Globe Valves Used Aboard Ships - Operation, Design, and Repair
Testing of Globe Valve
After the globe valve has been overhauled, it must be tested properly before use. The testing procedure is such that the globe valve is to be filled with water above the valve disc (after the valve is closed), and in first step, the engineer must check whether any water is leaking to the other side. If any leakage is there in the first test, then the valve and the valve seat have to be re-lapped and then re-tested. If the globe valve is now satisfactory and there is no leakage, then the second step of the testing should be done. In it, an appropriate flange has to be put and compressed air has to be put from the lower flange, below the valve seat at a pressure equal or more than the service pressure. If no bubbles are observed on the water at the top, then the valve is considered to be holding and it has been correctly overhauled.
The other method of testing is to put a compressed air connection, with a regulating valve and a pressure gauge to one side of the valve, with good gaskets and tighten it. Thereafter the globe valve should be closed tight, and compressed air at a pressure equal or more is put in and the regulating valve closed. Next the drop in pressure is observed. If there is no pressure drop for five minutes, then the valve is holding and the test is successful.
After the testing has been successful, then the valve should be put in a proper location, with a tag stating that the valve has been tested, the date of testing, and the name of the testing engineer.
In this article the classification of the globe valves, their routine maintenance, their overhaul procedures, and the testing procedures have been discussed in brief. It explains to shore and marine engineers the cautions and precautions to be observed during the operation. In our industrial work places and on ships, globe valves have often been taken for granted. Even good planned preventive maintenance plans often overlook them. They are only opened up for investigation when a problem in the flow or pressure, or if any leakage exists. Globe valves are widely used on the ships and are very sturdy, but like all machinery and devices, have to be maintained properly. It is hoped that this guide would create awareness among junior engineers and other marine engineers about the operational precautions and maintenance of globe valves.
- Marine Auxiliary Machinery, 7th Edition by H. D. McGeorge
- Introduction to Marine Engineering, Second Edition, by D. A. Taylor
- Control Valve Handbook , Fourth Edition, Emerson Process Management