There are many types of annual inspection.

Some maintenance staff only carry out the instructions of the compressor block manufacturer. We need to realise that the compressor block is just one part of a whole compressor unit. The manual instructions are only a guideline. Important user information fulfills the balanced maintenance plan. Effects like the start-stop cylus-part load or VSD drive can make a big difference in maintenance. It may not sound logical, but a compressor in 24-hour operation needs less maintenance than an installation that operates only 2000 hours a year with twice the number of stops and starts.

The capacity of most fixed-drive speed compressors is controlled by creating an internal leak in the compressor. The design is calculated on a working condition of roughly -35/+35°C.

Usually a compressor is designed to work at full load (100%) capacity. In reality, however, most compressors operate at part load capacity.

The compressor is the heart of the refrigeration system. In order to sustain its efficiency and low operating costs, it must be properly lubricated. The lubricant in an ammonia compressor must provide protection against friction and wear, and also serve as a coolant.

The majority of compressors used in refrigeration systems are oil-injected. Sometimes a compressor unit shows higher oil consumption than calculated.

Over the last five years we have investigated the most common causes of oil carryover. During our field investigations, we noted interesting findings related to oil carry over. We found that older compressor installations started to show more oil consumption than they had originally demonstrated.

The most common reason for shaft seal failure is blistering. Blisters form unexpectedly and degrade the surface of the seal face, causing irregularities in the  running area and resulting in poor performance -- higher leak rates and higher friction -- causing failure of the shaft seal.