Oil and gas equalisation between crankcases

For compressors with small to medium capacity, previously oil and gas equalisation between crankcases was frequently selected. This is a low-cost option, but has decisive drawbacks: Due to the pipe joint between the crankcases, suction gas (in the bypass) will keep flowing also through shut-off compressors. Under unfavourable conditions, this may lead to the migration of oil into compressors that are in operation. This can result in faults to the oil balance and to damage to the compressor ‒ a pressure differential of as little as 0.01 bar corresponds to an oil level difference of approximately 11 cm. This is why in particular the methods described below are recommended (Parallel compounding with optimized suction header, Parallel compounding with oil level controllers).

Bitzer compressors of series BE5 and BE6 (4JE-13 .. 6FE-50) can be designed with separate, generously sized oil and gas equalising lines between the crankcases. Suitable connections are available as standard (see operating instructions KB-100) and suitable adaptors are available as accessories. The connecting lines should be kept as short as possible. Deviations from the exactly straight horizontal connection by slight bends are allowed in the gas equalising line only upwards and in the oil equalising line only downwards. However, in view of the remarks made above, this version, too, is rather suitable for systems which (on the basis of practical experience and tests) are built either as standard or at least repeatedly.