Helidyne FAQ

What is waste pressure?

Fluid (gas, liquid, or mixture of both) pressure is energy that is dissipated by means of dropping (reducing) the pressure across a valve or orifice. No work is extracted from this process.

What type of applications and fluids are acceptable?


  • Natural gas regulator stations
  • Geopressurized oil & gas wells
  • JT gas processing plants
  • Any industrial process with sufficient pressure drop and flow rate to drive the expander.


  • Natural gas (methane)
  • Rich or dry field gas (raw gas produced from oil & gas wells)
  • Air, nitrogen, steam, or any inert gas

What is your competitive advantage?

The planetary rotor expander offers different benefits depending on which comparison is made.

Turbine comparison:

  • The planetary expander can accept “wet” (2 phase) gas entering the inlet.
  • Rotors are self-cleaning and will not bind or seize from scale formation on rotor surfaces
  • Low operating speeds of 4500 RPM or less reduces rotor vibration and bearing wear
  • Wear on moving parts is reduced because the process gas is not accelerated to Mach speeds through a nozzle
  • Performance maintained under a wide range of pressure and flow rates
  • Rotors are solid steel, making them very robust and resilient to changes in temperature and pressure

Rotary positive displacement (e.g. twin screw or roots blower) comparison:

  • High pressure rating of 1,440 psi. is 3X higher than the twin screw
  • Rotors are self-cleaning and will not bind or seize from scale formation on rotor surfaces
  • Oil- free rotors permit total flow operation
  • Shaft seals exposed only to exhaust pressure

What are Hydrates?

Also called methane clathrates or hydrocarbon clathrates, are ice-like solids that form when liquid or vapor water is present in natural gas pipelines. If temperatures are cold enough the water will bond with methane to each other and begin to accumulate on the interior wall of the pipe.

How do I buy a Helidyne expander?

Helidyne’s expanders are typically sold as part of an automated power generation or gas processing package. Helidyne sells direct except for customers residing in Mexico. Contact us for a project evaluation and sales quote.

What sizes are available?

Helidyne is working on new models sizes, but presently only offers Model 4400 which can generate up to 60kW of electricity.

How much does it cost?

Unit pricing is determined on a project-by-project basis. Some installations will required additional equipment, such as gas filters, and hydrate prevention downstream of the expander to prevent ice formation within exhaust piping.

Must the PRG set connect to grid or can it generate as stand-alone (off-grid) system?

It can generate power in either configuration. The stand-alone system is more costly because of the extra controls and support equipment required to maintain constant voltage and frequency.

Definition of Terms:


-Acronym for Natural Gas Liquids. Comprised largely of a mixture of propane, ethane, butane, pentane, etc. as part of the natural gas refining process.


-The practice of driving the expander directly on resource fluid. Rather than using a separate “working fluid” contained within a closed loop.

Pipeline Gas

-Natural gas that has been sufficiently processed (refined) to meet specification. Typical greater than 95% methane, less than 7lbs per MM water.

Turbo Expander

-Also known as a turbine. Uses dynamic fluid forces to produce torque and rotation. Fluid is accelerated and processed continuously as it flow through expander. Pressure drop used to accelerate fluid through a nozzle then directed across the turbine blade to produce torque.

Positive Displacement Expander

– Uses static fluid forces to produce torque and rotation. Fluid is processed in quantitative (positive) amounts (displacement) in repeated cycles as it flows through the expander. Pressure forces are used to push against rotor surfaces to produce torque.

Hydrate Formation Conditions