Single Phase Liquid Flow - Water Hammer and Surge Pressure Design Guide
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Water and Slurry HammerDescription complète
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All pipeline systems are susceptible to water hammer that can cripple critical infrastructure. One effective method to relieve excessive waterhammer pressures in pipelines is to use air chambers....
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water hammer
All pipeline systems are susceptible to water hammer that can cripple critical infrastructure. One effective method to relieve excessive waterhammer pressures in pipelines is to use air chambers....
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Detailed explanation of the effect and causes of water hammer
Description complète
Pressure drop is of paramount importance in a fluid flow. Single phase pressure drop occurs in a pure liquid or pure gas flow. Two phase pressure drop occurs in phase changing equipments like evaporators and condensers of refrigeration air conditioni
Solid-Liquid Phase Diagram of Naphthalene-Diphenylamine Two-Component System
SINGLE PHASE LIQUID FLOW - WATER HAMMER AND SURGE PRESSURE DESIGN GUIDE
A. Bourji REVISION DATE
REV.
22-Jan-2004
1.0 SCOPE
This design guide presents the basic physical principles involved in water hammer and pressure surge. In addition, this design guide provides a method for approximating surge pressure in simple cases (see Figure 1), which can be used for preliminary design or to check the results of commercially available programs. For detailed analysis of more complex systems, SURGE2000 software is available within the Process Engineering department. Figure 1.
Surge – Simple Case
2.0 RESPONSIBILITIES
The process engineer is responsible for calculating water hammer pressure and for determining the means of reducing it when it exceeds the pressure capabilities of pipe and/or components in a piping system. 3.0 Definitions a
β b D E L ∆ p
ρ
τ t c
∆V
147943599.doc
= = = =
= = = = =
pressure wave velocity liquid bulk modulus of elasticity pipe wall thickness internal diameter of pipe = modulus of elasticity of pipe wall = the distance from the valve to the pipe inlet maximum pressure rise liquid density [slugs/ft 3 (BG Units), or kg/m 3 (SI Units)] critical time valve closure time change in liquid velocity
2
PROCEDURE NO.
REV.
DATE
PTD-DGS-119
2
22-Jan-04
SINGLE PHASE LIQUID FLOW – WATER HAMMER AND PRESSURE SURGE DESIGN GUIDE
Note: Consistent units must be used for all formulas. It is recommended that the process engineer, when using the formulas supplied in this text, write out the units for each variable to ensure proper cancellation of units.
147943599.doc
PAGE OF
2
12
PROCEDURE NO.
REV.
DATE
PTD-DGS-119
2
22-Jan-04
SINGLE PHASE LIQUID FLOW – WATER HAMMER AND PRESSURE SURGE DESIGN GUIDE
4.0 WATER HAMMER AND SURGE PRESSURE
4.1
Potential Surge Pressure Hazards
A pressure surge is generated in a piping system whenever there is a change in flow rate of the liquid in the line. Surge pressures can cause extremely rapid changes in pressure, rapid enough to cause metallic percussions or a pounding of the line commonly known as water hammer. Potential causes of surge pressures are:
• • • • 4.2
Closure of an automatic valve Rapid closure or opening of a manual or power-operated valve Slamming shut of a non-return (check) valve Starting or stopping of a pump Pressure Wave Velocity
When a fast closing valve decelerates liquid flowing in a pipe, the kinetic energy of the flowing liquid is converted to surge pressure as the liquid compresses and the pipe wall stretches. The surge pressure propagates in a wave upstream to the pipe inlet at the speed of sound in the liquid, modified by the physical characteristics of the pipe. A return “negative” pressure wave is reflected back to the valve from the pipe inlet. The cycle of successive reflections of the pressure wave between the pipe inlet and valve result in alternating pressure increases and decreases which are gradually attenuated by fluid friction and imperfect elasticity of the pipe. Equation 4-1 will give the velocity of the pressure wave. a=
• • • •
β ρ 1 + ( β E )( D b)
(Eq. 4-1)
Notes See Figure 2 for average bulk modulus for crude oil, fuel oil, gas oil, and gasoline See Figure 3 for average bulk modulus for lubricating oils See Figure 4 for bulk modulus of water See Table 1 for modulus of elasticity for metals
