PUMC
Linked In Facebook Twitter YouTube PUMC Blog Subscribe (203) 743-6741
 

Most of us benefit from some sort of combustion every day. Whether for the release of heat or the expansion of gas to perform work, this special category of oxidation is probably the most widely-used chemical reaction in our daily lives. Like most chemical reactions, there are parameters that need to be present not only for the reaction to take place, but to be the most efficient.

For combustion, we follow the Three T’s…time, temperature, and turbulence.

The time of combustion refers to the rate of the reaction. The fuel (natural gas for example), is introduced to the furnace through injectors or pokers. These are usually pipes with a plate at the end with several holes (some call this a poker “shoe”). The volumetric rate, the size and the quantity of holes will result in a design gas velocity at each hole in the poker shoe. Remember also, most burners modulate, so as the firing rate changes so will the gas velocity. This range of gas velocities need to coincide with the rate of the combustion. Gas velocities too high result in the flame “leaving the zone” of combustion which can cause unburned fuel or flame outs. Gas velocities too low can result in “puffs” or a “punky” flame similar to when you shut the gas off to your grill (okay for barbecues, but not for your boiler).

The temperature of combustion is more intuitive. We all know we need to “ignite” the flame to start the reaction, but what does that mean? Simply, we are introducing heat with a spark or pilot flame at the point where air and fuel are mixed to start the reaction. Once the reaction is started, it provides the heat to maintain the temperature to keep the reaction going. Those familiar with gas pilots know adjusting the pilot gas pressure is key to making the pilot flame reliable. Make sure there is a separate pilot gas regulator to accomplish this.

The turbulence of combustion is the “mixing” of the ingredients…fuel and air. Those who have seen the heads of burners know the multitudes of designs to create turbulence at the combustion zone. This creates good mixing and efficient combustion. Poor mixing can allow unburned fuel to create unwanted compounds in the flue gas like carbon monoxide. Burner designers also consider the size and shape of the furnace. A turbulence pattern that makes the flame too wide or too long can result in flame impingement.

Burner technicians use a stack gas analyzer and a sight glass at the back of the boiler to make their final adjustments for the most efficient combustion. They also do this when the furnace is at normal operating temperature as a “hot” furnace has different combustion characteristics than a “cold” furnace.

So next time you’re in the boiler room, take a peek at the flame and look for the Three T’s.

 

– Robert Frohock, PE

 

FlexFit and flame safeguard installed in existing panel using existing wiring

Preferred is bringing something BIG to the industry! 

Tired of fuel and electric waste? Want a more reliable system that also meets strict emissions standards? You know you need to upgrade, but the installation time and expense of a modern linkageless control system often just isn’t plausible…Until now.

Preferred’s new flexible solution dramatically cuts the cost and time for a linkage to linkageless control system retrofit. Now, you don’t have to upgrade your whole boiler room in order to have modern linkageless control. 

So, what do you get? A deal on a modern efficient system, significant fuel and electric savings and rebates, and an intuitive system that will keep you ahead of any emergencies.

 

It’s the flexible retrofit solution…It’s the FlexFit.

 

 

While many boiler rooms and power plants have been swapping out old coal and oil-fired burners/boilers for natural gas and bio-fuels, there still will always be the need for oil burners/boilers in the world. With this need, come the multiple options of how to burn the oil. While there are many different variations, the two main methods of oil atomization for the burner are pressure and air atomization.

Pressure atomization depends on the oil pressure inside the nozzle tip to spray a fine mist of oil, very similar to a Windex spray bottle. The micronized oil droplets are flung into burner head, where they are thoroughly mixed with the combustion air and ignited. As mentioned above, the pressure at the oil nozzle is the key factor in the atomization process, therefore your oil pump and pressure regulator are the key components in this system. The pump needs to be able to meet the gallons per hour (gph) requirement for the burner/boiler to meet their load capacity. The pressure regulator is set in accordance to the firing rate which is normally between 100-300 (psi). The turndown ratio for a pressure atomizing burner is normally only 3:1 or 4:1.

