Sea Water Intake System

海水取水系统

SEA PUMP STATION OPERATION

1.Sea pump system2. Equipment Description3.Troubleshooting

1.Sea pump system

1.1 System process• The sea water enters the pump at the

inlet and leaves through its outlet to the 8000m3 reservoir in the plant. The process detail is as follows.

1.1.1 Start vacuum system before starting the pump(s)1.1.2 The air/water separator level must be at 169mm before vacuum pump outlet valve

is opened. The vacuum pump can now be started.

1.1.3 Air in the seawater pump inlet pipe is sucked by the S.O.P. valve is opened. The vacuum pump creates low pressure in the air extraction pipe and so air moves into the forwarding tank due to the pressure difference between the inside of the pipe line and the atmosphere. When tank water level is 100mm, the water level gauge sends a signal to control system and the control system closes the S.O.P. valve, stops the vacuum pump and starts the sea water pump.

1.1.4The control system then simultaneously open the vent and drain valves of the forwarding tank and drain valves of the forwarding tank and drains the water till it reaches 25mm then it closes both valves.

1.2 process diagram

Sea

Y-filter

Sea Water Pump

Forwarding Tank

Vent

S.O.P. Valve

Sea Water Outlet Motor

Valve

Drain Valve

Vacuum Pump

8000m3 Reservoir

2.Equipment Description

2.1 Sea Water Pump• KENFLO • Type: XA250/32 Speed: 1450 rpm Flow Rate: 1000m3/h• Head: 20 m Suction Lift: 3.1 m Power: 90 kW

2.2 Pump Motor• 3-Phase Asynchronous Motor• Type: YZ-280M Voltage: 380/660 V Current: 167/96.4 A

Frequency: 50 Hz Speed: 1485 rpm Power: 90 kW

3.Troubleshooting• Sea Water pump has been in operation from August

2010 till date. This is amounts to 10 months of operation. The sea water pumping system runs under a number of abnormal conditions. These are primarily cause by the presence of sand and rubbish in the sea and this prevents the pumps from functioning at their possible best. The sea pump outlet has no flow meter so only the pump motor’s current is used to determine if the pump is working well or not. The following are some of the problems that occur in the operation of the sea water pumps.

3.1 Sea water has too much rubbish and is uneasy to clean

• There is a lot of rubbish (plastic waste) in the sea water and it gathers at the inlet of the pump. This reduces the water that enters the pump inlet, making the pump motor’s current low. The operator must then stop the pump and clean the rubbish. The cleaning is done at the Y-filter, the flange at the pump’s inlet pump and/or the chemical dosing hole. Cleaning is also done outside, directly in sea, at the back of the pumps. There are times when the rubbish moves away from the pump when it is stopped and so when the inlet pipe flange is opened, no rubbish is seen. The rubbish then returns to the inlet pipe when the pump is started. When this occurs, after opening and cleaning the pump inlet, wait for about 15 minutes before restarting the pump to allow the rubbish to go further away from the pump. The problem of rubbish destroys the pump quickly through the low motor currents and frequent starts and stops.

3.2 Sea water level is too low

• When the sea water level is low, at 1.3m, there is a lot sand in the water and the pump has a problem starting. In this case, the pump records a low current of about 82A. The outlet pipe at the 8000m3 reservoir is also seen to have a lot of sand in it. The sand settles at the base of the reservoir, reducing its water carrying capacity.

• Strong waves also bring sand to the pump station and this sand settles at the base of the pump’s entry cavity. This reduces how much water the pump can suck in and in effect the pump sucks in air which causes cavitations on the impeller.

3.3Equipment problems that reduced the vacuum pressure.

3.3.1 Sea Pump Outlet Motor Valve Not Fully Closed• This causes the vacuum pump to suck in air from the valve

opening, hence fulfilling the forwarding tank start up conditions before the inlet pipe of the pump is completely full of water. Hence the pump starts with low current of about 60 – 80A.

3.3.2 SO.P. valve not fully closed When the SOP motor valve is not fully closed, water enters the

forwarding tank of the system when it is ‘idle’. The water can rise from the set minimum point of 25mm to about 50-110mm. Because of this, when a pump is about to be started, the control system starts it at the set forwarding tank level of 100m without having sucked in enough air from the pump’s inlet pipe. This causes low pump motor current and cavitations.

