Low compressor head pressure in a refrigeration system can be caused by ___.

A．insufficient condenser cooling water

B．excessive condenser cooling water

C．air in the refrigeration system

D．excessive refrigerant in the system

[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]Either a low injection pressure or a leakage of piston rings is able to lead （）.A . a high exhaust temperatureB . a high smoky exhaustC . a high outputD . a high compressio

[单选题]APU工作期间，“APU LOW OIL PRESSURE”灯亮：（）.A .要求机组关掉APUB .可以继续使用APU，但不能使用APU引气C .要求机组将APU电门放到”OFF”位后，再放到”START”位1-2秒松手D .APU自动关车

[单选题]APU LOW OIL PRESSURE”灯何时亮是正常的（）？A .APU电门放在”ON”位而APU还没有工作时B .APU关车后C .APU起动期间滑油压力上升到正常之前D .任何时候亮都是不正常的

[名词解释] 低压安全注射系统﹝压水堆﹞ low head safety injection system

[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]If a reciprocating air compressor has a knock occurring in frequency with its operating RPM, the cause is probably _____.A．misalignment or worn main bearingsB．insufficient cylinder lubricationC．defective or poorly fitted valvesD．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