Air atomization adds another variable to the equation. Like pressure atomization, the oil is pumped through the system and into the oil nozzle. There, the oil is sheared by a intersecting stream of air. These two elements are mixed rapidly and forced out the nozzle tip into the burner head where they mix with the combustion air and ignited. As mentioned above, not only is the oil pressure of importance, as seen in the pressure atomization, but the injection air is as well. The oil and atomizing air are both varied based on the firing rate of the burner. While the oil pressure will remain around 100 (psi), the atomizing air pressures can range from 5-75 (psi) based on the design of the burner and firing rate. The turndown ratio for an air atomized burner is normally 6:1 or 8:1.

Both main forms of oil atomization are acceptable and widely used throughout the industry. Depending on the application and resources available one may be better suited than the other. Pressure atomization requires a more powerful pump and motor assembly to create the amount of pressure at the oil tip, while air atomization does not. Air atomization requires an air compressor to be able to create the atomizing air needed to shear the oil in the tip while pressure atomization does not. The whole piping rack for the oil is not as complicated and requires fewer parts for the pressure atomization while air atomization requires piping for air, solenoid valves, air pressure regulators, etc. Air atomization allows for a better turndown ration, which will allow a burner to run at a lower rate while keeping up with the load, while the pressure atomized burner will have to run at a higher or lower rate and either vent the excess steam or cycle on and off to keep the base load. As mentioned before, the application and resources available will determine whether pressure or air atomization will be the better choice for an oil burner application.

 

Robert Bohn, Mechanical Engineer

 

Are there any fuel oil handling systems that don’t need return pumps? Are there any advantages to not having return pumps?  While it is true that I have worked on system designs and executions that have not included return pumps, my general answer is “no,” there are not any advantages.  And there are many different functional reasons why, especially within Mission Critical and First Response handling systems.  The purpose of this white paper is to list several different uses for return pumps under various circumstances, and to demonstrate how every single installation can benefit from them.

 

We all know that return pumps are great for keeping things under control, even if humans seem determined to find a way to spill fuel—running supply pumps in “hand,” or opening valves that should remain closed, and preventing a day tank overflow.  This is the most basic function of a return pump, and by far the most popular reason for their inclusion in both older and more modern designs.

 

FUEL RETURN:  Sending fuel from a day tank, to a main tank

Fuel return is a return pump’s most basic function.  During typical, normal operation, the return pump will be a lonely piece of equipment, but will also be one of the important safety features within the entire fuel oil handling system (FOHS), potentially saving very significant environmental and financial damages.

 

On many basic systems, the return pump will only activate when a “high” level float switch is activated, or similar signal, from a Controller.  An improvement is to have the return pump interlocked with a “high” level switch, which will start the return pump even in the event the Controller is offline or disabled.

 

Be sure to size the return pump appropriately to the application.  Calculate the highest possible rate of fuel entering the day tank.  On multiple day tank systems, this may mean the highest flow rate possible from all supply pumps running simultaneously, while filling that one particular day tank, and no others.  The return pump should be sized at a significantly higher rate than that potential high-flow rate.  How much higher will depend on pump type, available flow rates, etc., but should be 150-200% of the highest flow rate possible from the supply pumps.

 

 

INSPECTIONS AND REPAIRS:  Emptying a day tank for repair or replacement

What if you find fuel in your day tank’s secondary containment?  After looking for the usual leaking suspects, such as a threaded connection, weld, valve, etc., you may come to the conclusion that your primary tank is leaking.  Whether you intend on inspecting the tank, repairing or replacing it, you will need to drain it first.  But, if you have only a top/side-mounted overflow, how do you get the fuel out?

 

A return pump makes this process much faster and less messy, sending the good, clean fuel exactly to where you want it—back into the main tank.  You are also eliminating potential problems with big, messy barrels, which will contaminate the fuel and cause you to dispose of hazardous materials, increasing the hassle—not to mention the expense—even more.

 

 

FUEL FILTRATION:  Cleaning ALL of the fuel, not just the fuel in the main tank

One of the most common reasons for emergency generators to fail to run is bad fuel.  The best way to prevent bad fuel is to filter it.  ALL of it.  This means polishing the fuel that is trapped in supply lines, return lines, and day tanks.  Generators get their fuel directly from their day tanks, but most fuel is only polished in the main tank!

