NSMB 8 kPa
BSRA 10 kPa
KRISO Conventional Stern : 8 kPa Naval Ship : 4 kPa
Review of Hull Pressure Measurement
The conventional method, which is to install the pres- sure transducer on the inside of hull with a hole on hull surface for measuring the fluctuation pressure of actual vessel, is relatively safe work and possible to install at the accurate measurement position because it is possible to work after confirming the position of the construction drawing。
In comparison with previous method, the new method has features of installing the pressure transducer on the surface of hull from the exterior of ship, which requires more scrupulous attention due to installing the pressure transducer after choosing the basis position on the 3-D space and has dangerous factors of the safety accidents due to work at high place。 Table 2 shows the compari- son between new method and conventional method。论文网
Table 2: Characteristics of Pressure Transducers
Magnetic Sensor Pressure Transducer Cost(US $) 1,250 1,700
Maker 1 ( HHI ) Some
Installation Difficult Easy
Re-application Impossible Possible Work place No limit Limit (Dock)
Hole None Required
Fig。 3: Major Position of Pressure Sensor
Allowable Pressure Limit
For the allowable limit of propeller fluctuating pressure, no international standard is now established however some institutions provide the guidelines of pressure limits in Table 1。
Table 1: Allowable Pressure Limits
Institution Allowable Pressure Limit DNV 8 kPa
HSVA Merchant Ship : 4~8 kPa
Naval Ship : 2。5 ~ 4 kPa
LR Transom Stern : 6 kPa Conventional Aftbody Form : 8 kPa
The pressure measurement during sea trial of actual ship has to take care of the change of the environmental condition because it is changeable in accordance with a route of ship, weather and sea state etc。 For detecting the accurate propeller rpm, it is strongly recommended to directly measure rpm by tachometer installed on engine shaft。
Magnetic Sensor
The conventional method for fluctuating pressure meas- urement induced by propeller was recently applied on the trouble shooting of ships built by Hanjin Heavy Industry Co。 Ltd and Samsung Heavy Industry Co。 Ltd in Korea。 For improvement of conventional method, HMRI (Hyundai Maritime Research Institute) designs magnetic sensor which does not damage to hull surface and apply it to fluctuating pressure measurement of the actual ship。
The magnetic sensor is feasible to be installed anywhere because it is attached to hull surface and does not influ- ence the strength of hull surface owing to being de- tached naturally by the outside fluid force after definite
time。 Moreover, it can be quickly used to examine the cause of problem originated from fluctuating pressure after ship’s delivery。
The magnetic sensors were attached to hull surface and the line connection with the measurement system for data acquisition is required。 Fig。 4 showed the magnetic sensor installation for the LNG carrier at the dockyard of HHI。 液化天然气运输船螺旋桨脉动压力测量英文文献和中文翻译(2):http://www.youerw.com/fanyi/lunwen_95974.html