Principles of naval engineering - Historic Naval Ships Association

Chapter 14. -PIPING,FITTINGS, AND VALVESDISCHARGE STOP VALVESUCTION STOPCHECK VALVEDISCHARGEVALVESPUMPDISCHARGECONNECTIONPUMP SUCTION CONNECTIONFigure 14-29.— Valve manifold.47.63XIDENTIFICATION OF VALVES.FITTINGS, FLANGES. AND UNIONSMost valves, fittings, flanges, and unions usedon naval ships are marked with identificationsymbols of various kinds. The few valves andfittings that are made on board repair ships ortenders or at naval shipyards are usually markedwith symbols indicating the manufacturing activity,the size, the melt or casting number, andthe material. They may also be marked with anarrow to indicate the direction of flow.Commercially manufactured valves, fittings,flanges, and unions may be identified accordingto the requirements of the applicable specifications.However, many valves, fittings, flanges,and unions are now identified according to astandard marking system developed by the ManufacturersStandardization Society (MSS) of thevalves and fittings industry. Identification markingsin this system usually include the manufacturer'sname or trademark, the pressure andservice for which the product is intended, andthe size (in inches). When appropriate, materialidentification, limiting temperatures, and otheridentifying data are included.The MSS standard identification markingsare generally cast, forged, stamped, or etchedon the exterior surface of the product. In somecases, however, the markings are applied to anidentification plate rather than to the actualsurface of the product.The service designation in the MSS systemof marking usually includes a letter to indicatethe type of service and numerals to indicatethe pressure rating in psi. The letters used inservice designations are:AGLOWD-W-Vairgasliquidoilwaterdrainage, waste, and vent387