Sprinklers and Their Applications

Risk Management Information

Sprinklers and Their Applications

Fire Protection

Sprinklers and Their Applications

Report Number: / FP-22-06
Release Date: / October 26, 2005
Section Title: / Sprinkler Systems

Abstract

Automatic sprinklers have been protecting property from fire damage for more than 120 years. During this time, advances in technology have led to the development of many specialized sprinklers. This report outlines the types of sprinklers available and their applications.

Introduction

Automatic sprinklers are used for protecting property from fire damage. The primary advantage of automatic sprinklers is that they operate close to a fire and early in the combustion process, thus controlling fires while they are still small. They were originally developed around 1870 for use in controlling fires in New England textile mills. Since that time, they have undergone many changes that have improved their performance.

Sprinklers should be installed in accordance with NFPA 13, Standard for the Installation of Sprinkler Systems, published by the National Fire Protection Association (NFPA). NFPA requires that all sprinklers should be listed/approved by a nationally recognized testing laboratory, such as Underwriters Laboratories, Inc. (UL).

This report outlines the types of sprinklers available and their applications.

Sprinkler Listings

Sprinklers that are listed by UL will have the letters "SSU" or "SSP" stamped on the sprinkler. This refers to the type of sprinkler, either standard spray upright (SSU) or standard spray pendent (SSP). These sprinklers are specifically designed for use in their respective positions and should not be interchanged with one another type.

Only listed/approved sprinklers, used in accordance with their listing, should be used in sprinkler systems. Generally, ordinary temperature sprinklers are installed throughout a building, with the exception of when they are installed near a potential source of heat. NFPA 13 should be used to determine the temperature rating needed for sprinklers used near potential sources of heat, based on the distance from the heat source and the type of heat condition present.

Types of Sprinklers

Below is a list of common types of sprinklers, with a brief description of each. The most common sprinklers will be discussed as to their specific applications later in this report.

Concealed sprinklers. Sprinklers that are recessed and provided with cover plates.

Corrosion-resistant sprinklers. Sprinklers that have special coatings applied to them so that they may be used in an atmosphere that would corrode an uncoated sprinkler.

Dry-pendent sprinklers. Sprinklers designed for use in a pendent position, in either a dry-pipe or a wet-pipe system, with the seal located in a heated area.

Dry-upright sprinklers. Sprinklers designed to be installed in the upright position, in a wet-pipe system, to extend into an unheated area with the seal located in a heated area.

Early suppression fast response (ESFR) sprinklers. Sprinklers designed to react at a predetermined temperature to provide water in a specified pattern and quantity over a designated area, in order to provide early suppression of a fire.

Extended coverage sidewall sprinklers. Sprinklers designed with special extended, directional, discharge patterns.

Flush sprinklers. Sprinklers in which all or part of the body, including the shank thread, is mounted above the lower plane of the ceiling.

Intermediate level sprinklers. Sprinklers equipped with integral shields to protect their operating elements from the discharge of other sprinklers installed at higher elevations.

Large-drop sprinklers. Sprinklers designed with a K factor between 11.0 and 11.5 and which are capable of discharging large drops of water of such size and velocity as to effectively penetrate high-velocity fire plumes.

Large orifice sprinklers. Sprinklers that have a larger orifice than the standard sprinkler orifice.

Nozzles. Devices used in applications requiring special discharge patterns, directional spray, fine spray, or other unusual discharge characteristics.

Old-style sprinklers. Sprinklers that direct 40 to 60 percent of the total water spray, initially in the direction of sprinkler orientation (i.e. up for up-right) and that are designed to be installed either in the upright or pendent position.

Open sprinklers. Sprinklers from which the actuating elements have been removed.

Ornamental sprinklers. Sprinklers that have been painted or plated by the manufacturer to match building aesthetics.

Pendent sprinklers. Sprinklers designed to be installed in such a way that the water is directed downwards against the deflector.

Quick-response sprinklers. Sprinklers incorporating a fast-actuating heat responsive element.

