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Anatomy of a Barge Valve
Valve basics on a Higman Barge.
In the liquid cargo business, there is probably not a piece of equipment more important to the operation than the valve. Cargo on, cargo off; the valve is the regulator of flow in the system and is an integral part of the cargo's pathway on and off the barge.
So what type of valves are typical on a Higman barge? What are they specifically designed for and what is the purpose in our cargo systems? Let's look first at what we would find on a six tank clean barge.
Gate Valves
Gate valves are the main flow controllers on our barge. Our sample barge has one in each tank controlling in flow and out flow. Usually there is a block valve in the main cargo line and a block just before the pump well. The cargo header also has a gate valve on each end and a drop valve.
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Gate Valve. |
Gate valves are normally used when a straight-line flow of fluid with a minimum amount of resistance is required. Perfect for cargo lines. Gate valves are characterized as having either a rising or a non-rising stem. Rising stems provide a visual indication of valve position because the stem is attached to the gate such that the gate and stem rise and lower together as the valve is operated. Non-rising stem valves may have a pointer threaded onto the upper end of the stem to indicate valve position, since the gate travels up or down the stem on the threads without raising or lowering the stem. Ball Valves
Ball valves are found mainly in the stripping system of the barge.  | | Ball Valve. |
A ball valve is a valve with a spherical, the part of the valve which controls the flow through it. The sphere has a hole, or port, through the middle so that when the port is in line with both ends of the valve, flow will occur. When the valve is closed, the hole is perpendicular to the ends of the valve, and flow is blocked. The handle or lever will be in-line with the port position letting you "see" the valve's position. The design of a ball valve makes it suitable for throttling the fluid flow through it. Because of that quality, it is used primarily in our stripping lines. Butterfly Valve  | |
Butterfly Valve. |
The butterfly valve is used in the Vapor System. It is well suited for low pressure/vacuum applications. They are simple to install and simple to repair. They are light weight and take up less space than a gate valve. The butterfly valve may be used for throttling, set in any position from fully open to fully closed. In our operation though on a vapor line, they are always fully open or fully closed. Check Valve 
On the discharge side of the cargo pump is a check valve. A check valve will allow flow in one direction only. In our case, that direction is away from the cargo pump. A typical check valve as found on Higman barges is a "wafer" style check valve. A spring loaded disc or "wafer" swings open, activated by the pressure, to allow cargo to flow. Pressure in the opposite direction, aided by the spring pressure, swings the "wafer" closed. Since the operation of valves is what makes it all happen on a tank barge, tankermen should know them well. | 
