PUMP PANEL DETAILS
Pump panels and numerous gauges and controls on them. Gauges usually have a range of up to 600psi, some gauges also measure vacuum as well, up to 30" of mercury. There are also a variety of gauges to monitor critical engine functions, these are beginning to include electronic monitoring readouts.
As a safety feature pumps include a pressure relief valve to protect against sudden pressure increases, these come in several styles, but most include some kind of hand wheel for adjustment.
Most pumps include drains in the plumbing, the most simple of designs will have one or two so the pump and plumbing can be drained but many include a drain for each discharge or intake. These often use a push / pull or quarter turn valve.
Valves are operated in several ways, the most common method and one of the oldest is manually operated valves. This may be as simple as exposed hand operated valves or internal valves operated by handles connected by rods to the valve. Air actuated valves are becoming more common, hydraulic and electric powered valves are also used for some purposes. Most valves are 1/4 turn ball type valves but some valves require a slower operation. These slower valves often have a hand wheel attached to a worm screw and are usually used for large diameter intakes / discharges and monitors (water cannons).
The pump engine is usually operated with a hand throttle, these are a standardized design with only a few minor differences. Electronic throttles and engine governors are used occasionally, these often use push buttons or a toggle switch. Midship and PTO pumps are typically engaged from the cab, but pumps using an auxiliary motor usually have an ignition switch and starter button.
There are many ways to measure the water in a tank, very simple pumpers may not include a gauge, but most use one or more methods for monitoring the status of the water supply. One of the most common methods is a plastic or glass tube connected to the tank which shows the water level, these are known as a sight gauge or sight tube. They may be marked with lines to show 1/4, 1/2 and 3/4 or left plain, some include a cork to help see the water level. Electronic gauges using lights to show the tank level have become quite common. Fiberglass tanks started to be used in the late 70's, when used in the open like on many small brush trucks they usually have a translucent panel which is used to show the water level. Despite more advanced methods the sight gauge is still one of the most accurate and is often used to supplement other methods.
Foam has been used for many years when fighting flammable liquid fires, the foam used for these fires forms a barrier smothering the fire. More recently another type of foam has become common for use on ordinary combustibles, this type of foam helps the water penetrate burning materials allowing fires to be controlled with less water. There are several methods for adding foam to the water, most use a venturi or a small pump. The mechanism controlling the rate of foam being introduced my be electronic or mechanical. Compressed air foam systems are one of the most recent developments, these use an air compressor to combine air into the foam mixture which make the foam more versatile since it can make very thin wet foam or thick foam useful for flooding basements or other hard to reach areas.