 

Return pumps are great for circulating fuel.  Modern control systems can be programmed to run polishing sequences, including activating return pumps (and supply pumps) that will circulate the fuel through the day tanks and allow it to be cleaned at the main tank(s).  Running a day tank “turnover” sequence, in combination with a filtration/polishing sequence, ensures much cleaner fuel throughout your entire fuel system.  The best generators on Earth won’t run on bad fuel!*

 

*ALL Mission Critical facilities should be on a strict fuel filtration and polishing regimen (Please look out for other white papers about Filtration from Preferred Utilities).  In fact, any facility that requires a backup generator of any type has a responsibility to ensure, to the best of their ability, that the generator runs in an emergency.  That’s what they’re there for!

 

 

THERMAL MANAGEMENT:  Decreasing fuel supply temperatures for generators

Generators use diesel fuel oil not only for internal combustion, but also for cooling the engine’s injectors.  Less than half of the fuel that the generator draws from the day tank is actually used for combustion; the remainder of the fuel is returned to the day tank by the engine, and at a higher temperature.  As continuous running creates a continuous fuel temperature increase, this can adversely affect the performance of the generator, up to, and including, generator shutdown.

 

There are two main contributors to overheating a day tank’s fuel:

  1. Ambient temperature.  Perhaps the day tank is outside, or on a rooftop, in a warm climate, or all of the above.  If the fuel in the day tank is already at 95 degrees F, for example, it’s going to rise fairly rapidly when the generator engine starts.  Unfortunately, in places like California, many power outages occur during the hottest days of the year, due to excessive demand on the grid.
  2. Day tank size versus generator engine size.  A large generator engine paired with a small day tank will increase the day tank fuel temperature quickly, regardless of any other environmental conditions.  Local, state, or national code may inhibit the installation of larger day tanks.

 

Return pumps can assist in decreasing fuel temperatures for generators under both scenarios.  By simply circulating the hot fuel out of the day tanks, and replacing it with cooler fuel from the main tank(s), the generators will continue to run, and run more efficiently.

 

This fuel circulation can be automated.  The day tanks can be equipped with Resistance Temperature Detector (RTD) probes, which will monitor the day tank temperature.  When the day tank temperature reaches a pre-determined threshold, the RTD will signal the master control system (“Controller”), which will start a day tank cooling sequence.  We sometimes refer to a day tank cooling sequence as, “level bouncing.”  A level bouncing sequence would look something like this hypothetical example:

  1. RTD reports temperature threshold met on Day Tank 1 to Controller.
  2. Controller activates Day Tank 1 Return Pump.  Day Tank 1 begins to pump out.
  3. Day Tank 1 reaches “Supply-Pump-On” lower level, which creates a Call For Fuel.
  4. Controller turns Return Pump off.
  5. Controller activates Supply Pump, and opens Day Tank 1’s inlet valve.
  6. Supply Pump fills Day Tank 1.
  7. Day Tank 1 reaches “Supply-Pump-Off” high level.
  8. Controller deactivates Supply Pump.
  9. RTD monitors temperature, and…
    1. RTD reports temperature threshold met on Day Tank 1 to Controller, and sequence repeats… or…
    2. RTD reports temperature acceptable.  No action occurs.

Return pumps are useful for far more than just pushing fuel back to a main tank.  They are an integral part of any system and do not only save us from a messy cleanup and a lot of explaining, but also enable us to truly and completely clean a system, cool a day tank, or just do a more thorough inspection.

 

For more information, or if you have any questions, please contact:

 

Lee Carnahan

District Sales Manager, West

PREFERRED UTILITIES MFG. CORP.

209.890.9993 cell

LCarnahan@preferred-mfg.com

 

A linkageless control system uses a burner with individual servos to control fuel and air ratios, and provide more savings to the end user. This technology can cut boiler room costs and solve end-user headaches. Here are three reasons to choose linkageless controls:

  1. Higher efficiency: O2 levels may fluctuate, but will always return to position of highest fuel and electrical efficiency. In addition, turndown is often improved resulting in less cycling of the burner.
  2. Monitoring and communication: the system communicates via Modbus and reports on all functions. The main module monitors the positions of all fuel- and air-control devices. Any positioning error shuts the burner down safely.
  3. Automatic adjustments for ambient air and fuel changes: Linkage systems can cause major problems for technicians. Once all the linkage is set, the ambient air density may change, throwing the system off. In addition, instead of system readjustment every time there is a fuel switch, the positions of all servos are programmed and independent. This means that the system adjusts automatically to fuel/air ratio changes as well as fuel changes.

