Common Post-Tension Equipment Issues

Post-tension equipment is exposed to heavy-duty cycling in dirty, occasionally wet conditions, which means that equipment issues are expected. The question is how to identify and correct them.

Here’s a general approach to each:

• Loss or decline in power delivery – Your post-tension jacks should stroke fully and smoothly to allow for safe operation. When a hydraulic jack no longer does so, the reason is often a hydraulic fluid leak. First, check the hydraulic pump’s reservoir to verify adequate fluid levels.

  Next, inspect all post-tension equipment for fluid leaks. They can emerge from anywhere in the system, but leaks are most common around the hydraulic pump or cylinder. Check all fastening hardware, the bleeder valve, the pump body and any connections. The hydraulic jack’s cylinders are where you are most likely to see a leak spring on the jack. Check all hardware connected to the jack and the cylinder bodies. If the hydraulic pump and jacks are ruled out, inspect the hoses, filters, manifolds and all other in-line components.

Other common causes of hydraulic equipment power loss include fluid contamination, valve failures, overheating system components and improper system calibration.

• Cavitation or aeration – Cavitation and aeration are not the same thing, though they are loosely related. Aeration refers to the presence of air in the hydraulic fluid. Cavitation is the formation of vacuum “bubbles” that rupture and cause damage in the process. Both are bad for a post-tension system.

  Aeration is frequently caused by air leaks in the hydraulic pump’s seals and fittings. Aeration may also be caused by inadequate fluid levels, as air is drawn into the suction strainer without enough fluid to take in.

  Aeration adversely affects the hydraulic fluid’s properties, including its ability to manage heat and flow properly. This can lead to overheating and excessive component wear. To prevent aeration, check for any loose connections, check fluid levels, look for clogged filters or a breather vent, and verify the pump’s speed is correctly set.

  Cavitation is the product of inadequate fluid supply – which leads to pressure drops and the formation of gas bubbles. When these rupture, the resulting “hammer” will cause surface damage and wear to nearby components. It can emerge anywhere the system’s flow is restricted, but it’s most often present at the hydraulic pump. Pay special attention to the pump’s inlet and suction line. If these are restricted, it will alter the fluid’s velocity and, by extension, its thermal properties. This may fuel ongoing cavitation issues.

• Excessive component wear – If you’re noticing that certain post-tension system components need replacement or maintenance more often than is considered normal, it could be due to issues with the system itself.

  Hydraulic pumps and cylinders are the most likely spots for excessive component wear. Cavitation or aeration inside the pump may be why pump parts are failing early. The post-tension jack’s cylinders are where excessive wear is most likely to be seen. As these are responsible for the system’s force application, any issues with the cylinders can lead to extreme failure.

  The cylinder bodies will need to be opened to inspect the piston barrel, as poor piston alignment and failing seals are two of the most common reasons for early system failure. Look for wear along the inside surfaces of the piston barrel and for signs of wear on the piston rod, too.

• Damaged or failing seals – When post-tension systems go bad, it’s often the seals behind the failure. It is the post-tension jack where seals are likely to be a problem – the hydraulic cylinders, to be exact.

  The wiper seal, rod seal and piston seal are the ones to check, as failures here can lead to quickly worsening issues. The wiper seal, for instance, is responsible for keeping contaminants from entering the system, so contamination will immediately become a problem if the seal fails.

  To replace the seals, the worn ones will first need to be removed and the seal grooves cleaned out. This may take a level of hydraulic equipment expertise that many jack operators don’t possess, which makes partnering with a hydraulic equipment expert invaluable.