updated documentation

wallthick/dnvf101.py

@@ -1,11 +1,12 @@
 """
 Offshore Standard DNV-OS-F101 Subsea Pipeline Systems August 2012
 """
+
 from scipy.interpolate import interp1d
 # import matplotlib.pyplot as plt
 
-title = "DNV-OS-F101"
-year = 2012
+TITLE = "DNV-OS-F101"
+YEAR = 2012
 
 """
 (Table 2-4)

wallthick/pd8010.py

@@ -12,84 +12,106 @@
 import scipy.optimize
 import json
 
+TITLE = "PD 8010-2"
+YEAR = 2015
+
 n_s = 0.72
 
 
 def internal_pressure(P_d, P_h):
+    """Return total internal pressure [Pa].
+
+    :param float P_d: Design pressure [Pa]
+    :param float P_h: Pressure head [Pa]
+    """
     return P_d + P_h
 
 
 def water_depths(h, H_t, H_w):
+    """Return the minimum and maximum water depth [m] as a tuple.
+
+    :param float h: Water depth [m]
+    :param float H_t: Tide height [m]
+    :param float H_w: Wave height [m]
+    """
     d_min = h - (H_w/2)
     d_max = h + H_t + (H_w/2)
     return d_min, d_max
 
 
 def external_pressure(rho, g, d):
+    """Return the external pressure [Pa] at water depth.
+
+    :param float rho: Water density [kg/m^3]
+    :param float g: Acceleration of gravity [m/s/s]
+    :param float d: Water depth [m]
+    """
     return rho * g * d
 
 
 def hoop_pressure_thin(t, D_o, P_o, sig):
-    """
-    Number [Pa], Number [Pa], Number [m], Number [Pa] -> Number [m]
-
-    Returns the internal pressure that induces a stress, sig, in a thin
-    wall pipe of thickness t.
+    """Return the internal pressure [Pa] that induces a stress, sig, in a thin wall pipe
+    of thickness t - PD8010-2 Equation (3).
 
-    Equation (3)
+    :param float t: Wall thickness [m]
+    :param float D_o: Outside diamter [m]
+    :param float P_o: External pressure [Pa]
+    :param float sig: Stress [Pa]    
     """
     return ((sig * 2 * t) / D_o) + P_o
 
 
 def hoop_pressure_thick(t, D_o, P_o, sig):
-    """
-    Number [Pa], Number [Pa], Number [m], Number [Pa] -> Number [m]
-
-    Returns the internal pressure that induces a stress, sig, in a thick
-    walled pipe of thickness t.
+    """Return the internal pressure [Pa] that induces a stress, sig, in a thick walled
+    pipe of thickness t - PD8010-2 Equation (5).
 
-    Equation (5)
+    :param float t: Wall thickness [m]
+    :param float D_o: Outside diamter [m]
+    :param float P_o: External pressure [Pa]
+    :param float sig: Stress [Pa]  
     """
     return ((sig * (D_o**2 - (D_o - 2 * t)**2)) / (D_o**2 + (D_o - 2 * t)**2)) + P_o
 
 
 def hoop_thickness_thin(P_i, P_o, D_o, sig_y_d):
-    """
-    Number [Pa], Number [Pa], Number [m], Number [Pa] -> Number [m]
-
-    Returns the minimum wall thickness for internal pressure containment for a
-    thin walled pipe.
+    """Return the minimum wall thickness [m] for internal pressure containment for a
+    thin walled pipe - PD8010-2 Equation (3).
 
-    Equation (3)
+    :param float P_i: Internal pressure [Pa]
+    :param float P_o: External pressure [Pa]
+    :param float D_o: Outside diameter [m]
+    :param float sig_y_d: De-rated yield strength [Pa]
     """
     return abs(P_i - P_o) * D_o / (2 * n_s * sig_y_d)
 
 
 def hoop_thickness_thick(P_i, P_o, D_o, sig_y_d):
-    """
-    Number [Pa], Number [Pa], Number [m], Number [Pa] -> Number [m]
+    """Return the minimum wall thickness [m] for internal pressure containment for a
+    thick walled pipe - PD8010-2 Equation (5).
 
