P C McKenzie Company

Industrial Boiler and Natural Gas Compressor Sales

  • About
  • Blog
  • Contact Us

CALL US TODAY - 877-244-4883

  • Compressors
    • Sauer Natural Gas Compressor
    • IR Compressor Packages
      • IR 05H25NGSX
      • IR 05H25NGDX
      • IR 20H40NGSX
      • IR 20H40NGDX
    • CNG Rental Units
    • Small CNG Station for Fleet Vehicle Refueling
    • Natural Gas Compressor Valve Rebuild Program
    • IR Compressor Parts
    • IR Bare Blocks
    • Troubleshooting Guide
  • BOILERS
    • Boiler Service and Boiler Repair
    • Patterson Kelley Condensing Boilers
    • Patterson Kelley Non Condensing Boilers
    • Unilux Water Tube Boilers
    • Cast Iron Boilers
    • Hurst Boilers and Hurst Boiler Parts
    • Atlas Boiler
    • Ajax Boiler Gaskets and Ajax Boiler Parts
    • Venting Solutions
      • Engine Generator Turbine Exhaust
      • Zero Chase Grease Duct
      • Boiler Domestic Water Heater Venting
    • Draft Induction Fan
    • Boiler Burners
      • Industrial Combustion Lo-Nox Burners
      • Gordon Piatt Burner Parts
      • Weishaupt Burner Parts
  • AXELSON
    • Axelson Relief Valves
      • Axelson Relief Valve Maintenance
      • How Does an Axelson Safety Valve Work?
      • Garrett Safety Relief Valves
      • Axelson Orifice
      • How to Test Relief Valves – Axelson Test Stand for Pilot Valves
    • Axelson Spare Parts
    • Axelson ESP Pilot Sensor
    • Axelson ESPHL – High/Low Pressure Controller
    • Axelson Sand Probe Valve with Sensor
    • Axelson CRBBM Relay
    • Axelson Actuator Pneumatic Diaphragm Actuator
    • Axelson PRV Relay
    • Axelson Differential Pressure Sensing Unit
  • OIL CONTROL
    • Oil Level Regulator Davco Ren
    • Slow Flow Meter
    • Continuous Oil Change Module by Ren
    • Liquid Level Switch by Ren
    • Oil Supply Tanks
  • Boiler Parts
    • Boiler Pumps
    • A & F Chemical Feed Pumps
    • Chemical Feed Tanks
    • Everlasting Blowdown Valve
    • Kewanee
      • Kewanee Boiler Parts
      • Kewanee Vortex Damper Rebuild
      • Kewanee Boiler Gaskets
      • Kewanee Burner
      • Cam Assembly
      • Kewanee Burner Blower Wheel
    • Pressure Reducing Regulators
    • Boiler Gaskets
    • Flame Controls
    • Weishaupt
    • Gauge and Site Glass
  • AMOT
    • Amot Thermostatic Control Valves
    • 3-Way Control Valves
    • Diaphragm Operated Gas Valve
    • Air Intake Shut Off Valve
    • Bearing Temperature Detector
    • High Temperature Valve
    • Overspeed Sensing Valve
    • Master Safety Control
    • Metal Particle Detector
    • Amot Temperature Sensor
    • Amot Electric Trip Lever Switch
  • RESOURCES
    • CNG Safety – Is Compressed Natural Gas Safe?
    • CNG
    • CNG Storage Cascades
    • NGV Fast Fill Station
    • NGV School Bus Refueling
    • NGV Service Tips
    • NG Compressor Troubleshooting
    • Boiler Service Tips
      • Boiler Questions About Your Boiler
      • Boiler Glossary
      • Boiler FAQ
  • Charging Station

Proper Sizing of Boiler Feedwater Systems

Proper sizing of Boiler Feedwater Systems

How to Properly Size a Boiler Feedwater Systems

One of the most important factors in keeping your boiler on-line is to keep enough water in it. Otherwise the boiler will shutdown on a low water condition. This is especially true with firetube boilers that are fired automatically. That is why it is so important to size a feedwater system so that it has the capability of maintaining the proper water level in your boiler.

