Steam Trap Function: Guide To Selecting The Right Trap Systems

Steam trap function - Illustration of steam trap mechanism by Inko Engineering

Steam makes a valuable resource when it comes to heating systems. It offers the ability to efficiently generate and distribute heat for industrial operations. Behind its advantages, however, steam requires particular attention, one of which is the use of steam traps.

Steam traps are critical to the efficiency and safety of steam-based heating systems. Equipment maintenance, energy savings, and cost-loss prevention are parts of the support that industries gain from employing the right steam traps.

Given the fact that steam trap systems can help industries in the ways mentioned before, many industries are unaware of which ones to employ. This is where it becomes necessary for industries to understand each of the steam trap function before employing them.

In this article, we will go over steam traps in more detail, including their types, applications, and a guide to selecting the right ones based on the steam trap function. Let’s get into it.

What Is A Steam Trap?

A steam trap is an automatic valve used to filter out condensate (i.e., water material) and non-condensable gases from the steam. In essence, its role is to maintain the purity of the steam, ensuring that it remains a highly efficient heat carrier.

It’s common that as steam moves through the pipes, it gradually loses heat and condenses, forming liquid condensate. Aside from that, the pipes frequently contain non-condensable gases like air, which can hinder the steam’s ability to transfer heat.

The primary function of a steam trap is to address the two previously mentioned challenges. It effectively removes condensate, preventing its buildup, which impairs heat transfer. They also purge non-condensable gases, maintaining steam purity and preventing pipe corrosion.

Why Use Steam Traps Instead of Regular Valves?

Many people think that the condensate produced by dropping steam temperature can be manually filtered using regular valves. Although this is true in theory, it is nearly impossible to put into practice.

This is because the condensate accumulation continues to fluctuate. It is not easy to predict existing fluctuations because there are several influencing factors. For example, the amount of condensate generated during equipment startup and normal operation differs.

Other factors, such as product load and outside air temperature on the piping, have an impact on the amount of condensate, which cannot be precisely determined. As a result, using regular valves will make responding to fluctuating condensate difficult.

If condensate is not removed promptly, it will pool on equipment or pipes and cause the heating system to fail. On the other hand, if the attempt to dispose of condensate is too excessive, it could lead to leakage or a situation in which steam comes out with the condensate, resulting in waste.

Steam Trap Function: The Types

It is clear by now that stream traps function differently than regular valves. Apart from that, steam trap systems, which essentially work to filter out condensate and non-condensable gases, come in a variety of types to accommodate different plant requirements.

From thermodynamic and thermostatic to mechanical steam traps, we will review them further in the following:

Thermodynamic Steam Traps

Figure: Armstrong All Stainless Steel Thermodynamic Disc CD-33S Steam Trap

Thermodynamic steam traps use fluid dynamics principles to discharge condensate from systems. They work by measuring the flow rate of steam and condensate through them. When slow-moving condensate (i.e., water) enters the traps, it is allowed to flow freely out.

On the other hand, when fast-moving steam rushes in, it creates a strong force that closes the trap’s valve, preventing the steam from escaping. The valve will remain closed until the pressure of the steam above it drops, at which point it will reopen and allow steam to pass.

To achieve such mechanisms, thermodynamic steam traps rely on a disc or piston that moves in response to changes in fluid velocity. The choice of whether to use disc thermodynamic traps or piston thermodynamic traps is subject to the plant’s requirements.

Thermostatic Steam Traps

Figure: Armstrong All Stainless Steel Thermostatic TAVB Air Vent with Vacuum Breaker

Thermostatic steam traps are designed to monitor and respond to the temperature of liquids within a steam system.  They rely on the distinct temperature contrast between condensate that closely approximates the temperature of steam and subcooled condensate.

The thermostatic element built into thermostatic traps will move in a certain manner in response to elevated temperatures. This movement causes the installed valve to close, effectively preventing the passage of the scorching liquid or steam, making these traps suitable for applications that require sensible heat from condensate.

Finally, thermostatic steam traps are available in bi-metal, balanced, and expansion types. Different types serve different purposes, adhering to the specific needs of various industries or plants.

Mechanical Steam Traps

Mechanical steam traps are designed to get rid of condensate that forms when steam cools down. But unlike the previous traps, they use moving parts, like floats or buckets, to open and close a valve. The valve stays open when there is steam, allowing it to pass. But, when the condensate accumulates, the valve closes to filter it out from the steam.

In turn, this clever mechanism ensures that only water is removed from the systems while preserving the valuable steam. This makes mechanical steam traps an essential device for maintaining efficient steam systems.

Since mechanical steam traps utilise floats or buckets as a part of their functionality, it is worth acknowledging how floats and buckets operate differently within the traps, as explained below:

Float and Thermostatic Steam Traps

Figure: Armstrong AIC Series Ductile Iron Float & Thermostatic Steam Trap

Float and thermostatic traps utilise a combination of a float mechanism, which responds to changes in condensate level, and a thermostatic element, which reacts to temperature changes. This dual mechanism allows them to adapt to different load conditions, making them versatile choices for condensate removal.

Inverted Bucket Steam Traps

Figure: Armstrong 200 Series Cast Iron Inverted Bucket Steam Traps

Inverted bucket traps feature an inverted bucket-like component within the trap. When steam enters the system, the inverted bucket will rise, opening a valve and allowing condensate to drain. 

On the other hand, when steam condenses, the bucket descends and closes the valve. This makes inverted bucket traps reliable for applications involving fluctuating condensate loads.

