WHAT FACTORS MAY CAUSE FRICTION LOSS?
Friction loss can be calculated by theoretical or the fire ground method, and we are focusing on the latter.
The pump operator’s job is to provide as much as water flow for the fire attack crew so that the fire can be put out successfully. As a matter of fact, the pump operator does more things than you can imagine at the initial stages of a fire. Among those things, one is considered the most important — determining the right pump discharge pressure.
This is not an easy task for a pump operator because he must have a detailed knowledge of the total gallons per minute flow (gpm) best suited for each supply or hand line. How well a pump operator can conduct this task directly influences the effectiveness of the working end of the hose.
Apparently, the decisive factor in a successful firefighting operation is gpm, which is determined by which nozzle type being selected among those of smooth-bore, automatic nozzle, and adjustable gallonage. For the pump operator, the desired gpm is closely related to the size and lengths of hoses being used, along with any appliances deemed as part of the hose layout (i.e., a gated wye).
Based on such knowledge, a pump operator can accurately and quickly calculate the friction loss and the remaining ingredient to get the right mixture offered to other crew members.
Friction is the resisting force against, when in interplay with each other, the relative motion of solid surfaces, fluid layers, and material elements. Friction loss is defined as the loss of pressure caused by the friction.
Initially in practical application, the friction occurs when water sliding against the pump inner surfaces, ranging from any connected appliances (i.e., gated wyes, manifolds, or water thieves) to standpipes, or fire hoses.
Anyone who wants to be a qualified pump operator must bear in mind the five friction loss principles as follows:
- Friction loss in fire hoses is unavoidable.
- Friction loss varies according to change sizes of the hoses and couplings.
- Friction loss is determined by three key factors: gpm flowing, the size of a hose, and its length.
- Never stick to the fog nozzle whose flow rates range between 95 and 200 gpm. Flow rates are always determined by the fire.
- What the incident commander really needs to put out the fire is correct gpm rather than psi.
GETTING COMFORTABLE WITH FRICTION LOSS
While it is essential that all pump operators thoroughly understand friction loss, new pump operators seem to have a hard time grasping it as if they are absorbing some abstract theory of quantum physics. To tell the truth, it doesn’t take a rocket scientist to figure out friction loss.
Indeed, special attention needs to be paid to knowing how friction loss is related to hose lines and fire streams, but it’s never been a daunting task as many would imagine.
The top priority, sometimes a challenge, for the pump operator is to produce the exact pump discharge pressure required to address the problem of friction loss on the fireground so that the nozzleman can suppress the fire with adequate amount of water supply.
Friction loss can be calculated by either the theoretical method or the fireground one. The former, based on mathematical equations, are best suited to pre-fire planning, creating specifications documents, and assessing potential risks. Therefore, it is not a practical tool to be used on the fire scenes.
The latter, however, is based on rule of thumbs free from mathematical equations.