PROPERLY SIZED

A properly sized feedwater system will have a tank adequately sized to feed your boiler and pumps selected to deliver that water at the correct rate and pressure.

CALCULATE THE STORAGE TANK NEEDED

In most cases ten minutes of water should be readily available for your boiler. One boiler horsepower = 34.5 lbs/hr of steam (or water) from and at 212o F. We also know that one-gallon of water weighs 8.37 lbs. To calculate the storage tank needed use the following formula:

BHP X 34.5 ÷ 8.337 lbs ÷ 60 min. X 10 = minimum useable capacity in gallons.
For example, if you have a 500 HP boiler the calculation will be as follows –

500 x 34.5 ÷ 8.337 ÷ 60 X 10 = 345 gallons

Now, it stands to reason that you can’t operate your tank totally flooded so you have to allow for some extra room. A safety factor of 1.5 is generally the accepted rule of thumb.

We then take the 345 gallons and multiply by 1.5 to get 517.5 gallons and choose a tank size of 500 gallons (one of the standard tank sizes available).

Keep in mind that your boiler system requirements might demand a larger reserve especially if you have a process steam load that returns large slugs of water intermittently. In this case you may need a larger tank.

The next step is to select the correct pump for your application. There are three areas that must be considered.

  1. The correct flow rate in GPM
  2. The correct pressure needed
  3. NPSH (net Pump Suction Head)

To calculate the flow rate in GPM, use the following formula:

BHP X 34.5 ÷ 8.337 ÷ 60 X 1.5 = gpm

(Please note that the 1.5 is, once again, a safety factor.)

For the example we have been using the calculation will look like this:

500 BHP X 34.5 ÷ 8.337 ÷ 60 X 1.5 = 52 gpm

Another quick rule of thumb is that 1/10 of a gallon is needed for every boiler horsepower. So a 500 HP boiler will need a pump capable of delivering 50 gpm.

An 800 HP boiler will need an 80 gpm pump.

The next step is to determine the proper discharge of the pump. ASME code requires that you furnish feedwater to your boiler at 3% higher than what the relief valve setting is on the boiler. In addition, you must take into consideration any pressure drops between the pump and the boiler. This would include any valves and piping.

For this example we will say that our relief valve is set at 150 psig and there is a 5 lb. pressure drop. The calculation will look like this:

150 x 1.03 + 5 lb drop = 160 psig required.

The last piece of the puzzle is the correct NPSH, net positive suction head. This is the amount of liquid, in feet, required at the pump suction to prevent cavitation and insure the pump is working correctly. This will help determine the tank stand height you will need

To chose the correct NPSH refer to the pump selection tables. These tables are based on the pumps having the lowest possible NPSH needed. This is done to ensure the lowest tank stand and thus reduce the overall height of the boiler feed system. NPSHA is the feet available under the tank and NPSHR is the feet required by the pump. Check the pump curve for the NPSHR and then add one foot.

 

Natural Gas for Our Future
Natural Gas an ideal fuel source for many reasons, including safety. Natural Gas is lighter than air. This means that it will not puddle (like gasoline) or sink to the ground like propane, which is heavier than air. Instead, Natural Gas will rise and dissipate in the atmosphere. Natural gas also has a higher ignition temperature. This means that it is much harder to ignite. Also the storage systems used for compressed natural gas are infinitely stronger that the gasoline tanks found on cars and trucks today.
Learn more >>

CONTACT US

Toll Free: 1-877-244-4883
Fax: 412-257-8890
Phone: 412-257-8866

SHIPPING ADDRESS
P.C. McKenzie Company
1365 McLaughlin Run Road
Pittsburgh, PA 15241

MAILING ADDRESS
P.C. McKenzie Company
P.O. Box 112638
Pittsburgh, PA 15241

- P.C. McKenzie Company is located South of Pittsburgh, Pennsylvania -


Julie Good is a Pittsburgh based photographer. Please visit her site to view her gallery.

>> JG Photography >>

© Copyright 2021 PC McKenzie · All Rights Reserved ·