-    Returns the minimum wall thickness for internal pressure containment for a
-    thick walled pipe.
-
-    Equation (5)
+    :param float P_i: Internal pressure [Pa]
+    :param float P_o: External pressure [Pa]
+    :param float D_o: Outside diameter [m]
+    :param float sig_y_d: De-rated yield strength [Pa]
     """
     eq = math.sqrt((((n_s*sig_y_d - abs(P_i - P_o))) * D_o**2) /
                    (n_s*sig_y_d + abs(P_i - P_o)))
     return 0.5 * (D_o - eq)
 
 
 def hoop_thickness(P_i, P_o_min, D_o, sig_y_d):
-    """
-    Number [Pa], Number [Pa], Number [m], Number [Pa] -> Number [m]
-
-    Returns the minimum (note not nominal) wall thickness for internal pressure
+    """Return the minimum (note not nominal) wall thickness for internal pressure
     containment.
 
     Considers:
     - Allowable hoop stress
     - Worst case maximum pressure difference
     - Appropriate wall thickness theory, i.e. thick or thin
+
+    :param float P_i: Internal pressure [Pa]
+    :param float P_o_min: Minimum external pressure [Pa]
+    :param float D_o: Outside diameter [m]
+    :param float sig_y_d: De-rated yield strength [Pa]
     """
     t_min_thin = hoop_thickness_thin(P_i, P_o_min, D_o, sig_y_d)
 
@@ -103,16 +125,13 @@ def hoop_thickness(P_i, P_o_min, D_o, sig_y_d):
 
 
 def req_thickness(t_min, t_corr, f_tol):
-    '''
-    Number [m], Number [m], Number [-] -> Number [m]
-
-    Returns the required wall thickness based on the following mechanical
-    allowances:
-    - Corrosion allowance
-    - Fabrication tolerance
+    """Return the required wall thickness [m] based on the mechanical allowances - 
+    extrapolated from PD8010-2 Equation (4).
 
-    Exrapolated from Equation (4)
-    '''
+    :param float t_min: Minimum wall thickness [m]
+    :param float t_corr: Corrosion allowance [m]
+    :param float f_tol: Fabrication tolerance [-]
+    """
     try:
         return (t_min + t_corr) / (1 - f_tol)
     except ZeroDivisionError:
@@ -125,47 +144,41 @@ def req_thickness(t_min, t_corr, f_tol):
 
 
 def collapse_thickness(P_o, sig_y_d, E, v, D_o, f_0):
-    """
-    Number [Pa], Number [Pa], Number [Pa], Number [-], Number [m], Number [-]
-    -> Number [m]
-
-    Returns the nominal wall thickness for local buckling due to external
-    pressure.
+    """Return the nominal wall thickness [m] for local buckling due to external
+    pressure - PD8010-2 Clause G.1.2.
 
     Considers the worst case maximum external over pressure, i.e.:
-    - Minimum internal pressure (zero)
-    - Maximum external pressure (at water depth, d)
-
-    (Clause G.1.2)
+    - Minimum internal pressure(zero)
+    - Maximum external pressure(at water depth, d)
+
+    :param float P_o: External pressure [Pa]
+    :param float sig_y_d: De-rated yield strength [Pa]
+    :param float E: Young's modulus [Pa]
+    :param float v: Poisson's ratio [-]
+    :param float D_o: Outside diameter [m]
+    :param float f_0: Pipeline ovality [-]    
     """
 
     def P_e(t):
-        """
-        Number [m] -> Number [Pa]
+        """Return the critical pressure [Pa] for an elastic critical tube - PD8010-2
+        Equation (G.2).
 
-        Returns the critical pressure for an elastic critical tube.
-
-        Equation (G.2)
+        :param float t: Wall thickness [m]
         """
         return 2 * E / (1 - v**2) * (t / D_o)**3
 
     def P_y(t):
-        """
-        Number [m] -> Number [Pa]
-
-        Returns the yield pressure.
+        """Return the yield pressure [Pa] - PD8010-2 Equation (G.3).
 
-        Equation (G.3)
+        :param float t: Wall thickness [m]
         """
         return 2 * sig_y_d * (t / D_o)
 
     def char_resist(t):
-        """
-        Number [m] -> Number [Pa]
-
-        Returns the characteristic resistance for external pressure
+        """Return the characteristic resistance [m] for external pressure - PD8010-2
+        Equation (G.1).       
 
