We have a great new course available for continuing education, taught by a new instructor, Karl Wiegand, who really knows his stuff. The course is titled Introduction to Fire Sprinklers, Valves, and Hydraulic Calculations.
This is an introduction to the basics regarding fire sprinklers, valves and hydraulic calculations. By the end of the course, students will be familiar with the parts of a sprinkler assembly and the significance of sprinkler orientation. They will also learn the basics of sprinkler system valves and the types of systems they service. Finally, hydraulic calculations are discussed as they relate to water supply, water flow and friction loss.
Read on for a sneak peak from the first lesson in the course all about Sprinkler Basics:
Most sprinklers have six main components: the deflector, frame arm, activating link, orifice cap, threads and the orifice.
- Orifice. “K-factor” is the relationship between the pressure and the flow in the sprinkler. See the equation below:
- K = Q/sqrt(P)
- Q = flow (gpm)
- P = Pressure (psi)
There are a large range of K factors, the larger the orifice, the more flow you can get without increasing the pressure. K-factors typically range from 1.4 to 28.0, with the most common K-factor at 5.6.
- Threads. Usually you are looking at the size of the connection that the sprinkler will screw into. Smaller orifice sprinklers have smaller threads.
- ½ in thread: K 1.4 – K 11.2
- ¾ in thread: K 8.0 – K 16.8
- 1 in thread: K 19.6 – K 28.0
This is important, especially when replacing systems, The thread dictates the size of the opening.
3. Orifice Cap. The orifice cap is used on automatic sprinklers to keep water from flowing, it keeps the water in the system. Open sprinklers do not have orifice caps, the norm is a closed system.
4. Activating Link. This a heat sensitive device that holds the orifice cap in place on automatic sprinklers and keeps them from going off at the wrong time. Open sprinklers do not have an activating link. Sprinklers are designed to react at different speeds, to operate at different temperature ranges (depending on what they are protecting). There are two different types of links - solder and glass bulb.
Activation speed is dictated by the thickness of the link. Typical bulb links are either in 3mm or 5mm bulb sizes. The 3mm is a quick response link, whereas the 5mm bulb is the standard response because it activates slower. All can be fit on a RTI (Response Time Index), which is the relationship between how fast the sprinkler activates with different heat velocities at different temperatures.
Temperature Ranges. Normal temp sprinklers are designed to be in areas up to 100° F. Other commonly used temperatures are intermediate and high with are allowed in 150° F and 225° F respectively. Temperature ranges go up to 625° F. Links are color coded to the temperature range they fall in. The set temperature can be regulated by increasing or decreasing the size of the air bubble in the ampule itself.
Solder Links. Like most typical solders, eutectic solders are used in sprinkler systems. Solder links have a few pros and cons. One advantage to a solder link is that it is more robust than a glass bulb. Any jostling, or rough handling on the bulb can cause damage. Soldered links can also tell you more about the physical cause of an activation that may not have been caused by heat. Soldered links are, however, more difficult to control in terms of the melting temperature.
Glass Bulbs. Glass bulbs are filled with a sugar solution that expands when it is heated. An advantage to glass bulbs are that they are easy to design to activate at a specific temperature. And as discussed above, a disadvantage is that glass bulbs are easier to damage than solder links.
5. Frame Arm. The frame arm holds the deflector, the orifice cap, and the activating link in place. It needs to be able to keep the deflector in position when water is flowing through the sprinkler. The frame arm actually does have an effect on the spray pattern because the water hits the frame arm before the deflector.
6. Deflectors. These are arguably the most important component of the sprinkler. Deflectors are used to create spray patterns. Deflectors come in different shapes, each shape creates a different pattern with a different purpose or application. Most shapes are proprietary from one manufacturer to another.
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