Gas compressor installation and maintenance

Compressed gas is used everywhere. While there are several different types of compressors to pressurize gas, here we will talk about the reciprocating type which is widely used in all types of industry. Laser measurement and alignment of these types of compressors is essential both during the installation phase and to ensure reliable operation for many years.

Compressor package installation

Manufacturers of large reciprocating compressors have clear guidelines for how the equipment should be installed and maintained for best performance. And with laser alignment equipment, you can perform 90% of the measurements that are required:

  • Measure flatness and level of foundation and compressor and driver sole plates.
  • Check soft foot of compressor and driver.
  • Perform shaft alignment between driver and compressor.
  • Perform bore alignment verification:

    – Measure flatness and level of the top plane of the compressor frame.
    – Check main bearing and connecting rod bearing clearance.
    – Check connecting rod and crankshaft thrust clearance.

  • Measure engine thrust.
  • Perform dynamic measurement to check thermal expansion and pipe strain.
  • And more.

All this can be done with a single system, the Easy-Laser® XT770 Shaft+GEO, which gives the technician full control of the whole process. After installation you need to perform these checks with regular intervals.

Machine foundation with sole plates
Foundation with sole plates

Foundation flatness and level

For any machine that contains rotating parts, it is essential that the foundation on which the machine is placed is completely flat and level. To perform this type of measurements, the Flatness program should be used together with the XT20 or XT22 laser transmitter and the XT70 measuring unit. 

The Flatness program.
The Flatness program. Select between All points negative, All points positive, Best fit around zero, or custom reference points.

Soft foot check and shaft alignment

Soft foot is a condition that must be avoided, since it can cause great damage to bearings, shafts, and other parts of the machine. The occurrence of soft foot can be detected within the Shaft alignment program. Once you have checked and taken the necessary action to fix any soft foot problem, shaft alignment between the driver and compressor can take place using the XT770 shaft alignment equipment.

Learn more: The four different types of soft foot.

Shaft alignment program
Shaft alignment program.

Main bearing bore alignment

The mounting surface of the top cover on a compressor frame is precision-manufactured to be flat and aligned with the main bearing bores and the bottom of the compressor feet. To ensure the best running conditions for the compressor main bearing and crank shaft, it is important to measure this surface, so it is aligned within the recommended tolerances.

The mounting surface essentially consists of two rails which are measured using the XT20 or XT22 laser transmitter and the Flatness program (the same as when measuring the foundation). The number of points you need to measure is determined by the compressor manufacturer.

Setting up the laser equipment for flatness measurement of the top cover rails.
Setting up the laser equipment for flatness measurement of the top cover rails.

Checking of clearance and thrust

Bearing clearance refers to the space between the shaft and the bearing surface which is filled with lubricating oil. It’s important to keep this within tolerance to avoid bearing failure. On the compressor, we need to measure the main bearing clearance and the connecting rod bearing clearance. The clearance space is measured by lifting the shaft/rod and measuring the gap.

Measurement of main bearing clearance.
Measuring main bearing clearance.

We also need to check that there is no excessive thrust in the crankshaft or connecting rod, which could cause serious damage to bearings, pistons, or other components. We do this by measuring the horizontal movement. We mount the detectors, set them to zero and then by using a prey bar, we force the crank shaft to move axially to its end. Then we record the travel which is our clearance. Engine thrust is measured in the same way.

Checking crank shaft thrust.
Checking crank shaft thrust.

Measure machine movement

A dynamic measurement is conducted while the machine is running, to check whether there are any external forces that can have a negative effect on machine performance. This can be for example pipe strain or thermal growth. A dynamic measurement check is done using special brackets and the EasyTrend program. The brackets are placed on the machine and measurement values are recorded during a set period of time. This will reveal if there is any unwanted angle or offset movements that need to be corrected.  

Dynamic measurement curve.
Dynamic measurement curve.

Continued maintenance for optimal performance

Once all measurements and adjustments have been made and the compressor is up and running, it is important to establish a routine for regular maintenance. Large compressor manufacturers recommend that you perform bore alignment verification, engine thrust measurement, shaft alignment and dynamic measurement every 4000 hours. And every 8000 hours you need to do an even more thorough check. Be sure to always follow the manufacturer’s recommendations. And if you have any questions, don’t hesitate to contact us!