Section 4 Design symbols and definitions
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Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Special Service Craft, July 2022 - Part 15 Piping Systems and Pressure Plant - Chapter 1 Piping Design Requirements - Section 4 Design symbols and definitions

Section 4 Design symbols and definitions

Parent topic: Chapter 1 Piping Design Requirements

4.1 Design symbols

4.1.1 The symbols used in this Chapter are defined as follows:

a = percentage negative manufacturing tolerance on thickness
c = corrosion allowance, in mm
d = inside diameter of pipe, in mm, see Pt 15, Ch 1, 4.1 Design symbols 4.1.3
e = weld efficiency factor, see Pt 15, Ch 1, 4.1 Design symbols 4.1.1.
p = design pressure, in MPa, see Pt 15, Ch 1, 4.2 Design pressure
p t = hydraulic test pressure, in MPa
t = the minimum thickness of a straight pipe, in mm, including corrosion allowance and negative tolerance, where applicable
t b = the minimum thickness of a straight pipe to be used for a pipe bend, in mm, including bending allowance, corrosion allowance and negative tolerance, where applicable
D = outside diameter of pipe, in mm, see Pt 15, Ch 1, 4.1 Design symbols 4.1.2
R = radius of curvature of a pipe bend at the centre line of the pipe, in mm
T = design temperature, in oC, see Pt 15, Ch 1, 4.3 Design temperature 4.3.1
σ = maximum permissible design stress, in N/mm2.

4.1.2 The outside diameter, D, is subject to manufacturing tolerances, but these are not to be used in the evaluation of formulae.

4.1.3 The inside diameter, d, is not to be confused with nominal pipe size, which is an accepted designation associated with outside diameters of standard rolling sizes.

4.1.4 The weld efficiency factor, e, is to be taken as 1,0 for seamless and electric resistance or induction welded steel pipes.

4.2 Design pressure

4.2.1 The design pressure, p, is the maximum permissible working pressure and is to be not less than the highest set pressure of the safety valve or relief valve. In systems which have no safety valve or relief valve, the design pressure is to be taken as 1,1 times the maximum working pressure.

4.2.2 The design pressure of piping on the discharge from pumps is to be taken as the pump pressure at full rated speed against a shut valve. Where a safety valve or other protective device is fitted to restrict the pressure to a lower value than the shut valve load, the design pressure is to be the highest set pressure of the device.

4.2.3 For design pressure of steering system components and piping, see Pt 14 Steering Systems.

4.3 Design temperature

4.3.1 The design temperature is to be taken as the maximum temperature of the internal fluid, but in no case is it to be less than 50oC.

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