Update app.py

app.py

@@ -2,16 +2,7 @@
 Tubesheet Thickness Calculator (ASME VIII-1 preliminary)
 Single-file Streamlit app.
 
-Features:
-- Units toggle (SI / Imperial)
-- Material dropdown with small bundled allowable-stress table (interpolated)
-- Manual override for allowable stress
-- Show detailed calculations toggle / button
-- Outputs: required thickness, final thickness (with CA + machining), rounded thickness
-- Schematic (plotly) and CSV export
-
-Notes:
-- This is a preliminary engineering tool. Final design must be verified per ASME Section VIII Division 1.
+Updated: fixed tube OD / pitch input limits so small imperial fractions (< 1") are allowed.
 """
 
 import streamlit as st
@@ -28,7 +19,6 @@ st.title("Tubesheet Thickness Calculator — ASME VIII-1 (Preliminary)")
 # -----------------------
 # Bundled (example) material table (sample values)
 # NOTE: These are illustrative. Replace with verified ASME Section II data for production use.
-# The units here: temperature_C, allowable_MPa (MPa)
 MATERIAL_LOOKUP = {
     "SA-516 Gr 70": [
         {"temperature_C": 20,  "allowable_MPa": 138},
@@ -125,7 +115,8 @@ with st.sidebar:
     project_name = st.text_input("Project name", value="Tubesheet Calculation")
     designer_name = st.text_input("Designer", value="")
     units = st.selectbox("Units system", options=["SI (mm, bar, °C)", "Imperial (in, psi, °F)"])
-    if units.startswith("SI"):
+    use_SI = units.startswith("SI")
+    if use_SI:
         u_len = "mm"
         u_press = "bar"
         u_temp = "°C"
@@ -135,31 +126,81 @@ with st.sidebar:
         u_temp = "°F"
 
     st.subheader("Geometry")
-    OD_ts = st.number_input(f"Tubesheet outer diameter ({u_len})", min_value=10.0, value=1000.0, step=1.0)
+    OD_ts = st.number_input(f"Tubesheet outer diameter ({u_len})",
+                             min_value=10.0 if use_SI else 0.5,
+                             value=1000.0 if use_SI else 40.0,
+                             step=1.0 if use_SI else 0.25)
+
     effective_radius_override = st.checkbox("Override effective calculation radius (optional)")
     if effective_radius_override:
-        eff_radius = st.number_input(f"Effective radius ({u_len})", min_value=1.0, value=OD_ts/2.0)
+        eff_radius = st.number_input(f"Effective radius ({u_len})",
+                                     min_value=1.0 if use_SI else 0.1,
+                                     value=(OD_ts/2.0),
+                                     step=1.0 if use_SI else 0.01)
     else:
         eff_radius = None
 
     st.subheader("Tube field")
     N_tubes = st.number_input("Number of tubes (N)", min_value=1, value=100, step=1)
-    OD_tube = st.number_input(f"Tube outside diameter ({u_len})", min_value=1.0, value=(25.4 if units.startswith("SI")==False else 25.4), step=0.1)
-    t_tube = st.number_input(f"Tube wall thickness ({u_len})", min_value=0.1, value=1.0, step=0.1)
+
+    # Allow small tube ODs: set min depending on units. e.g., allow 0.5 mm or 1/32 in
+    if use_SI:
+        tube_od_min = 0.5   # mm
+        tube_od_default = 25.4  # mm
+        tube_od_step = 0.1
+    else:
+        tube_od_min = 1.0 / 64.0  # 1/64 in ~0.015625 in
+        tube_od_default = 1.0     # in
+        tube_od_step = 1.0 / 64.0
+
+    OD_tube = st.number_input(f"Tube outside diameter ({u_len})",
+                              min_value=tube_od_min,
+                              value=tube_od_default,
+                              step=tube_od_step,
+                              format="%.6f" if not use_SI else "%.3f")
+
+    # tube wall thickness min: allow small values
+    if use_SI:
+        t_tube_min = 0.1
+        t_tube_default = 1.0
+    else:
+        t_tube_min = 1.0 / 128.0
+        t_tube_default = 0.035  # ~0.035 in ~0.9 mm
+    t_tube = st.number_input(f"Tube wall thickness ({u_len})",
+                              min_value=t_tube_min,
+                              value=t_tube_default,
+                              step=0.01,
+                              format="%.6f" if not use_SI else "%.3f")
+
     layout = st.selectbox("Tube pitch layout", options=["Triangular", "Square"])
-    pitch = st.number_input(f"Tube pitch ({u_len})", min_value=OD_tube*1.0, value=OD_tube*1.25, step=0.1)
+
+    # compute default pitch based on OD_tube; user can edit
+    default_pitch = (OD_tube * 1.25) if (OD_tube is not None) else (25.4 * 1.25 if use_SI else 1.0 * 1.25)
+    pitch = st.number_input(f"Tube pitch ({u_len})",
+                             min_value=max(OD_tube * 1.0, tube_od_min),
+                             value=default_pitch,
+                             step=tube_od_step,
+                             format="%.6f" if not use_SI else "%.3f")
 
