Piping Layout Considerations | Calgary, AB
Project Client and Owner Requirements
Most projects have project-speciﬁc requirements imposed by the owner. These usually include additional requirements above the codes and standards which may have direct impact on both pipe layout and equipment location. Most of these requirements derive from operations feedback which the owner contractually invokes on future projects. Owners may not have a thorough understanding of all the levels of detail required to produce a piping design, but they know the ﬁnished product. It is very important that all project personnel and designers know and understand these requirements..
Hierarchy of Reference Design Information
To commence the routing and design of any piping system, the designer is referred to Hierarchy of Design Documents. In the ever-expanding electronic engineering environment, the documents identiﬁed can and will be replaced with databases, but the ﬂow of required information to design the piping systems will remain the same.
System Piping and Instrumentation Diagrams (P&ID). These are the schematic single line process diagrams which deﬁne the sequence of equipment, valves, in-line components, pipeline sizes, and overall system arrangement required for proper system function. Computer-aided P&IDs that link the schematic diagrams to electronic design data are preferred in order to perform computerized P&ID compliance checks.
P&ID Implementation and Physicalization. Piping and instrumentation diagrams are the piping designer’s road map for laying out piping systems. The designer should understand the P&ID and the speciﬁc system characteristics. With this knowledge the designer is required to develop the P&ID and arrange connections and branches as required to best suit the process to actual physical design.
Project Piping Speciﬁcations. These documents or databases deﬁne the following essential information: the system design and operating pressures and temperatures; piping materials; pipe wall thickness or schedules; types of ﬁttings to be used, e.g., butt weld, socket weld, or screwed; and the valve and ﬂange pressure rating and insulation requirements. In addition, the piping speciﬁcation deﬁnes the fabrication, examination, testing, inspection, and installation requirements, including the requirements for seismic installations, where applicable.
Equipment Outlines. These documents can be either imported computer-aided design and drafting (CADD) ﬁles or prints of the equipment being piped. They include overall dimensions and the pipe size, wall thickness, ﬂange pressure rating, and locating dimensions of all pipe nozzles and other connections.
General Arrangements or Equipment Location Drawings. These drawings will indicate the location of all major pieces of equipment in the plant which the designer will either verify or relocate, as required, to accommodate the physical pipe routing as designed or redesign the piping to accommodate the particular piece of equipment.
Generally equipment location drawings are developed by senior-level piping designers during the proposal preparation and are taken over by the project team upon award of the contract. From this point on they are revised and updated as part of the normal process of design development. Equipment should be arranged with the piping layout in mind. Equipment locations and relational arrangements should be evaluated during the piping layout design process. Adjustments and occasionally major changes to equipment arrangement are required to solve major piping arrangement problems. Piping system design is dependent on the input from numerous reference sources prior to the start of piping design.
Collection of As-Built Information
CADD and electronic surveying capabilities have changed and are continuously changing. Photogrametry (photographs that are input into three-dimensional CADD models) and laser mapping (laser scanning using a time of ﬂight laser connected to a computer that translates the scanned points to a three-dimensional CADD model) are applications that enable the designer to collect existing conditions which can be imported into the designer’s CADD ﬁles. Total Station Surveying is the computerized surveying system which engineering should request for the collection of survey data points with the electronic transfer of information being able to be translated directly into the CADD environment.
Piping Layout Considerations and Planning Studies for Improved Piping Economics
Proper planning is an important activity performed by the piping designer in the early stages of a project. Space conservation and a symmetric piping arrangement are achieved when all the systems are evaluated in the preliminary stages of design. This study will become the ﬁnal design. It is important to consider the cost of the piping material at this time for the expensive lines. These lines should be kept as short as possible, while maintaining proper piping ﬂexibility even if this requires changing the equipment arrangement.
Detailed design should not start until the planning studies are complete. Ex-pending engineering work hours on details that are subject to change pending thecompletion of the planning study is not recommended.
Piping layout then becomes a matter of designing dimensioned routings from one point to another point with the branches, valves, piping specialties, and instrumentation as indicated on the P&ID. This statement, however, is an over simpliﬁcation of the process, since many other factors must be considered, such as interference,piping ﬂexibility, material costs, pipe supports, operation and maintenance, and safety and construction requirements.
An example would be moving a pump 3 in (75 mm) to avoid a compound elbow offset in order to connect to the top discharge nozzle. Perhaps the equipment was arranged while planning on a side suction and discharge. Refer to Fig. B3.1.
