Rider bands support the piston while its moving through the cylinder. They are used to correctly position the piston in the cylinder, to prevent metal-to-metal contact between the cylinder wall and the piston. These rider bands wear out over time, which results in a vertical displacement of the piston and the piston rod (the vertical displacement is called rod drop). To prevent damage to the piston and the cylinder wall, the condition of the rider bands should be monitored and this is done by measuring the rod drop.
The RecipSys 200 system is said to deliver accurate real-time data of rider band wear, in so doing is claimed to eliminate the need for periodic shutdowns to do manual rider band wear inspections. The transmitter-based system is affordable and extends the range of compressors that can be monitored. After multiple successful pilot installations, it is now globally available.
The RecipSys 200 offers a flexible alternative for traditional and complex rack-based monitoring systems, which are not solely dedicated to rod drop monitoring. By using a phase triggered signal, as opposed to an overall signal, the transmitter-based system provides unparalleled accuracy and reliability, Istec says.
The rod position is measured by the rod position sensor continuously and this results in a raw rod position sensor. Because of external forces, the rod position is vibrating a lot so this raw signal is not reliable to correlate to the wear of rider bands directly. Therefore it is important to measure the rod position on a specific point of the cycle.
By using a phase trigger, it is possible to measure the rod position every cycle at the same phase angle. This way the raw signal is ‘filtered’. This filtered signal can then be correlated to rider band wear. Other reciprocating compressor systems do have a rod position measurement, but since this is not a ‘phase triggered signal’ (not filtered), it is not reliable to correlate this signal to the wear of rider bands, the company adds.