Steam Trap Applications

There are plenty of different kinds of steam traps, each with its function. Given this, industries frequently struggle to select a trap that effectively filters out condensate and non-condensable gases to use in their steam-based plants.

This issue can be managed by paying attention to the intended application, whether it is for steam distribution piping, steam heated equipment, tracer lines, or power drive equipment. We will review further on steam trap applications below:

Steam Distribution Piping

Steam distribution piping serves to supply steam to the steam-based equipment or tracer lines. Steam traps maintain the steam to be in its highest purity and prevent water hammering caused by sudden condensation which can hinder the steam’s effectiveness in delivering heat.

Aside from hindering the steam’s effectiveness in delivering heat, water hammer also puts industries at risk, including leakage, ruptured pipes, and property damage. These are often costly to repair, causing industries to experience financial losses.

Thus, when it comes to this particular application, a steam trap whose main function is to prevent condensate from pooling is the most ideal choice. This type of trap is typically designed with little to no condensate subcooling (i.e., float and thermostatic steam traps).

Steam Heated Equipment

The performance of steam-heated equipment is directly related to productivity and product quality. For this particular application, events such as uneven heating or low heat transfer due to condensate pooling in the equipment should be avoided.

Steam-heated equipment will also benefit from a quick start-up time. A quick start-up time adapts to the versatile nature of steam, allowing the equipment to be heated more efficiently. As a result, traps that can continuously drain condensate and have a quick start-up time are preferable for this application.

Thermostatic steam traps are the recommended type for this specific concern as they are fully open during the start-up. It is further advised to employ an air venting within the trap to remove non-condensable gases from the equipment.

Tracer Lines

Tracer lines, like any other piece of heat transfer equipment (i.e., pipes), require steam traps. The main purpose of using traps on tracer lines is to hold the steam until its latent heat is fully utilised before releasing the condensate and non-condensable gases.

Therefore, steam traps with sub-cooling or the ability to use sensible heat from condensate before discharging it make an ideal choice. Thermostatic steam traps belong in this category, making them a great pick for tracer line applications.

However, this is not the case for tracer lines used to locate high-temperature steam pipes. Steam traps with little to no sub-cooling function (i.e., thermodynamic steam traps), on the other hand, are preferred because the devices aid in retaining the potent heat delivered by the steam.

Power Drive Equipment

Compressor, pump, and generator are a part of power drive equipment. To keep the effective power generated by the steam heat moving the steam hammers or wheels, power drive equipment requires high-purity steam.

As a result, the primary steam trap function is to tightly sealing the steam and quickly discharging condensate is preferable for this application. Leaking and condensate pooling should be avoided as they can cause system damage and financial losses.

In this case, float and thermostatic steam traps make a number one choice. Apart from that, inverted bucket steam traps can also be employed due to their versatility, suitable for a wide range of applications, including both high-pressure and low-pressure steam systems.

General Steam Trap Feature Requirements

In certain cases, plants remain prone to experiencing steam leakage despite already employing steam traps. As explained by What is Piping, this condition can be avoided by paying attention to the general feature requirements that should exist within the steam traps:

  • Steam traps should be able to drain condensate without compromising the steam (i.e., by trapping it).
  • Steam traps should ensure that only clean, dry steam fills out the steam space for energy conservation.
  • Steam traps should come with a reliable air venting function to filter out non-condensable gases like air, which can reduce steam temperature.
  • Steam traps are sometimes used in extreme or unpredictable environments, thus they should have strong resilience against corrosion, water hammer, and dirt/debris accumulation.

Should Steam Traps Be Inspected Regularly?

Steam traps, even those with superior features or materials, still require regular inspections. With regular inspections, industries can ensure that the traps installed in their systems are in prime condition, reducing the risk of potential losses.

Steam trap surveys are the right solutions that industries can opt for. Through this procedure, they can reduce energy losses within the heating system by up to 20%. This will result in cumulative savings for years.

Final Thoughts

Steam trap function indeed is useful for heating systems. Such devices make the heating process of steam more effective by filtering out elements that decrease the steam’s temperature, including condensate and non-condensable gases, all without causing the steam to leak through.

Moreover, steam traps come in a variety of types, including thermodynamic, thermostatic, and mechanical. Each of the steam trap types has its distinct functionality that adheres to specific applications and requirements.

With the right steam traps, industries can optimise their steam-based heating operations, maximise steam resources with less leakage, and minimise the risk of financial losses from equipment damage.

Uncertain Which Steam Traps Fit Your Needs? Let INKO Engineering Supplies Help You Out.

Despite knowing how important steam traps are for optimal steam-based heating systems, many industries are unsure which type to use. This is completely normal, given that heating systems are complex, requiring the use of multiple types of traps at the same time.

If this is the case in your industry, we will gladly assist you. With extensive experience in the field, INKO Engineering Supplies can recommend steam trap systems that fit your plants precisely. 

Contact us today!

Frequently Asked Questions

What are the three functions of the steam trap?

The primary three steam trap function include:

  • Draining condensate (water) from the steam
  • Filtering out non-condensable gases (air) to maintain steam’s purity
  • Preventing steam leakage that puts industries at risk of financial losses

Where are steam traps needed?

Steam traps are needed in industries that rely on steam-based heating systems to operate. This includes manufacturing, power generation, petrochemicals, and more. 

What happens if there is no steam trap?

When there is no steam trap, assuming that a plant only uses a regular valve, steam within the pipes will pass through along with condensate. This makes the heating process to be inefficient and puts industries at risk of equipment damage.

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