Pipe bending has become increasingly widespread due to a desire for a decrease in fabrication costs. If bending is to be used, the designer should consider special requirements imposed by the process (i.e., tail ends and clamp dimensions are required by the bending machine, and increased distances and space are required because bends have a greater center-to-face dimension than conventional ﬁtting dimensions).
One of the most important aspects of piping layout is the avoidance of interferences with other facilities in the plant such as other piping systems; structural steel and concrete; heating, ventilating, and air-conditioning (HVAC) ductwork; and electric cable trays and conduit. For engineering ﬁrms using 2D CADD (two-dimensional computer-aided design and drafting) or manual drafting and design, the search for interferences is very tedious and time-consuming since the designer must mentally and visually look for interferences between the systems currently being designed and previously designed or the existing system or facilities, not to mention those systems or facilities in design concurrently. This process is extremely complex at best. Traditionally, this has been accomplished by the use of area composite drawings (see Fig. B3.2) and plastic scale models.
The composite drawings and plastic models show all plant facilities designed to date and are used by the designers to select an interference-free route for the system currently under design; however, the designer still must search out those systems or facilities in design concurrently. Once the designer is satisﬁed that the current system layout is interference-free, it will be added to the area composite drawing and the plastic model.
An alternative to composite piping drawings and plastic models for interference detection is the use of computer-aided design (CAD). Speciﬁcally, three-dimensional (3D) computer modeling can provide an efﬁcient, accurate, and cost-effective alternative to the traditional manual methods for interference detection. This and other CAD applications for piping layout are addressed in the section ‘‘Application of Computer-Aided Design to Piping Layout.’’ Refer to Fig. B3.3.
The effects of the thermal expansion of pipe and ﬁttings as a result of system operating temperature changes cannot be overlooked during the layout and routing of any piping system. The function of piping ﬂexibility or stress analysis has, for the most part, been delegated to the computer particularly in the case of high-temperature, high-pressure piping systems. The piping stress analyst translates and enters the piping design data into the computer, reviews the output data, and if the system is too rigid, may suggest appropriate corrective redesigns. However, it is the piping designer’s responsibility to ensure that the ﬁnal stress analysis results are incorporated into the ﬁnal pipe support and pipe routing design.
In the past, a computer stress analysis, including the development of input data and the interpretation of the output, could be expensive and time-consuming if numerous iterations of computer runs were needed to arrive at an acceptable system design. The experienced piping designer, with the knowledge and capability of
designing piping systems that are inherently ﬂexible, was relied on to keep the number of computer iterations to a minimum. Today, this is much less of a problem with the advent of the personal computer and many computer programs for calculating stresses in piping systems due to thermal expansion and other static and dynamic loads. However, the piping designer must integrate piping ﬂexibility considerations into the piping layout.
The piping designer should route piping with ﬂexibility designed into it, using the minimum amount of pipe, ﬁttings, and expansion loops by considering the following:
Avoid the use of a straight run of pipe between two pieces of equipment or between two anchor points.
A piping system between two anchor points in a single plane should, as a minimum, be L-shaped, consisting of two runs of pipe and a single elbow. This type of arrangement should be subjected to a ‘‘quick-check’’ analysis to determine if a formal computer stress analysis is required. A preferred solution in this case may be a series of two or more L-shaped runs of pipe.
A piping system between two anchor points with the piping in two planes may
consist of two L-shaped runs of pipe, e.g., one L-shaped run in the horizontal plane and another in the vertical plane. This arrangement should also be subjected to a quick-check analysis.
A three-plane conﬁguration may consist of a series of L-shaped runs and/or U-shaped expansion loops designed into the normal routing of the system.
When the expected thermal expansion in any given run of pipe is high, considerthe use of an anchor at or near the center of the run, thereby distributing theexpansion in two directions.
For systems consisting of a large-diameter main and numerous smaller branchlines, the designer must ascertain that the branches are ﬂexible enough to withstand the expansion in the main header.
Systems which are to be purged by steam or hot gas must be reviewed to ensure that they will be ﬂexible during the purging operation.
System or equipment bypass lines may be cold due to lack of ﬂow while the main runs are at operating design temperature, resulting in excessive stresses.
Temperatures during initial start-up and testing are often greater than those atoperating conditions.
Closed relief valve and hot blowdown systems should be given special attentiondue to rapid transients in temperature.
In addition, the piping designer may use a variety of single- and multiplane piping arrangements, such as the L-shaped, the U-shaped, and the Z-shaped conﬁg-urations, in the normal routing of any system, as shown in Figs. B3.4 through B3.9.
