Compared to a conventional diesel bus, hybrid buses are fundamentally different when it comes to producing the compressed air for the braking and auxiliary systems, as they feature standalone electrically driven compressors. A principal OEM supplier to the hybrid market is Gardner Denver, which supplies its Hydrovane Compressor range to leading bus manufacturers, including ADL, Optare and Wrightbus.
Gardner Denver Hydrovane compressors
Unlike diesel engine-driven compressors that are lubricated and cooled by the engine’s oil circuit, Gardner Denver Hydrovane Compressors have a standalone lubrication system. Also, unlike conventional compressors which are fed air from the engine filter, Hydrovane Compressors have a built-in air filter and therefore require periodic maintenance to ensure extended service life.
Research by supplier of hybrid bus parts, Imperial Engineering, has found that in some instances, these essential checks are not being undertaken, causing problems to occur.
To help detect Compressor problems, the leading PSV parts distributor has identified the basic checks required on routine servicing to increase service life and reduce operating costs:
- Regular oil level checks: Every four weeks is the recommended minimum interval.
The compressors either have a sight glass on the side of the body, or a sensor connected to the CAN system. The oil level must be a minimum of three-quarters full on the sight glass at zero pressure. The sensor connected to the CAN system will display a warning on the dashboard if oil requires topping up, but it is also important to check the condition of the sensor/wiring during routine checks. - Sufficient air flow across the compressor is important to prevent overheating.
Ensure there are no obstructions blocking the air flow and no excess debris build-up on the compressor’s cooling matrix (air cooled versions). - Check for any leaks in the air system, as they can increase the duty cycle of the compressor. Repair any leaks in the air system.
- Check for excess oil carryover by visually inspecting air valves downstream.
Carryover can be related to one of the following:- Oil separator cartridge or the separator air dryer unit cartridge requires changing
- Compressor has excess oil
- Due to the internal workings, it is essential to use the correct oil, Gardner Denver oil specification HPO-198.
- Ensure the Hydrovane Compressor is not running hot!
Common hot running causes include:
- Low oil level
- Obstructed air flow
- Blocked intake filter
- Blocked air dryer or oil separator cartridge
Imperial Engineering has introduced a range of service kits to make servicing of Gardner Denver Hydrovane Compressor easier and more cost-effective, which include OE filters and HPO-198 compressor oil. OE bus parts specialist Imperial Engineering has a wealth of compressor system knowledge and works closely with Gardner Denver and approved service centre, PSI Compressors, to support operators with technical advice and guidance. For further information, please call 01992 634255, email enquiries@imperialengineering.co.uk
