Loading arm
Encyclopedia
A loading arm permits the transfer of liquid
or liquefied gas from one tank to another through an articulated pipe system consisting of rigid piping and swivel joints to obtain flexibility
.
Transfer to or from a truck
transported tank or rail transport
ed tank requires a Top Loading Arm or a Bottom Loading Arm. Transfer to or from a ship
or barge
requires a marine loading arm
.
Both types of loading arms are typically made of 3 pipe
s – respectively called inner arm, outer arm and drop pipe.
The size can be from 2” to 6”. These 3 pipes are connected by swivel joints. Swivel joints are required to provide the flexibility needed. The loading arm unfolds to get the required working envelope to load or unload the tanker, and the reverse is to retract or get a minimal space for parking or storage.
Both types of loading arms may be mounted on a column or via a plate to an existing wall.
Balancing is needed due to the weight of the steel
piping. Balancing of the arm is made by counterweight
or by a spring balance cylinder.
s.
Loading or unloading is done through the manhole
on the top of the tanker.
Depending on the nature of the product (not dangerous, without any toxic vapors…), the connection may be “open”, this means that the manhole is not sealed.
A “Semi-Closed” connection can be made by a cone on the manhole of the tanker.
A “Closed” connection is required for all dangerous and toxic products. This connection is made by a flange
to the top of the tanker.
A cone can be equipped with a vapour hose to prevent the vapors from being released to the atmosphere.
Numerous accessories are available to make a loading arm more ergonomic and more effective: press down system, pneumatic up/down system, top level control, safety break valve, purge, drain…etc.
The location of the connection has an influence on the length of the pipes. As an example, a rear connection requires a longer length of arms than for a side connection.
The connection of this kind of loading arm can be made by flange, thread or by quick connection coupler such as a Dry Disconnect.
There are also a numerous accessories which can be fitted to the Bottom loading arm to make it more ergonomic and more effective as described for the Top loading arm.
, wind
and other factors.
A Marine Loading Arm offers a significant improvement over a hose in the transfer of liquids between vessel and shore because It provides an easier and more ergonomic operation, gives longer service life and permits Emergency Release Action without any spillage of product and without any pollution
.
Like the Top and Bottom loading arm, the Marine Loading Arm is a system consisting of rigid piping and swivel joints to obtain flexibility. The OCIMF (Oil Companies International Marine Forum
) and ASME
have established guidelines for matters of strength calculations, working envelope and accessories. However the design of the loading arm is not included in this guideline and left to the individual manufacturer.
The product line reposes on a fixed stand post or riser and is connected by an inner and an outer arm – both arms are movable parts. Balancing is needed due to the weight of the steel piping. Balancing of the Marine Loading Arm is done by a rotating counterweight, which is connected to the inner arm and the outer arm via a rigid pantograph
.
Small loading arms may be manually operated. The bigger ones are hydraulically
operated.
The product line can be self supported or mounted on an independent support frame.
Since the swivels are strong enough to absorb the weights of the product line, the liquid in the arms and the forces of the wind, the marine loading arm can be built as a self supporting structure.
Nowadays marine loading arms can also be built on an independent support frame as is required for LNG
and highly corrosive liquids.
Recently the design of the marine loading arms has been significantly improved by the symmetric
design. This new concept offers many advantages such as the equal distribution of forces on the swivel joints under all conditions, less force within the structure, reduces the weight of the loading arm, and permits larger working envelopes without requiring significantly stronger construction
.
Since the symmetric design has proven its effectiveness and its reliability. The symmetric design is also applicable to marine loading arms requiring an independent support frame.
Liquid
Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...
or liquefied gas from one tank to another through an articulated pipe system consisting of rigid piping and swivel joints to obtain flexibility
Flexibility
Flexibility may refer to:* Flexibility , the distance of motion of a joint, which may be increased by stretching* Flexibility , in the field of engineering systems design, designs that can adapt when external changes occur...
.
Transfer to or from a truck
Truck
A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...
transported tank or rail transport
Rail transport
Rail transport is a means of conveyance of passengers and goods by way of wheeled vehicles running on rail tracks. In contrast to road transport, where vehicles merely run on a prepared surface, rail vehicles are also directionally guided by the tracks they run on...
ed tank requires a Top Loading Arm or a Bottom Loading Arm. Transfer to or from a ship
Ship
Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...
or barge
Barge
A barge is a flat-bottomed boat, built mainly for river and canal transport of heavy goods. Some barges are not self-propelled and need to be towed by tugboats or pushed by towboats...
requires a marine loading arm
Marine loading arm
A marine loading arm, also known as a mechanical loading arm, loading arm, or MLA is a device consisting of articulated steel pipes that connect a tankship such as an oil tanker or chemical tanker to a cargo terminal...
.
Top and Bottom loading arm
- General feature of Top and Bottom loading arms
Both types of loading arms are typically made of 3 pipe
Pipe
Pipe may refer to:* Pipe , a hollow cylinder following certain dimension rules* Smoking pipe* Pipe or butt, a cask measurement* Pipe , a type of metal casting defect...
s – respectively called inner arm, outer arm and drop pipe.