3.3.3 Forwarding tank drain valve not fully closed When the vacuum system starts it sucks in air from the valve leakage,

hence causing the starting condition of the forwarding tank (100mm water level) to be reached before the pump inlet pipe is full of only water. The pump therefore starts with a low motor current of 80A and the possibility of cavitations.

3.3.4 Inlet pipe flange and Y-filter gaskets aging (or in bad condition)

In this condition, the vacuum pump needs about 3minutes to start. The pumps motors start at about 110A but drops to about 80A in about 1-2 minutes. The Air leaks can also cause cavitations in the pump.

• The operator on duty should observe the water level to decide when to start or stop a pump or clean a pump. However he cannot control the rubbish or the strength of the waves. The sand and equipment problems require the help of other departments to solve.

• Upon last inspection, at sea water level of 1.6m, the pump currents were as follows:

• A= 105A B= 106A C= 113A• And at 1.3m, • A= 82A B= 82A C= 84A

泵及阀门动作条件：共同条件：急停按钮处于正常位置 （没有按下），急停按下后，各控制柜就地控制也将不能启动。

部件名称 动作 条件

A水泵在 PLC柜手动开泵 A泵处于远程控制， A泵无故障，取水池水位高PLC自动控制状态，

A泵引水开泵 A泵处于远程控制， A泵无故障，取水池水位高，A出口阀处于远程状态， A出口阀全关， A引水阀可以打开。

B水泵在 PLC柜手动开泵 B泵处于远程控制， B泵无故障，取水池水位高PLC自动控制状态，

B泵引水开泵 B泵处于远程控制， B泵无故障，取水池水位高，B出口阀处于远程状态， B出口阀全关， B引水阀可以打开。

C水泵在 PLC柜手动开泵 B泵处于远程控制， B泵无故障，取水池水位高PLC自动控制状态，

C泵引水开泵 C泵处于远程控制， C泵无故障，取水池水位高，C出口阀处于远程状态， C出口阀全关， C引水阀可以打开。

1号真空泵 在 PLC柜手动开泵 真空泵处于远程控制，真空泵无故障，储水罐水位高

2号真空泵在 PLC柜手动开泵 真空泵处于远程控制，真空泵无故障，储水罐水位高PLC自动控制状态，真空泵引水启

动自动系统启动，真空泵处于远程控制，真空泵无故障，储水罐水位高，取水池水位高，调畜水池水位低，引水罐水位低，排水阀关闭，对应需引水水泵的引水阀打开，

A泵引水阀在 PLC柜手动开阀 阀门动作次数每分钟不超过 2次。PLC 自动控制状态 自动系统启动， A泵自动引水启动条件成立（见 A泵），阀门动作次数每分钟不超过 2次。

B泵引水阀在 PLC柜手动开阀 阀门动作次数每分钟不超过 2次。PLC 自动控制状态 自动系统启动， B泵自动引水启动条件成立（见 B泵），阀门动作次数每分钟不超过 2次。

C泵引水阀在 PLC柜手动开阀 阀门动作次数每分钟不超过 2次。PLC 自动控制状态 自动系统启动， C泵自动引水启动条件成立（见 A泵），阀门动作次数每分钟不超过 2次。

补水阀 在 PLC柜手动开阀 阀门动作次数每分钟不超过 2次。PLC 自动控制状态 储水罐水位低，阀门动作次数每分钟不超过 2次。

排水阀在 PLC柜手动开阀 真空泵处于停止状态，阀门动作次数每分钟不超过 2次。PLC 自动控制状态 真空泵处于停止状态，引水罐水位高，阀门动作次数每分钟不超过 2次。

A水泵出口电动阀 PLC自动控制状态 电动阀无故障，电动阀处于远程状态， A水泵已启动，电动阀开启；调畜水池水位高， A水泵需停泵，电动阀关闭。B水泵出口电动阀 PLC自动控制状态 电动阀无故障，电动阀处于远程状态， B水泵已启动，电动阀开启；调畜水池水位高， B水泵需停泵，电动阀关闭。C水泵出口电动阀 PLC自动控制状态 电动阀无故障，电动阀处于远程状态， C水泵已启动，电动阀开启；调畜水池水位高， C水泵需停泵，电动阀关闭。