Heated Regulators For Vapor and Liquid Hydrocarbons

19th September 2023
Heated Regulators for Vapor and Liquid Hydrocarbons
Summary:
Process analyzers are an expensive investment but can only deliver valid results if presented with
a representative sample during calibration and online use. In instances where heated regulators are
deployed to vaporize liquid hydrocarbons it is critical to recognize the chances of sample
fractionation / evaporation /condensation and how cumulative errors can impact the final result.
In such cases, an expensive analyzer installation can be held hostage to an in-expensive heated
regulator. Today, our understanding of these problems coupled with modern manufacturing
techniques has allowed for a new design of regulator that is better suited for vaporizing liquid
hydrocarbons whilst maintaining the same familiar packaged product.
The following discussion re-focuses on understanding the working design principles of heated
regulators with a historical background on how they were introduced to analytical systems.
Acknowledgements:
Pressure Tech UK
ASaP nl
Dirk Horst
David Tamez
Tony Waters
No ChatGPT or AI was used in the production of this paper J
wajopek@process-analytical-me.com 1
19th September 2023
Background:
Heated regulators were introduced in the early 1980’s. Construction consists of a pressure
regulator assembly with a centrally located heating element that is uniquely designed to address
various problems whilst handling vapor samples. This design still remains valid today and is found
in many brands of heated regulators that provide an inexpensive solution to pressure reduction.
The heated regulator transitioned to vaporizing liquid hydrocarbons in the days when Liquid
Sample Injection Valves (i.e. LSV - flash vaporizers) used on process gas chromatographs could
not handle high pressures or were not as reliable as they are today. As heated regulators found
their way into sample handling systems they became a low-cost generic solution for many vapor
and liquid applications including cryogenic installations such as LNG Loading- thus becoming
commonly known as the continuous flow vaporizing regulator.
As installations evolved, so have many different problems associated with vaporized samples such
as unstable readings, polymerization, burned out heating elements or plugged vaporizers mostly as
a result of misapplication or incorrect temperature control settings. Today we know that using
existing designs of vaporizing regulators have very limited uses on liquid hydrocarbons. This has
led to new innovative developments in flash vaporizers (specifically on LNG applications) and
improved LSV arrangements in other equipment. It should be noted that, flash vaporizers inject
or pass a microlitre-sized amount of liquid sample into a fixed volume, temperature-controlled
chamber. This attains instant homogenous vaporization resulting in accurate analysis results.
Continuous flow vaporizing regulators operate in an opposite manner to flash vaporizers yet
expected to deliver the same performance. Most vaporizing regulators have a heating element
located within the sample inlet path. This can have a significant negative impact on liquid sample
integrity thus becoming nothing more than a fractionating regulator.
The illustration below shows what happens to a liquid hydrocarbon sample as it passes over a
heating element inside a typical heated regulator. This effect is more evident in liquid samples
having a wide boiling point, typically C1 to C4+. Obtaining any reasonable balance of outlet
pressure, flow and temperature can be a major challenge.
Courtesy: ASaP nl
Courtesy: Pressure Tech UK
19th September 2023
Heated Regulators for Vapor Samples
Heating is achieved by an electrical heating element positioned

centrally within the regulator body. The position of this element
allows for a desired heat conductance path to the regulator
body in a radial manner extending upwards.
The vapor sample is passed through the inlet towards the heated
chamber and around the heater to ensure the vapor is kept
above its dewpoint whilst eliminating droplets or mists. As
pressure is reduced via the poppet and seat arrangement a Joule-
Thompson (J/T) effect is formed within the diaphragm and
orifice locations.
The heater temperature is adjusted to overcome the J/T effect

whilst providing a relative limited amount of heat to keep the
whole regulator body above the sample dewpoint under normal
flow conditions. The amount of heat required will vary
depending on stream composition, process pressure, sample
flow and surrounding temperatures for the given application.
Single central heater
The sample exits from around the diaphragm towards the outlet
which is in close proximity to the heated chamber ensuring the Images courtesy: Pressure Tech UK
sample remains warm. After a while, an overall equilibrium
temperature is reached which may require further optimization
during use.
Certain high pressure vapor applications can exhibit a significant

amount of J/T effect during pressure reduction where there is
simply not enough heat available to overcome J/T or icing
effects during operating conditions. This leads to vapor samples
condensing to liquids at the outlet as well as internal mechanical
diaphragm failures resulting in fugitive gas releases through the
bonnet vent port. These problems cannot be overcome via a
single heating element but may require flash vaporizers, multi-
stage pressure reduction or a dual element heated regulator
whilst maintaining minimal flow rates.
Dual heater
Courtesy: ASaP NL
200 Barg Natural Gas Sample reduced to 5 Barg

This sample is considered spoilt
19th September 2023
Heated Regulators for Vaporizing Liquid Samples
Liquid hydrocarbons need to be kept below their

bubble point and away from any heat source.
The following design incorporates an insulated inlet

made from a Polyimide material having a low thermal
conductivity of 0.12 W/(mK) compared to that of
16.3W/(mK) for 316 stainless steel.
The polyimide insulation material provides thermal

insulation of the liquid sample from point of entry into
the vaporizer through to the vena contracta where the
pressure is the lowest and fractionation is greatest. By
ensuring the integrity of the insulation is maintained up
to this point, a supercritical liquid is transformed to a
supercritical vapor avoiding fractionation. (Note: Not all
liquids are suitable for such vaporization therefore
application dependent).
Insulating Material
Heated Regulator for

Vaporizing Liquids
Images courtesy: Pressure Tech UK
Bore and CV sizes can be made to suit specific liquid

densities and flow requirements. Various sized Service
Kits are available for easy retrofit.
The outlet heater is offset and biased towards applying

heat in the post pressure reduction area. A heater
cartridge sits within a solid spiral insert having a large
surface area to promote good heat transfer to the
outward flowing sample. By using a spiral insert, the
electrical power density is increased by 11.4% to 4.93
W/cm2 on a 100w heater. The heater temperature is
adjusted to overcome any J/T effects and to keep it
above the sample dewpoint during operational use.
Higher flowrates are achievable due to the regulator
having a large body mass enabling it to retain
temperature whilst transferring heat to the sample.
Typical applications: Refinery, chemical and ethylene

plants, liquefied propane, butane, labs and limited Spiral Insert
(heater element not shown)
cryogenic samples.

Heated Regulators For Vapor and Liquid Hydrocarbons

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19th September 2023

Heated Regulators for Vapor and Liquid Hydrocarbons

No ChatGPT or AI was used in the production of this paper J

Heated Regulators for Vapor Samples

Heating is achieved by an electrical heating element positioned

The heater temperature is adjusted to overcome the J/T effect

Certain high pressure vapor applications can exhibit a significant

200 Barg Natural Gas Sample reduced to 5 Barg

Heated Regulators for Vaporizing Liquid Samples

Liquid hydrocarbons need to be kept below their

The following design incorporates an insulated inlet

The polyimide insulation material provides thermal

Heated Regulator for

Images courtesy: Pressure Tech UK

Bore and CV sizes can be made to suit specific liquid

The outlet heater is offset and biased towards applying

Typical applications: Refinery, chemical and ethylene

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