LPG & LNG Transfer Pumps

LPG & LNG Transfer Pumps

AxFlow supplies LPG and LNG transfer pumps for the safe and reliable handling of volatile liquefied gases across storage terminals, tank farms, loading and unloading systems, marine installations and industrial processes.

Our range includes canned motor, magnetic drive, submerged in-tank, side channel, regenerative turbine and rotary vane pumps, allowing the pump technology to be selected around the liquid, temperature, flow, pressure and available NPSH of the application.

From LPG tanker unloading and cylinder filling to demanding cryogenic in-tank duties, AxFlow can engineer pump solutions for applications where high vapour pressure, low viscosity, low NPSH and fluid containment are critical.

What is an LPG or LNG transfer pump?

An LPG or LNG transfer pump is designed to move liquefied gas while maintaining the pressure and temperature conditions required to keep the product in its liquid phase.

This is more demanding than pumping conventional hydrocarbons. Liquefied gases can operate close to their vapour pressure, so relatively small pressure losses at the pump inlet can cause vaporisation, loss of performance and cavitation.

LPG and LNG also require different pump considerations.

LPG (Liquefied Petroleum Gas) generally consists primarily of propane, butane or mixtures of the two and is commonly stored as a liquid under pressure.

LNG (Liquefied Natural Gas) consists predominantly of methane and is stored at cryogenic temperatures of approximately −162°C at atmospheric pressure. LNG pumps therefore require materials and pump designs specifically engineered for cryogenic service.

For this reason, an LPG pump should not automatically be assumed to be suitable for LNG.

Challenges When Pumping LPG and LNG

Low NPSH and high vapour pressure

LPG and LNG are frequently pumped close to their boiling point. If the pressure at the pump inlet falls below the liquid's vapour pressure, part of the liquid can vaporise.

This can result in:

• cavitation and unstable operation
• reduced pump capacity
• increased vibration
• loss of discharge pressure
• damage to hydraulic components
• difficulty emptying storage tanks to low liquid levels

Pump selection must therefore consider NPSHa, NPSHr/NPSH3, vapour pressure, suction losses and tank operating pressure, rather than flow and differential pressure alone.

Low viscosity and lubricity

Liquefied gases are thin liquids and may provide relatively poor lubrication compared with conventional oils and hydrocarbons. Bearing design, internal clearances and pump technology therefore become important considerations.

Cryogenic temperatures

For LNG service, the pump and its materials must tolerate extreme low temperatures. LNG is normally maintained at approximately −162°C, making it fundamentally different from most pressurised LPG transfer duties.

Fluid containment

Propane, butane, LNG and other liquefied hydrocarbons are flammable. Preventing uncontrolled releases is therefore an important part of pump selection.

Where the application requires enhanced containment, canned motor and magnetic drive pumps eliminate the conventional rotating mechanical shaft seal, removing a potential leakage point.

LPG & LNG Pump Applications

AxFlow can support liquefied-gas pumping applications across LPG storage depots, LNG terminals, tank farms, petrochemical plants, refineries, marine installations and industrial gas facilities.

Typical duties include bulk tank transfer, storage-tank unloading, road-tanker and rail-tanker loading or unloading, LPG bottle filling, plant-to-plant transfer, process circulation, marine fuel transfer and bunkering, high-pressure boosting and cryogenic in-tank pumping.

For LPG installations where recovering the remaining liquid and vapour from tanks or tankers is required, AxFlow can also provide vapour recovery systems using specialist liquefied-gas compressor technology.

Which Pump Type Is Best for LPG and LNG?

There is no single pump technology that is ideal for every liquefied-gas application.

How to Choose an LPG or LNG Transfer Pump

Selecting the correct pump starts with identifying the exact liquefied gas and its operating conditions.

Consider:

• Liquid composition – Confirm whether the product is propane, butane, mixed LPG, LNG or another liquefied gas.
• Temperature and tank pressure – These determine vapour pressure and whether cryogenic construction is required.
• Flow and discharge pressure – Define the minimum, normal and maximum duty.
• NPSH available – Review tank level, suction losses, pump elevation and vapour pressure.
• Vapour content – Determine whether gas may enter or form within the suction line.
• Containment – Decide whether a mechanical seal, magnetic drive or canned motor design is appropriate.
• Hazardous area – Confirm the required equipment marking, gas group and temperature class.
• Installation – Consider above-ground, skid-mounted, vertical or submerged in-tank construction.

Why Choose AxFlow for LPG & LNG Pumps?

AxFlow combines multiple pump technologies rather than trying to apply one design to every liquefied-gas duty.

Our portfolio includes rotary vane, side channel, regenerative turbine, magnetic drive, canned motor and submerged in-tank pump technologies, allowing the equipment to be selected around the actual process conditions.

AxFlow UK has more than 30 years' experience with cryogenic pump applications, while its long-standing HERMETIC relationship provides access to specialist canned motor technology for demanding containment and liquefied-gas duties.

Need help selecting an LPG or LNG pump?

Send us your liquid, temperature, flow, required pressure/head, tank pressure and available NPSH, and our engineers can recommend the most suitable pump technology for your application.

Frequently Asked Questions

What is the difference between an LPG pump and an LNG pump?

An LPG pump normally transfers propane, butane or mixed LPG stored as a pressurised liquid. An LNG pump handles predominantly methane at approximately −162°C and therefore requires purpose-designed cryogenic materials and construction.

What is the best pump for LPG transfer?

Rotary vane pumps are commonly selected for LPG loading, unloading and cylinder filling. Side-channel, regenerative turbine or canned motor pumps may be better for high-head, vapour-containing or high-containment duties.

Which pump is used for LNG transfer?

LNG commonly requires a submerged cryogenic or canned motor pump designed specifically for very low-temperature service. The correct pump depends on flow, pressure, tank arrangement and available NPSH.

Why is NPSH important when pumping LPG and LNG?

LPG and LNG operate close to their boiling conditions. If inlet pressure falls too low, the liquid can vaporise and cause cavitation, vapour locking and loss of pump performance.

Can an LPG pump be used for LNG?

Not unless the pump is specifically designed and approved for LNG temperature and operating conditions. Most conventional LPG pumps are not suitable for service at approximately −162°C.

Do LPG and LNG pumps require ATEX certification?

Suitable hazardous-area equipment may be required where the risk assessment identifies a potentially explosive atmosphere. The correct zone, equipment category, gas group and temperature class must be confirmed for the installation. LPG cylinder filling and bulk LPG storage are subject to DSEAR assessment in the UK. (hse.gov.uk)

Can a pump transfer LPG vapour?

Liquid pumps are intended to transfer LPG in its liquid phase. A gas compressor is normally used for vapour transfer, vapour recovery and evacuation of tanks or tankers