Valves matter! It is used in all machinery as a flow regulating device.

Valves reduce the energy in fluid flow, but their use is essential in operations requiring limited flow. Therefore, it is very important to have a good understanding of the structure and operation of the various types of valves used on ships.

Each type of valve has a specific function, including reducing/increasing flow, regulating pressure, starting/stopping flow, relieving pressure in piping systems, and controlling flow direction.

Valves are made up of many different parts. First comes the body, which holds all the parts of the valve together, and then the bonnet, which covers the opening. Valve internal parts consisting of valve stem, valve seat material, components, valve disc, valve plug and support ring are collectively referred to as valve trim. The valve disc is designed to throttle or stop the flow, the seat of the valve disc is provided by the sealing ring. The stem facilitates the closing of the valve.

gate

This is one of the most common types of valves used on boats. They help control the flow of liquid through pipes by raising or lowering, similar to gates. It should be noted that the gate valve can only work under no flow or full flow conditions, so it can only have one position. It provides full port flow without changing direction; it is not suitable for operations that require the valve to be partially open. Gate valves have a simple design and function, but there are also many variations, namely rising stem types and non-rising stem sections.

In a rising stem gate valve, the threads on the stem mate with integral threads in the yoke or bonnet. In operation, steam rises above the actuator and the valve connected to the stem opens. In non-rising stem gate valves, the disc or disc itself has internal threads and is attached to the stem. The stem threads mate with the disc and the valve will open or close without lifting the stem.

To avoid any kind of leakage through the space around the main shaft in the gate valve, gland packing is used. In the long run, the gland packing will be damaged and must be replaced periodically. Gate valves are used in applications requiring minimal pressure loss and also in applications requiring bi-directional flow. The material commonly used to manufacture these valves is cast iron.

Shut-off valve

This is a linear motion valve designed to start, stop or regulate flow. The disc of the globe valve can be completely removed from the flow path for enabling flow, or it can be completely closed for the flow path of shutting off flow. The valve is available in three main body designs, a three-way (Z-body), an angle body, and a Y-body. These valves typically have a rising stem, with male threads and yoke construction on larger sizes. The components of globe valves are similar to those of gate valves. The seat of the globe valve is located in a plane parallel or inclined to the streamline.

Globe valves are suitable for systems that need to regulate flow and fuel systems that need to regulate flow and tightness. They are also used in water feed, condenser air extraction, chemical feed, and air extraction drainage systems. Compared with gate valves, globe valves have good closing ability, moderate to good throttling ability, and shorter stroke. Because the disc is attached to the stem, the globe valve can be used as a stop check valve.

butterfly valve

This is a lightweight valve for use on containers for fuel, fresh water, lube oil, or chilled water systems. To better understand this valve, imagine a butterfly moving its wings. It is a quarter turn rotary valve used to stop/start and regulate flow. These valves are manufactured on the principle of pipeline dampers. The flow-controlling element is a disc with a diameter approximately equal to the inner diameter of the adjacent pipe rotating about the vertical/horizontal axis. When the disc is parallel to the pipe, the valve is fully open; when the disc is vertical, the valve is closed.

Butterfly valves are ideal for handling large volumes of fluid at relatively low pressures, and for handling slurries containing large amounts of suspended solids. Offers many advantages over globe, plug, gate and ball valves, most notably weight, space and cost savings. These valves are also very low maintenance because there are very few moving parts.

safety valve

These valves are specifically designed to relieve pressure in pipelines. When the internal pressure increases, the spring inside the valve opens and releases the pressure. The spring can be adjusted to make the valve open faster or slower as needed. To prevent major damage to equipment, machinery and worker safety valves relieve elevated pressure before it reaches its limit. It can be adjusted and regulated so that it pops up when the internal pressure exceeds a predetermined setting. Once the internal pressure reaches the normal level, the safety valve closes.

Diaphragm valve

This is a two-way on/off throttle valve that controls fluid flow by adjusting the area in which media enters and exits the valve, effectively varying its speed and velocity. A flexible membrane is used to control the opening and closing of the valve, hence the name diaphragm valve. These are similar to pinch valves, but they use a linear compressor to push the diaphragm into contact with the valve body. Diaphragm valves provide discrete and variable pressure control and are available for manual and automatic operation. They are also clean, leak-proof, easy-to-maintain, safe and effective valves best suited for medium-pressure and high-temperature operations requiring start/stop fluid control.

pinch valve

It is a 2/2-way valve for shutting off or regulating the flow of corrosive, abrasive or granular media. Pinch valves use compressed air to open or close the valve. The valve is unrestricted and, when in the open position, allows a range of media to pass through the orifice. The valve consists of a flexible inner rubber sleeve which isolates the media and prevents the risk of contamination. Best suited for granular products, these valves offer cost-effectiveness, reliability and ease of use.

ball valve

This is a globe valve that controls fluid flow through a rotating ball with a hole. By rotating the ball a quarter turn around its axis, media can be blocked or flow through the valve. Ball valves are characterized by long service life and provide reliable sealing throughout their service life, even if the valve has not been used for a long time. Ball valves are used in control valves in some special versions, an operation that is less common due to the relatively limited precision with which flow can be controlled compared to other types of control valves.