The size can be from 2” to 6”. These 3 pipes are connected by swivel joints. Swivel joints are required to provide the flexibility needed. The loading arm unfolds to get the required working envelope to load or unload the tanker, and the reverse is to retract or get a minimal space for parking or storage.
Both types of loading arms may be mounted on a column or via a plate to an existing wall.
Balancing is needed due to the weight of the steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
piping. Balancing of the arm is made by counterweight
Counterweight
A counterweight is an equivalent counterbalancing weight that balances a load.-Uses:A counterweight is often used in traction lifts , cranes and funfair rides...
or by a spring balance cylinder.
Top loading arm
Top loading arms are used to load or unload road or rail tankerTank car
A tank car is a type of railroad rolling stock designed to transport liquid and gaseous commodities.-Timeline:...
s.
Loading or unloading is done through the manhole
Manhole
A manhole is an opening used to gain access to sewers or other underground structures, usually for maintenance.Manhole may also refer to:* Manhole , a metal band from Los Angeles* The Manhole, a computer game...
on the top of the tanker.
Depending on the nature of the product (not dangerous, without any toxic vapors…), the connection may be “open”, this means that the manhole is not sealed.
A “Semi-Closed” connection can be made by a cone on the manhole of the tanker.
A “Closed” connection is required for all dangerous and toxic products. This connection is made by a flange
Flange
A flange is an external or internal ridge, or rim , for strength, as the flange of an iron beam such as an I-beam or a T-beam; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc., or on the lens mount of a camera; or for a flange of a rail car or tram wheel...
to the top of the tanker.
A cone can be equipped with a vapour hose to prevent the vapors from being released to the atmosphere.
Numerous accessories are available to make a loading arm more ergonomic and more effective: press down system, pneumatic up/down system, top level control, safety break valve, purge, drain…etc.
Bottom loading arm
This kind of arm is reserved for the unloading of road/rail tanker from the bottom, at the rear or side.The location of the connection has an influence on the length of the pipes. As an example, a rear connection requires a longer length of arms than for a side connection.
The connection of this kind of loading arm can be made by flange, thread or by quick connection coupler such as a Dry Disconnect.
There are also a numerous accessories which can be fitted to the Bottom loading arm to make it more ergonomic and more effective as described for the Top loading arm.
Marine loading arm
To load or unload a ship, a hose or loading arm is needed to follow the movement of the ship due to the dynamics of changing draft, changing tideTide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....
, wind
Wind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...
and other factors.
A Marine Loading Arm offers a significant improvement over a hose in the transfer of liquids between vessel and shore because It provides an easier and more ergonomic operation, gives longer service life and permits Emergency Release Action without any spillage of product and without any pollution
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...
.
Like the Top and Bottom loading arm, the Marine Loading Arm is a system consisting of rigid piping and swivel joints to obtain flexibility. The OCIMF (Oil Companies International Marine Forum
Oil Companies International Marine Forum
The Oil Companies International Marine Forum is a voluntary association of oil companies having an interest in the shipment and terminalling of crude oil and oil products....
) and ASME
American Society of Mechanical Engineers
The American Society of Mechanical Engineers is a professional body, specifically an engineering society, focused on mechanical engineering....
have established guidelines for matters of strength calculations, working envelope and accessories. However the design of the loading arm is not included in this guideline and left to the individual manufacturer.
- Different design for Marine loading arm
The product line reposes on a fixed stand post or riser and is connected by an inner and an outer arm – both arms are movable parts. Balancing is needed due to the weight of the steel piping. Balancing of the Marine Loading Arm is done by a rotating counterweight, which is connected to the inner arm and the outer arm via a rigid pantograph
Pantograph
A pantograph is a mechanical linkage connected in a special manner based on parallelograms so that the movement of one pen, in tracing an image, produces identical movements in a second pen...
.
Small loading arms may be manually operated. The bigger ones are hydraulically
Hydraulics
Hydraulics is a topic in applied science and engineering dealing with the mechanical properties of liquids. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties. In fluid power, hydraulics is used for the generation, control,...
operated.
The product line can be self supported or mounted on an independent support frame.
Since the swivels are strong enough to absorb the weights of the product line, the liquid in the arms and the forces of the wind, the marine loading arm can be built as a self supporting structure.
Nowadays marine loading arms can also be built on an independent support frame as is required for LNG
Liquefied natural gas
Liquefied natural gas or LNG is natural gas that has been converted temporarily to liquid form for ease of storage or transport....
and highly corrosive liquids.
Recently the design of the marine loading arms has been significantly improved by the symmetric
Symmetry
Symmetry generally conveys two primary meanings. The first is an imprecise sense of harmonious or aesthetically pleasing proportionality and balance; such that it reflects beauty or perfection...
design. This new concept offers many advantages such as the equal distribution of forces on the swivel joints under all conditions, less force within the structure, reduces the weight of the loading arm, and permits larger working envelopes without requiring significantly stronger construction
Construction
In the fields of architecture and civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking...
.
Since the symmetric design has proven its effectiveness and its reliability. The symmetric design is also applicable to marine loading arms requiring an independent support frame.