A recurring question asked about the Engineering process is the frontier between BASIC and DETAIL Engineering. Engineering design is indeed a continuum and one may wonder to what level of details corresponds the BASIC Engineering.

This question finds its answer while considering the purpose of BASIC Engineering, which is define the facility to high enough a level of details so that

1)      contractors can estimate the costs for the EPC execution of the facility with enough accuracy to submit a lump sum bid,

2)      the documents define the facility in enough details to secure a certain standard of quality in design, materials and workmanship for the Owner

It is in both the owner and the contractor’s interest that the plant is as well defined as possible at BASIC Engineering stage.

This is rather obvious for the EPC bidder, in order for him to properly assess its costs and the required resources. An insufficiently developed BASIC engineering is likely to show quantities significantly inferior to the actual ones. This may lead to an underestimated cost and resources allocation by the EPC Contractor. This will create a strain in the project execution, as contractor will exceed its budget or will not have planned and mobilized sufficient resources.

An ill defined BASIC engineering will also lead to a large number of changes in EPC phase, which will generate delays in Engineering, extra costs etc.

The owner will also benefit from a well defined BASIC Engineering, as its requirements will be precisely defined, ensuring compliance by contractor.

One could think, however, that a too high level of details in the Engineering basis of a lump sum EPC contract could be detrimental to the owner. A precise definition at an early stage is very likely to require numerous changes as design develops later on. The EPC Contractor could then claim extra costs for such changes to what he bid for.

Let’s consider a facility whose BASIC Engineering package included drawings of its equipment supporting structures. As the piping routing and location of manifolds, instruments, filters etc. will not have been developed as this stage, the structure will most probably lack floors to accommodate these equipment while providing access to the operator. Should drawings of these structures be issued at BASIC engineering stage, these floors will be missing. As these floors will prove necessary as design progresses, the EPC contractor may very well consider them as additions that were not quoted for. The EPC contractor could compare the final design (with operating floors) and that of the BASIC design and claim for the incremental cost.

To protect the owner against such risk, the EPC Contract includes a clause that specifies that the EPC contractor endorses the BASIC Engineering. This means that the EPC contractor takes responsibility for the content of the BASIC Engineering and forfeits its rights to claim for any change, including changes required due to design development, such as that the additional floors discussed above.

Although the higher BASIC Engineering is defined, the better it is for both parties, the Owner will want to limit its duration to launch the EPC as soon as possible. BASIC Engineering will therefore focus on a limited number of activities and deliverables.

First of all, a BASIC design package, that will form the Engineering basis of the EPC Contract, will contain generic documents, not specific to the particular facility being projected, but aimed at defining certain standards to the EPC Contractor for the design, materials and workmanship. These are the General specifications, usually that of the owner.

The general specifications will include specifications for the various types of materials and works.

The specific document describing the facility will come next, starting with the 3 most important ones, that almost by themselves nail down the price of the facility: the P&IDs, heat and material balance and General Plot Plan, to which could be added the Electrical One Line Diagram.

The Process and Utilities P&IDs along with the Heat & Material balance will set the duty of all process equipment.

The Plot Plan will set the overall dimensions of the facility and the distance between equipment, which will determine the length of all networks (piping, cables, roads, sewage etc.) directly impacting their supply and installation costs.

Once these are defined, BASIC Engineering, whose aim is to allow an accurate estimate of the cost of the facility, will focus on the definition of the most expensive pieces of equipment, whose data sheet and specification will be prepared in order to issue inquiry to vendors.

Installation costs will be estimated from Engineering list and MTO: The Project equipment list for equipment erection, the civil BOQ for earthworks, foundations, concrete and steel structures, underground networks and buildings, and the Piping MTO. Ratios, rather than precise MTO, will mainly be used by the estimator to evaluate the cost of E&I works.

Safety discipline will conduct the first HAZOP. Safety will issue its philosophies, including Fire Fighting & Protection, Fire & Gas detection, Human Factors etc. Safety will issue Fire Water P&IDs and data sheets of main Fire Fighting equipment. Hazardous area classification drawings will be issued. An ENVID (Environmental Identification) study will register all environmental aspects. No Quantitative Risk Assessment will be carried out at this stage, as required detailed data is missing.

Process will first of all develop the P&IDs from the PFDs and produce/update the Heat & Material balance. For inquiry purpose, Process will be required to issue Process data sheets of all main equipment and functional specifications of all main packages. All Process “philosophy” documents will be issued, such as the Process description and Operation philosophy, Emergency shutdown and depressurization philosophy. Cause & Effects diagrams will not be developed at this stage. Process will participate in the HAZOP of the BASIC design P&IDs. The Flare study will be limited to the identification of the largest relief case.