Recessed sprinklers. Sprinklers in which all or part of the body, other than the shank thread, is mounted within a recessed housing.

Residential sprinklers. Sprinklers designed and specifically listed for use in residential occupancies.

Sidewall sprinklers. Sprinklers having special deflectors that are designed to discharge most of the water away from the nearby wall in a pattern resembling one quarter of a sphere, with a small portion of the discharge directed at the wall behind the sprinkler.

Small orifice sprinklers. Sprinklers that have a smaller orifice than the standard sprinklers.

Standard sprinkler orifice. The standard size of a sprinkler orifice is considered ½ in (12.7 mm).

Upright sprinklers. Sprinklers designed to be installed in such a way that the water is directed upward towards the deflector.

Sprinkler Applications

There are a number of different sprinkler designs and applications currently available. Before selecting a sprinkler design, the risk to be protected should be evaluated and nationally accepted codes reviewed to determine the type of sprinkler components required. The following is a general description of the most common sprinkler types.

Large Orifice Sprinklers

Large orifice sprinklers have a larger orifice, typically 17/32 in (13.5 mm), than the standard sprinklers. These sprinklers discharge approximately 40 percent more water than the standard sprinkler due to the increased opening size. Because they are designed to deliver more water, the piping must also be specially designed to accommodate this increased amount of water. These sprinklers are generally used in areas that require higher densities than normal.

Large orifice sprinklers are available in both the ½-in (12.7-mm) and ¾-in (19-mm) threaded sizes for installation into sprinkler piping.

Small Orifice Sprinklers

Small orifice sprinklers are similar to the standard sprinklers, but with an orifice size smaller than standard sprinklers. These sprinklers discharge about 50 percent less water than the standard sprinkler at the same pressure, due to this smaller orifice. Typical orifice diameters found on small orifice sprinklers range from ¼ in (6.3 mm) to 7/16 in (11 mm)

Small orifice sprinklers can be used in light-hazard occupancies. Small orifice sprinklers are generally not recommended for use on dry-pipe, pre-action, or combined dry-pipe and pre-action systems. In addition, a strainer must be installed in the riser or feed main when the orifice size of the sprinkler is less than 3/8 in (9.5 mm).

Large-Drop Sprinklers

Large-drop sprinklers are designed to discharge water down to the seat of a fire through the updraft of the fire plume generated by high-challenge fires. Sprinkler discharge of at least 55 gal/min (205 L/min) per sprinkler is normally required. Large-drop sprinklers cannot be used to compensate for weak water supplies, because high levels of penetration and cooling are required and can only be achieved by an adequate supply. The K factors of these sprinklers are between 11.0 and 11.5.

Types of occupancy/storage hazards that may be protected with large-drop sprinklers are:

· Palletized storage

· Solid-piled storage

· Double-row rack storage with a minimum 5.5 ft (1.6 m). aisle width

· On-end storage of roll paper

· Record storage

Note: Prior to recommending the use of large-drop sprinklers, NFPA 13 should be consulted for specific requirements.

Quick Response Sprinklers

Quick response sprinklers, as the name implies, incorporate a fast-acting, heat-responsive element along with an ordinary temperature rating. This design results in a sprinkler that will react faster than the standard sprinkler at the same temperatures. Quick response sprinklers are acceptable for use in wet-pipe systems only for protecting light or ordinary hazard occupancies.

Sidewall Sprinklers

Sidewall sprinklers are designed with a special deflector that forces the water discharge outward from the wall. These sprinklers are designed to be installed near the junction of the ceiling and the wall, in areas where the wall will act as a banking device for the heat. They are also used for their limited appearance. These sprinklers are intended for use in light hazard occupancies, unless specifically listed for use in ordinary hazard occupancies.

Extended Coverage Sidewall Sprinklers

Extended coverage sidewall sprinklers are designed to discharge water over a much larger area than standard sprinklers. These are used primarily in light hazard occupancies with smooth, level ceilings.

