- Author
- Ingason, H.
- Title
- Response Characteristics of Sprinkler Heads Mounted in a Paint Box. BRANDFORSK Project 726-911.
- Coporate
- Swedish National Testing and Research Institute, Boras, Sweden
- Report
- SP REPORT 1992:28, 1992, 33 p.
- Keywords
- sprinkler heads | paper | sprinklers | tunnel tests | wind tunnels | quick response sprinklers | plunge tests | sprinkler activation
- Identifiers
- paint box; paint layer; paper bag; glass bulb sprinkler
- Abstract
- The response of sprinklers mounted in a paint box is usually influenced by paint covering the heat-sensitive element. To avoid this problem, sprinklers are often covered with bags to prevent the paint accumulating on the heat-sensitive element. The influence of various numbers of paint layers and different types of bags on the response time of two types of sprinkler heads has been investigated. Both wind-tunnel tests and full-scale fire tests were performed with glass bulb sprinklers. The thickness of the paint was limited to ensure a uniform distribution of the paint over the heat-sensitive element. Plunge Tests were performed in the wind-tunnel. This is a standardized testing procedure for investigating response of sprinklers. The full-scale fire tests were performed in a test room measuring 9.6 m x 6 m and 3 m in height. The sprinkler was mounted at the center of the ceiling of the test room and a heptane fire was used located 1.5 m or 2.8 m from the sprinkler. It was found that bags delayed the activation of the sprinklers considerably. The gas temperature inside the bags at sprinkler activation was found to be considerably lower than the gas temperature outside the bags. Covered with a bag, faster response was obtained with a quick response sprinkler than with a standard response sprinkler. It was found that the accumulated paint on the heat-sensitive element also affected the response time, but not nearly as much as the bags. The maximum paint layer thickness tested was only 0.4 mm. In a real installation the paint layer can be much thicker. The bags tested did not burn off during the tests despite the fact that the bags were located relatively close to the flames. One problem, which is perhaps more important than the problem of long response times, was observed in the tests. A paint layer covering both the glass bulb and the frame acted as a glue; the consequence being that the glass envelope and the button are sometimes glued to the frame after operation. In some of the fire tests, the spray pattern of the sprinkler was considerably affected. This occured despite the fact that the paint layer thicknesses used were small compared to what can be expected in a real paint box. Every influencies on the spray pattern should be avoided. Materials, which burn off at low gas temperatures but are at the same time very durable, are probably most appropriate for use as covers over the sprinklers. This would mean faster response of the sprinkler and problems with paint acting as a glue would disapear. Further investigations of alternative materials with which the sprinklers may be covered are desirable.