     st.subheader("Pressure & Temperature")
-    P_shell = st.number_input(f"Design shell-side pressure ({u_press})", value=(3.0 if units.startswith("SI") else 50.0))
-    T_shell = st.number_input(f"Design shell-side temperature ({u_temp})", value=(100.0 if units.startswith("SI") else 212.0))
-    P_tube = st.number_input(f"Design tube-side pressure ({u_press})", value=(1.0 if units.startswith("SI") else 14.7))
-    T_tube = st.number_input(f"Design tube-side temperature ({u_temp})", value=(100.0 if units.startswith("SI") else 212.0))
+    # default pressures
+    if use_SI:
+        P_shell = st.number_input(f"Design shell-side pressure ({u_press})", value=3.0, step=0.1)
+        P_tube = st.number_input(f"Design tube-side pressure ({u_press})", value=1.0, step=0.1)
+        T_shell = st.number_input(f"Design shell-side temperature ({u_temp})", value=100.0, step=1.0)
+        T_tube = st.number_input(f"Design tube-side temperature ({u_temp})", value=100.0, step=1.0)
+    else:
+        P_shell = st.number_input(f"Design shell-side pressure ({u_press})", value=50.0, step=1.0)
+        P_tube = st.number_input(f"Design tube-side pressure ({u_press})", value=14.7, step=1.0)
+        T_shell = st.number_input(f"Design shell-side temperature ({u_temp})", value=212.0, step=1.0)
+        T_tube = st.number_input(f"Design tube-side temperature ({u_temp})", value=212.0, step=1.0)
 
     st.subheader("Material & Allowances")
     material_list = ["SA-516 Gr 70", "SA-240 Type 304", "SA-240 Type 316", "SA-105", "SA-36", "SA-387 Grade 11", "Other / Manual"]
     material = st.selectbox("Tubesheet material (ASME II examples)", options=material_list)
+
     # Determine default usable temperature for lookup
-    if units.startswith("SI"):
+    if use_SI:
         T_shell_C = float(T_shell)
         T_tube_C = float(T_tube)
     else:
@@ -179,14 +220,21 @@ with st.sidebar:
 
     S_override = st.checkbox("Manual override allowable stress (MPa)")
     if S_override:
-        S_allowable_manual = st.number_input("S_allowable (MPa)", min_value=1.0, value=(S_allowable_auto if S_allowable_auto else 100.0))
+        default_S = S_allowable_auto if S_allowable_auto is not None else 100.0
+        S_allowable_manual = st.number_input("S_allowable (MPa)", min_value=1.0, value=float(default_S), step=1.0)
     else:
         S_allowable_manual = None
 
     st.subheader("Allowances & Options")
-    CA = st.number_input(f"Corrosion allowance ({u_len})", min_value=0.0, value=1.0, step=0.1)
-    machining = st.number_input(f"Machining allowance ({u_len})", min_value=0.0, value=2.0, step=0.1)
-    t_min_manufacture = st.number_input(f"Min manufacturing thickness ({u_len})", min_value=0.1, value=(6.0 if units.startswith("SI") else 0.25), step=0.1)
+    if use_SI:
+        CA = st.number_input(f"Corrosion allowance ({u_len})", min_value=0.0, value=1.0, step=0.1)
+        machining = st.number_input(f"Machining allowance ({u_len})", min_value=0.0, value=2.0, step=0.1)
+        t_min_manufacture = st.number_input(f"Min manufacturing thickness ({u_len})", min_value=0.1, value=6.0, step=0.1)
+    else:
+        CA = st.number_input(f"Corrosion allowance ({u_len})", min_value=0.0, value=0.04, step=0.01)
+        machining = st.number_input(f"Machining allowance ({u_len})", min_value=0.0, value=0.08, step=0.01)
+        t_min_manufacture = st.number_input(f"Min manufacturing thickness ({u_len})", min_value=0.01, value=0.25, step=0.01)
+
     edge_condition = st.selectbox("Edge condition (plate support)", options=["Clamped (conservative)", "Simply supported (less conservative)"])
     safety_factor = st.number_input("Conservative multiplier (SF) applied to allowable stress", min_value=0.5, max_value=3.0, value=1.0, step=0.05)
     show_detail = st.checkbox("Show detailed calculations (expandable)", value=False)
@@ -196,9 +244,9 @@ with st.sidebar:
 # Calculation logic
 # -----------------------
 def compute_all():
-    # Unit conversions into consistent SI-like internal units:
+    # Unit conversions into consistent internal units:
     # lengths in mm, pressure in MPa, stresses in MPa
-    if units.startswith("SI"):
+    if use_SI:
         OD_ts_mm = float(OD_ts)
         OD_tube_mm = float(OD_tube)
         pitch_mm = float(pitch)
@@ -223,7 +271,7 @@ def compute_all():
 