-        Equation (G.1)
+        :param float t: Wall thickness [m]
         """
         term_1 = ((P_o / P_e(t)) - 1)
         term_2 = ((P_o / P_y(t))**2 - 1)
@@ -179,15 +192,13 @@ def char_resist(t):
 
 
 def buckle_thickness(D_o, P_p, sig_y):
-    """
-    Number [m], Number [Pa], Number [Pa] -> Number [m]
-
-    Returns the nominal buckle thickness based on the propagation pressure.
-
+    """Return the nominal buckle thickness [t] based on the propagation pressure.
     Considers the worst case maximum external pressure and ignores internal
-    pressure.
+    pressure - PD8010-2 Equation (G.21).
 
-    Equation (G.21)
+    :param float D_o: Outside Diameter [m]
+    :param float P_p: Propagation pressure [Pa]
+    :param float sig_y: Yield strength [Pa]
     """
     return D_o * (P_p / (10.7 * sig_y))**(4 / 9)
 
@@ -197,17 +208,22 @@ def buckle_thickness(D_o, P_p, sig_y):
 
 
 def strength_test_pressure(t_sel, f_tol, sig_y, D_o, P_d, P_o, P_h):
-    """
-    InputData -> Number [Pa]
-
-    Returns the strength test pressure, i.e. the minimum of:
+    """Return the strength test pressure, i.e. the minimum of:
     - 1.5 * design pressure:
         Note that hydrostatic head is not multiplied by 1.5 (interpreted by
         last paragraph of Section 11.5.2)
     - the pressure that induces a hoop stress of 90 percent SMYS at nominal
         wall thickness.
 
-    (Section 11.5.1, Ref.1)
+    PD8010-2 Section 11.5.1, Ref.1.
+
+    :param float t_sel: Selected wall thickness [m]
+    :param float f_tol: fabrication tolerance [-]
+    :param float sig_y: Yield strength [Pa]
+    :param float D_o: Outside Diameter [m]
+    :param float P_d: Design pressure [Pa]
+    :param float P_o: External pressure [Pa]
+    :param float P_h: Pressure head [Pa]
     """
 
     # Determine nominal wall thickness (no corrosion)
@@ -230,6 +246,8 @@ def strength_test_pressure(t_sel, f_tol, sig_y, D_o, P_d, P_o, P_h):
 
 
 class Pd8010(object):
+    """A PD8010-2 design code object.
+    """
 
     def __init__(self, data):
         self.t_sel = data['t_sel']
@@ -253,6 +271,8 @@ def __init__(self, data):
 
     @property
     def t_h(self):
+        """Required wall thickness [m] to satify bursting criteria.
+        """
         P_i = internal_pressure(self.P_d, self.P_h)
         # min water depth
         d, _ = water_depths(self.h, self.H_t, self.H_w)
@@ -262,6 +282,8 @@ def t_h(self):
 
     @property
     def t_c(self):
+        """Required wall thickness [m] to satify collapse criteria.
+        """
         P_i = internal_pressure(self.P_d, self.P_h)
         # max water depth
         _, d = water_depths(self.h, self.H_t, self.H_w)
@@ -272,6 +294,8 @@ def t_c(self):
 
     @property
     def t_b(self):
+        """Required wall thickness [m] to satify buckling criteria.
+        """
         # max water depth
         _, d = water_depths(self.h, self.H_t, self.H_w)
         # propagation pressure equal to max external pressure
@@ -280,7 +304,8 @@ def t_b(self):
 
     @property
     def P_st(self):
-        ''' Strength test pressure '''
+        """Strength test pressure [Pa].
+        """
         # min water depth
         d, _ = water_depths(self.h, self.H_t, self.H_w)
         P_o = external_pressure(self.rho_w, self.g, d)
@@ -289,9 +314,6 @@ def P_st(self):
 
     @property
     def P_lt(self):
-        """
-        Return leak test pressure: 1.1 * MAOP (design pressure) at LAT
-
-        Section 11.5.3
+        """Leak test pressure [Pa] - PD8010-2 Section 11.5.3.
         """
         return 1.1 * self.P_d