Key Considerations for LPG Coupling Applications

LPG can be dangerous if not handled correctly. That’s why it’s critical to use the right equipment when transferring and transporting bulk quantities of product. It’s also important for colleagues to understand the different specifications of available products and how they can be used to make common tasks simpler, safer and more efficient.

TODO has been providing fluid and gas handling solutions for over 50 years. This article shares some of the company’s knowledge gained over that time, including best practice, key considerations and the solutions that are ideally matched for LPG coupling applications.


LPG is an adaptable fuel often used in heating and cooking appliances, as well as industrial processes and vehicles. It’s also used as a propellant and refrigerant. LPG is usually obtained as propane or butane, or as a mixture of the two. Powerful odorants are added to make it easily detectable.

todo lpg transfer coupling

Flexibility is a big draw for LPG, but it also burns cleanly and is a reliable source of energy in remote locations. It produces less air pollutants, particularly black carbon emissions formed through incomplete combustion, and emits 33% less carbon emissions when compared to coal and heating oil. This makes it an ideal transition fuel source as society heads towards net zero and part of the reason the market is expected to grow solidly up to 2030.

Key LPG Transfer Considerations

LPG is a very useful fuel but also carries a number of risks which handling and transfer solutions need to be factored in. These include:

Flammability

LPG should never be transferred in an area that has open flames or other sources of ignition.

Density

LPG is denser, and therefore heavier, than both air and natural gas. Operators should avoid poorly ventilated areas that pose an explosion and asphyxiation hazard.

Combustibility

LPG can combust when it comes into contact with oxygen, halogens and metal halides.

Temperature

LPG has a boiling point of -42°C, making it a potential burn hazard should free-flowing gas come into contact with skin.


These properties highlight the need for safe and reliable solutions that minimize the risk inherent during storage, transport and transfer of LPG products.


Managing Risks Around LPG Transfer

Every connection point between an LPG cylinder and its intended destination (e.g appliance, tool, container or vehicle) poses a threat to operators and the local environment. Substandard materials and poorly designed fittings can raise the chances of catastrophic failure from leaking gas. As such, connecting hoses and fittings must be compatible with flammable gases and secured by fully qualified technicians. Terminals on bulk storage and coupling should therefore be checked regularly and maintained to ensure risks are managed effectively.


todo lpg coupling for rail

Key LPG Coupling and Accessory Solutions

TODO-GAS

The TODO-GAS dry-break offers the same performance and functionality as the TODO-MATIC but is designed specifically for LPG. Its push-and-twist coupling allows for easy connection between LPG and vapor lines with virtually zero spill upon disconnection.

Good solutions will focus on the transfer of LPG in both liquid and vapor phases. These product states are common across different transfer applications, including loading arm, rail tank, storage facility or hose loading. TODO-GAS can be used for any of these.


As a hose unit to tank unit connection, the product automatically starts flow of fluid or gas as it’s coupled. The maximum working pressure for brass is 10 bar (145 psi) and stainless steel is 25 bar (363 psi), while standard working temperature ranges between -20°C to +80°C (-4°F to +176°F). There is also capacity for the dry-break to go as low as -45°C (-49c) if the application calls for it.


There are three sizes available for the TODO-GAS – ranging from 1” to 3”. Depending on the volumes of product being transferred, TODO-GAS is often supplied in two of the available sizes, with the larger size used for handling the liquid phase and the smaller size for the gas phase.

The 1” and 2” sizes are dimensionally different with the STANAG 3756 coupling standard to prevent cross-contamination, but do offer cross-compatibility with other LPG dry-break manufacturers. 3” classifications, however, are compliant with STANAG 3756.


TODO is committed to using the best materials. This helps to ease operational demands when handling and transferring LPG. Our 1" and 3" tank units and 1-3" hose units use 316L Stainless Steel while our 2" Tank Units use Duplex Stainless Steel. Duplex stainless steel is used to withstand the vigorous requirements of conveying LPG vapors at fluctuating pressures – especially in warmer climates.

