It is required to evaluate the condition of screw compressors and Roots blowers with vibration measurements for many European manufacturers, customers and users. This is the main task of the VDI 3836 guideline.

The vibration measuring procedure is very efficient in indicating whether the condition of the machine is worsening. However, it is not a 100% safety check and is not possible if the machine fails all of a sudden. One of the reasons for this is that cyclic measurements, where quick damage development takes place between two measuring periods, is very difficult. Also defects resulting from improper machine operation and machine overload cannot be forecasted.

Even if vibration measuring procedures are the best means for early detection of roller bearing damages, the general problem is that failure-relevant vibrations are being superposed by “natural” machine noises.

The difficulty of the vibration analysis of screw compressors and positive displacement blowers is to exclude the interfering pressure pulsation vibrations upon evaluation of the vibration intensity. This is obtained with the configuration of the evaluation parameter.

The VDI 3836 guideline provides remarks about fairs and the evaluation of vibrations of two-shaft positive displacement machines (screw compressors and roots blowers), and about measurements that are carried out by non-rotating and/or rotating parts of such machines during operation mode.

Evaluation of the machine condition by means of vibration measurements / machine diagnosis

Measurement and evaluation of vibrations with screw compressors and positive displacement blowers according to VDI 3836 (DIN ISO 10816 – 1 / 3)

• Intake of measuring data and evaluation
• Result discussion and optimisation proposal with quotation
• Identification of the critical machines
• Development of the data bank and the route
• Collection of data
• Inspection of data for irregularities / alarm

Vibration measurement

The vibration measurements are carried out with a vibration measuring device, type B1910
analyser (Messrs. CSI) – resp. with the analyser, type 6230, with the sensor
A0720GP – serial no. P30649.
This device fulfils the following standards:

• EN 50081-2: 1994
• EN 50082-2: 1995
• EN 61010-1: 1993

The measurements are recorded as narrow band analyses.