The Joule-Thomson Effect: What It Is and How It Affects Oil and Gas

What is the Joule-Thomson Effect?

The Joule-Thomson Effect, also referred to as the JT effect, is an important concept that can negatively affect oil and gas production if not accounted for.

Discovered by British physicists in the 19th century, this principle states that when the pressure of a gas changes, its temperature also changes.

Chart illustrating how pressure affects the temperature of gas

In natural gas production, this means that when you reduce gas pressure across a control valve or pressure reducing regulator, you also reduce its temperature.

Flow of Gas Pressure through a Kimray Valve

Joule-Thomson Effect Formula

According to the Joule Thomson Effect, a 100 psi pressure drop results in a temperature drop of 6-8 degrees Fahrenheit.

The Joule-Thomson Effect: A 100 psi pressure drop results in a temperature drop of 6-8 degrees Fahrenheit.

What Problem Does the JT Effect Cause in Valves? 

Because all gas carries some element of moisture in it, this temperature drop can present the potential for freezing when your gas line drops below 32 degrees Fahrenheit. 

For example, if you are cutting the gas pressure from 900 to 200 PSI across a pressure reducing regulator, the temperature of the gas would drop approximately 42-56 degrees when flowing across the regulator.

Change in Pressure and Temperature in a Pressure Reducing Regulator

how to prevent freezing valves

To prevent freezing, operators sometimes wrap insulation and heat tape around their valve. This method presents a challenge when you need to check or repair the valve.

A good alternative is a gas catalytic heater.

Frozen Valve at a Well Site

This heater uses supply gas to provide a flameless, radiant heat that keeps your valve above freezing. It features a side door that allows operators easy access for maintenance or repair. The surface of the heater reaches a maximum of 700°F and is approved for hazardous environments.

For more information about catalytic heaters or any other Kimray product, contact your local Kimray store or authorized distributor.