Gas Injection Flow Meters & Solenoids in Industrial Ovens

Changing the Atmosphere in a Kiln or Oven: How It Works and Why It Matters

When utilizing high-temperature kilns, ovens, and furnaces, regulating the environment within the firing chamber is equally crucial as managing the temperature.

In procedures such as heat treating, jewelry fabrication, and several specialized industrial applications, the introduction of an inert gas into the chamber can facilitate the necessary conditions for desired outcomes.

This is where a gas injection and flow measurement system is utilized.

Paragon Industries and Hot Shot Ovens and Kilns provide gas injection and flow meter alternatives on certain furnaces, allowing users to introduce and control the flow of either Argon or Nitrogen gas during the firing process. However, what is the precise functioning of this system, and what information should you possess prior to utilizing it?

Let us analyze it thoroughly.

What Is a Gas Flow Meter?

A gas flow meter is an instrument that quantifies and controls the volume of gas entering a kiln, oven, or furnace.

Paragon's gas injection and flow measurement apparatus employs a Dwyer flow meter, which has a specified calibration range of 1 to 20 SCFH (Standard Cubic Feet per Hour).

SCFH quantifies gas flow under established reference parameters, enabling users to regulate the volume of gas that enters the combustion chamber over a specified duration.

Depending on the context, implementing a regulated gas environment could be beneficial:

Minimize oxidation and scaling during the thermal treatment of metals.
Restrict the quantity of oxygen within the combustion chamber.
Facilitate specialist procedures necessitating a specific furnace environment.
Enhance uniformity when environmental factors influence the final output.

The suitable gas, flow rate, and operational methodology are contingent upon the material being treated and the intended outcomes.

Hot Shot Ovens do not incorporate the flow meter in their configuration; nevertheless, the injection nozzle and its connections are integrated into the unit when requested. The user must supply the flow meter as an integral component of their gas cylinder tank and pipe configuration. This is a basic product available at home enhancement or industrial supply stores.

How Does Gas Injection Work Inside a Furnace?

Paragon and Hot Shot's heat treating ovens and furnaces are constructed with insulating substances and metallic casings that lack total airtightness.

Rather than completely sealing the chamber, gas injection functions by perpetually adding gas to aid in displacing the ambient air. Paragon's nozzle introduces gas laterally, whereas Hot Shot's nozzle dispenses gas from an above position.

The objective is to sustain a marginally positive pressure within the furnace, promoting the outward flow of air while diminishing the levels of oxygen or other undesirable gases inside.

Can I Turn On and Off the Gas That Enters The Kiln Automatically? Yes, it's Called a Solenoid.

Units outfitted with the Bartlett Genesis 2.0 controller use the auxiliary relay output (Output 4) to drive auxiliary devices such as a vent fan, pneumatic damper, or gas/purge solenoid. To operate the solenoid safely and effectively, configure the controller's software behavior and ensure proper electrical drive.

If you are retrofitting your current unit with a GIFM and solenoid, then follow these directions. If you have purchased a unit with a GIFM and solenoid preinstalled, skip to step 2.

Step 1: Verify Hardware Wiring

Locate the Output: On the back circuit board (or interface header) of the Genesis 2.0, locate the terminals for Output 4.
Interposing Relay: Ensure the 12V DC coil of your intermediate pilot relay is connected across Output 4 and ground/common.
Solenoid Power: The line voltage or dedicated power source for your solenoid should pass through the dry contacts of this pilot relay to the solenoid coil.
Verification: When Output 4 energizes, the pilot relay clicks, and the solenoid receives power and actuates.

Step 2: Configure Output 4 in the Controller

The Genesis controller must be configured to know how Output 4 will be used during firings.

From the Home / IDLE screen, press Menu.
Scroll to and select Configuration (Enter passcode 443 if prompted for factory/technician access).
Select Output 4 Options.
Choose the mode matching your solenoid application:
1. Option A: Output 4 turns on at firing start and remains energized until the kiln has cooled below 150°F (ideal for continuous venting solenoids).
2. Option B: Output 4 energizes from the start-up to 1450°F, de-energizes during the high-heat soaking/glazing zone, then turns back on during cooling between 1000°F and 150°F.
3. Option C (Most Common for Custom Solenoids): Output 4 stays OFF during standard preset/Ceramic firings, allowing you to explicitly toggle it ON or OFF on a per-segment basis inside Custom (User) firing profiles.
Press Save or Back to confirm.
Verification: Re-enter the menu to confirm your selected option (A, B, or C) remains highlighted.

Step 3: Programming Solenoid Actuation in Firing Profiles

For Option A or B (Automatic Kiln/Vent Modes):

Solenoid actuation occurs automatically during any standard preset firing (ceramic bisc/glaze) according to the programmed temperature thresholds.

