Box Pins - insure that they are well greased and not cracked, broken, or loose. Loosing a box pin could allow the box and / or truck to fall over while dumping.
Tailgate - check that it fits tight and material can not leak out. High lift tailgate is needed on gravel transfer unit to allow loading of trailer into truck. video
Tires - check often for rocks between dual tires. Severe damage or loss of both tires can and has happened. Side walls are sliced and tires ruined. Some operators will carry a chain to remove rocks in tires. Wrap chain around rock then attach to solid place on truck. Backing up slowly will usually pull the rock out. If rock is jammed badly, it is recommended to deflate or remove tire if needed. If big sharp points are deeply jammed into sidewall, then it is probably best not to try and pull it out.
Hydraulic Ram - insure pins on both ends are lubricated and mounts are not cracked. Air can get into hydraulic system making the hoist operate erratically. Bouncing or slow operation are common signs. Most system have a bleed point to allow escape of trapped air. This could happen after a maintenance fix or other issue. The hoist can be raised a few feet then an inspection cap is usually removed on top of box hoist allowing access to the bleed screw. Slowly opening the bleed screw releases trapped air, and the gravel box will lower. Insure this is done in a safe manner. Wear eye protection and make sure work area is clear. If air continues to build in system then it probably a sign that there is other problems with the hydraulic system.
Packing needs to be inspected routinely. Most gravel trailer rams will have from 3 - 5 stages. A gravel truck usually will have 3 - 4 stages. Packing caps will have a lock such as an Allen screw to keep it tight. Some have been know to come loose and the lock ring will back off. This will usually result in a leak. If backed right off, the ram could pull apart creating a big equipment failure and possible safety hazard. A bent ram will also jam up and the gravel trailer will not function correctly.
Wheels and Frame - take a lot of pounding and stress. Check for cracks between the wheel stud holes. This is often the first place fatigue will show. Loosing a wheel can be very dangerous and has resulted in death. A 200 pound tire loose is like a cannon hitting a car. It has happened numerous times. Mandatory inspections has greatly reduced incidents but still needs to be watched carefully. If you are an equipment operator for any length of time, you know some equipment takes a brutal beating, if even by accident.
(we all know that person that you would not let run your wheel barrow, let alone equipment!)
Dumping on level ground is always recommended. Many job sites may not allow it but, great care is needed when raising the box at an angle. Material stuck in the top can easily topple a gravel trailer or gravel truck. When the box is raised, all the weight is transferred onto the back of the truck. The ground should be firm where the truck or trailer is sitting.
Power Lines - hazard for many equipment operators. Sometimes over looked and have caused many incidents. Look up and around your job site. If working with others, bring any hazard to their attention also. If they have a problem, it could well affect the whole job site and come back to affect your ability to work later. The sooner a problem is addressed, the better.
Hitches and Attachments - inspect for cracked or loose bolts. Make sure it is rated for the weight to pull. 5th wheel pins wear after time. The grease and dirt combine to act like a grind stone on the steel. Heavier loads will also increase pin and 5th wheel locking jaw wear. Also the tilt pins on 5th wheel deck plate should be examined often. If equipment has a sliding 5th wheel attachment, make sure it is clear of dirt and foreign material before use. It may not lock properly if dirty. There is rebuilt kits available for most 5th wheel brands. A trailer pin change will have to be done by a qualified welder and inspected.
Side Board - although not all equipment allows the use of side boards, they are a good cheap investment. Increased box height is also needed for some material. Having a side board gives some protection while loading. A loader or backhoe will often hit the gravel box or trailer with their bucket or material falls off. The side board will take the blunt of the beating saving the sides of the gravel box. Use a strong but cheap material for your side boards. Some experienced operators will have a few spare side boards ready. Depending on the job or operators, they know they will be needed.
Cover Tarp - come in many makes and models. The first models were mainly all hand driven with a winch and cables. Today air and electrically tarp systems are installed on most new gravel trailers. They are cab controlled allowing the operator faster and easier operation.
Electric Connections - often get pinched or broken. Rocks batter the electrical cords or they get pinched while dumping. Jack-knife is needed to dump a pony trailer in a pile. Tires can hit or bend the reach on trailer. Be careful not to jack knife too far. Mudflaps on back of truck are often ripped off this way. Some gravel equipment operators will have removable flaps or a means to tie them up. Then they can lowered or installed when road travel is needed.
Wiring is prone to corrosion especially where salt is used on roads. Some equipment operators take a page out of the "boaters book" and install zinc erosion blocks on their gravel equipment. The electrolysis is drawn to the zinc and greatly slows wiring problems.