The piping designer must be familiar with proper application of all types of valves including gate, globe, plug, butterﬂy, ball, angle, diaphragm, check, pressure relief, and control valves and their methods of operation including manual, chain, gear, air, hydraulic, or motor. The following general guidelines should be applied when locating valves in any piping system:
Valves should be installed with the stems between the vertically upward and horizontal positions with particular attention given to avoiding head and knee knockers, tripping hazards, and valve stems in the horizontal plane at eye level that may be a safety hazard. Large motor-operated valves should be installed in the vertical upright position where possible to facilitate support and maintenance.
Valves in acid and caustic services should be located below the plant operator’s eye level or in such a manner as to not present a safety hazard.
The location of valves, with consideration for operating accessibility, should be accomplished in the natural routing of the system from point to point, avoiding the use of vertical loops and pockets.
Valves in overhead piping with their stems in the horizontal position should be located such that the bottom of the hand wheel is not more than 6.5 ft (2 m) above the ﬂoor or platform. Only infrequently operated valves should be located above this elevation, and then the designer should consider the use of a chain operator or a platform for access.
Where chain operators are used, the valves should be located such that the chain does not present a safety hazard to the operating personnel.
A minimum of 4 in (100 mm) of knuckle clearance should be provided around all valve hand wheels.
Valves should not be installed upside down.
Space should be provided for the removal of all valve internals.
Improper application and placement of valves in the piping system can be detrimental to system function. This can result in malfunction of the valve and in water-hammer, and this can cause the valves to literally self-destruct. What follows are some speciﬁc recommendations and methods of avoiding these problems for some speciﬁc types of valves.
Control Valves. All control valve stations should be designed with the valve stem in the vertical upright position and a minimum of three diameters of straight pipe both upstream and downstream of the control valve, in order to reduce the turbulence entering and leaving the valve and to provide space for removal of the ﬂange studs or bolts. Where applicable, this straight pipe will include the usual reduction in pipe size required to match the control valve size. Space must be provided for ﬂange stud bolt removal where control valve bodies are designed for through-bolt installation.
Butterﬂy Valves. Butterﬂy valves should be provided with a minimum of ﬁve diameters of straight pipe upstream of the valve; and if this requirement has been met, the valve stem and operator may be oriented in the position best suited for operation and maintenance. When a butterﬂy valve is preceded by an elbow and this straight-pipe requirement cannot be met, the valve stem must be oriented in the same plane as the elbow. That is, if the elbow is in the vertical plane, the valve stem must also be in the vertical plane. This recommendation is based on the fact that the velocity proﬁle of the discharge of an elbow is not symmetric. The result can be ﬂuid dynamic torque that is twice the magnitude of that found for a valve with a straight run of pipe upstream. The resultant eccentric forces applied to valve disk produces excessive vibration and disk ﬂutter which eventually may completely destroy the valve.
Check Valves. The preferred installation of any check valve is in a horizontal, continuously ﬂooded run of pipe with cap up; however, swing check valves will function properly in vertical runs of pipe with the ﬂow up. However, the velocity and the rate of ﬂow must be adequate to move the valve disk away from the seat and to maintain the valve in the open position, as required.
Experience has indicated that check valves are highly susceptible to chattering due to upstream turbulence caused by elbows and branches. Therefore the designer should provide upstream straight pipe in accordance with the valve manufacturer’s recommendations. However, where this information is not available, the preliminary design should include a minimum of ﬁve diameters of straight pipe upstream of all check valves. In addition, the designer should be aware that this requirement can be as much as 10 diameters of straight pipe depending on the type of valve and the manufacturer.
Safety Relief Valves. The arrangement for installation of safety and relief valves is very critical and involves the actual location of the valve itself, the design of the vent stack, and the design of any associated drain piping. The designer should adhere to the valve manufacturer’s recommendations and the following guidelines; however, these guidelines relate to the power industry and may be used elsewhere, as applicable.
All relief valves must be in the vertical upright position and ﬁtting-bound to the top of a horizontal run of pipe, the pressure source, and must not be located less than one nominal header diameter from any butt weld.
A safety valve inlet connection in a high-velocity steam line should be located at least 8 to 10 nominal header diameters downstream of any bend in the header, to minimize the possibility of acoustically induced vibrations. In addition, it should be at least 8 to 10 nominal header diameters either upstream or downstream of any diverging or converging T or Y ﬁtting.
