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Christian P. Koop |
I recently wrote an article on basic preventive maintenance (PM) and how important it is for apparatus operators to perform their required daily and weekly inspections properly.
By properly, I mean conscientiously performing all the checks on the list and no pencil whipping. Statistically, apparatus operators should be able to find approximately 30 percent of all potential problems before they become issues that would ultimately be more costly to address later or that could cause a breakdown or a failure of some sort. Because of this, apparatus operators are the first vital link in the PM chain, and the success of the PM program relies heavily on dedicated, conscientious apparatus operators.
The same concept applies to apparatus aerial devices. In this article, I will address some points about aerial device operation, maintenance, inspections, and safe operation. These can apply to both the apparatus operators as well as emergency vehicle technicians (EVTs). I will also include some important recommendations from NFPA 1911, Standard for the Inspection, Maintenance, Testing, and Retirement of In-Service Automotive Fire Apparatus, which includes all aerial devices. But, first let me give you a little background information that should help you understand what has helped to shape my perspective on this very important and critical area, particularly one that can affect the life safety of those using the equipment and of others who are on or nearby during aerial operation.
Physics
More than 20 years ago, I spent a weekend attending a seminar in North Florida named “Aerial Dynamics” that dealt with the physics of aerials. The seminar was designed for not only those involved in purchasing but also for aerial apparatus engineers (operators) and the EVTs who maintain them. The instructor was James Burrell, PhD, a college physics professor affiliated with the International Association of Fire Chiefs (IAFC) and the National Institute of Emergency Vehicle Safety (EVS). The seminar was a condensed version of a 40-hour course that covered aerial design, equilibrium (stability), torque, characteristics of the different materials (metals and alloys) used in construction of aerials, stress vs. strain, the different modes of material failure, stabilizers, turntables, bolts and other fasteners, physical inspection, and the nondestructive testing (NDT) generally accomplished by a third party.
Burrell was heavily involved with the study of physics and how it applies to aerial ladders, platforms, and articulated booms. He pointed out, from a physics standpoint, that aerial devices are essentially structures divided into two categories: the entire structure itself and the members that compose it. Second, the main concepts of physics that apply to aerials are stability of the structure (aerial) and how a dynamic force (starting and stopping motions) imposed during aerial operation stresses and affects the different materials and components that make up the device. His main point was that there are no perfect aerial designs or materials, and they all will wear out and eventually fail. The biggest measure of prevention against this is to be aware of this and to properly educate all involved to help pinpoint and address issues before they cause a failure. His course also delved into center of gravity, static and dynamic forces, kinetic energy, momentum and impulse, nozzle reaction, equilibrium, and how these affect aerial devices. He also taught some of the mathematical equations necessary to calculate how these forces affect aerials.
I am sure many reading this have heard of horrific cases where aerial devices overturned because of operator error and even by experienced operators. Many accidents have also resulted from poor design and manufacturing defects that have since been addressed by improvements in design, materials, and electronic interlocks. The newest of these interlocks has considerably improved aerial devices to reduce the possibility of operator-error incidents. However, there are many older aerials still in service that do not have these modern improvements and that rely heavily on the operator’s knowledge and understanding of an aerial’s physical limitations. Some accidents could have been avoided if operators fully understood physical concepts and how they affect the aerial device they operate. This is not to say that all operators are not aware of these factors. However, I firmly believe this is where properly trained, certified apparatus operators and EVTs who fully understand these important concepts will make a positive difference in your organization because they can save dollars and potentially save lives.
Keep in mind also that the forces imposed on an aerial device while it is being driven down the road will also cause wear. The latest information I have heard on this states that more than 80 percent of aerial device wear and damage can be caused by road shock in high-mileage units. For example, the area of the ladder directly in contact with the cradle, when bedded for road travel, can be affected by ironing-also known as cold working steel-particularly if the ladder is not bedded with sufficient hydraulic force to keep it from bouncing in the cradle as the vehicle traverses bumps in the road. The affected metal in this area will become hardened and brittle and can fail later.