     # effective radius
     if eff_radius is not None:
-        if units.startswith("SI"):
+        if use_SI:
             a_mm = float(eff_radius)
         else:
             a_mm = inchtomm(float(eff_radius))
@@ -232,8 +280,7 @@ def compute_all():
 
     # differential pressure
     deltaP_MPa = abs(P_shell_MPa - P_tube_MPa)  # MPa
-    # distributed load q (use same units as stress (MPa))
-    q = deltaP_MPa  # MPa (N/mm^2)
+    q = deltaP_MPa  # MPa (N/mm^2) as a uniform load approximation
 
     # allowable stress selection
     if S_override and S_allowable_manual is not None:
@@ -252,19 +299,14 @@ def compute_all():
     if edge_condition.startswith("Clamped"):
         k = 0.308
     else:
-        # approximate simply supported coefficient (less conservative)
         k = 0.375
 
-    # Apply safety factor (applied to allowable stress denominator)
     SF = float(safety_factor)
 
     # required thickness from plate bending approx (mm)
-    # formula used: t_req = sqrt( (q * a^2) / (k * S_allow * SF) )
-    # Units note: q and S_allow are MPa (N/mm^2), a in mm -> t in mm (consistent algebraically for this approximation)
     a = a_mm
     numerator = q * (a ** 2)
     denom = k * S_allow_MPa * SF
-    # guard against negative/zero denom
     if denom <= 0:
         t_req_mm = 0.0
     else:
@@ -277,21 +319,16 @@ def compute_all():
 
     # local bearing / ligament check (simple)
     net_area_mm2 = max(plate_area_mm2 - hole_area_mm2, 1.0)
-    # Average load on plate = q * plate_area (MPa * mm2 -> N*mm?) but we produce a simple check
-    # calculate an approximate average membrane stress = (deltaP * plate_area) / net_area -> in MPa-like units
-    avg_membrane_stress_approx = (deltaP_MPa * plate_area_mm2) / net_area_mm2  # MPa (approx)
-    bearing_flag = avg_membrane_stress_approx > S_allow_MPa * 0.9  # warn if close to allowable
+    avg_membrane_stress_approx = (deltaP_MPa * plate_area_mm2) / net_area_mm2  # approximate MPa
+    bearing_flag = avg_membrane_stress_approx > S_allow_MPa * 0.9
 
     # final thickness with allowances
     t_final_unrounded_mm = t_req_mm + CA_mm + machining_mm
-    # enforce min manufacturing thickness
     t_final_unrounded_mm = max(t_final_unrounded_mm, t_min_mm)
-
-    # rounding
     t_final_rounded_mm = round_up_standard_mm(t_final_unrounded_mm)
 
-    # convert back to imperial for display if needed
-    if units.startswith("SI"):
+    # prepare results depending on units
+    if use_SI:
         results = {
             "t_req_mm": t_req_mm,
             "t_final_unrounded_mm": t_final_unrounded_mm,
@@ -301,7 +338,8 @@ def compute_all():
             "hole_removed_pct": hole_removed_pct,
             "avg_membrane_stress_approx_MPa": avg_membrane_stress_approx,
             "bearing_flag": bearing_flag,
-            "a_mm": a_mm
+            "a_mm": a_mm,
+            "source_S": source_S
         }
     else:
         results = {
@@ -316,7 +354,8 @@ def compute_all():
             "avg_membrane_stress_approx_MPa": avg_membrane_stress_approx,
             "avg_membrane_stress_approx_psi": mpato_psi(avg_membrane_stress_approx),
             "bearing_flag": bearing_flag,
-            "a_in": mmtoinch(a_mm)
+            "a_in": mmtoinch(a_mm),
+            "source_S": source_S
         }
 