No other header branch penetration, for any purpose, should be made in the same circumferential cross section containing the safety valve inlet nozzle.
Where more than one safety valve or a service branch is to be installed in the same header run, a minimum distance of 24 in (600 mm) or 3 times the sum of the nozzle inside radii, whichever is greater, shall be provided between the nozzles.
Where more than two safety valves are located in the same header run, the spacing between valves should be varied such that the distance between two adjacent valves differs by at least an inlet nozzle diameter.
Open Discharge. Open-discharge safety valve installations (see Fig. B3.10) should be in accordance with the following guidelines:
Open-vent stack diameters shall be the calculated minimum ﬂow diameter required for discharge venting without blow-back, except as required to accommodate the movement of the relief valve discharge from the cold to hot position such that the outlet pipe will be centered in the vent stack in the hot position. See Fig. B3.10.
The vent stack entry diameter shall be maintained throughout the length of the vent stack; enlarged entry spools, later reduced in size to the calculated minimum ﬂow diameter, are not acceptable.
The relief valve outlet shall consist of the mating ﬂange and a ﬁtting-bound short-radius elbow, in order to minimize the moment and forces imposed on the valve body.
Vent stacks should be routed, where possible, to provide a straight stack of minimum length. Where offsets or changes in direction are unavoidable, it is desirable to limit the change in direction to 30 or less; however, it could be more. The vent stack should terminate a minimum of 7 ft (2.2 m) or higher above the roof level.
Closed Discharge. Closed-discharge piping systems (see Fig. B3.11) are those piped continuously from the valve discharge ﬂange to a closed receiver, such as a condenser or blow-off tank. This type of system is required for feed water heater shell side relief valves to provide protection against the effects of tube rupture, and may be used in other applications. Other than the normal considerations for designing pipe, there are no speciﬁc guidelines for the design of closed systems.
Drains. Relief valve and open-vent stack drains are important, in varying degrees, as discussed in the following:
The discharge elbow and above seat body drain points are the most critical for safe valve operation. These drains should be collected into a common, closed drainage system and routed to a point where the drain can safely blow to atmo-sphere. This system must be sloped continuously downward and stress-analyzedto ensure that no strain is imposed on the valve body.
Some relief valves now incorporate a relatively large valve top vent connection that is pressurized when the valve blows. This connection may be piped into the combined discharge elbow and valve body drain system and continued, at full-vent pipe size, to the point of the drain discharge.
The open-discharge vent stack drip pan drain connection is of the least importance and is only intended to carry away any rainfall entering the stack and the residual condensate from the stack following a steam blow.
Piping of Centrifugal Pumps
The piping of centrifugal pumps, particularly the suction piping, can seriously affect the operating efﬁciency and life expectancy of the pump. Poorly designed suction piping can result in the entrainment of air or vapor into the pump and cause cavitation, which displaces liquid from within the pump casing, results in vibrations, and throws the pump out of balance. The cavitation alone can result in severe erosion of the impeller. The out-of-balance condition may result in a slight eccentric shaft rotation, which will eventually wear out the pump bearings and seals, requiring a pump shutdown for overhaul. When routing piping at pumps, the designer should follow the manufacturer’s recommendations, the Hydraulic Institute Standards, and the following guidelines:
The suction and discharge piping must be supported independently of the pump such that very little load is transmitted to the pump casing. The designer may consider the use of expansion joints on either the suction or discharge, or both, as necessary. However, expansion joints should be used only when it is unavoidable.
The suction of any centrifugal pump must be continuously ﬂooded, and the suction piping shall contain no vertical loops or air pockets.
When a reduction in pipe size is required at the pump suction, provide an eccentric reducer ﬂat side up. See Fig. B3.12.
The suction side elbow in the piping at horizontal double suction pumps may be ﬁtting-bound and in the vertical plane with the ﬂow from either above or below the pump.
When the suction piping is in the horizontal plane, provide a minimum of three to four diameters of straight pipe between the pump suction connection and the ﬁrst elbow; the eccentric reducer noted above may be included in this straight section.
Only long-radius elbows are to be used at or adjacent to any pump suction con-nection.
All pump suction lines must be designed to accommodate a conical-type tempo-rary strainer.
A pipe anchor must be provided between any expansion joint or nonrigid couplingand the pump nozzle that it is designed to protect.
When pump ﬂanges are cast-iron ﬂat-faced, the mating ﬂanges must also be ﬂat-faced and the joint made up with full-face gaskets and common steel bolts (ASTMA 307, Grade B), not high-strength bolts (ASTM A193, Grade B7). Refer to the Hydraulic Institute Standards for arrangement of pump piping.
