Handline Branches & Nozzles

Q1. What is the purpose of handline firefighting branches and nozzles?

To fight small and medium size fires, it is necessary to direct water from a safe distance onto the fire area, in the required form (large/ small droplets). Pressurized water can be conveyed to the affected area using fire fighting hoses. However, to project it to the fire area, it is required to convert the pressure energy of the water into velocity energy. At the same time, it is necessary to project the water in the desired form i.e. jet, spray or fog, to ensure maximum effectiveness depending upon the situation. Handline firefighting branches and nozzles do the job of converting the pressure energy to velocity energy and projecting the water in the required form.

Q2. What are the basic types of handline nozzles?

There is no standard classification of handline nozzles, as they can be sub-divided into different types depending upon on pattern, flow quantity, etc. Normally they are classified as follows –

  • Solid bore nozzles (which discharge water in form of a solid jet only)
  • Combination or Spray nozzles (or Jet/Spray type nozzles) which discharge in form of a hollow jet, narrow fog or wide fog. These can be further sub-divided into –
    • Constant flow nozzles (those discharging same flow at a given pressure)
    • Variable flow nozzles (flow can be varied manually for a given pressure)
    • Automatic nozzles (flow varies depending upon pressure)
  • Multipurpose nozzles (those discharging water in form of a solid jet as well as spray, even simultaneously).
Q3. What are the shortcomings of short branch with nozzle?

In short branch with nozzle, the pattern of flow is only in form of a solid jet, which means that this branch is unable to project water in form of fog, or spray for protection. At the same time, due to the absence of a valve in the nozzle, it could not be shut off by the nozzle man, which means that he has no control over the branch.

Q4. What are the advantages and shortcomings of the basic spray (combination) nozzle?

The main advantage of the combination or spray nozzle is that it is provided with a pattern changeover mechanism as well as a shut off arrangement. The pattern changeover mechanism allows changing the pattern from jet to spray or vice-versa, while the shut-off mechanism allows the operator to shut down the flow, when required.

In the basic spray nozzle, the flow varies as the pattern changes from the hollow jet to the spray pattern (normally the flow in jet pattern is lesser and increases as the pattern changes to fog)

Q5. How are constant flow nozzles different from Combination nozzles?

In certain combination nozzles, the flow changes with pattern. However, in Constant flow nozzles (also known as Single gallonage nozzles), the flow remains constant throughout the different range of discharge patterns i.e the flow will remain same whether discharging in form of a jet or spray.

Q6. What are the advantages of using a selectable flow nozzle?

Selectable flow nozzles incorporate an arrangement to vary the outlet orifice size, hence the flow can be varied by changing this orifice size. The operator can set the flow without shutting down the line, depending upon the pressure available, and other operational considerations. This means that the nozzle can be used effectively even in varying pressure conditions by the operator himself, without any dependence on the pump operator.

Q7. What are automatic nozzles and how do they function?

An automatic nozzle maintains a relatively constant pressure over a wide range of flows. Such nozzles have an arrangement in the nozzle which controls the flow by restricting the orifice outlet to maintain pressure.

If the pressure is relatively low, the nozzle orifice will automatically restrict the flow, causing pressure buildup at the outlet, and consequently resulting in a good quality discharge pattern. Similarly, if the pressure increases, the orifice opens to allow more flow, again adjusting to a constant pressure at the outlet of the nozzle.

Q8. How is quality of fog improved by providing teeth on nozzle outlets?

Providing teeth on the nozzle outlet serves two purposes; first, in the narrow fog position, it deflects part of the water to the centre of the spray (which is otherwise hollow). Secondly, in the wide fog position, it caused the water curtain to break up into streams which then impinged on one another to create a better quality fog. A variety of different designs of teeth (fixed/ spinning/ flexible) can be used to create this fog.

Q9. As far as quality of fog is concerned, how do spinning teeth compare with solid teeth?

There is no clear research data to prove superiority of spinning teeth over solid teeth. Certain trials show that spinning teeth rotating in the fog position, cause the break up of the water curtain into fine droplets, which are ideal for fire gas cooling operations. It may be noted, however, that there is no conclusive evidence on the superiority of spinning teeth.

Q10. Which type of valves are provided on handline firefighting nozzles?

For a long time, manufacturers have been using the ball valve for controlling the flow in the nozzle, as it is a proven design, operates well at the pressures used, and is relatively maintenance free. The ball can be of metal, or polymer based materials.

Another type of valve used nowadays is the slide valve, in which a hollow cylinder moves back and forth along the central axis, and seals against a polymer seat. Due to the movement of the cylinder, it causes a variation in the orifice gap between the cylinder and the seat and hence controls the flow.

Q11. What are the factors to be considered when procuring firefighting handline branches?

When procuring handline nozzles, the following factors are normally considered –

  • Suitability to risk (whether the nozzle is suited to the type of fires likely to be encountered)
  • Pattern & Flow range (what are the discharge patterns available & whether nozzle flow is suited to risk and to the operators).
  • Material of construction
  • Maintenance and durability
  • Ergonomics (whether comfortable to handle for the type of operators present)
Q12. What are the normal maintenance requirements for handline nozzles?

Maintenance requirements can vary from one handline nozzle to another. Simple jet nozzles require virtually no maintenance, while new combination nozzles can require periodic replacement of components. Normal maintenance activities include –

  • Periodic visual inspections (at least monthly)
  • Periodic operational tests (as mandated by manufacturer)
  • Periodic replacement of rubber washers/ O rings (as mandated by manufacturer).
  • Periodic replacement of valve seats/ springs/ spinning teeth (as mandated by manufacturer).
Youtube to Facebook Live StreamHD WallpaperOnline Shopping CartPure HD WallpapersBollywood Teasers VideosLatest NewsBollywood GossipFunny News