Aerial Checks
For daily and weekly inspections, use a systematic approach and use the checklist the manufacturer provides. Be sure to check and operate each item listed. It is very important to follow the checklist and to not skip any items. Be vigilant and look for cracks at all weld points along the entire aerial, the turntable, and the stabilizers. Report any for further inspection by a qualified EVT.
During aerial operation, the operator must pay attention to the speed and smoothness of all functions. If the device is equipped with a prepiped waterway, remember to keep it clean of dirt, sand, and grit and to wipe it down with oil according to the manufacturer’s recommendation. Failure to do this on a regular basis can cause water seal failure and can score the waterway, which will be expensive to repair. I have also seen it cause chatter (vibration) during extension and retraction if it is not properly lubricated.
Yet another component that needs special attention is the sliding monitor if you have it on your rig. These monitors are designed to be pinned back or locked several yards back from the ladder tip to allow the ladder tip to rest against a building safely without damaging the waterway or nozzle. This is also known as “rescue mode” when the monitor is placed at the lower position vs. “firefighting mode” when the monitor is pinned or locked at the ladder tip. My point here is to make sure the device is operating smoothly and is not damaged in any way. Ensure the locking device-whether it is a pin type or lever lock-is working correctly. If you flow water in rescue mode, ensure the monitor is firmly locked into position. If it is not, water pressure can force it up to the tip of the aerial with such great force it can cause serious damage to the ladder or even break away from the ladder tip. Over the years, I have seen many damaged sliding monitor assemblies from improper use.
This brings to mind an unfortunate incident that happened a few years ago. A fire chief was killed on a fireground because a monitor flew off the ladder tip and landed directly on top of him. I bring this up only to make sure those reading understand how important it is to ensure these devices are operating properly and firmly locked into position. If not, they need to be inspected and repaired by an EVT.
Make sure all slides, pads, and guides that require grease are properly lubricated and not worn. Pay special attention to electrical harness guides, sheaves, and tracks to make sure nothing is out of alignment, binding, or broken. Look for cracks in electrical harness outer jackets and make sure there are no bare wires exposed. During operation, pay attention to the ladder sections and ensure they go up evenly and smoothly and are properly aligned. Any alignment issues are generally because of cables that are not properly adjusted. Cables will stretch with time, so departments must maintain proper adjustment. Ensure there are no hydraulic leaks at any of the hoses, hydraulic cylinders, or valves and that hydraulic hoses are not showing signs of weathering or outer jacket cracking.
Other Considerations
Operating an aerial smoothly by feathering the controls to eliminate harsh and jerky movements-whether they are direct hydraulic or electric over hydraulic-is very important. This will go a long way toward reducing the great dynamic forces developed during rough operation, which will stress and eventually cause damage to an aerial device and to the components it is bolted to such as the turntable, torque box, and the fasteners that hold everything together. It is also important to monitor the hydraulic pressure gauge at the control panel while performing various functions and noting the normal operating pressures. This information will prove helpful for EVTs in the event of a hydraulic problem during diagnosis.
Corrosion and rust are other enemies of the aerial device and must be addressed before they cause serious damage. This is where vigilant and conscientious operators and EVTs come into play. If they are doing the inspections correctly, they should be able to find these issues before they become major problems. If rust or corrosion is left unchecked in critical areas, it can cause stress risers that can cause eventual failure. Most manufacturers have made huge improvements in this area with better options for protecting steel aerials, such as galvanizing and powder coating, and with better quality primers and paints that are very rust- and corrosion-resistant.
NFPA 1911 Criteria
According to NFPA 1911, if there are any missing or broken fasteners in the turntable or torque box, this will require the aerial device to be placed out of service. If bolts are found to be loose in these areas, most manufacturers recommend replacement rather than retorquing. Additionally, keep in mind that all the structural fasteners for the device are required to be certified under the Society of Automotive Engineers (SAE) grade 8. There have been cases where counterfeit bolts were being sold mismarked as SAE grade 8 but in fact were grade 8.2. There is a large difference in the heat treatment process between these two grades, correlating to a difference in the yield strength and ultimate strength of these fasteners. If these bolts end up in critical areas such as the turntable and torque box, they could potentially fail. A failure in these critical areas could spell disaster. So, make sure you are purchasing SAE-certified grade 8 fasteners from a reputable source. While on the subject of materials, keep in mind that aluminum (6061 T-6) loses its hardness or becomes annealed at a relatively low temperature, and welding on it can lower its mechanical properties unless it is heat-treated back to T-6 properties after welding.