For Option C (Segment-Specific Custom Programs):

On the Home screen, tap Load > Other > choose an editable User Program (e.g., User 1).
Tap Edit (ensure Novice Mode is set to OFF in settings to access custom segments).
On the segment where the solenoid must open, locate the Fan / Output 4 column/toggle.
Toggle the indicator to ON for the specific ramp or hold segments requiring actuation (e.g., atmosphere purging or assisted downdraft).
On segments where the solenoid must close, ensure the toggle is set to OFF.
Save the program.
Verification: Tap View on the loaded profile; each segment screen will list whether the auxiliary output/fan is designated ON or OFF.

No worries if your unit does not have a solenoid installed. You can turn the gas on and off manually at your designated times during the firing. A solenoid is not a necessary piece of equipment to introduce inert gas, but it sure makes the process more convenient.

Paragon’s Gas Nozzle System: A Traditional Approach

Paragon's nozzle injects argon into the chamber from either the lateral or posterior side. This is conventionally the manner in which the majority of ovens are designed to accept the intake. The benefit of this is that an operator can effortlessly detach hoses or replace connections while the device is in operation. The flow meter is affixed to the dimensions of the kiln rather than positioned nearer to the tanks for enhanced visibility.

Hot Shot's Ceramic Nozzle; A Unique Approach to Gas Distribution

Select Hot Shot kilns and ovens that can be upgraded to feature a proprietary ceramic nozzle designed to distribute argon efficiently throughout the heating chamber.

Hot Shot’s nozzle introduces gas from the roof of the chamber by directing argon flow downward to maximize oxygen displacement and minimize atmospheric mixing. The centered nozzle helps create a more uniform, low-oxygen environment. This can reduce oxidation and surface scaling during heat treating.

Engineered specifically for Hot Shot's kiln systems, the nozzle supports consistent heat-treating performance while helping to preserve material surface quality. Its integrated design also promotes cleaner, more repeatable results while using argon efficiently.

The Significance of Uninterrupted Gas Flow

The intermingling of the entering gas with the pre-existing furnace atmosphere is inevitable due to the chamber's lack of vacuum sealing. Nevertheless, when gas persists in its passage, the ratio of the initial atmosphere will diminish considerably.

The essential factor is ensuring a sufficient and steady gas flow for the application while avoiding superfluous gas expenditure.

Why Furnace Size and Temperature Matter

A critical element in calibrating a gas flow meter is the dimensions of the furnace chamber.

Paragon and Hot Shot employ their gas injection and flow meter technologies on furnaces with both minor and major internal capacities.

A diminutive chamber typically necessitates a reduced volume of gas to accomplish a certain number of theoretical atmospheric exchanges compared to a bigger chamber.

Understanding Atmosphere Exchange

Paragon’s engineers provided this great illustration and example: Consider a furnace with an internal volume of 0.2 cubic feet.

At room temperature, introducing gas at 1 SCFH provides a theoretical gas volume equal to five times the chamber volume per hour.

That means one chamber-volume equivalent is introduced approximately every 12 minutes.

But temperature changes the equation.

As incoming gas heats up inside the furnace, it expands. This increases its actual volume and changes the relationship between gas flow, chamber volume, and atmosphere exchange.

At elevated temperatures, a relatively small amount of incoming gas can occupy a much larger volume inside the firing chamber.

However, theoretical atmosphere exchange is not the same as complete air removal. Actual atmospheric purity depends on factors such as leakage, mixing, gas distribution, temperature, and operating conditions.

For this reason, finding the appropriate gas flow setting often requires testing and adjustments based on the specific application.

Using Protective Gases to Reduce Scaling During Heat Treating

One application for gas injection is reducing oxidation during metal heat treating.

When certain metals are heated, oxygen in the surrounding atmosphere can react with their surfaces, producing oxidation or scale.

Introducing a protective gas, such as argon or nitrogen, can help reduce the amount of oxygen available for these reactions.

Why Argon? Why Nitrogen?

Both argon and nitrogen are commonly used to control furnace atmospheres, but they have different properties, advantages, and applications.

Argon: Protection for Reactive Materials

Argon is a noble gas that is chemically inert under typical heat-treating conditions. It is often preferred when processing reactive metals such as titanium, zirconium, and tantalum, or materials that may react with nitrogen at elevated temperatures.

By reducing the amount of oxygen present in the furnace chamber, argon can help minimize oxidation and surface scaling without introducing unwanted chemical reactions.

Nitrogen: A Cost-Effective, But Tricky Alternative

Nitrogen is widely used in industrial heat treating because it provides a protective atmosphere for many common metals at a significantly lower cost than argon.

Since nitrogen makes up approximately 78% of Earth's atmosphere, it is readily available through industrial gas production methods.

