Water Washable 

-    - Usually for small parts

- Water (spray, dip, wipe, rinse) is used to remove the excess penetrant

- The procedure will specify water temperature (typically 50-100°F), pressure (typically       not more than 40 psi), etc.

- Cheap

• Post Emulsifiable

- When there is concern about removing much of the penetrant from the defect, a post emulsifiable system is used.

- This involves an additional step in which an emulsifier is applied to the surface of the part after the penetrant dwell time.

- The emulsifier is given just enough time to react with the penetrant on the surface to render it water washable but not enough time to diffuse into the penetrant trapped in the defects.

• Solvent Removal

- The part is wiped with a clean dry cloth to remove the bulk of the excess penetrant.

- Then, a cloth lightly dampened with solvent (cleaner / remover) is used to remove any remaining penetrant on the surface.

- Any time a solvent is used in the penetrant inspection process, a suitable flash time is required to allow excess solvent to evaporate. For outboard inspection use Solvent Removal methods because appropriate with size of material and also to make easy inspection.

        The next process is Developer application. After Penetrant application afterwards Developer is applied on the surface of outboard. The purpose of Developer application is to pulled out the penetrant out of the smooth crack. Developer application is one of important process in Dye Penerant test (DPT). Something that has special care is distance between surface and spraying can because it will influence the result of process. Normal distance spraying can and surface between 25-30 cm. If distance between spraying can and surface is too near, developer possible to wetting the surface so it will make the developer enter to surface slowly, if distance between spraying can and surface is too far, developer that enter to surface is little and the result is not good.

 (my friend)

After that, inspector is commissioning and check the condition of outboard, if penetrant appear from crack it means the surface is defect. To ensure penetrant that appear from the crack in the surface, penetrant is cleaned back with cleaner on the surface and then developer is applied. If there are visible penetrant from the surface so there are crack on the surface of outboad. And then marked the crack and the last process is post cleaning and reporting.

 

After that will be continued to repair outboard depend on defect in the surface.

Thankyou for your attention and sorry if my english is bad :)
feel free, if you want to sharing with me.

pendekar