In a world of high electric and fuel costs, this technology is indispensable to the modern boiler room.

 

Preferred’s Fuel Oil Handling and Boiler Control Cabinets now have California’s OSHPD Seismic Preapproval. This certification, required by the building code for all hospitals and large nursing facilities in California, verifies the integrity of manufacturer’s equipment and components in event of a seismic disturbance, an earthquake. Through “shake table testing,” Preferred’s boiler and fuel oil handling panels have received the certification that proves its functional ability survive an earthquake and keep your facility running.

 

Top tier American college chooses Preferred Utilities as their partner in a major burner and controls retrofit project on their existing (700 hp) Johnston Boiler. With the installation of the dual fuel Preferred Utilities API-InjectAire burner, the college will reduce its electric consumption on this unit by more than 75% while increasing combustion efficiency by more than double.

With the new ability to have Low NOx 10:1 turn down on natural gas and 8:1 turn down on oil along with precise draft control, and O2 trim, greenhouse gas emissions will be significantly reduced along with wear and tear on the boiler.

We manufacture in the USA and provide single source responsibility for burners, fuel trains, combustion controls and factory start up.

 

Preferred is happy to announce Simoneau Sterling Midwest is Preferred’s new exclusive representative for Minnesota, Iowa, North Dakota, South Dakota, and Wisconsin. Todd Moore, now with Simoneau Sterling Midwest, has been a valuable partner to Preferred over the years. We look forward to working with Todd on many more great projects, supported by Simoneau Sterling’s engineering and manufacturing.”

 

The PCC-IV loop controller is the next generation of Preferred’s loop controllers AND upgraded technology for the entire industry. The PCC-IV is more flexible, has extensive memory, and not only replaces the Preferred PCC-III, but also can replace the Siemens Moore 352 and 353, obsolete and no longer supported starting October 2017.

Preferred Utilities’s controls are just that- preferred. Consider a case study of a longtime PCC controls customer:

Preferred Utilities has been supporting this facility in New York since 1988 with our PCC II and III loop controllers. This site installed one PCC-IV and is now considering this next generation of upgrade, the PCC-IV, in their plant with four (4) 50kpph boilers, each with steam, gas, and oil flow meters.

In 1988, the facility installed 16 PCC-IIs and 5 control panels, plus field instruments for a burner/controls upgrade. Almost 10 years later in 1997, they updated the system with the purchase and installation of 17 PCC-IIIs. In 2002, they decided to upgrade again and add O2 trim. Satisfied with the Preferred product, they installed 21 of the PCC-III units.

Now, in 2017, the plant installed a PCC-IV in parallel with one of the PCC-III controls to observe the performance and is considering upgrading the rest of the PCC-II and PCC-III controls. With the auto-converting functionality of the PCC-IV, the existing PCC-III programs can be re-used without modification and re-programming.

Preferred Utilities is pleased to offer generations of quality products that age gracefully and come with a pledge of full service support and solutions for upgrades in the future.

PCC-IV Loop Controller Front

PCC-IV Loop Controller internal

 

 

 

A New Jersey paper mill came to Preferred Utilities recently needing a quote for a new burner for their 1961 Preferred Utilities Unit Steam Generator. What is wrong with their existing Preferred burner? Nothing. The plant is being forced to convert from No. 6 heavy fuel oil to natural gas.

Will their next burner last 56+ years? Maybe. It depends on who they buy it from.

Note, Preferred still had the documentation on the existing burner and boiler. But we had to go to 49 year Preferred veteran engineer Ricky Erickson to find it.

This plant needs a Low NOx burner that meets the emissions regulations in New Jersey. Preferred designs and builds burners that can meet the strictest regulations, and provides configurable NOx settings, “future-proofing” them against lower emissions requirements that states may adopt in the coming years.

Built for the environment. Built to last.