Commissioning and Startup Training Curriculum

Mod 4 - Pressure Testing

Module from the Commissioning and Startup Training Curriculum curriculum.

Module 4 — Pressure and Tightness Testing · Learning Objectives · 1. Plan and execute hydrostatic testing per ASME B31.3 / ASME Section VIII requirements. · 2. Select between hydrotest, pneumatic test, and sensitive leak test based on service and risk. · 3. Calculate test pressure including temperature correction factor. · 4. Apply safe work practices for pneumatic testing stored energy hazards. · 5. Verify tightness with soap, ultrasonic, or helium leak detection techniques. · Test Methods

Method	Code Basis	Use Case
Hydrotest	ASME B31.3 §345.4 / ASME VIII UG-99	Default for pressure piping/vessels
Pneumatic	ASME B31.3 §345.5	Water-sensitive or water-removal-impractical
Sensitive leak (bubble)	ASME V Art. 10	Tightness; new joints and seals
Helium mass spec	ASME V Art. 10 App. IV	Cryogenic, high-integrity seal systems
Service leak test	ASME B31.3 §345.7	Combined with startup for Cat. D fluid service
Initial service leak	ASME B31.3 §345.7	Low-hazard category D only
Hydrotest Pressure Calculation (B31.3)
Parameter	Formula
Test pressure minimum	P_T = 1.5 × P × (S_T / S)
P	Design gauge pressure, psig
S_T	Allowable stress at test temperature
S	Allowable stress at design temperature
Max ratio cap	(S_T/S) capped at 6.5
Example	CS A106-B, P=300 psig, ratio=1.0 → P_T = 450 psig
Pneumatic Test — Safety Requirements
Item	Requirement
Test pressure	1.1 × design, ASME B31.3 §345.5.4
Initial pressurization	25 psig hold; examine joints
Pressure increments	50% target → 100%
Exclusion zone	Calculated energy zone — typical 200–500 ft
Relief device	Set ≤ 110% of test pressure
Stored energy	E = (P×V)/0.2 × [1 − (Patm/P)^0.286]
Personnel	Clear all non-essential; remote read
Hydrotest Procedure
Step	Action
1	Install blind flanges / isolation
2	Review test pkg: P&ID markup, test boundary, relief
3	Fill from low point; vent all high points
4	Pressurize to 50%; hold 10 min; inspect
5	Raise to 100% test pressure; hold 10 min minimum
6	Reduce to design pressure; walk and inspect joints
7	Drain, dry, remove blinds, reinstate lines
Tightness Test Acceptance
Test	Acceptance
Soap bubble	No continuous bubbling at 1.1 × P
Ultrasonic	No signal above background
Helium mass spec	Leak rate ≤ 1e-6 std cc/s
Pressure decay	<1% of abs pressure over 24 hr (T-corrected)
Vacuum decay	<2 mbar/hr
Common Problems
Symptom	Cause	Fix
Pressure drift	Temperature change	Correct using ideal gas law; re-time
Slow leak at flange	Low bolt torque	Re-torque per spec, dont overtorque
Gasket leak	Wrong gasket material	Replace with spec gasket (spiral wound)
Weld leak	Porosity	Excavate, re-weld, re-NDE
Test water retention	No low-point drain	Install temporary drain; N2 purge
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Source: Commissioning_and_Startup_Training_Curriculum_v1.xlsx · Sheet: Mod 4 - Pressure Testing

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