Via a temporary PROGNOST®-NT Swift system to a permanent PROGNOST®-NT compressor condition monitoring system

In order to get to the bottom of the problems on a Hyper Compressor, a company in the LDPE industry approached PROGNOST with the question, would the PROGNOST system have detected the damage on a central screw? As a first step to get to the bottom of this question or to prove the answer, it was decided to install a temporary PROGNOST®-NT Swift system to monitor this machine. After the successful deployment of the PROGNOST®-NT Swift rental condition monitoring system, and thanks to the perceived benefits of having a monitoring system with 24/7 diagnostic support, the company decided finally to go for a permanent PROGNOST®-NT installation. This will be used to monitor all six critical machines.

Customer challenges

Damage to and problems with compressors have increased. Therefore, the company was looking for a suitable monitoring system to prevent hazards for people and machines.

Solutions in this compressor condition monitoring project

In the first step, a temporary PROGNOST-®-NT Swift condition monitoring system was installed for one machine at the customer’s request. After its successful use and the positive experience gained, the implementation of a permanent PROGNOST®-NT condition monitoring system on six machines followed.

Insights from the Case Study

• PROGNOST systems protect the machine with the limit values specified by the machine manufacturer.
• Individual limit value adjustments to the respective machine type and application improve machine protection.
• Limits that are set too tightly increase the risk of false alarms.
• It is important to set the system correctly to protect the machines in the event of damage, but also to avoid false alarms.

The customer’s challenge and PROGNOST’s corresponding solutions are explained in more detail below.

Temporary compressor condition monitoring with the PROGNOST®-NT Swift System for a Hyper Compressor

During machine maintenance, the customer discovered a defect in an older eight-cylinder hyper compressor (built in 1971). The compressor has an output of 6800 kW and operates at a rather slow speed of 186 rpm.
In order to better monitor the machine and detect renewed problems at an early stage, the company was looking for a monitoring solution. They decided to cooperate with PROGNOST. After initial discussions, a temporary PROGNOST®-NT Swift system was initially installed for a period of seven months. This type of monitoring system is quickly available and is not comparable to a permanent installation in terms of installation effort. Therefore, the Swift system is ideally suited as a temporary solution or even for a performance test. It collects and analyzes data in the same way as a permanent PROGNOST®-NT system.

Due to the system performance, the reliable analysis and the service package offered, the company decided to replace the temporary installation with a permanent PROGNOST®-NT monitoring system and expand to six machines.

Expansion to permanent compressor condition monitoring by a PROGNOST®-NT system for a total of six machines

The permanent compressor condition monitoring installation includes two Hyper compressors and four piston compressors. The collected and analyzed data of the temporary Swift system from the past seven months are transferred to the PROGNOST®-NT system for individual limit setting.

The permanent installation of the condition monitoring system for the six machines consists of:

• vier PROGNOST®-SILver Racks,

• four PROGNOST®-SILver racks,
• four PROGNOST®-NT monitoring units and
• two PROGNOST®-NT communication servers.

Example machine incident on reciprocating compressor

The PROGNOST monitoring system showed high vibrations in the vibration signals of the first cylinder of the 1971 compressor. The reciprocating compressor has an output of 820 kW (1115 hp) and operates at a speed of approx. 296 rpm.

The customer was informed about the high vibrations by PROGNOST’s customer service and first checked the individual mechanical connections. However, no problems could be detected on the machine here.

After a further signal check and more detailed analysis, everything still pointed to a machine problem. In the next step of the check, the affected valves of the cylinder were replaced by the customer and the machine was restarted. The vibration signals then returned to normal.

This particular application example shows that the problem was in the vibration signal of the machine. The signal analysis on the reciprocating compressor is based on a time signal and not on a frequency analysis. Solving a problem is more complex because the reason is not directly visible to the naked eye. Therefore, the system offers some options for operators, including automatic early fault detection based on a fault pattern database and signal analysis by PROGNOST customer service or an employee on site.

Pressure sensors, for example, can also be used to support the vibration signal analysis. These are not used for a machine shutdown, but the measured pressure signals show very well the working process of a machine. For example, it is possible to observe exactly which valve is working at the moment of increased vibration. In the analysis, empirical values play an important role in determining whether the vibration and pressure signals indicate a problematic or a normal operating condition. The protection limits in the PROGNOST system are set on the basis of these empirical values and individually to the respective machine behavior.

Example machine incident on a Hyper Compressor

The customer contacted PROGNOST’s customer service after one of the monitored Hyper compressors was shut down by an alarm. About the compressor, it has a power of 5880 kW (7997 hp) and runs at a speed of 187 rpm. After detailed signal analysis through our analysis experts, it appeared that the machine was stopped due to a machine protection alarm. Critical vibration values were detected at several points in the machine:

• Strong vibration values were measured inside the fifth cylinder. Only minor vibrations were measured on the outside of the cylinder.
• Smaller vibrations were also measured on the inside of the sixth and seventh cylinders.
• Between the first and the third bearing of the crankshaft, there were increased vibration signals at the same point of rotation.

The PROGNOST system was able to narrow down the area of the vibrations to the fifth cylinder. The customer then found a broken piston in cylinder five as the reason for the high vibrations. After replacing the piston, the machine was working properly again.

Generally, PROGNOST’s systems are initially preset based on the machine manufacturer’s protection limits. However, each machine works individually. The protection limits must be individually adjusted for each machine based on collected values over a longer period of time.

• Individually tighter configured protection limits allow an earlier shutdown of the machine.
• Basically, the shutdown works with the pre-configured protection limits in the PROGNOST®-NT system.

As this case study shows, the PROGNOST®-NT monitoring system can help protect machines and ensure smooth and reliable machine monitoring.

We will be happy to support you in finding a suitable monitoring system for your machines.