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When using those codes which define a stress intensification factor for reducers, one would have to he calculated and specifically applied at that location. There are a number ofreasons for performing stress analysis on a piping system.
It may be necessary to model it as three rigid elements if the weigh t of the operator is significant in com parison to the valve body.
The Expansion Joint Manufacturers Association recommends that the first guide be placed a distance no further than 4 pipe diameters from voade expansion joint, with the second guide placed no further than 14 pipe diameters from the first.
Or more simply, the “theoretical” cold load is the cold load to be specified in the factory order of the spring, while the “actual” cold clade is an approximation ofthe reading ofthe spring load after pulling the pins upon initial installation.
Previous Topic Index Next Topic. Since the failure coads of expansion joints is fatigue, the relative expansion displacements hetween the start and end ofthe expansion joint must be checked against the manufacturer’s allowables.
COADE Pipe Stress Analysis Seminar Notes
If the engineer supports a piping system such that no span in the system exceeds the standard spans listed in the table, it is virtually certain that the system is adequately supported for weight loading. The elements are further defmed by a constant non-varying along the element length set of stiffness parameters i. A discussion of pressure design of components is included here for the sake of completeness, and is based upon an amalgam of the requirements of various codes.
Or, examining the formulas above, it is evident that, as the shorter portion of the span b approaches zero length, the moment, and therefore the stress, approach zero as weIl. The question is what beam stress equation should be used?
An element such as this is usually modeled as a single, or as a series of elements, each having average parameters. In less pronounced cases such as those shown in Figures B and Cnots from the response of an unstiffened bend is usually ignored. Unless otherwise noted herein, the information contained in these cpade notes is proprietary and may not be translated or duplicated in whole or in part without the expressed written consent of COADE Engineering Software, Jones Rd.
The bending stiffness that should be used is exactly four times the hending flexibility.
Tension in the pipe wall is not continuous when there are expansion joints or slip joints present in the system. Node is In the event that the manufacturer only gives axial stiffness, the other two can be calculated once the effective diameter and length are known. Separators modeled as pipe Location Figure An angle valve could be modeled as shown in Figure Figure Simplest Model: Elbows ovalize significantly when subjected to bending loads. These alternating stress intensities are designated as SaltlSa1t2, The equation give in the part John mentions may be conservative in some situations.
For mitered elbows, the maximum allowable pressure is calculated differently depending on whether the angle of the miter cut is less than or greater than With nonlinear systems, the effect the occasionalload has on the system is linked to the effect of the operating loads on the system.
The most important point was made by Rich Ay. Reliefvalve jet loads are normally provided by the valve manufacturer. This method will provide the best approximation of the distribution of the piping semlnar to the vessels. The actual installed load case should be run with the cold spring in order to determine the installed hanger settings semiinar the presence of cold spring. Therefore, substituting this value for the weight component ofthe stress equation: Expansion joints may vary in terms of the number and type of convolutions, the material, the number of plies, all ofwhich effect the pressure capacity, the stiffness, and the allowable movement.
A system’s behavior can be quantified through the aggregate values of numerous physical parameters, such as accelerations, velocities, displacements, internaI forces and moments, stresses, and external reactions developed under applied loads. A Rotating Equipment Centerline B Figure In the Figurea small, but heavy process monitor and actuator is mounted on the line. Sh is roughly defined as the minimum of: Esminar, pipe stress software cannot be used to accurately determine the effects ofthe piping system on rigid elements.
These are designated as NI, N2, A 8 C Figure These attachments almost certainly affect the flexibility, and more importantly, semijar stress intensification factors for the bends.
Figure The maximum moment in seminxr beam is in the center of the span, and has a value of: Therefore, standard practice dictates that standard spans be applied subject to the following four caveats: In this case it is necessary to ignore the “actual” cold load, and in some cases it may be preferable to adjust the springs in the field to carry the cold load once the system has been filled.
Old Hanger Redesign – In cases where part of a piping system is redesigned, it is preferable that the hanger design algorithm re-select the existing springs in the system wherever possible.
The minimum thickness for a blank is calculated as: Consider an expansion joint with the following parameters: Building codes provide ways to calculate seismic g-factors, based upon earthquake potential, structure type, and structure fundamental frequency.
Additionally, support manufacturers typically limit the range of a hanger rod’s arc in to values such as 60, where the seminaar can be calculated as: In order to provide margin against analytical uncertainties, it is best to use the recommended range. Seminaar that torsional stiffnesses are not usually provided, since unprotected expansion joints are not designed to carry nites and may fail catastrophically if inadvertently exposed to even moderate torsional moments.
If seismic response spectra are available for the piping system, then, given the natural frequency of the lowest mode of vibration of a piping system, the analyst can find a semibar acceleration from one of the curves.
Available Space – In certain cases, the distance between the top ofthe pipe and the steel overhead; or between the bottom of the pipe and the foundation or platform below, govern the type and number of springs which may he used at a specific location.
Therefore, even if a system has been running successfully for many years, it is no evidence that the system has been properly designed for secondary notfs. Pipe connections to thin walled vessels: Note that primary loads are usually classified further, according to their duration ofloading.
COADE Pipe Stress Analysis Seminar Notes – Free Download PDF
Cold load design balances the weight loads in the cold, rather than semiar hot, condition. The properties ofthat bellows are then inserted into the piping model.
Note that some engineers may prefer to model the effects ofthis equipment by applying a force equal to the weight and a moment equal to the weight times offset at botes centerline ofthe pipe. In Figurethe system consists of a 12″ diameter, standard schedule steel pipe filled wi th water, wi th a design pressure of psi, and a design tem perature of F, which runs hetween two equipment nozzles.