Other NFPA 1911 out-of-service criteria are obvious but include a power take-off (PTO) that will not engage, a stabilizer system that is inoperative, an aerial device that is inoperative, hydraulic components that are not operational, cable sheaves that are not operational or not rotating as they should, frayed cables, and any deformity of the aerial device. NFPA 1911 also has a list of deficiencies that will require an EVT to conduct an out-of-service evaluation and subsequent written report. They are the hydraulic relief valve, hydraulic components, emergency hydraulic backup system, visual and audible alarms, lighting system, intercom system, warning signs and labels, water delivery, and the water delivery system.
Nondestructive Testing (NDT)
NFPA 1911 also requires performance testing of all aerial devices, and these tests are to be done annually, after major repairs, when the device has been subjected to unusual stress or load, or even if there is reason to believe the aerial device has exceeded the manufacturer’s recommended aerial device operating procedures. NFPA 1911 also recommends NDT every five years, when visual inspection spots a potential structural problem and if someone in the organization just wants to confirm that the ladder is safe for continued use.
If a third-party testing agency is used for NDT, which is customary with most fire departments, NFPA 1911 recommends the company be accredited under the requirements of ISO/IEC 17020. These are requirements for various types of organizations that provide these types of services and inspections and are in place to ensure testing is performed by accredited agencies, to standards, and by trained and certified NDT technicians. The required tests are all listed in NFPA 1911. They include load testing, hydraulic cylinder drift tests, time test requirements for deploying the stabilizers and the aerial device, and a host of other tests and inspections.
They also look for cracks in the aerial, welds, torque box, turntable, stabilizers, and fasteners by employing methods that must be consistent with ASTM E 1316, Standard Terminology for Nondestructive Testing. The tests the NDT technician employs also depend on an aerial device’s construction material and include the ultrasonic pulse-echo straight beam by contact method, manual ultrasonic for measuring thickness, magnetic particle inspection, liquid-penetrate inspection (three types used to find cracks in aluminum), hardness testing (five different types of tests), acoustics emissions testing (two types), and eddy current testing (determines electrical conductivity).
On Operators’ Shoulders
I feel it is extremely important to teach and train aerial operators to perform the daily and weekly inspections required by aerial manufacturers and to aggressively look for potential problem areas before failure. Having qualified, dedicated, conscientious, and vigilant operators as well as certified EVTs can prevent possible catastrophic aerial failures by spotting the telltale signs that can lead to them. Most in this field have probably heard of or have even seen serious aerial accidents caused by either failure to operate the aerial within its design limitations or by structural failure. That is why I feel courses that cover the physical limitations of aerial devices from a physics standpoint would be highly beneficial.
Any time an apparatus operator or an EVT can spot a problem before it causes a breakdown or failure, you are ahead of the game. Not only will this practice reduce equipment downtime, it will also positively affect safe operation and response time, potentially save lives, and improve the bottom line of any organization while at the same time greatly reducing liability exposure.
CHRISTIAN P. KOOP is the fleet manager for the Miami-Dade (FL) Fire Department. He has been involved in the repair and maintenance of autos, heavy equipment, and emergency response vehicles for the past 35 years. He has an associate degree from Central Texas College and a bachelor’s degree in public administration from Barry University and has taken course work in basic and digital electronics. He is an ASE-certified master auto/heavy truck technician and master EVT apparatus and ambulance technician. He is a member of the board of directors of EVTCC and FAEVT and a technical committee member for NFPA 1071, Standard for Emergency Vehicle Technician Professional Qualifications.
