If a reciprocating air compressor has a knock occurring in frequency with its operating RPM, the cause is probably _____.

A．misalignment or worn main bearings

B．insufficient cylinder lubrication

C．defective or poorly fitted valves

D．All of the above

[单选题]The loss of （） from an air compressor could lead to an overheated air discharge and possibly an explosion in the pipelines leading to the air reservoir.A . lubricating oilB . compressed airC . cooling waterD . sealing ring

[单选题]The starting air system usually has （） to prevent starting if anything is not in order.A . stop valvesB . interlocksC . non-return valvesD . air vent

[多选题]The combination of sea/air transportation has in itself some advantages， su

[多选题]The combination of sea/air transportation has in itself some advantages，suc

[单选题]If the head pressure of a reciprocating refrigeration compressor is excessiveA．the relief valve should open before the high pressure cutoutB．the relief valve should open and allow the excess refrigerant to flow to the receiverC．the high pressure cuto

[单选题]If the refrigeration compressor crankcase is sweating, the cause may be due toA．a shortage of refrigerantB．the compressor running continuouslyC．liquid refrigerant returning to the compressorD．the compressor short cycling on the high pressure cutout

[单选题]If a refrigeration compressor is short cycling on high head pressure, you shouldA．purge the condenser if the waterside is dirtyB．check for proper water flow through the condenserC．increase the high pressure cutout settingD．reduce the cooling water fl

[单选题]If a refrigeration compressor is short cycling on high head pressure, you should _______.A．purge the condenser if the waterside is dirtyB．check for proper water flow through the condenserC．increase the high pressure cutout settingD．reduce the cooling

[单选题]Low compressor head pressure in a refrigeration system can be caused by ___.A．insufficient condenser cooling waterB．excessive condenser cooling waterC．air in the refrigeration systemD．excessive refrigerant in the system

[单选题]Compressed air is supplied by air compression to （）.A . the air receiversB . the starting valvesC . the cylinder coversD . the distributor