Paper poster presented at the 10th Global Congress on Process Safety (GCPS). New Orleans, LA, USA, March 31, Apr. 1 – 2, 2014.

1. Liquid Fuels Release Rate Calculation In Transport Pipelines With Complex
Topographical Conditions
C. Manjarrés*, J. Cadena, F. Muñoz
Chemical Engineering Department, Universidad de los Andes, Bogotá, Colombia
*ca.manjarres10@uniandes.edu.co
Abstract
Pipelines are the most efficient and economical mean of transportation of hazardous materials (HazMat)
through long distances. The main concern related to the operation of these systems is the loss of
containment events (LoC). In order to ensure a safe and reliable operation of these systems, it is required to
perform risk analysis. One of the main inputs to risk analysis is the release rate. This work presents a tool
that allows a simple, non-phenomenological calculation for a quick estimation of available volume for release
and the associated release rate profile. In a previous version, the flow of liquid through a hole in a tank
source model was used. This version employs an inclined pipe with bottom hole source model in an attempt
to reproduce the actual geometry of the pipeline. These calculations are performed at a very low
computational cost, with running times in the order of minutes. The tool was developed using MS Excel®,
macros and VBA programming. The results provided become a key input to perform a priori risk analyses of
pipeline systems.
Introduction
Description of the Tool
This work provides a simple method to compute release rates in liquid phase, in static pipelines,
considering automatic active safety barriers (check & automatic block valves), by quick a non-
phenomenological calculation. This supports the construction of risk analysis scenarios.
Methodology
Figure 1. Graphical representation of the algorithm.
Figure 2. Dead volume and Source model (Inclined pipes).
Assumptions of the model:
 Once the failure takes place, and just after the pumps shut-off, the operating pressure is reduced to cero
(0) psi, being the liquid column height the only driving force of the release rate.
 The tool is restricted to onshore pipelines. The model is based on 1-D axial flow.
 The model is restricted to liquid-phase. No phase change is considered.
 Isothermal flow. No heat transfer calculation is performed.
 No transient flow effects are considered (e.g. water hammer).
Case Study
The case study corresponds to a gasoline transport pipeline, located within an urban, populated zone, with a
total length of 10 km, and 6” NPS. The following summarizes the parameters used in the simulation.
Figure 3. Case study – Pipeline profile.
Results
Dead volume (V):
Figure 4. Dead volumes.
Total release time (t) and Peak release rate (Q)
Figure 5. Peak release rate (left) and Total release time (right).
Release rate profile: Low point (great liquid column) High point (small liquid column)
Figure 6. Release rate profile – Low point (left) and High point (right).
Conclusions
The developed tool:
 Constitutes a simple and fast approach that allows the quick estimation of the release rates and times of
hazardous materials in liquid phase.
 Supports the construction of analysis scenarios for risk analysis (e.g. QRA) due to its low running time.
 Friction plays an important role in the low points of pipeline (higher liquid column).
It is important to estimate the dead volumes in mountainous regions (e.g. Andean Countries), because static
contribution to release rate might be much higher than the dynamic contribution.
References
1. C. Manjarrés, J. Cadena, M. Montoya, F. Muñoz. Cálculo de tasas de liberación de materiales peligrosos en fase líquida en tuberías de transporte en zonas
montañosas. Oral presentation at the 5th Latin American Conference on Process Safety (LACPS). Cartagena, Colombia, August 2013.
2. D. A. Crowl and J. F. Louvar. Chemical process safety fundamentals with applications. Prentice Hall, 3rd Ed., 2011.
3. Eva Romeo, Carlos Royo, Antonio Monzón, Improved explicit equations for estimation of the friction factor in rough and smooth pipes, Chemical Engineering
Journal, Volume 86, No. 3, 2002.
Pipeline (new) Gasoline transport
- Length, km 10 - Check valves 1
- Diameter, in 6.065 - Block valves 2
- Operating pressure, psi 80 - Material of construction Carbon steel
- Roughness, ft 0.00015
Substance Gasoline Failure
- Density, kg/m³ 750 - Leak size, in 0.25
- Viscosity, cP 0.65 - Discharge coefficient 0.61
Increasing fuels needs,
means increasing fuel
transport demand, which
denotes the expansion
of pipeline systems.
Colombia has over
10000 km of liquid fuels
transport pipelines.
Pipelines pose a risk to
people, the environment
and infrastructure.
LoC events might have
severe consequences in
terms of human lives
and economic losses.