PLTB Liquid Services - Pipeline Testing

Introduction

The Pipeline Toolbox is home to many tools and calculators. The PLTB User’s Guide presents information, guidelines and procedures for use during design, construction, operations and integrity tasks for field or office applications.

Pressure testing is an industry-accepted method for validating the integrity of pipelines. This integrity assessment method can be both for strength and leak integrity testing. These methods are appropriate for the type of testing and functions performed. Results of a risk assessment and the types of anomalies expected are used to determine when to conduct inspections utilizing pressure testing.

Module/Application

API 1104 Appendix A: Weld Imperfection Assessment
Pipeline Hydrostatic Testing
Gas Pipeline Pressure Testing – Maximum Pressure Drop
Purging Calculations

References

Pipeline Design for Hydrocarbons Gases and Liquids, Committee of pipeline planning, American Association of Civil Engineers, 1975
Engineering Data Book, Volume II, Gas Processor Association, Revised Tenth Edition, 1994
Pipeline Design & Construction, A Practical Approach, American Society of Mechanical Engineers, 2000

Appendix of Definitions

ACTUAL PIPE SIZE – The measurement equal to the outside diameter of the pipe.

BURST PRESSURE – The level of pressure at which a component, pipe, tube, hose or other fluid passage will burst during application of internal pressure. Normally 4.0 times working pressure.

COMPRESSIBILITY – The change in volume of a unit of fluid when it is subjected to a unit change in pressure (in2/lb).

COEFFICIENT OF THERMAL EXPANSION – A physical property value representing the change in length per unit length, the change in area per unit area or the change in volume per unit volume per one degree increase in temperature.

DIAMETER – The distance between one edge of a circle and the other as measured on a straight line through the center of the circle.

DIFFERENTIAL PRESSURE – The value or magnitude of pressure measured as the absolute difference of the inlet pressure and outlet pressure

DOWNSTREAM – The passage beyond a device, normally at the outlet of direction of flow.

EXPANDED PIPE – Pipe which has been enlarged circumferentially by mechanical or hydraulic pressure.

FATIGUE – The tendency for a metal to break under conditions of repeated cyclic stressing;
stresses that are considerably below the ultimate tensile strength.

FLOW RATE – The volume, mass, or weight of a fluid passing through any conductor per unit of time.

FLUID VELOCITY – The speed of fluid through a cross section expressed in length divided by time.

GRADE – A class of steel defining amongst others, chemistry, tensile strength, and yield strength requirements.

HEAD – The measure of pressure at the base or other reference point of a column of fluid. Normally measured in feet of water.

HYDRAULICS – Engineering science pertaining to liquid pressure and flow.

HYDROSTATIC TEST – A mill test that is normally required by specifications. The ends of the pipe are sealed, and high-pressure water is applied into the pipe at predetermined pressure for specific period of time as required by the various specifications.

INSIDE DIAMETER (ID) – The distance of a straight line passing through the center of a pipe from one inside pipe wall to the opposite inside wall.

LAMINAR FLOW – A condition of flow in a passage that is typified by slow movement of fluid in a relatively straight path along the centerline of a passage.

MASS FLOW RATE – The mass of fluid per unit of time passing through a given cross-section of a flow passage in a given direction.

MODULUS OF ELASTICITY – The slope of the elastic portion of the stress-strain curve in mechanical testing. The stress is divided by the unit elongation. The tensile or compressive elastic modulus is called Young’s modulus; the torsional elastic modulus is known as the shear modulus, or modulus of rigidity.

NITROGEN – An inert gas used to serve as an energy source for accumulators or to be used as a cleaning agent when pure, nonexplosive gases are required.

OPERATING PRESSURE – The maximum level of pressure at which a component, pipe, tube, hose or other fluid passage will experience during application of maximum expected fluid pressure. See also BURST PRESSURE and PROOF PRESSURE.

OUTSIDE DIAMETER (OD) – The distance of a straight line passing through the center of the pipe from one outside rim of the pipe to its opposite outside rim.

PRESSURE – Force per unit area. Usually expressed in pounds per square inch (psi), bar or kilopascal (kPa).

PRESSURE DIFFERENTIAL (Drop) – The difference in pressure between any two points in a system or a component.

PRESSURE REVERSAL – The phenomenon of pressure reversal occurs when a defect survives a higher hydrostatic test pressure but fails at a lower pressure in a subsequent repressurization.

PSI – Pounds per Square Inch.

PSIG – Pounds per Square Inch Gage.

RADIUS – The distance of a straight line from the center of a circle to its edge.

RATED FLOW – The maximum flow that a manufacturer assigns to a specific component as the maximum desirable flow at which the device will function properly. Also the flow that a designer assigns to a system as the nominal maximum flow.

RATED PRESSURE – The maximum pressure that a manufacturer assigns to a specific component as the maximum desirable pressure at which the device will function properly.

RELIEF VALVE – A valve that limits the pressure at its inlet port by exhausting flow present at its inlet port to another chamber of lower pressure potential through its outlet port.

RESTRICTION – A reduced cross-sectional area in a line of passage producing a pressure drop.

SAFETY FACTOR – The ratio of burst pressure to rated pressure under specific static pressure and temperature conditions. See BURST PRESSURE.

SPIKE TEST – is a variant of the hydrostatic test in which the pressure is initially raised to a prescribed level above the minimum test pressure, or stress level, for a short period then reduced for the remaining duration of the test.

STATIC HEAD – A measurement of pressure that is present when no fluid flow exists in a passage. The static head is normally expressed in feet of water.

STRESS – The load per unit of area. Ordinarily stress-strain curves do not show the true stress
(load divided by area at that moment), but a fictitious value obtained by always using the original area.

SURGE – An increase in pressure that occurs for a specified short period of time over the normal expected working pressure.

TENSILE STRENGTH – The value obtained by dividing the maximum load observed during tensile straining until breakage occurs by the specimen cross-sectional area before straining. Also called ultimate strength.

TURBULENT FLOW – A condition of flow in a passage that is typified by rapid movement of fluid in a passage, where the fluid is churning and bouncing off the passage walls.

UPSTREAM – The passage ahead of a device, normally at the inlet of direction of flow.

VELOCITY – The speed of fluid flow through a hydraulic line. Expressed in feet per second (fps), inches per second (ips), or meters per second (mps). Also, the speed or a rotating component measure in resolutions per minute (rpm).

VOLUME
The size of a space or chamber in cubic units. Loosely applied to the output of a pump in gallons per minute.

WORKING PRESSURE – The maximum pressure to which a hose will be subjected, including momentary surges in pressure, which can occur during service.

YIELD STRENGTH – The stress at which a material exhibits a specified limiting deviation from proportionality of stress to strain. An offset of 0.2 percent is used for many metals such as steel, aluminum base, and magnesium base alloys, while a 0.5 percent total elongation under load is frequently used for copper alloys.

Related Links

Pipeline Toolbox: User Guides
Pipeline HUB — User Resources