Vents and Drains
During the course of physical routing of any system, the designer should provide high-point vent and low-point drain connections for the following purposes:
The ﬁlling of the piping system with water for hydrostatic testing and operation and the evacuation of entrapped air in the process
The evacuation of all water used for hydrostatic testing and operation during periods of start-up and maintenance
High-point vents that will be used frequently should be piped down to an area where they can be accessed from the ﬂoor. When these vents are left out of reach, they tend not to be used. Systems subject to thermal expansion should be reviewed to ensure that they can be properly drained in both the hot and cold positions.
Buried Piping Systems
The economics of installing piping systems have proved that burying pipe in lieu of installing pipe above ground provides a signiﬁcant cost savings in both bulk footage and pipe supports. All system piping should be evaluated for underground installation if possible to decrease the TIC. Low-pressure and low-temperature systems such as for component cooling and demineralized water are good examples of piping that should be buried. Nonmetallic piping materials can be successfully used for buried applications in lieu of metallic piping, carbon steel, or stainless steel which need to be coated and wrapped to protect against galvanic corrosion, resulting in an expensive installation.
Pipe racks are structures designed and built speciﬁcally to support multiple pipes where adequate structure is not available. Pipe layout on pipe racks should follow the Pipe Planning Study concepts. Avoid designing one pipe at a time in order to avoid unnecessary overcrowding and ﬁttings for pipes to enter and depart from the rack. Where possible, pipes should rest directly on the rack with the use of an insulation, if required. Steam piping should exit the rack with a vertical up-and-over to avoid condensate collection points, while water piping should exit the rackwith a vertical down-and-under to avoid a high-point air pocket collection point.
Pipe supports require structural support, which means that piping should be located in close proximity to steel or concrete. Do not locate the pipe too close to the structure, so as to allow adequate space for the pipe support hardware to facilitate installation. Additionally the pipe insulation needs to be considered for clearances and insulation saddles. The most preferred location is either resting directly on structural steel for bottom support or using a single rod to the structure directly above the pipe.
The design and engineering of pipe support systems are covered in detail in Chap. B5; however, it is the responsibility of the piping designer to give serious consideration to the means of support during the piping layout, and in doing so, many pipe support problems may be either minimized or avoided altogether. For this reason, the piping designer should be familiar with the commercially available pipe support components and their application. Piping should be routed such that the support designer can make use of the surrounding structure to provide logical points of support, anchors, guides, or restraints, with ample space for the appropriate hardware. Banks of parallel pipelines at different elevations should be staggered horizontally and spaced sufﬁciently apart to permit independent pipe supports for each line. Piping on pipe racks should be routed using bottom-of-pipe (BOP) elevations. The piping stress engineer should work closely with the structural engineer in the spacing of the pipe rack supports and the method of intermediate support to prevent pipe sagging.
The engineering and selection of thermal insulation materials are covered in "Piping Thermal Insulation | Calgary, AB", and the piping designer should be familiar with these requirements and speciﬁcally with the thickness of insulation for any given system. In the location and spacing of piping systems, there must be clearance space between the insulation of one pipe and any adjacent pipe and/or other possible interference such as structural steel. The piping designer should also recognize that in some applications insulation may not be required for the prevention of heat loss but will be needed for personnel protection, and the spacing and clearances should be adjusted accordingly.
Heat tracing is required when there is concern that the pipe may be damaged due to freezing or that the line needs to maintain a temperature higher than ambient (i.e., caustic piping). The designer must provide the space and clearances for either electric or steam heat tracing and its outer insulation when routing the primary system pipe.
Operability, Maintenance, Safety, and Accessibility
Operability, maintenance, safety, and accessibility are interdependent, and certainly if any given piping component is accessible, it is also assumed to be operable and maintainable. However, maintenance may require additional space for dismantling the component, as noted elsewhere in this chapter. It is the responsibility of the piping designer to design a piping arrangement that satisﬁes all these (and other) requirements with the lowest total cost, i.e., resulting in the shortest pipe runs and the fewest ﬁttings and pipe supports.
