What is a fire sprinkler head shield or baffle plate?

A fire sprinkler head shield or baffle plate ("baffle") is a device (typically made of sheet metal) that is used to prevent the first operating sprinkler from wetting (and cooling) the lower or adjacent fire sprinkler heads.

CEO, Firewize
06 Jan, 2021
Fire Sprinkler Head Baffle

Australian Standard AS2118 describes (but does not define) the use of a fire sprinkler head baffle plate that is used to prevent the first operating sprinkler from wetting, cooling and adversely affecting the spray pattern of a lower or adjacent fire sprinkler head.

There is an industry term that also describes these plates as a "heat collector plate" which is not used or referenced with AS2118.

This article covers the use of a fire sprinkler head baffle plate consistent with the application set out in AS 2118:2016.

In the image included with this article, the photograph shows a fire sprinkler head with a baffle plate fitted below some water pipes which has a sprinkler head immediately above it.  In this case, the baffle plate is smaller than the size set out in the Standard.

Other than the size of the baffle plate, this is a typical use of a baffle plate, consistent with the requirements of the note in Table 3.1.2.4 and the requirements for Clause 5.3.

Shields & Baffle Plates

The use and application of fire sprinkler head baffle plates and shields are referenced in AS2118:2016 in the following locations;

  • Page 22, Clause 3.1.2.3 - Shielding;
  • Page 22, Table 3.1.2.4;
  • Page 60, Cause 5.3 - Minimum distance between sprinklers;
  • Page 68, Clause 5.6.5 - Hoists, lift shafts, building services shafts and enclosed chutes.

In each case, the use of a fire sprinkler head baffle plate or shield is used to prevent wetting or cooling from an adjacent operating sprinkler.

Clause 3.1.2.3 provides details of circumstances when building features do not shield sprinklers to prevent cooling from sprinklers operating above as follows;

Where building features do not shield sprinklers to prevent cooling from sprinklers operating above, such sprinklers shall be fitted with metal shields not less than 80 mm dia.

Clause 5.3 provides information about the size and preferred construction material (sheet metal) for sprinkler head baffle plates as follows;

Baffles shall be 200 mm wide × 150 mm high and preferably of sheet metal. They shall be located approximately midway between sprinklers and arranged to baffle the actuating elements. The top of the baffles shall extend above the sprinkler deflectors by 50 mm to 75 mm.

From my reading of AS2118, there is some confusion about the use of the terms shield and baffle which could be rectified in a subsequent edition of the Standard.

What is a heat collector plate?

Sprinkler Head Heat Collector Plate

According to an old (redundant) edition of the National Construction Code, a heat collector plate ("HCP") is installed to "ensure activation by a rising fire plume." 1

Specification G3.8 relates to the fire and smoke control systems in buildings containing atriums. It does not apply to other building classifications or buildings without atriums.

The requirement for a heat collector plate has been removed from the 2019 edition of Volume One of the National Construction Code.

Research exists that there is little benefit in respect to thermal sensitivity from the use of heat collector plates as follows;

Experimental data show that HCP is not able to shorten the sprinkler head activation time in the standard plunge test. Results suggest that the plunge test is not appropriate for studying the thermal sensitivity of sprinkler heads with HCP. This is because the HCP will change the physical environment assumed in the plunge test. 2

Heat Collector Plates - National Construction Code

This section was amended to the original article after we learned that the Building Code of Australia ("BCA") BCA 1996 to BCA 2016 has two references to the use of a heat collector plate in buildings containing atriums as described below;

Note: The requirement for a heat collector plate was removed from the 2019 edition of the National Construction Code and was replaced as follows;

BCA 1996 to 2016 BCA 2019

2.3 Atrium floor protection
The floor of the atrium must be protected by sprinklers with—

  1. the use of sidewall pattern sprinkler heads together with overhead sprinklers where dictated by the dimensions of the atrium; and
  2. sprinkler heads of the fast response type, installed with suitable non-combustible heat collector plates of 200 mm minimum diameter to ensure activation by a rising fire plume.