Depending on the supplier and delivery method, Argon can cost several times more than nitrogen, making nitrogen an economical option for processes requiring continuous gas flow.

Nitrogen is particularly useful for:

Protective atmospheres: Helping reduce oxidation during the heat treatment of compatible metals and alloys.
Continuous purging: Providing an economical gas supply when frequent door openings or furnace leakage require ongoing gas replacement.
High-volume operations: Reducing operating costs in processes that consume substantial quantities of gas.
Blended atmospheres: Serving as a carrier gas in specialized industrial processes that use carefully controlled gas mixtures.

Nitrogen is also used in applications such as high-pressure gas quenching, nitriding, and carbonitriding. However, these processes require specialized equipment and operating conditions and should not be assumed compatible with standard Paragon or Hot Shot furnaces.

Which Gas Should You Choose?

For many conventional heat-treating applications involving compatible steels and other metals, nitrogen may offer an economical protective atmosphere.

Argon is generally preferred for highly reactive metals or alloys that could experience unwanted reactions with nitrogen at elevated temperatures.

However, nitrogen is not chemically inert under all conditions. Certain metals and alloys can absorb nitrogen or form nitrides during heating, potentially affecting their properties.

The right choice depends on the material, processing temperature, desired results, and furnace specifications. Always verify gas compatibility with the furnace manufacturer and consult the material supplier's processing recommendations before selecting a gas.

What Should You Consider When Setting Gas Flow?

There is no single gas flow setting that works for every furnace or material.

Before establishing a process, consider the following factors:

1. Furnace chamber volume

The internal dimensions of the furnace help determine the amount of gas needed for the desired atmosphere exchange.

2. Material and oxidation behavior

Different metals and alloys begin oxidizing more rapidly at different temperatures. Consult the material supplier's technical specifications to understand the appropriate processing conditions.

3. Timing of gas introduction

For some applications, gas must be introduced before the furnace reaches temperatures at which significant oxidation occurs.

4. Gas flow rate

The flow rate must be appropriate for the furnace size, operating temperature, gas type, and required atmospheric conditions.

5. Final results

Inspecting the finished material for oxidation or scaling can help determine whether the established process is achieving the desired results.

Changes to gas flow or timing should be based on a validated process, equipment specifications, and appropriate safety procedures.

Gas Supply and Pressure Requirements

Paragon's described gas injection and flow meter configuration uses a 1/4-inch NPT female inlet fitting and specifies a low-pressure gas supply.

The manufacturer's documentation describes an inlet pressure below 20 psig, with a nominal inlet pressure of 20 psig also referenced. These details should be confirmed for the specific furnace and installed flow meter before operation.

Compressed gas cylinders generally require an appropriate pressure regulator. Other gas supply systems may have different pressure-control requirements.

Always verify that the regulator, connections, flow meter, and gas supply are compatible with one another and with the intended process.

Gas systems should be installed and adjusted by personnel qualified to work with the equipment and gases involved.

Important Safety Considerations

Gas injection can be useful, but it also introduces additional safety considerations.

Ventilation Is Essential

Argon is non-toxic, but it can displace oxygen in the surrounding air.

Because it does not support breathing, an argon leak or discharge can create an oxygen-deficient atmosphere, especially in enclosed or poorly ventilated areas.

Appropriate ventilation, gas-handling procedures, and any required oxygen monitoring are essential.

Not Every Furnace Atmosphere Is Suitable

The type of gas introduced into a furnace can affect its components.

Reducing atmospheres, for example, may shorten the life of certain heating elements. Inert or oxidizing atmospheres may be compatible with specific furnace designs, but compatibility should always be verified with the manufacturer.

Never assume a furnace is suitable for a particular gas or chemical process simply because it has a gas inlet.

Understand Your Process

Gas injection systems help regulate gas delivery, but they do not determine whether a chemical reaction or heat-treating process is safe.

Users are responsible for understanding the gases, materials, reactions, exhaust requirements, and operating conditions involved.

Always consult the furnace manufacturer's instructions and qualified process specialists before using a modified atmosphere.

Finding the Right Furnace for Your Application

Whether you're heat treating metal, working with specialized materials, or exploring applications that require atmospheric control, understanding gas flow is an important part of choosing the right furnace.

Paragon and Hot Shot offer a variety of furnaces for different industries, and certain models can be configured with gas injection and flow meter options.

At Heat Treat Now, we're here to help you explore furnace options and find equipment that fits your needs.

Have questions about furnaces or gas flow meter options? Contact Heat Treat Now to learn more about available equipment and configurations.

Disclaimer: This article is intended for general educational purposes and is based on technical information provided by Paragon Industries and Hot Shot Oven and Kiln. Equipment features, gas compatibility, and operating requirements vary by model and application. Always consult the manufacturer's instructions and qualified personnel before operating a furnace with a modified atmosphere.