Operability, from the standpoint of operating personnel, means being able to perform daily functions in an efﬁcient manner. This is done with consideration for the frequency of operation and the degree of physical effort required to perform it. The designer cannot make every valve and instrument ideally accessible, but will concentrate on those requiring the most frequent operation. Safety-related equipment and valves that are required to be operated during an emergency or to perform critical system functions must be accessible without exception. To ensure success, the designer, system engineer, and operating personnel work out the ﬁnal arrangement. Sometimes input from construction, start-up, and vendor personnel is needed. Formerly in difﬁcult cases, models or even full-size mock-ups have been used as design aids. Today the trend is toward virtual reality. Under today’s conditions the whole process can be accelerated and, when done effectively, accomplished at lower cost than formerly. Additional considerations are discussed in other sections of this chapter. In general, an operable valve or instrument is one that can be readily reached when standing at grade or on an elevated ﬂoor or platform provided for that purpose. The position of the valve hand wheel should be such that the force necessary to operate it can be applied without strain or unduecontortions or interference from valves, lines, or other equipment. It is recognized that plant operating personnel will occasionally have to reach for a drain from akneeling position or a vent valve from a ladder, but these are infrequent operations and as such can be tolerated.
Ease of maintenance actually begins with the development of the plant arrangement and equipment locations by providing sufﬁcient space around each piece of equipment not only for the maintenance of the machinery alone but also for the pipe and the maintenance of the related components. These space allocations should include the pull spaces, lay-down spaces, and rotor and tube removal spaces for the dismantling of all pieces of equipment. The engineering of the system P&IDs will indicate the need for maintenance facilities in the form of bypasses and block valves that would permit certain pieces of equipment or components to be worked on while the system is operating, or at least with a minimum of downtime. However, it is then up to the designer to design these facilities into the system and to provide the accessibility necessary to accomplish that maintenance, including the provision for any lifting gear such as cranes, davits, monorails, and hoists.
There are numerous national, state, and local codes and standards relating to safety, the most notable of which is the Occupational Safety and Health Act of 1970 (OSHA), which became law on April 28, 1971. Several thousand speciﬁc safety and health standards are being enforced under OSHA. These standards have been selected from the key safety standards developed by the American National Standards Institute (ANSI); the American Society of Mechanical Engineers (ASME);and the American Society for Testing and Materials (ASTM); and others, such as the American Water Works Association (AWWA), the American Petroleum Institute (API), and the National Fire Protection Association (NFPA). Stairs, platforms, ladders, aisles, means-of-egress aisle ways, and minimum head-room allowances designed in accordance with OSHA will provide a safe place to work. It is the responsibility of the piping designer to place equipment, valves, and other piping components in such positions that they do not create hazards. These hazards could include any piping components that presented themselves as ‘‘head knockers,’’ ‘‘knee knockers,’’ or trippers. The most common cause of these problems is valve stems, and common sense would say to place a valve in a horizontal run of pipe with the stem vertical, wherever possible. When this cannot be done, the designer should ascertain that the stem does not project into an access area and become a hazard. The designer should make every effort to keep such projections out of heights of 4¹⁄₂ to 6 ft (1.5 to 2 m), or speciﬁcally at face level. Steam system valves must not be placed at face level in the horizontal position since a packing gland leak may blow steam into the face of an operator; if this were a super-heated steam leak, the vapor would not be visible. This same principle applies to hazardous and toxic ﬂuids. However, this may be too restrictive, and it is not meant to rule out any perfectly safe arrangement of valves at face level if
They are outside the limit of a platform.
They are a part of a manifold of valves, all projecting about the same distance and with adequate access space in front of them.
It is an isolated valve guarded by an adjacent pipe or structural steel.
Accessibility has already been discussed at length in terms of space and the normal platforms and stairways provided in any plant; however, the designer should review the layout and determine if there is a need for any platforms which access a remotely located valve or component.
Interfacing Disciplines and Organizations
Piping design requires coordination and cooperation with all interfacing disciplines including civil, electrical, instrumentation, and construction. Piping arrangements should blend with the layout design of interfacing disciplines. Pipes that require extensive support schemes in lieu of being conveniently located near structural support steel should be avoided. Pipes or electrical trays that twist and turn to avoid one another should be uniformly designed in a coordinated design effort which reduces congestion and reduces TIC. Most piping designs are not completed by a single designer or company, which makes the coordination between designers and different organizations critical. The best way to address this concern is to agree to speciﬁc divisions of responsibility in the planning phase of the project.
Electrical Tray and High-Temperature Piping Interfaces
High-temperature piping must not be located near electrical trays, wherever possible. This piping should cross over trays, not under them. The radiant heat could have an adverse effect on the cables. Electrical equipment maintenance space should be identiﬁed and accounted for in all piping passing near this equipment.
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