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Years ago, it was not uncommon to read news about tragic boiler explosions, sometimes resulting in mass destruction. Today, boilers are equipped with important safety devises to help protect against these types of catastrophes. Let’s take a look at the most critical of these devices: the safety valve. 

What:

The safety valve is one of the most important safety devices in a steam system. Safety valves provide a measure of security for plant operators and equipment from over pressure conditions.

The main function of a safety valve is to relieve pressure. It is located on the boiler steam drum, and will automatically open when the pressure of the inlet side of the valve increases past the preset pressure. 

All boilers are required by ASME code to have at least one safety valve, dependent upon the maximum flow capacity (MFC) of the boiler. The total capacity of the safety valve at the set point must exceed the steam control valve’s MFC if the steam valve were to fail to open. In most cases, two safety valves per boiler are required, and a third may be needed if they do not exceed the MFC. 

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How:

There are three main parts to the safety valve: nozzle, disc, and spring. Pressurized steam enters the valve through the nozzle and is then threaded to the boiler. The disc is the lid to the nozzle, which opens or closes depending on the pressure coming from the boiler. The spring is the pressure controller.

As a boiler starts to over pressure, the nozzle will start to receive a higher pressure coming from the inlet side of the valve, and will start to sound like it is simmering. When the pressure becomes higher than the predetermined pressure of the spring, the disc will start to lift and release the steam, creating a “pop” sound. After it has released and the steam and pressure drops below the set pressure of the valve, the spring will close the disc. Once the safety valve has popped, it is important to check the valve to make sure it is not damaged and is working properly.

Why:

A safety valve is usually referred to as the last line of safety defense. Without safety valves, the boiler can exceed it’s maximum allowable working pressure (MAWP) and not only damage equipment, but also injure or kill plant operators that are close by. Many variables can cause a safety valve on a boiler to lift, such as a compressed air or electrical power failure to control instrumentation, or an imbalance of feedwater rate caused by an inadvertently shut or open isolation valve. 

Once a safety valve has lifted, it is important to do a complete boiler inspection and confirm that there are no other boiler servicing issues. A safety valve should only do its job once; safety valves should not lift continuously.

Lastly, it is important to have the safety valves fully repaired, cleaned and recertified with a National Board valve repair (VR) stamp as required by local code or jurisdiction. Safety valves are a critical component in a steam system, and must be maintained. 

All of Nationwide Boiler’s rental boilers include on to two safety valves depending on the size; one set at design pressure and the other set slightly higher than design. By request, we can reset the safeties to a lower pressure if the application requires it. In addition, the valves are thoroughly checked after every rental and before going out to a new customer, and they are replaced and re-certified as needed. 

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As stack emission regulations become more and more demanding, plant facilities will often seek the lowest possible emissions to meet or exceed the newest standards. There are two options currently available to lower NOx emissions: front-end burner technology and back-end selective catalytic reduction (SCR) technology. 

Nationwide Boiler’s CataStak™ SCR system was originally tested and utilized in our boiler rental fleet, and is now offered for both rent and for sale to lower NOx on many different types of fired equipment. 

What is a CataStak™ SCR?

Nationwide Boiler developed the CataStak™, a low-temperature SCR system capable of reducing post combustion NOx emissions by as much as 95%. The CataStak SCR system consists of a single-reactor housing with low temperature catalyst and an ammonia (aqueous or anhydrous) or urea (diesel exhaust fluid) injection skid. 

How Does it Work?

The CataStak SCR system is typically located between the flue gas exhaust and the economizer. As the flue gases exit the boiler, they are routed through the ammonia injection grid to the SCR housing with DeNOx catalyst. As the gases exit the housing, the NOx is released as nitrogen and water. 

One unique feature of our CataStak SCR system is that the catalyst that we supply facilitates the reaction of NOx and ammonia, allowing the reaction to occur at a lower temperature.

Why Choose a CataStak™ SCR System?

Three key advantages of the CataStak SCR system include easy field retrofit, low operating cost, and minimum operator intervention. When installing the SCR system, there is no need to change out burner controls or the fan, providing a simple installation and a major cost savings. Additional cost savings and increased efficiency are seen due to better turndown, lower O2, and reduced motor horsepower without FGR. Lastly, the CataStak can operate independently causing less boiler trips and less interference with plant operations.

