A truck loading arm is a large mechanical arm used to transfer liquid, gas or dry goods from one storage container or tank to another. The liquefied or dry bulk contents run through a rigid pipe system that is normally comprised of steel pipe and swivel joints to give flexibility to allow for movement and easier handling.
There are a few types of loading arms based on the setting and requirements for use. Contents that are transferred from the truck and rail tanks utilize either a bottom loading arm or a top loading arm. When the contents are transferred from a barge or a ship, it would require the use of marine loading arms.
Bottom and Top Loading Arms
Generally, both types of loading arms consist of 3 pipe parts: the drop pipe, outer arm, and inner arm. They can come in sizes ranging from two inches to six inches. The pipes are normally joined together with a set of swivel joints. Since the pipes are hard and sturdy, it needs the help of swivel joints so that the pipe system becomes more flexible.
There are two ways that a top or a bottom loading arm can be placed. They can either be placed through a plate on existing walls or they can be mounted on a steel fabricated column. Additionally, it is important to always have a balanced loading arm to make loading easier. To help maneuver the loading arm and heavy steel pipes, a counterweight or cylinder that has a spring balance built in will help increase the usability of the loading arm rig.
Bottom Loading Arms
This is the type of arm that can be used when the transfer is done on the bottom of the truck or the rail from ground level. The connection placement is vital to identify how long the pipes should be. For example, the rear connection would need a lengthier arm compared to the connections on the side.
Bottom loading arms are also more open to modules and other accessories to widen its function. When the bottom loading arms are fitted with the right tools and used in the right situation, they can be more efficient than top loading arms.
Top Loading Arms
Top loading arms are utilized by most, if not all, of the rail-transported tanks. The transfer usually starts at the manhole located on top of the carrier. The connection can either be open, semi-closed and closed depending on the type of content that will be transferred.
As with bottom loading arms, there are also different accessories that can be attached to the top loading arms to provide it with more functionality.
Marine Loading Arms
When it comes to transferring fuel to a barge or a ship, a special kind of loading arms is used. These marine loading arms can handle the changes in the draft, the tide, and the wind. Using a marine loading arm is a tried, tested and proven method to move liquid diesel faster into boats or ships compared to using a hose.
Though it is specifically made for marine transfers, this type of loading arms uses similar structure and parts as that of truck loading arm. The components include swivel joints for flexibility and solid steel or carbon steel piping.