6-Month Checkup Urged In Preparation for Winter
It is that time of year again for the six-month maintenance inspection and servicing of apparatus before winter arrives. This should be a complete checkup which will require the apparatus to be out of service for approximately one day.
Most fire departments have a check list for inspection and maintenance (see pages 11 and 56 of the book, “Preventive Apparatus Maintenance,” published by Fire Engineering), but such a list becomes incomplete and must be updated each time new apparatus is acquired.
With the adoption of the diesel engine and automatic transmission, to mention only two of the important changes, the number of items scheduled for inspection and servicing, such as listed on page 67 of “Preventive Apparatus Maintenance,” has increased.
Before starting an inspection, be sure the apparatus is clean. Actually, this is essential to permit detection of any cracks, rusting or defects that require correction for operating safety or prevention of an operational breakdown. The sequence of inspection is not important. What is important is a complete and observant inspection, particularly during any servicing.
Oil and filters: Changing engine oil and replacing the filter (or cleaning a wire filter) are usually the first things to do. If the oil has been changed and the filter replaced or cleaned every three months, all you have to do is drain the oil.
But when oil has been used for six months or more, an oil change requires removal of the oil pan to clean out the sludge in the pan and on the crankcase walls.
If the oil feels gritty or contains metallic particles, the filter is plugged and should be changed more often. Also, metallic particles indicate rapid wear that leads to a premature major overhaul of the engine. If there is evidence of water, a thorough inspection should be made to determine if the leakage is from the cooling system. This would also be indicated if the cooling system level keeps dropping.
Engine oil with the new markings is now coming on the market. The new classifications were explained in this column in the March 1971 issue of Fire Engineering, page 50.
Diesel filters: Two types of filters are usually provided on the diesel engines. A full-flow filter (strainer) which filters out particles larger than 30 microns (0.0012 inch) to 40 microns (0.0016 inch), depending on the manufacturer of the engine, and a bypass filter which filters out particles larger than 5 microns (0.0002 inch) to 10 microns (0.0004 inch). The bypass filter may be a single or dual element type. However, all bypass filter elements are the throw-away type.
Diesel engines with turbochargers also have a filter that must be changed at each oil change. This is very important. The turbocharger is lubricated under pressure as part of the engine lubricating system. Turbochargers operate at speeds to 48,000 rpm at an engine speed of approximately 2100 rpm, indicating that correct lubrication is essential. When changing the replaceable element filter, be sure the shell is filled with clean oil before the filter and shell are reassembled.
When servicing a turbocharger, check for air leaks indicated by an accumulation of dust at the turbocharger air inlet. A dirty air cleaner element can create such a restriction in the air inlet that vacuum in the air cleaner to turbocharger line can cause a leak at one of the air connections. Dirt entering a turbocharger will damage the turbocharger and the engine. Make sure all air connections to and from the turbocharger are air-tight.
Servicing air cleaner: The air cleaner should be given close attention at this time. If the cleaner is an oil type, make certain that the oil is at proper level and the base is clean. If the cleaner is a dry type, make sure the element is clean and free from pinholes by holding a light inside the element ring and viewing it from the outside. If holes are found, replace the element and make sure the tray is clean.
Inspect the oil line fittings to the turbocharger to be sure there is no leakage. Also, be sure the oil line tubing has no dents restricting oil flow to or from the turbocharger.
Fuel strainers require inspection and cleaning. Diesel fuel systems have a strainer between the fuel tank and the fuel pump. In some cases, it may be in the fuel pump housing as an integral part of the pump assembly. The strainer has a capability of filtering out particles of 30 microns (0.0012 inch) and is usually the replaceable type. Some are ceramic.
The second and most important filter in a diesel fuel system is between the primary fuel pump and the fuel injection pump or the fuel inlet manifold. A fuel injection pump is on 4-cycle engines and an inlet manifold is on 2-cycle engines. The fuel filter is usually a paper element for filtering particles of 10 microns (0.0004 inch) or over, which is necessary to protect the injectors. A careful inspection and replacement is essential at the sixmonth checkup.
New battery ratings: The electrical system requires a careful inspection to avoid embarrassing delays of no-starts in the winter months ahead. If new batteries are needed, the buyer faces a new set of ratings that have no relation to the previous ones.
The Society of Automotive Engineers last year adopted Standard J-537f, which replaces the battery rating at the 20-hour discharge figure. This rating was expressed in amperehours, which was the product of a certain rate of current discharge for 20 hours to completely discharge the battery. There was also a standard for a discharge rate of 300 amperes at 0°F. Now there are two standards.
The first is to check on the cranking power with a minimum of 7.2 volts (for 12-volt battery) at an ambient temperature of 0°F sustained for 30 seconds.
The second standard is an evaluation of the reserve capacity of a battery when the alternator or generator does not charge. This reserve is given as the time required to decrease the terminal voltage below 10.5 volts at a sustained discharge of 25 amperes at an electrolyte temperature of 80°F. This time, expressed in minutes, is also the time for the voltage per cell to drop to 1.75 volts.
For example, a battery rated at 150 ampere-hours at the 20-hour rate, would discharge at a 7.5-ampere rate for 20 hours. The same battery under the new standard would discharge 640 amperes at 0°F ambient temperature for 30 seconds. The same battery would have a rating of 285 minutes for a discharge at 25 amperes before the terminal voltage falls below 10.5 volts.
A battery rated at 200 ampere-hours would now be rated for 900 amperes at 0°F ambient temperature for 30 seconds. It also would be rated at 430 minutes for a discharge of 25 amperes before the terminal voltage drops below 10.5 volts.