The Piping Designer

In this analysis the designer must consider two conditions and base the pipe design on the one that is worse. One condition is where the temperature differential is one half the difference between the maximum temperature and minimum temperature. The second condition considers the temperature differential between the maximum pipeline temperature at installation and the minimum design temperature. 

The moisture removal from the subslab can be very substantial, and could amount to many gallons of water per day.13-15 Unless the piping design allows for that water to drain back into the soil, the water could block flow of air in the piping or interfere with the fan operation. Evidence of moisture and other debris has also been found in the staining of roofs near the exhaust pipes of the SSD systems. 

A heavier wall thickness than is required by the pipe design factor, F, in accordance with Table PL-3.7.1(b)(6)-l or Table PL-3.7.1(b)(6)-2, may be used. 

The piping design limits variations in gas flow to the tubes and burners to +2.5% to keep tubewall temperatures uniform. The PSA offgas flow is available to the burners at only about 3 psig. If preheated combustion air is used, the differential air pressure across each burner is typically less than 2 inches of water. The distribution is aided with symmetrical piping. 

Appendix F defines the method used by the piping designer to determine allowable piping loads. 

Note Flange loading on the pump may increase when the unit is bolted down and must be addressed in the piping design. 

Although it was implied, the investigation report did not specifically state that there was also human error on the part of the piping designer/installer that contributed to the deceptive appearance and by the people who reviewed the installation. These types of situations cannot be seen on P IDs. Piping systems and situations that appear counterintuitive can yield mistakes more easily. 

The task of the piping designer is to size the line so that the flow of fluid will create a pressure gradient that is near the economical optimum. The economic optimum conditions take into account both the capital cost of equipment and operating costs of pumping, energy, etc. 

Welded fittings must be examined in the piping design to ensure that surface finishes are not compromised and that piping and equipment are accessible for maintenance, repair and cleaning. 

The piping designer needs three essential source documents engineering flow diagrams, nomenclature, and equipment elevations. These documents are usually furnished by the piping analyst. 

Engineering flow diagrams do not present all the essential information for the piping designer. They do not include equipment elevations and insulation specifications, which may be obtained from the equipment elevation summary and from the nomenclature list. 

On the average-size process plant engineering flow diagram, there are approximately 1,500 separate pipe lines. Information on each of these lines is absolutely necessary for the piping designer. The information that must be shown on each line includes the size, the line specification showing... 

If the piping designer blindly follows an exchanger designer s nozzle locations and flow requirements, he can end up with the piping... 

In exchanger maintenance either the complete unit is removed, cleaned and repaired, or only the tubebundle is removed for cleaning and repair — the shell is cleaned in place. If the complete unit is removed, all piping must be disconnected. If only the tubebun e is removed, only the channel nozzle piping need be disconnected. The piping designer can help maintenance in three ways ... 

When a 3/4-inch thermowell is to be used, the pipe designer is cautioned not to use the conventional 3/4-inch full pipe coupling for mounting it. If the 3/4-inch full coupling is welded on equipment, the narrowness of the inside of the coupling where the two pipe threads meet may prevent thermowell insertion. If, instead, a 3/4-inch, 6,000-pound thread adapter or elbow... 

The other advantage of this method is that it will also reduce the number of types of thermowells that have to be ordered. The types that must be carried in stock for future maintenance work are kept to a minimum. When the piping designer knows in advance the thermowell insertion lengths preferred, he will be in a better position to provide for their installation in the process piping. Time will be saved and he will be able to complete his drawing sooner. 

In Figures 7-95 to 7-108, the many piping details shown will suggest to the piping designer the various schemes that can be used. The importance of these details is that each has been provided with a scale in inches shown on the centerline run of the thermowell. This scale will enable the instrumentation engineer to select a thermowell. With it he can pinpoint the active effective flow area, preferably in the turbulence zone, where the thermal element of the instrument will be located. 

Table 7-22 lists the thickness of conventional low temperature piping insulation for all the common materials except the foamed resins. Before beginning the piping design, the types and thickness of insulation must be firmly established so that proper line clearances may be set. Because the clearances required are much larger than conventional process piping, this aspect is... 

The pipe designer has been given process and engineering flow sheets and equipment layout drawings with or without scale models. He has chosen pipe sizes and materials according to the methods discussed in... 

Grades of PE have been specially developed for the gas pressure pipe market. Eirst-generation HDPEs were not used in the UK. The second generation of MDPE copolymers has superior creep rupture resistance at the pipe design lifetime of 50 years (Fig. 14.5). The data falls on one or more lines lines of shallow slope are associated with ductile failure and lines of steeper slope with brittle plane strain crack growth (Fig. 14.3). The... 

P IDs may be the more appropriate type of diagrams to show some of the above details and to display the information for the piping designer and engineering staff. The P lDs are to be used to describe the relationships between equipment and instrumentation as well as other relevant information that will enhance clarity. Computer software programs which do P lDs or other diagrams useful to the information package may be used to help meet this requirement. 

All extrusion processes require some form of melt transfer from the extruder to the feedblock or die. The transfer device can be short, such as an extruder adapter, or longer, as required in coextrusion piping. The pipe design is integral to coextrusion success in general, the inside diameter... 

The final EPR solution proposes today two 25% safety valves and one 50% relief valve per steam generator. The induced savings are very significant on the equipment cost and on the piping design. The overall safety is also improved due to a reduction of the risk and consequences of overcooling accidents. 

In processes where materials are transported mainly in the fluid phase, such as most oil refinery units, the piping design considerations tend to dictate the layout, whereas for plants processing solids, such as metallurgical reduction plants, the bulk solids handling design is the major consideration. 

Incorrect statement of pipeline design conditions as a result of lack of consistency between the process engineers practice and the requirements of the piping design code. ... 

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