EN 1591-1 Bolted Flange Load-Balance Screening Calculator — Sample Report

1 · Design inputs

NPS 6-class gasketed joint: effective gasket diameter 8.8 in, width 1.0 in, 8× 3/4 in bolts (root area 0.302 in² each) at 25,000 psi allowable, internal pressure 300 psi. Gasket constants Q0min = 1,800 psi, Qsmin = 1,200 psi, Qmax = 15,000 psi.

2 · Method

Force balance in the EN 1591-1 framework, worked in the order the calculator evaluates it:

A_Ge = π·d_Ge·b_Ge F_Q = (π/4)·d_Ge²·P

F_B,assembly = A_Ge·Q_0min F_B,operating = F_Q + F_ext + A_Ge·Q_smin

F_B,available = n·A_bolt·f_B Q_assembly = F_B,available/A_Ge Q_operating = (F_B,available − F_Q − F_ext)/A_Ge

where d_Ge and b_Ge are the effective gasket diameter and width, P the internal pressure, F_ext any external axial force from the connected piping (tension positive, zero by default), and Q_0min, Q_smin, Q_max the gasket's minimum seating pressure, minimum operating (tightness) pressure, and maximum crush pressure. The governing bolt-load requirement is the larger of the assembly and operating conditions. The calculator compares the available bolt load against that requirement (bolt-load verdict) and compares the gasket pressure produced by the full available bolt load against Q_max (gasket-crush verdict); it also flags an operating gasket pressure that falls below Q_smin even when bolting is otherwise adequate — a joint that seats fine but may not stay tight at pressure. The same relation carries an EN-1591-style bolted-flange check found in general piping-stress packages (CAESAR II’s “EN-1591 Flanges” check is one) — this card runs the identical force balance for a quick screen, not a substitute for that or for a full EN 1591-1 design run.

3 · Calculation

1. Effective gasket area: A_Ge = π·d_Ge·b_Ge = π·8.8·1.0 = 27.64602 in².
2. Pressure end force: F_Q = (π/4)·d_Ge²·P = (π/4)·8.8²·300 = 18,246.37 lbf.
3. Assembly (seating) requirement: FB_assembly = A_Ge·Q0min = 27.64602·1,800 = 49,762.83 lbf.
4. Operating requirement: FB_operating = F_Q + F_ext + A_Ge·Qsmin = 18,246.37 + 0 + 27.64602·1,200 = 51,421.59 lbf — governs, being the larger of the two.
5. Available bolt load: FB_available = n·A_bolt·f_B = 8·0.302·25,000 = 60,400 lbf ≥ 51,421.59 lbf required → bolt load ok.
6. Gasket pressure at full bolt load: Q_assembly = FB_available/A_Ge = 60,400/27.64602 = 2,184.763 psi ≤ Qmax = 15,000 psi → gasket ok.
7. Gasket pressure in operation: Q_operating = (FB_available − F_Q)/A_Ge = (60,400 − 18,246.37)/27.64602 = 1,524.763 psi, above Qsmin = 1,200 psi → stays tight.

4 · Results PASS

5 · Verification statement

The result values above are locked as fixture en1591-screen.json, case “NPS6-class gasket dGe=8.8 bGe=1.0, 8x 3/4in bolts (root 0.302), P=300 -> pass (PVP Age anchor)”, tolerance 0.001, in the calc-core continuous verification gate (see https://pipingtoolset.com/trust/validation.html). Allowable-stress and factor data are user-supplied inputs; citations: EN 1591-1, Flanges and their joints — Design rules for gasketed circular flange connections — Part 1: Calculation method (force-balance framework reproduced here as a screen, not the full iterative method). · EN 1591-2, Flanges and their joints — Design rules for gasketed circular flange connections — Part 2: Gasket parameters and test procedures (source of Q0min, Qsmin, Qmax when not taken from the gasket manufacturer's data sheet).