Intermediate Level Sprinklers

These sprinklers are used in rack storage arrays and are available in both standard and large orifice, and in upright or pendent positions. Discs mounted above their normal thermal-sensing element protect the sprinkler from water being discharged by nearby sprinklers at higher elevations that could otherwise delay or prevent sprinkler actuation.

Corrosion-Resistant Sprinklers

Corrosion-resistant sprinklers are designed in one of two ways: either by the use of a corrosion-resistant material, such as stainless steel or lead, or coated with a corrosion-resistant material, such as wax. These sprinklers are used to protect areas where the atmosphere, due to the type of on-going operation, may corrode a normal sprinkler.

Residential Sprinklers

Listed residential sprinklers are designed to be installed so that the deflector is within 1 to 4 in (2.5 to 10.1 cm) of the ceiling, unless the specific sprinkler has been listed for installation otherwise. In addition, sidewall residential sprinklers are designed to be installed so that the deflectors are within 4 to 6 in (10.1 to 15.2 cm) of the ceiling.

The maximum allowable protected area by a residential sprinkler, according to NFPA 13R, Installation of Sprinkler Systems in Residential Occupancies up to Four Stories, and NFPA 13D, Standard for the Installation of Sprinkler Systems in One- and Two-Family Dwellings and Mobile Homes, is 144 ft2 (43.9 m2) per sprinkler.

ESFR Sprinklers

ESFR sprinklers are designed, as the name implies, to respond quickly, at a predetermined temperature, to control a fire in its early stages. These sprinklers are suitable for use in buildings with a maximum height of 45 ft (13.7 m) and with one of the following types of roof construction: smooth ceiling, bar joist, beam and girder, or panel. ESFR sprinklers are intended for use (per NFPA 13) in the following occupancies:

· Single-, double-, and multiple-row and portable rack storage (no open-top containers or solid shelves) and solid-piled or palletized storage of Class I thru IV commodities.

· Roll paper on end (either heavyweight or medium-weight paper), with open/standard/closed array, whether banded or not.

When discussing early suppression, three terms are used: Response Time Index (RTI), Required Delivered Density (RDD), and Actual Delivered Density (ADD):

Response Time Index (RTI)

The response time of a sprinkler is determined by the sensitivity of the thermal-sensing element to temperature increase. The lower the RTI, the more responsive the element is to temperature change. Therefore, a sprinkler with a lower RTI will operate quicker than a sprinkler with a higher RTI.

Required Delivered Density (RDD)

The Required Delivered Density is the amount of water needed to reach the top of the storage array and suppress a fire before it operates other heads outside the initial fire area. This takes into consideration the material involved, the storage arrangement, the quantity of storage, the height of storage, and the time at which the water is applied.

Actual Delivered Density (ADD)

The Actual Delivered Density is the amount of water that reaches the top of the burning storage array and is available to extinguish the fire. This takes into consideration the sprinkler's penetration capability and the distribution pattern of the spray in the presence of a fire plume. The ADD will decrease as the fire intensity increases.

The ESFR sprinkler head was so named to emphasize the need for early suppression as opposed to fast response. In order for ESFR sprinkler heads to operate as designed and suppress the fire in its early stages, the ADD must be greater than the RDD. When water is applied to a growing fire in its early stage, the RDD is lower than the ADD, thus providing the necessary amount of water to suppress the fire.

References

1. National Fire Protection Association (NFPA). Fire Protection Handbook. 19th ed. Quincy, MA: NFPA, 2003.

2. ---. Standard for the Installation of Sprinkler Systems in One- and Two-Family Dwellings and Manufactured Homes. NFPA 13D. Quincy, MA: NFPA, 2002.

3. ---. Standard for the Installation of Sprinkler Systems. NFPA 13. Quincy, MA: NFPA, 2002.

The information contained in this publication was obtained from sources believed to be reliable. ISO Services Properties, Inc., its companies and employees make no guarantee of results and assume no liability in connection with either the information herein contained or the safety suggestions herein made. Moreover, it cannot be assumed that every acceptable safety procedure is contained herein or that abnormal or unusual circumstances may not warrant or require further or additional procedure.

E&S Technical Information