Specialist engineers in the various equipment disciplines (Rotating, Packages, Fires Equipment, Pressure vessels, Heat Exchangers) will issue the Mechanical Data Sheets, Inquiry Requisition and Technical Bid Tabulations after receipt of vendor bids.

Clarifications with vendors might take place for the vendors of major equipment however placing of Purchase Orders and vendor follow-up (review of vendor drawings etc.) will not take place at BASIC design stage.

Piping installation discipline will develop the General Piping Layout for main pipes, e.g. above 4”. The first Piping MTO will be issued, based on the later for length and P&IDs for item count. Construction drawings (Piping General Arrangement drawings and isometric drawings) will not be not developed at this stage.

Piping Material will issue the Piping Material Classes specifications as well as General specifications for the various types of Piping Materials (fittings, valves etc.).

Piping Stress will simply issue the criteria for the Piping stress calculations. No calculations or support studies will be done at BASIC stage.

The instrument engineer will specify the various systems to be provided. This will include the usual PCS, ESD, and F&G systems, for which specification, including I/O count, and architectural drawings, will be issued.

Other systems, such as a security system, advanced process control systems, telecom systems etc. will also be defined, by means of a specification, an architectural drawing and, for systems expanding throughout the field (e.g. security system), a General Layout drawing.

The data sheet of motorized valves will be produced, due to their cost. No other instrument data sheet will be produced.

No Material Requisition will be issued by the Instrument Engineer at BASIC Engineering stage. Cost will be estimated by the EPC contractor from data base and ratio, e.g. so much for each instrument, I/O etc.

Typical installation drawings will be issued. Although no cable routing will be issued at this stage, width of the main cable routed will be advised to the Piping Layout discipline for incorporation in the Plot Plan. Equipment arrangement drawings for instrumentation and control room will be issued as input data for civil discipline’s architectural drawings.

The Civil Engineer will issue the initial soil investigation specification, aimed at identifying the soil geotechnical parameters and any geo hazard. The specifications for the various types of civil works will be issued, together with the bill of concerned quantities. No drawings will be issued, neither calculations done, for any foundation or structure at this stage. Standards design drawings only will be issued. Building architectural drawings will also be produced..

The Electrical Engineer will not go beyond the General One Line Diagram. The One Line Diagram of switchboards will not be developed at this stage. The Electrical Consumers list will be produced, from which the Power requirement and the size of the power generators will be derived.

The Electrical Engineer will issue the specification, data sheet and inquiry requisition for the High and Medium Voltage equipment – the most expensive - only. Cable routing drawings will be limited to the Main routings only, allowing to allocate required space on the Plot Plan and to define cable lengths and issue the cable MTO. Standard drawings related to design, i.e. equipment, only will be produced at this stage. Installation standard drawings will be developed at DETAIL stage. Equipment arrangement drawings will be issued for electrical sub-stations as input data to Civil’s architectural drawings.

Painting, Coating etc. specifications may also be issued, especially where onerous requirements apply, e.g., coating of underground pipes etc.

 Building detailed design is not usually developed by the EPC Engineer, which merely defines its needs to the building construction contractor.

The EPC Engineering produces guide drawings, which will include:

   • Architectural drawings, showing all dimensions of the buildings, the dispositions of rooms, as defined by the concerned discipline (Mechanical for a building housing machinery, E&I for technical rooms etc),

  • Equipment dimensions and weight, for the design of supporting floors,

  • Equipment access requirements (size of doors, handling),

  • Building blast resistance requirement,

  • Cable entry requirements: raised/false floor, floor openings,

  • Climate requirements (temperature etc), and equipment heat dissipation,

  • Fire & Gas detectors and equipment layout,

  • Telecom equipment layout (LAN etc.),

  • Tie-in points for connection of the building to the PLANT’s utilities.

 The structural design, calculations and all structural drawings for the building and its foundation will be done to the civil contractor. So will the HVAC detailed design (equipment selection, flow diagram, ductwork routing), Fire & Gas and Telecom cable routing, design of the lighting and small power, plumbing networks, finishing schedules (doors etc.) etc.

The latter will particularly entail co-ordination all these trades, to avoid interferences.

The rationale for the EPC contractor to leave the building detail design to the construction contractor is that it has little cost impact and is time consuming. The EPC engineer’s always stretched resources concentrate on either critical or high cost items.

