Would appreciate to have some views on PV valves maintenance and inspection procedures, considering compliance with regulations as well as good practices.
The correct operation and sealing of the PV valves is essential for the safety of oil tankers.
Please refer to the below good practices related to their routine maintenance and inspection procedures:
- Frequent cleaning of the discs and seats using clean cotton rags. Ideally, cleaning is to be performed once during every ballast voyage, provided that the ballast leg is long enough. In this way, the surfaces will be kept clean and pitting will be avoided. Depressurization of the tanks is necessary before proceeding.
- Frequent checking / confirmation of the free lifting of the PV valve using the manual handle.
- In the case that pitting is present, carry out lapping according to makers instructions, the soonest possible, while the pitting is still at an early stage. This is very important, because there is a “point of no return” in cases of deep pitting where re-welding and machining by specialist would be required for the repair.
- For the lapping, use self-adhesive emery paper or standard emery cloth with double faced adhesive tape. It is recommended to exchange the PV valve with a spare PV valve, do the lapping at the workshop and exchange again. The adhesive glue is to be removed from the surfaces upon completion of the lapping.
- Upon completion of the lapping, do a leak test with soapy water on the PV valve testing device and confirm that the leakage rate and pressure values are close the shop tests.
- Do not try to remove the pitting by machining on the workshop lathe. It is very likely that the sealing/contact surfaces will not be machined to the correct/matching sealing angles. This is a job carried out by specialists, if necessary.
- Do not use silicon or other compounds on the sealing surfaces.
- Keep a spare PV valve onboard, at all times