The pumps are one of the most important components of oxygen extraction system (OES). They are intended to supply considerable volume of sea water to OES. Taking into account that designed OES is proposed to install onboard of AIP submarines, the stated below features of pumps define exclusive importance of pumps’ correct selection.
- The pumps are the main of electric power consumers among OES components;
- The pumps have considerable weight and occupy considerable volume ;
- The pumps are the main sources of noise and vibration among OES components.
Stated above features compel to select pumps with exclusive liability. The correct selection (or design) of pumps give possibility to obtain maximal value of oxygen extraction per unit of electric energy input and provide minimal weight and volume of equipment per mass of oxygen consumption.
PUMP SELECTION SCOPE
The scope of the pump selection process includes analysis of input and output conditions influencing on work capacity of selected pump.
- Operating fluid is sea water with temperature range from 0C to +35C. Materials applied for pump have to provide high resistance to corrosion at contact with sea water.
- Selected pump is a part of hydraulic system filled by operating fluid under pressure from 2 to 40 atm (static head 2 – 40 atm).
- Power of pump has no to exceed … kW. In this case the head of pump has no to exceed … m. The head … m is enough to move sea water through all hydraulic resistances of OES.
- Operating capacity through pump can reach up to … m3/hr. Taking into account the capacity, a pump’s flow path at suction side has to have diameter about …mm and at pressure side – diameter about … mm. Such dimensions provide flow speed about … m/s at suction and … m/s at pressure side. In this case, the pump provides reliable work capacity with low level of noise and vibrations.
- Impeller’s shaft seal has to provide hermetic of pump’s work space. Water leakage through seal is not permitted. There are technical solutions that provide operation of pump without leakage. These technical solutions will be considered in the next publications.
- Pump efficiency.
FACTORS INFLUENCING ON PUMP EFFICIENCY
Operating efficiency of pump has to be close by the best efficiency point (BEP). The value of attainable overall pumping system efficiency is defined as:
Effoverall = Effm*Effp*Effg
Effm – is motor efficiency (90 – 95%)
Effp – is a pump efficiency (75 – 85%)
Effg – is gear (transmission) efficiency (95 – 99%)
The value of the practically attainable pump efficiency is mainly influenced by factors such as surface roughness of parts which are in contact with the flow as well as the internal leakage flows through the sealing gaps.
Especially, the surface roughness of hydraulic parts strongly depends on technique that is used during pump industrial process. Further on, the surface quality is a property which can get worse during life time of a pump and thereby causes energy losses during pump operation.
PUMP SELECTION SCOPE
- Lubrication system has to provide reliable work capacity of pump’s bearings. All pump bearings have to be protected. Contaminated grease or oil will be cause faster bearing erosion. Tests have shown that 20ppm of water in oil can reduce bearing life from 24,000 hours to 2,200 hours. Oil for bearings lubrication should be replaced at regular intervals. External oil‐supplying system has advantages.
- Noise and vibration of the pumps. The pump speed has a strong effect on noise compared to displacement and pressure. To reduce the noise levels, electric motors are used and the most advantageous combination of size and pressure is selected to produce the needed power. One of the causes of noise and vibration is cavitation.
There are following rules have to take into account to control cavitation:
- Keep pumps operating point closed by pump best efficiency point (BEP).
- Keep suction line velocities below 1.2 m/s.
- Keep the pump inlet lines as short as possible.
- Minimize the number of fittings in the inlet line.
- Mount the pump as close as possible to the reservoir.
- Use low‐pressure drop inlet filters and other equipment.
- Use proper oil as recommended by the pump manufacturer.
|1.||NTRODUCTION. PUMP SELECTION SCOPE||3|
|2.||PUMP SELECTION GUIDELINE||9|
|2.1.||SPECIFY A PUMP REQUIRED PERFORMANCES||12|
|2.2.||DETERMINING A TYPE OF PUMP||14|
|2.4.||PUMP SPECIFIC SPEED||24|
|2.5.||THE DROP POINTS OF THE BEST EFFICIENCY||38|
|2.6.||THE ATTAINABLE EFFICIENCY||41|
|2.7.||AXIAL‐FLOW PUMP SUBTYPES||46|
|2.8.||PUMP CATALOGUES SELECTION||52|
|2.9.||PUMP PERFORMANCE SELECTION||56|
|3.||ELECTRIC MOTORS FOR PUMPS||132|
|4.||PUMP NOISE AND VIBRATION||136|
|5.||PUMPING SYSTEM IMPROVING. FURTHER WORKS||139|
- Title – WATER PUMP SELECTION.
- Classification – UNCLASSIFIED Author – Bakst A.
- Issue Data – 2016-08
- Updated – 2016-04
- Pages (Slides) – 148 (including Cover and References); Cover – 2 slides;
- Tables – 21;
- Figures (pictures, graphs) – 97
- References – 27
- Format – Adobe PDF Size – 16.5MB
- Price – US$40
The price of full version is $40. If you are interested in purchasing of full version of the article-presentation then contact me through e-mail: bakst.alexander[at]gmail.com or through contact form below.