2.3 Atrium floor protection
The floor of the atrium must be protected by sprinklers with—

  1. the use of sidewall pattern sprinkler heads together with overhead sprinklers where dictated by the dimensions of the atrium; and
  2. sprinkler heads of the fast response type.

2.4 Sprinkler systems to glazed walls
2.4.1  Location of protection
Where an atrium is separated from the remainder of the building by walls or doors incorporating glazing, a wall wetting system with suitable non-combustible heat collector plates of 200 mm diameter must be provided to protect the glazing as follows:

  1. On the atrium side of the glazing — to all glazed walls which are set back more than 3.5 m from the atrium well.
  2. On the atrium side of the glazing — to all glazed walls which are not set back, or are set back 3.5 m or less, from the atrium well, for all levels which are less than—
    1. 12 m above the floor of an atrium or the floor of the highest storey where the bounding wall is set back more than 3.5 m from the atrium well if a Class 2, 3, 5 or 9 part of the building is open to the atrium; or
    2. 20 m above the floor of an atrium or the floor of the highest storey where the bounding wall is set back more than 3.5 m from the atrium well if a Class 6, 7 or 8 part of the building is open to the atrium.
  3. On the side of the glazing away from the atrium well—to all glazing forming part of the bounding wall at each storey.

2.4 Sprinkler systems to glazed walls
2.4.1 Location of protection
Where an atrium is separated from the remainder of the building by walls or doors incorporating glazing, a wall wetting system must be provided to protect the glazing as follows:

  1. On the atrium side of the glazing — to all glazed walls which are set back more than 3.5 m from the atrium well.
  2. On the atrium side of the glazing — to all glazed walls which are not set back, or are set back 3.5 m or less, from the atrium well, for all levels which are less than—
    1. 12 m above the floor of an atrium or the floor of the highest storey where the bounding wall is set back more than 3.5 m from the atrium well if a Class 2, 3, 5 or 9 part of the building is open to the atrium; or
    2. 20 m above the floor of an atrium or the floor of the highest storey where the bounding wall is set back more than 3.5 m from the atrium well if a Class 6, 7 or 8 part of the building is open to the atrium.
  3. On the side of the glazing away from the atrium well—to all glazing forming part of the bounding wall at each storey.

 

Survey of Fire Sprinkler Sytems

Australian Standard AS1851:2012 sets out the requirements for the routine servicing of fire protection systems and equipment.  Section 2 of the Standard covers the routine inspection, test and survey of automatic fire sprinkler systems.

Table 2.4.2.3 of AS1851:2012 provides criteria for the survey (yearly) of various elements of the fire sprinkler system including;

  • 3.17 - Pipes and hangers
  • 3.18 - Sprinkler condition
  • 3.19 - Escutcheons, cover plates or guards
  • 3.20 - Sprinkler obstructions
  • 3.21 - Unprotected areas
  • 3.22 - Sprinkler compatibility
  • 3.23 - Sprinkler ambient conditions
  • 3.24 - External sprinklers
  • 3.25 - Occupancy

While it is not clear what a "cover plate" is in AS1851, it can be assumed that it has the same meaning as the terms shield or baffle plate as described in AS2118.1:2016.

This yearly activity exists to ensure that fire sprinkler systems are operating and to maintain the reliability of fire protection systems and equipment such that they continue to meet the requirements of the approved design and are likely to do so until the next scheduled activity.

Conducting the survey of cover plates, inspectors should look for and report any non-conformances where a fire sprinkler head could be adversely affected by the discharge of water from an adjacent fire sprinkler head or a sprinkler head mounted above as follows;

  1. automatic fire sprinkler heads that are too close to each other;
  2. automatic fire sprinkler heads that are mounted above one another;
  3. automatic fire sprinkler heads that are mounted in a duct, shaft or enclosed chute;
  4. automatic fire sprinkler heads that are mounted adjacent to a deep fat fryer.

In addition, inspectors should be looking for physical damage, contamination, poor fitting, missing cover plates, or cover plates with foreign attachments.