Working with heavy construction vehicles is necessarily a noisy endeavour, but that doesn't mean that a contractor shouldn't do all they can to reduce it. Excessive noise levels on a site don't just make conversations more difficult—without proper preventative measures they can damage the hearing of both workers and nearby members of the public, and stiff legal penalties await contractors who run equipment which exceeds legal noise limits.
When a construction vehicle or other piece of heavy plant machinery relies on hydraulic cylinder systems to provide power, the hydraulics can often be the loudest component. However, there are a number of ways you can reduce the noise levels generated by these powerful devices without affecting efficiency or productivity.
In many places where hydraulic systems power static machinery (such as automotive factories) soundproof enclosures are a common sight, and for large, long-term construction projects they can be a great aid when it comes to reducing noise levels from your larger hydraulic machines. These enclosures are essentially large boxes made from sound-insulating materials, and are positioned so that they enclose and isolate noisy hydraulic systems, greatly reducing noise levels outside of the enclosure. However, these structures are large and ungainly, and while some can be constructed on-site around your machinery, pre-fabricated enclosures are expensive and difficult to install. As such they are only a viable option for large builds, where they can be used to deaden sound coming from static cranes and other heavy hydraulic machinery.
Avoiding fluid aeration
If a hydraulic pump makes an alarming knocking or banging noise while functioning, it's likely that it is suffering from aeration problems. If air is allowed into the cylinder it creates air pockets within the viscous hydraulic fluid, which make the characteristic knocking noises as they are compressed and decompressed. These air bubbles can also accelerate degradation of hydraulic fluid and cause serious internal damage to the cylinder, so it's important to keep the cylinder as airtight as possible.
Air can leak into a cylinder from a number of places, but is often introduced into the system by an old or damaged inlet line. Flexible rubberised intake lines are particularly vulnerable to this, as they can perish with age and UV exposure and become porous. You should also check all seals and gaskets for signs of damage or degradation, and make sure that the hydraulic fluid used in your cylinders has appropriate air-releasing additives to impinge the formation of bubbles. In these cases, it is generally best to call in professional hydraulic repair services, as leaks can be small and almost impossible (not to mention dangerous) to detect without specialised equipment.
Another source of knocking noises coming from a hydraulic cylinder is cavitation, and is also caused by air pockets within the cylinder -- however, these pockets are not caused by air leaks, but by insufficient levels of hydraulic fluid. Insufficient fluid causes pockets of extremely low air pressure to form within the cylinder, turning a portion of the hydraulic fluid to vapour with each decompression. This vapour then implodes, causing a loud knocking sound and potentially dealing serious damage and metal erosion to the affected cylinder.
Topping up your hydraulic fluid levels is generally enough to solve this problem, but if your cylinder still knocks it suggests that your system is either losing fluid through leaks or the fluid supply is blocked. There are a number of potential diagnoses here; fluid inlet lines can become clogged by detritus (particularly if fitted with a fluid filter) or simply collapse with age, while isolation valves can fail or vibrate into a closed position to impinge fluid flow. Once again, it is best to call in professional repair services here, particularly if your cylinder requires disassembly to remove a clog or blockage.