Answer
A Hull roughness Analyzer (HRA) is a crucial tool used to assess the roughness of a ships hull.
1.Components:
◦ The HRA consists of a portable microprocessor and a display unit.
◦ A computer connects to a handheld stylus with a measuring head.
◦ The operator moves the sensor around the hull surface to measure and record the hull roughness
profile.
2.Measurement Process:
◦ The stylus head collects information from 10 samples, each with a length of 50 mm.
◦ For each 50 mm sample, the microprocessor assesses the mean gradient through the peaks and
valleys.
◦ It calculates the highest peak to lowest valley measurement for that sample, known as Rt (50).
◦ The roughness check covers approximately 100 selected locations on the hull, including the bow,
stern, mid ship, and boot topping area (between the loadline and ballast water line).
◦ Multiple traverses provide ‘n’ readings, allowing calculation of the Mean Hull roughness (M.H.R) at
each station as the average of Rt (50) values:
M.H.R=n∑Rt(50)
◦ The average hull roughness (A.H.R) across all stations is then calculated as the average of the
M.H.R values:
A.H.R=m∑M.H.R
3.Hull roughness Significance:
◦ Hull roughness directly affects the frictional resistance of the ship.
◦ Increased roughness leads to higher power consumption, fuel costs, and operating expenses.
◦ New ships typically have an A.H.R of around 120 microns, while older vessels may reach 300-400
microns due to fouling and deterioration.
To check paint thickness we have two methods
1.WET FILM THICKNESS method –using a PHYSICAL SLIDER(comb) which gives thickness reading as per the teeth which is submerged in the paint.
2.DRY FILM THICKNESS method- using Elcometer which when held against dry paint gives reading digitally using principle of ultrasonic principle.