Valve Slamming Loads

[jailanis]

How Valve slamming loads to be modeled in Caesar-II?

We have 30 inch oil and 28 inch Gas check valves and axial loads due to sudden closure of valves is 223 tonne and 97 tonne respectively (huge forces).

The valve "shock loading" is assumed to occur from only reverse flow resulting from instantaneously " full bore" pipeline rupture upstream of valve.

 

[LSThill]

jailanis (Mechanical)

Dear jailanis (Mechanical, Team member the solution application for your question is FE-PIPE and BOS Fluids. Set up the CAESAR II Modle then let the FE-PIPE AND BOS FLUIDS GIVE YOU THE SOLUTION.

BOS Fluids is the engineering software package that analyzes fluid transients in pipe systems and relates this information back to the mechanical piping system transferring the fluid.

For years piping engineers have labored with simplifying hand methods, cumbersome analog computers, or user-unfriendly software products when needing basic steady state and transient fluid analysis capability. BOS Fluids was written specifically to address the need of the piping engineer for fluid reaction forces, and to provide a system whereby the fluid simulation results can be easily integrated back into the piping system design and analysis.

BOS Fluids is an interactive computer simulation package that models steady state and transient flow in liquid or gas carrying piping systems. The procedure is easy to use and interfaces with most pipe stress programs. The package contains the elements required to model most common unsteady flow conditions. The elements included in the simulation package are pipes, valves, pressure relief valves, vacuum breaker, air valves, pumps, equipment, surge vessels, inlets, outlets, and orifices. BOS Fluids makes fluid simulation simple and easily accessible and yet gives the analyst pressure transients and dynamic force results with an engineering accuracy.

Based on a number of realistic assumptions a simplified form of the time dependent conservation (Navier-Stokes) equations are solved for the internal channel flow. The assumptions made are:

1. Fluid behavior in pipes is one dimensional i.e. similarity of cross sectional distribution of properties does exist.
2. Fluid transport velocity is small compared to wave speed.
3. Wave fronts remain plane while propagating.
4. Gas simulations assume that flow velocities are below sonic, and that pressure drops through the system are less than 30%.

Based on these approximations friction effects are lumped. The present friction model used is Colebrook-White. The Darcy-Weisbach flow model is used for steady state pressure drop calculations and the basic theory applied in BOS Fluids can be found in Wylie & Streeter's "Fluid Transients" published by FEB Press. BOS Fluids is capable of simulating both the steady and transient behavior of liquid carrying closed conduit systems of pipes, valves, pumps and surge relief devices. The following special features are available:

1. Pipe stress models from either CAESAR or PipePak can be downloaded for fluid analysis.
2. The analyst can pick different fluids from a database or add their own fluids to the database
3. Two different models are available to simulate column separation: Concentrated Air Pocket (CAP) model and the Vapor Cavity Model (VCM).
4. Various pipe materials can be applied-both isotropic (Metals) and Orthotropic (FRP) materials are included.
5. Based on geometry typical pump properties are generated automatically.
6. Buried and above ground systems can be simulated.
7. Simultaneously the transient response of multiple sources: Pump starts, Pump Failures, Valve Operations can be simulated.
8. Harmonic option allows an analysis of the occurrence of standing waves.
9. Maximum and minimum pressures and velocities occurring during transient and/or harmonics are traced.
10. The force processor allows an analyst to survey the time history of the unbalanced forces on pipe sections and preprocesses the force time histories to be used in the dynamical module of the pipe stress program.
11. A spectrum breakdown of force time histories is available. The analyst can see the natural frequencies of the fluid response that tend to excite the piping system.
12. Both Metric (SI) and English Units can be selected.

Typical analyses using BOS Fluids include: water transmission and distribution systems, main cooling water systems for chemical plants, sewage water systems, combined power and drinking water cycle power stations, oil product transport lines, tanker loading and unloading systems and dynamical behavior of chemical liquid transport lines. Acoustic analyses for compressors and pumps.


Please contact Tony Paulin,

http://www.paulin.com

11211 Richmond Avenue Suite 109 Houston TX 77082 USA Ph: 281-920-9775 Fax: 281-920-9739

"Fluids Analysis make Piping Sttress Analysis go away"

Leonard@thill.biz

http://www.thill.biz