With our CataStak SCR system, Nationwide Boiler can guarantee results as low as 2½ ppm NOx @ 3% O2, which is well below all current state implementation plan levels. Being able to achieve 2½ ppm NOx will give your plant peace of mind for any future changes to emissions regulations. The CataStak delivers exceptional performance, reliability, and compliance assurance. 

With over eighteen years of experience, a 100% success rate and over 120 installations, we have more experience and satisfied customers than any other competitor for boiler SCR systems. In addition to selling the system, Nationwide Boiler is an active user of the CataStak on our rental fleet for ultra low NOx boiler requirements.

The CataStak SCR system is available as an add-on for existing and new package boilers, gas-fired turbines, refinery heaters, and for other demanding combustion applications. Contact us today to learn how you can decrease your facility’s operating costs and lower your carbon footprint with a CataStak SCR system.

 

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What Is an Economizer?

Economizers are mechanical devices intended to reduce energy consumption or perform a useful function such as preheating a fluid. In basic terms, an economizer is a heat exchanger. The orientation of an economizer can be vertical, horizontal, or cylindrical depending on boiler size and space available, and it is fitted directly to the boiler near the flue gas outlet.

How does it Work?

In a boiler system, an economizer captures the heat of the flue gas and transfers it to the feed water. The process is simple. As the flue gas exits the boiler, it enters an economizer with finned tubes. The finned tubes absorb the heat and raises the temperature of the boiler feed water, lowering the needed energy input.

Why Add an Economizer?

Adding an economizer will increase boiler efficiency by 10-12%. In addition, the reduced amount of energy required for heating results in reduced fuel consumption and cost.

Nationwide Boiler’s EconoStak Economizers

A Nationwide Boiler EconoStak consists of the economizer and all of the associated piping and structural supports required for very efficient and safe operation. It is a fabricated assembly of finned tubing that uses hot stack gases to heat the boiler feed water. The EconoStak economizer reduces stack emissions and thermal pollution, as well as provides fuel cost savings. It can be can be utilized with one of Nationwide’s trailer-mounted rental boilers, or can be purchased with a new or reconditioned boiler.

 

 

 

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One of the leading causes of poor boiler performance is improper water treatment.  Improper water treatment, or not treating your boiler water at all, can cause irreversible boiler tube damage called scaling. To avoid scaling, boiler water should be circulated through a water softener before it is fed to the boiler. A water softener removes hard water minerals, like calcium and magnesium, which can cause scaling and damage in the boiler tubes. Acting as an insulator, scale deposits can prevent proper heat transfer, decrease boiler efficiency, and lead to costly downtime and even premature boiler failure. 

The Chemical Process – Ion Exchange

Hard water contains positively charged ions, like magnesium, calcium, and iron. An ion exchange in the water softener removes the positively charged ions from the water through the use of resin beads. The resin beads that are inside the resin tank are negatively charged by brine, which contains salt and potassium. As the water  goes through the resin tank, the magnesium, calcium, and iron are chemically attracted to the negative charge of the resin beads, sticking to the resin as the water runs through the tank. This process removes majority of the “hard” minerals from the water, creating “soft” water. 

The Cleaning Process – Regeneration

Regeneration cycles are required to clean the resin beads, allowing the system to continually remove hardness from the water supply. The regeneration process, which can take roughly one to two hours, consists of flushing out the solids, drawing brine from the brine tank, and recharging the resin beads. If your softener only has one resin tank, the boiler will be supplied with hard water during the regeneration process. In a system with two tanks, the standby resin tank will become operational during regeneration of the first tank to continue the flow of soft water to the boiler.

The Bottom Line – Soft Water Supply

It is important to supply your boiler with soft water at all times to avoid damage and costly repairs. Water softening, when combined with a reliable water treatment chemical program and blowdown schedule, can lead to many years of reliable boiler system performance.

Nationwide Boiler has installed duplex water softening systems in all of our mobile boiler rooms, mobile steam plants, and mobile feedwater systems to ensure optimal boiler performance 24/7. We also have larger skid-mounted, stand-alone water softeners available for rent or for purchase. For more information on products and services available, visit our website at www.nationwideboiler.com.

 

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