For all of the hose units, there is an integrated swivel to support quick and accurate connection. Both the hose and tank units can be configured with a wide variety of end connections including threaded or flanged.

Viton 90 shore O-rings are sold as standard with this product, which is an important difference from the TODO-MATIC. These O-rings reduce the risk of failure due to rapid gas decompression – a phenomenon commonly seen in LPG applications which can cause softer elastomers to degrade very quickly. The harder 90 shore standard is more adept at coping in these situations.

All TODO-GAS couplings are ATX compliant and certified to Pressure Equipment Directive (PED) requirements.


TODO-GAS Accessories

The TODO-GAS product range has a number of accessories available:

 

Pressure Equalization Valve (PEV) One of the most important accessories to consider when purchasing the TODO-GAS tank unit. The PEV is a small additional valve situated in the main piston of the tank unit, and actuates upon connection when being coupled. This allows for a small amount of pressure to be released into the piston cavity. The hose unit can then be connected to the tank unit under pressure, which is particularly important in warmer climates where pressure may have built up between the tank unit and the closure valve.

Long Handle Recommended option for applications where space is restricted.

Rubber Dust Cap To keep debris away from the tank or hose unit.

Locking Mechanism This is installed as standard on three-inch hose units. The locking mechanism ensures that if any problems arise with the swivel function, it will not cause the hose unit to disconnect under tension.

Rotational Block The rotational block can be installed to allow only a single 360-degree revolution of the swivel. This is most commonly used in conjunction with the magnetic switch to stop wires becoming tangled.

Magnetic or Inductive Switch This can be used to detect and provide indication when the hose unit is fully connected to the tank unit. Magnetic and inductive switches are available in a number of lengths such as 3, 6, 10 or 12 meters to suit the application.


NGX BreakAway Coupling

The NGX break-away is a safety product designed to prevent pull-away incidents, where the connection is still intact as a vehicle moves away from a loading/unloading station. This is critically important when transferring LPG, which can combust when exposed to oxygen.


When subjected to excessive force, the NGX’s break pins holding the two symmetrical halves together shear away. This causes the pistons to spring forward and shut off the two severed ends as the break-away simultaneously separates.


todo lpg breakaway coupling

While the break pins can be sized to suit specific applications, 3mm is supplied as a standard as TODO has found this size offers the best stress resistance across the board. However, pin sizes can be adjusted for applications where a weaker or stronger break-away is required.

The NGX has a working pressure of up to 40-bar or 580 psi, with a standard working temperature range of -20°C to +80°C. There is an option to go as low as -45°C if required. The product is also designed to maintain an uninterrupted flow of fluid and gas where possible.

TODO can provide a reset kit to easily achieve full refurbishment of the break-away on site. These kits contain brand new break pins, screws and all of the required O-rings. Operators only have to screw the two halves back together using the bolts provided. As with all products, the NGX is PED-certified and complies with the requirements of ATEX.


Pressure Tight Cap (PTC)

PTCs are PED- and ATEX-compliant stainless-steel caps that contain pressure up to 25-bar (363 psi) and can be fitted to the TODO-GAS tank unit. Fitting is easy – simply push the cap over the tank unit connection, depressing the lever until the click is felt and then releasing the lever to fully lock the cap in place. From this point the cap will contain any pressure behind it.

PTCs act as a safety device. In the event of line failure, the cap will not only hold the pressure but also provide the operator with a visual warning. A red O-ring is installed on the central valve and will protrude when pressure is present. Operators should investigate the fault before opening the cap if this occurs.

The product may also be used as an official third point of closure when other safety systems are absent. For example, rail applications in Europe will usually lock a rail car in position when loading. This will be safety measure number one, while the second will be a ball valve. From here, the third safety point would be the tank unit. In applications that lack such safety functionality, the PTC can be recognized as the third safety closure.



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