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Fire Protection Systems

2 Posts authored by: cduffy Employee

Why do only horizontal split-case fire pumps require elbows and tees to be installed a minimum of 10 pipe diameters from a pump suction flange when in a horizontal plane parallel to the pump shaft?

 

Placing an elbow or tee with the centerline in the horizontal plane within 10 pipe diameters of the suction flange creates an unbalanced flow of water into the impeller. An unbalanced flow causes an axial load to be placed on the pump shaft and bearings, causing excessive wear to the bearings and subsequent damage to the pump over time and/or severe cavitation if not corrected. The requirement for elbows within 10 pipe diameters of the suction flange applies only to horizontal shaft fire pumps. In an inline (vertical shaft) fire pump, gravity already creates an axial load imbalance so the imbalance from an elbow is of less concern.

 

6.1.2 of NFPA 14 protection of aboveground pipe criteria for standpipe systems. As Staff Liaison to the Technical Committee on Standpipes I often receive questions where users struggle to understand what must be protected and how it is to be accomplished. In an effort to clarify the issue the Technical Committee on Standpipes has proposed revisions to 6.1.2 for the 2016 edition. So, if you have questions on 6.1.2 please take some time to read the following changes as I hope these will help to clarify the requirements.

 

Replace Section 6.1.2 with text as shown below.

 

6.1.2 Protection of Aboveground Piping.

 

6.1.2.1* Standpipe system piping shall be protected from mechanical and fire damage in accordance with this section.

 

A.6.1.2.1 Standpipes should not be installed in non-sprinklered areas of combustible construction.

 

6.1.2.2* Standpipe systems shall be protected in accordance with Table 6.1.2.2.

 

A.6.1.2.2. Where pipes that supply combined systems in areas or buildings that are sprinklered, or are installed in non-sprinklered, combustible buildings or areas the piping should be protected. Protection of pipe should also be provided in any area of a structure or building that poses a degree of hazard greater than that normal to the general occupancy of the building or structure. This includes areas for the storage or use of combustibles or flammables; toxic, noxious, or corrosive materials; and heat-producing appliances.

 

Table 6.1.2.2 - Protection of Aboveground Piping

 

High Rise

Non High Rise

Construction Type

Sprinkler Protection

Standpipe

Horizontal1

Branchline

Standpipe

Horizontal1

Branchline

I

AS2

N/A

N/A

N/A

N/A

I

NS3

N/A

N/A

II

AS

N/A

N/A

N/A

N/A

II

NS

N/A

N/A

III, IV & V

AS / NS

N/A

N/A

1 - Refers to either a horizontal standpipe or the horizontal portion of any standpipe such as a feed main.

2 – AS = fully sprinklered building in accordance with NFPA 13

3 – NS = non sprinklered or partially sprinklered building

 

6.1.2.2.1 Protection shall consist of one of the following methods:

a.) Enclosure in a fire rated exit stairway.

b.) Enclosure in fire rated construction with such rating equal to that of the enclosed fire rated exit stairway.

c.) Listed fire wrap or other insulating material applied directly to the pipe with such rating equal to that of the enclosed fire rated exit stairway.

 

6.1.2.2.2 Where exit stairways are not required to be enclosed in fire rated construction, standpipe systems shall not be required to be protected.

 

6.1.2.2.3 Class II standpipe systems are not required to be protected.

 

6.1.2.2.4 Where additional standpipes are needed to meet travel distance requirements in non-high rise buildings, protection of piping is not required.

 

6.1.2.2.5 Seismic bracing, where required, shall be in accordance with NFPA 13.

 

6.1.2.2.6 Piping subject to mechanical damage shall be protected by steel posts, concrete barriers or other approved means.