Section two Working Principle and Technical Specification of Main Equipment
I. Seawater Booster Pump:
The seawater booster pump selects Dalian Acid-resistant Pump, LH vertical type single-stage and single-suction submergible pump, 3 sets. The model: LH50—400; the flow rate: 34m3/h; the pressure: 0.35 MPa; the axial length: 4.5m; the axle, axle sleeve and impeller of the seawater booster pump are all made of 316L stainless steel form abroad. The bearing of vertical long-axle submerged pump is an inlet one; the motor speed is 1450r/min.
II．Automatic Backwashing Filter:
1．Working Principle:
Automatic backwashing filter utilizes the pressure difference of system to implement backwashing without any influence on flowing of seawater and no special cleaning fluid is required during the cleaning process. In the normal operation, crude seawater runs into sieve through the inlet of filter, all impurities with diameter larger than 0.5mm will be retained on the sieve. This process carries on until the impurities accumulate to a certain degree, which causes the increase of pressure difference, when the pressure differential controller achieves the preset value（0.035Mpa）, automatic backwashing starts up. Sliding seal plate connected to the backwashing outlet will clean each part of sieve effectively. The internal pressure in the filter shell is higher than that of backwashing outlet pipe, thus some seawater flows in an opposite direction through sieve and cleans all accumulated impurities effectively, discharging them into trench through the blowdown valve.
The whole process is carried out by the differential pressure controller automatically. After all sieves of filters were cleaned, the automatic backwash cycle stops, and filters restore to the normal mode till next action of the pressure controller takes place, washing repeatedly.
2．Characteristics of Equipment:
- It is unnecessary to shut down during backwashing and the water consumption for backwashing is quite low.
Backwashing adopts small and light motor with low power for convenience of maintenance.
● The lid of filter shall be easily disassembled for maintenance of the sieve,
● Unique structure of sieve prevents from being blocked by impurities with strong anti-mechanical wear and anti-scour abilities.
● The possibility of damage is eliminated due to the separation of sieve and backwashing components.
● The import 316L stainless steel has strong anti-corrosion ability to seawater and longer service life.
● The low inertia of backwashing components ensures the minimum power consumption.
● The blowdown valve adopts an electric ball valve, which opens automatically during backwashing and closes after it.
3．Equipment Specification:
ZHG56-LA Automatic Backwashing Filter, water treatment capacity is 68m3/h.
III．Sodium Hypochlorite Generator:
1．Working Principle:
The seawater that passes through the electrolytic cell shall be electrolyzed at both anode and cathode with chemical reactions as below:
Anodic reaction： 2Cl—2e→Cl2 （1）
Cathodic reaction： 2H2O+2e→2OH-+H2↑ （2）
Reaction between electrodes of electrolytic cell: Cl2+ 2NaOH→2NaClO+H2↑ （3）
Hypochlorous acid and hypochlorous acid ion are all called effective chlorine, and prevention of sea biological defile is realized by using effective chlorine which is generated from electrolyzing seawater.
2．Characteristics of Equipment:
Lid of electrolytic cell: the lid is made of UV-resistant organic glass which is transparent so that the operator is able to directly observe chemical reactions in the cell through the lit during operation which is helpful for operators to judge and master maintenance of electrolytic cell and time of acid rinsing well.
Shell of electrolytic cell: the shell is made of PVC with perfect corrosion resistance to the sodium hypochlorite. This material possesses features of high strength, anti-aging and corrosion resistance compared with other materials with higher safety and stability, eliminating the leakage of liquid.
第二节 汽、水分析方法
一． pH的测定（pH电极法）
1 ． 概要
当氢离子选择性电极—pH电级与甘汞参比电极同时浸入水溶液后，即组成测量电池。其中pH电极的电位随溶液中氢离子的活度而变化。用一台高输入阻抗的毫伏计测量，即可获得同水溶液中氢离子活度相对应的电极电位，以pH值表示。即
pH = -lga[H+]
2 ． 测定
（１）仪器校正：仪器开启半小时后，按仪器说明书的规定，进行调零、温度补偿以及满刻度校正等手续。
（２）pH定位：定位用的标准缓冲溶液应选用一种其pH值与被测溶液相近的。在定位前，先用蒸馏水冲洗电极及测试烧杯2次以上，然后用干净滤纸将电极底部残留的水滴轻轻吸干。将定位溶液倒入测试烧杯内，浸入电极，调整仪器的零点、温度补偿及满刻度校正。最后根据所用定位缓冲液的pH值将pH计定位。重复1~2次，直至误差在允许范围内。定位溶液可保留下次再用。但如有污染或使用数次后，应当更换新鲜缓冲溶液。
（３）复定位：复定位就是将上述定位后的pH计对另一pH值的标准缓冲溶液进行测定，如所测结果与复定位缓冲溶液的pH值相差±0.05pH以内时，即可认为仪器和电极均属正常，可以进行pH测定。复定位溶液的处理，应按定位溶液的规定进行。
（３）水样的测定：将复定位后的电极和测试烧杯，反复用蒸馏水冲洗2次以上，再用被测水样冲洗2次以上。然后将电极浸入被测溶液，即可读取仪表指示的pH值。测定完毕后，应将电极用蒸馏水反复冲洗干净，最后将pH电极浸泡在蒸馏水中备用。
３．注释：
（１）新电极或长时间干燥保存的电极在使用前，应将电极在蒸馏水中浸泡过夜，使其不对称电位趋于稳定。如有急用，则可将上述电极浸泡在0.1M盐酸中至少1h，然后用蒸馏水反复冲洗干净后才能使用。
（2）对污染的电极，可用蘸有四氯化碳或乙醚的棉花轻轻擦净
电极的头部。如发现敏感泡外壁有微锈，可将电极浸泡在5~10%的盐酸中，待锈消除后再用，但绝不可浸泡在浓酸中，以防敏感薄膜严重脱
（3）进行pH测定时，还必须考虑到玻璃电极的“钠差”问题，即被测水样中钠离子的浓度对氢离子测定的干扰。特别是对pH>10.5的高pH测定，必须选用优质的高碱pH电极，以减少“钠差”的影响。
（4）温度对pH值测定的准确性影响较大。对于pH大于8.3的水样，在相同的酚酞碱度下，出现实测pH值随水温升高而直线下降的现象。其原因是由于温度变化，引起了众多影响pH值的因素改变，仪器上的温度补偿仅能消除一个因素的影响。为了消除温度影响，水样可采取水浴升温或降温的措施，使pH的测定在25℃时进行。当采用记录温度并进行温度校正的方式测定碱性水的pH值时，那么实测酚酞碱度计算出的pH值与温度校正后的pH值，两者相差小于±0.1pH，测定的pH值才符合要求。
（5）要保证玻璃电极中的饱和KCL不能缺，如缺少应及时加满。