For On-shore Steel structures, such as pipe-racks etc, the EPC Engineer will perform the design, calculation and sizing of the members but no detail any further. Its work will stop at the issue of the Steel structure design drawings, such as the one shown on page 84. These are "on-line" drawings, indicating of the size of profiles, dimensions & elevations.

Connections between steel members, in particular, will not designed/sized by the EPC Engineer but left to the steel structure fabricator. The EPC contractor will simply provide the latter typical drawings, design criteria and individual loadings. The steel structure fabricator will perform the sizing of the connections and produce the corresponding calculations note and detailed drawings.

The fabricator will also produce all drawings used in fabrication (shop drawings) and erection. See samples shown on pages 85 and 86.

In Piping, the level of details to which the EPC Engineer goes is very high, with the issue of the Piping Isometric drawings. The latter are nevertheless not directly used for construction. Indeed, these are "Design" Isos, to which fabrication information (indication of welds following split in spools) must be added. Spooling, resulting in the issue of Shop Isos, is done by the piping construction contractor. Difference between Design and Shop isos are shown on page 114.

While leaving design work to the construction sub-contractors, the EPC Contractor must ascertain the latter’s design office resources and capability. Early follow-up of production of the latter (through put and quality) will allow early identification and mitigation of a bottleneck.

First, let’s take a look at the location of the settings for these two options in Primavera P6 Professional.

Critical Activity Definitions

Go to the Projects view of you Primavera P6 Professional application, select a project and then click on the Settings tab in the bottom layout.

You’ll see the default setting for defining critical activities in the area imaginatively named “Define Critical Activities”, in the lower area of the Settings tab.

This is the default behavior that will be offered to the scheduler when running the Schedule function.

However, this can be overridden at any time in the Schedule Options dialog, accessible from the Schedule dialog (accessed by clicking the F9 key or selecting Schedule from the Tools menu).

In here you select the Total Float less than or equal to [value in hours] or go with Longest Path.

Total Float vs. Longest Path

The difference between Total Float and Longest Path can be summed up in the following way. Total Float calculations look at the Total Float for each activity in the network. If its Total Float value is zero, then it will be flagged as a critical activity. However that doesn’t necessarily mean the activity is on the longest path; it just tells us that the activity is critical, and it may be so due to other factors.

The following example shows how the critical path appears when the Total Float method is used to calculate the Critical Path. Activity A1050 has a ‘Finish On or Before’ constraint that is equal to its planned finish date, so it and its predecessors are showing critical. If they slip, they probably won’t impact the end date of the project, but they will overrun their constraint date; which is why they are showing as critical from a ‘Total Float <= 0’ perspective.

However,  if the Longest Path method of calculation is used these same activities will not appear as critical because there is a constraint somewhere along that path.  They will not in this case affect the end date of the project, so they are not on the longest path.

In this next example you can see the identical project schedule when it is calculated using the Longest Path method.

Previously critical activities are now showing as non-critical. Interestingly, they still have zero days Total Float, but P6 is ignoring them because they are not part of the longest path through the network.

The Longest Path through the schedule network will only consider activities as critical if they are on a contagious path from the start of the project to the end. Typically this is a single path upon which any activity that slips will impact the end date of the project.

Usage

Schedulers often use the Longest Path method when first developing the schedule. This gives them a clear idea of the activities that are driving the scheduled finish date for the overall project, without concerning themselves with complicating factors such as constraints, resource leveling, path divergence and convergence and other items that come into play when working a large and complex schedule.

Primavera P6 even has a “Longest Path” Boolean field that allows you to create a filter to see only activities on the longest path.

The Critical column and the Longest Path column will hold different values once a calculation of each type has been performed on the schedule at least one time.

With Primavera P6, you’re not committed to one method or another. At any time during the project lifecycle you can switch from Total Float to Longest Path depending on what you need to see. And at any time you can report on one or the other methods by using the Critical and Longest Path column values.

Source : https://tensix.com/2014/04/the-longest-path/

A lot of people are using Primavera with SQL Express database. And after using Primavera for a long time, we may realize the software become slow.

Our database is become bigger and bigger. And the slow performance is may be because of the limitations of SQL Server Express Edition, not because of the CPU or RAM.

Based on the table you can see SQL Express only support:

• 1 CPU
• 1 GB RAM
• 10 GB for database size.

No matter how your PC is strong, it only take a few resource from it.

So you may consider buy SQL Standard Edition before upgrade your PC hardware.