In Japan, when mega earthquake occurred, we found several problems of the existing fire mains in refineries and chemical plants, such as water leakage from the underground fire mains, insufficient pressure for fire fighting, less coverage by hydrants caused from insufficient block valves, problems caused from simultaneous running of the various type of fire pumps etc.  Now, fire main system including fire pumps shall be totally reviewed in accordance with newly established regulation in Japan, if the fire mains is aged longer than 39 years.

The aged fire mains is usually corroded and roughness of internal surface of the pipe becomes too big, resulting in big pressure drop. 
So it is strongly recommended to investigate, to review, and to improve the existing aged fire mains, since old fire main system may have various problems as described below.

1. Fire main drawings not updated　　→　　Update the fire main drawings

   • Long time has been passed from the construction.
   • Additional fire mains had not been reflected to whole fire main grid system
     
     

2. Installation of additional fire pumps　→　confirmation of simultaneous running of multi fire pumps.

   Problems may be possible in such cases
   • Multi pumps, which differential heads are quite different from each other , are running simultaneously to supply water to the fire main grids.
   • Both vertical pumps and horizontal pumps are connected to the fire main grid, and running simultaneously, even if the rated heads are almost same.
     
     

   Such problems may occur possibly

   • Water discharge load may be concentrated to a single pump, which has the highest differential head, and increased to more than 150% load beyond the capacity of the driver.
   • The lower head pumps may be running at no discharge.
     
     

3. Deterioration of the aged fire main grids →　Pressure loss calculation and improvement planing

   Pressure loss is calculated by the network hydraulic calculation method by using PIPENET software (developed by Sunrise Systems Limited, adopted by Major Oil Companies), which program allows pump performance curve of multi pumps as inputs.
   FPEC estimated the relation between roughness of internal surface of the pipe (e/D) and C value of Hazen-Williams formula as shown below.
   The roughness (e/D) will be increased yearly and then C-value is decreased to increase the pressure loss.
   

FPEC will do the review and improvement planing of the aged fire main grid system as an entrusted business.

Job Performance Example

Followings are example which FPEC had performed overall review of the aged fire mains. 

1. To prepare overall fire main grids layout drawing including block valves by reviewing the existing document and site survey.
   
   

   
   
   

2. To estimate C value of Hazen-Williams formula 

   • prediction of C-value depending on test data and  roughness of internal surface of the pipe (e/D)
   • prediction of C-value improvement after pig-cleaning
     
     

3. Hydraulic calculations of the fire mains for fire water demand of each sectional area

   • Before pig-cleaning
   • After pig-cleaning
   • single leg failure of the fire main case
     
     

4. Study for parallel operation of the fire water pumps

   • To calculate operation load for each fire water pump when operated simultaneously.
   • If a pump is running at more than 150% load, then restriction orifice is inserted at the discharge line, and calculate again.
     
     

5. Summary of the calculation results

   
    

6. Improvement Planning for the existing fire main system

   • Improvement of roughness of internal surface of the pipe (e/D) by pig-cleaning.
   • To ensure fire water supply routes by adding the block valve in case of single fire main leg failure.
   • Size up of a portion of the fire main grids.
   • To add a water supply route.
   • To provide the restriction orifice plate at he discharge of the fire water pump.
   • To provide the pressure control valve at he discharge of the fire water pump.