Loading arms have represented a tested solution for transferring liquid substances, including liquefied gasses, for decades. 

Distribution loading arms follow particular specifications depending on the type of liquid and where liquids come and go from: LNG loading arms will present different characteristics compared to marine ones for non-cryogenic purposes, or a truck loading arm.

For this reason, and from our expert position at cryogenic engineering, at Cryospain we’ve made the following guide about loading arms. Keep reading to find out more.

What are loading arms?

Loading arms are mechanical structures that facilitate the transfer of liquid substances or liquefied gasses from one tank to another. 

They can be described as a pipe system that includes both rigid pipes and swivel joints that help articulate the system. A common configuration includes three pipes: inner arm, outer arm and drop pipe, all of them connected by swivel joints. 

Additionally, they can be mounted on plates attached to a wall or mounted on a column. As piping is often made of heavyweight materials such as steel, balance must be achieved to guarantee safety. This can be achieved by counterweight systems or spring balance cylinders. 

Today, loading arms are used across a number of industries, which include oil companies, mining sites or chemical manufactures, among many others. 

As such, substances such as fuel, petroleum products, and chemicals are typically transferred through loading arms. The case of liquefied gasses is particularly distinct, as these substances will require adapted cryogenic piping to guarantee the product remains safe and maintains its quality.

Differences between Top and Bottom loading arms

Loading arms can be divided between top and bottom arms, depending on the type of tanks presented for the liquid transfer.

  • Top loading arms use manholes on top of tankers, which might be sealed or not depending on the product stored within. A transfer from or to a tank that is transported in a truck or a train typically requires top loading arms. They allow for “closed connections” in case the transferred products potentially present significant hazards. 
  • Bottom loading arms are often used for loading and unloading substances from tanks in ships, as these often need a loading location from the bottom. Marine ones will often employ bottom loading arms. 

Truck & rail loading arms

As explained above, truck and rail loading arms typically require top loading arms structures. Some of these systems’ characteristics include:

  • They must adapt to open, semi-closed or closed connections depending on the type of manhole present in the tank. These differences respond to the transferred substances and their potential hazards.
  • They must also provide sufficient protection against potential risks involved with loading arms, such as the release of toxic vapors or spillages.
  • Additionally, these structures’ ergonomy is often improved through the use of various accessories, including purges, safety brake valves or pneumatic up and down systems, among others.

Related content: Ships powered by methanol: an alternative fuel to LNG

Marine loading arms uses

Marine loading arms are mechanical structures that, through articulated steel pipes, are able to transfer liquids from vessel to shore. 

Common transportation methods that benefit from marine loading arms include tankships such as oil and chemical tankers, which regularly need to transfer cargo to shore terminals. They’re also a key part of bunkering projects that involve LNG loading arms and pipe-in-pipe structures.

Like other arms described above, marine ones present rigid piping structures and swivel joints. However, this particular type of loading arms must adjust to the specific needs of marine context. As such, they must take into account factors such as changing tides, wind and drafts, and be ready to follow these dynamic movements. 

Connections typically include a flange, thread or couplers, while a secure seal to a ship’s flange will incorporate a gasket or o-ring arrangements.

While alternatives such as hoses have been used, marine loading arms present significant improvements to this process: they optimize transfer efficiencies, present a longer life cycle and avoid dangerous spillages. Accessories can also be employed to improve these loading arms’ ergonomy, and common add-ons involve quick connect couplers, systems to monitor position and emergency release systems.

It’s key for marine loading arms to follow ASME and OCIMF (Oil Companies International Marine Forum) standards to guarantee security. These guidelines include recommended strength calculations, working envelope and the type of accessories that manufacturers must include in their designs to ensure top quality and safety in their equipment.

Types of marine loading arms

  • Marine loading arms can present manual or hydraulic control
  • Some include quick-connect fittings
  • Two types of marine loading arms arise when it comes to ensuring these are drained or closed before connection to the shiptank is finished: arms that are in charge of transferring fuels such as gas oil or diesel are blown out using high-pressure air. Kerosene or petrol arms, on the other hand, are stripped using pumps
  • They can be made custom adjusting to a given port’s needs, particular vessel sizes or cargo temperatures. For instance, these structures will present specific insulation features for the transportation of cryogenic substances. 

Parameters for marine loading arms

  • Changes in draught
  • High or low water
  • Drift & surge contexts
  • Envelopes
  • Loading times
  • Flow rates

You must be interested: Cryogenic liquid gases: differences and common uses of LNG, LIN, LOX, LAR and LC02

Technical notes about loading arms 

Balance mechanisms 

Balance mechanisms in loading arms guarantee arm operations such as vertical movements are safely performed. Among these techniques, counterweight systems or spring balance cylinders can be included.

Sizes

Ideally, loading arms will adjust to the particular operations they’re built for. As such, sizes can range from from 2” to 6”. 

Materials

Aluminum, stainless steel and galvanized steel loading arms exist in order to adjust to the needs of each substance transfer method.

Industries

  • Oil and gas
  • Food processing
  • Fuel for rail, trucks and ships 
  • Food processing
  • Chemical sector
  • Pharma
  • Petrochemical industry
  • Mining

Keep reading: New Vacuum Insulated Piping (VIP) Project for an ASU in Spain

Total engineering with Cryospain

Loading arms must ensure the highest quality in materials and manufacturing processes in order to guarantee total safety and operation efficiencies. Additionally, they must be thoroughly tested and comply with relevant industry standards.

Through our project management consulting in cryogenic engineering, at Cryospain we’re able to provide specialized and personalized engineering expertise that ensures high-quality, reliable cryogenic equipment.

Based on our two-decade experience in global cryogenic projects, we offer the possibilities of designing, manufacturing and implementing cryogenic loading arms projects, putting our global team of engineers to work to achieve the best results. This is joined by our in-house production plants, which allow us to guarantee the highest quality and add the possibility of developing custom projects where the most materials and other systems can be incorporated.

Get in touch with us to learn more about cryogenic loading arms and what Cryospain can do for your project. 

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