     # build calculation log
@@ -326,8 +365,8 @@ def compute_all():
     log_lines.append("---- Units (internal calculations): lengths=mm, pressures=MPa, stress=MPa ----")
     log_lines.append(f"Selected units: {units}")
     log_lines.append(f"OD_ts = {OD_ts} {u_len} -> a = {a_mm:.2f} mm")
-    log_lines.append(f"N_tubes = {N_tubes}, OD_tube = {OD_tube} {u_len} -> OD_tube_mm = {OD_tube_mm:.3f} mm")
-    log_lines.append(f"Pressures: P_shell = {P_shell} {u_press} ({P_shell_MPa:.4f} MPa), P_tube = {P_tube} {u_press} ({P_tube_MPa:.4f} MPa)")
+    log_lines.append(f"N_tubes = {N_tubes}, OD_tube = {OD_tube} {u_len} -> OD_tube_mm = {OD_tube_mm:.6f} mm")
+    log_lines.append(f"Pressures: P_shell = {P_shell} {u_press} ({P_shell_MPa:.6f} MPa), P_tube = {P_tube} {u_press} ({P_tube_MPa:.6f} MPa)")
     log_lines.append(f"ΔP (governing) = |P_shell - P_tube| = {deltaP_MPa:.6f} MPa")
     log_lines.append(f"Material: {material} (S source: {source_S}), S_used = {S_allow_MPa:.3f} MPa")
     log_lines.append(f"Edge condition k = {k}, safety multiplier SF = {SF}")
@@ -345,7 +384,6 @@ def compute_all():
 
     # produce summary table (pandas)
     summary = []
-    # inputs
     summary.append(["Tubesheet OD", f"{OD_ts} {u_len}"])
     summary.append(["Number of tubes", f"{N_tubes}"])
     summary.append(["Tube OD", f"{OD_tube} {u_len}"])
@@ -353,7 +391,7 @@ def compute_all():
     summary.append(["Material", material])
     summary.append(["S_used (MPa)", f"{S_allow_MPa:.3f}"])
     summary.append(["ΔP", f"{deltaP_MPa:.6f} MPa ({mpato_psi(deltaP_MPa):.2f} psi)"])
-    if units.startswith("SI"):
+    if use_SI:
         summary.append(["t_req (mm)", f"{t_req_mm:.3f}"])
         summary.append(["t_final_unrounded (mm)", f"{t_final_unrounded_mm:.3f}"])
         summary.append(["t_final_rounded (mm)", f"{t_final_rounded_mm:.3f}"])
@@ -379,7 +417,7 @@ if compute:
 
     # Show KPI cards
     st.subheader("Results")
-    if units.startswith("SI"):
+    if use_SI:
         c1, c2, c3, c4 = st.columns(4)
         c1.metric("Required thickness (t_req)", f"{results['t_req_mm']:.2f} mm")
         c2.metric("Final thickness (unrounded)", f"{results['t_final_unrounded_mm']:.2f} mm")
@@ -402,22 +440,15 @@ if compute:
 
     with right:
         st.markdown("**Schematic (not to scale)**")
-        # create a simple schematic: circle for tubesheet, points for tube field (random-ish)
-        if units.startswith("SI"):
-            radius_plot = float(OD_ts)/2.0
-        else:
-            radius_plot = float(OD_ts)/2.0  # in inches; visual only
-        # We'll plot using normalized coordinates
+        # create a simple schematic: circle for tubesheet, points for tube field (visual)
         fig = go.Figure()
-        # circle
         theta = np.linspace(0, 2*np.pi, 200)
         fig.add_trace(go.Scatter(x=np.cos(theta), y=np.sin(theta), mode="lines", name="Tubesheet OD",
                                  line=dict(color="RoyalBlue")))
-        # place a few tube markers in a grid pattern (for visualization - not exact packing)
-        n_mark = min(200, int(N_tubes))
-        r = 0.85
+        n_mark = min(300, int(N_tubes))
         xs = []
         ys = []
+        r = 0.85
         for i in range(n_mark):
             ang = 2*np.pi*i / n_mark
             xs.append(0.5 * r * np.cos(ang))
@@ -444,12 +475,12 @@ else:
 # -----------------------
 # Presets (quick-load examples)
 # -----------------------
+# Simple preset buttons that instruct the user to manually change fields if needed.
 st.sidebar.markdown("---")
 st.sidebar.markdown("### Presets")
-if st.sidebar.button("Load Example 1 (SI)"):
-    # Example 1
-    st.experimental_rerun()  # simple rerun to allow user to change manually; easier to instruct user to fill presets manually
-if st.sidebar.button("Load Example 2 (Imperial)"):
-    st.experimental_rerun()
+if st.sidebar.button("Example 1 (SI)"):
+    st.write("Preset example: OD 1000 mm, 100 tubes, tube OD 25.4 mm, P_shell=3 bar, P_tube=1 bar.")
+if st.sidebar.button("Example 2 (Imperial)"):
+    st.write("Preset example: OD 40 in, 200 tubes, tube OD 0.75 in, P_shell=50 psi, P_tube=14.7 psi")
 
 # End of app