Abrupt failures demand automatic shutdown

But what if operators are reluctant to utilize all capabilities - the entire technological horsepower of their systems, for example, automatic shutdown functionality? Many systems are not set to automatically trip a machine in case of a critical event.

Quite a substantial percentage of operators we have talked to over the last two decades have more confidence in a slow chain of reporting with a manual machine stop at its end than in a super-fast, automatic shutdown feature. One incident topped it all.

The monitoring system sent alarm notifications over all configured channels, such as email, sms and fax. Ultimately, the shutdown alarm was recognized in the control room because the fax machine beeped constantly due to a paper jam due from the continuous printing of alarm notifications sent by the monitoring system. With a delay of several minutes after the first safety limit violations, the compressor was shut down manually.

This case study describes the detection of an abrupt event on a reciprocating compressor as an example of how important activated, automatic shutdown functions are. The operator of the reciprocating compressor is located in northern Germany.

lt is an underground natural gas storage facililty that operates four compressors to inject and store the gas until winter. The article showcases the sequence of a piston rod breakage based on monitoring data and findings after the inspection of the affected machine.

One day, the our customer support department in Rheine, Germany, received a hotline call from the customer’s control room. The customer requested the verification of the signals recorded because of an automatic machine shutdown.

The monitoring system detected a catastrophic piston rod failure at 08:07:26 AM and triggered an automatic shutdown of the machine. Only four seconds later, the compressor was stopped (rpm = 0) and consequential damages were avoided.

The piston rod failure was abrupt with zero early indications. The analyzed crosshead RMS vibration (36 segments = 360° crank angle = 1 revolution) and the piston rod position peak-to-peak value (eight segments) was displayed over one hour in a 3D waterfall view.

For a detailed analysis, it is necessary to examine the signals revolution by revolution to understand the sequence of this event. The revolution-based analysis is possible with the ring buffer, which is automatically triggered, records all signals and analyzes subsequent root causes. This enables the machine operator to determine the failure – with all information recorded seven minutes before and three minutes alter this event (here: 1000 revolutions).

The case study illustrates, based on an automatic trip at a decisive moment with no human interaction, how important it is to protect a machine with a modern monitoring technology to detect abrupt failures. An automatic shutdown based on proven reliable analyses makes it possible to stop machines without wasting time and with no consequential damage.

lt is also important to set the safety limits individually per measuring point. Even if one probe is defective, for whatever reason, other probes take over and shut down the compressor. Close cooperation of all parties involved allows efficient root cause analysis and focused maintenance measures.

The integrated ring buffer enables the operator to have directed repair activities; the affected cylinder was identified in a glance and the failure mode pinpointed based on the ring buffer data.