Valves are being used for most machinery systems on ships for controlling and regulating fluid through pipes
All valves applied to ships hold the basic functionality of money flow on the liquid inside the pipes.Valves are being used for most machinery systems on ships for controlling and regulating fluid through pipes. Although valves are called efficiency decreasing device because they reduce the energy inside liquid flow, their use is imperative in applications where limited flow is essential.Therefore, for virtually any aspiring or serving marine engineer, it is rather necessary to be aware of construction and dealing of various forms of valves like Stainless steel foot valve applied to ships.
In this first article on the series “Types of valves officially used on ships”, understand one with the most important valves officially used on board ships – Gate valve.Globe valves operate by using a convex disc shaped plug raise reducing via a rising stem in to a circular seat about the inside with the globe shaped body in the “equator”. The flow enters the “lower hemisphere” from side, then travels up with the seat and exits throughout the outlet around the opposite side in the “northern hemisphere”. Globe valves are suitable for both on/off and throttling applications.
There are 2-way globe valves which can be a preferred selection for precise flow control and 3-way globe valves that are frequently used for mixing media from two inlet ports and directing that mixture by using an outlet port.
the discs have no choice but against the valve seats using a wedging mechanism because stem is tightened. Some double-disc parallel seat valves hire a design which depends mainly upon the fluid pressure exerted against one side on the disc or perhaps the other due to its tightness. The major selling point of this type could be that the disc is not jammed to the body, an action which may make it difficult to spread out the valve. This is particularly important where motors are used by opening and closing the valve.
Unlike the wedge inside a wedge-gate valve, which only enters contact nearly closed, each disc within the parallel seat valve slides against its seat as the valve has opened or closed. Consequently, these factors must be created from metals, which don't gall or tear while in sliding exposure to each other.
Recently, a new customers are not particularly aware in the characteristics of cast steel gate valves. Based on recent work practices, Weldon summarized the benefits and disadvantages of cast steel gate valves. Hope it might make more clearly through this information.
Cast steel gate valve, otherwise known as "API cast steel gate valve", is correct for ANSI Class 150 - 2500 LBs, working temperature < 600 °C under various working conditions of petroleum, chemical, thermal power plants like pipelines, cutting or connecting pipeline media.
Thermal binding occurs a valve is tightly turned off while the temperature system is operational. Later when the product is shut down and able to cool, thermal contraction on the valve seats move inward in excess of the wedge shrinkage. This can bind the wedge and seats tight enough never to allow the wedge to unseat or move if your hand-wheel or perhaps the valve actuator is activated to spread out the valve.
Parallel seated gate valves are the most suitable for applications having possibility of thermal binding. Split-wedge or flexible-wedge type gate valves are hoped for to perform superior to solid-wedge gate valves when thermal binding is usually a concern.
Sometimes in high-temperature applications, the flow medium, for instance water or steam, is kept in the valve bonnet area in the event the valve is closed for system shutdown. The valves that will not permit this trapped liquid or even the condensate to reenter the piping either upstream or downstream can suffer excessive pressures from the bonnet cavity once the system returns to operating temperature. This built-up pressure inside the bonnet cavity can steer clear of the valve from opening and might cause damage to valve parts.
