8/6/2019 Time Saving Golden Rules

http://slidepdf.com/reader/full/time-saving-golden-rules 1/5

Time Saving Golden Rules – An Engineering DesignPerspective

05 October 2010

3 Comments Tags: time , saving , tips , design , engineering Posted by ankur2061 Working in an engineering design consultancy for almost 15 years has given me someinsight into what needs to be done to work more efficiently and save time. Following aresome rules that I would recommend:

1. Collect all data beforehand before starting any calculation. For example, if you aredoing a pump hydraulic calculations have the following input data available before youstart the actual calculations:

a. Pumped liquid properties @operating temperature (vapor pressure, viscosity, specificgravity)

b. Layout of the pump suction source (tank, vessel), pump and the pumped liquiddestination (tank, vessel)

c. If available, the P&ID (Piping & Instrument Diagram) showing the pipe size, isolationvalves, in-line instruments and equipment.

d. If available, pressure drop data for in-line instruments and equipment. Assumptions based on accepted good engineering practices and sound logic could be utilized if such

data is not available from the basic project documents or from the in-house referencedatabase.

e. Tentative pipe routing (suction and discharge) sketch from the piping engineer whichestimates the type and number of pipe fittings (elbows, reducers, tees etc.), elevations atthe suction source, pump suction nozzle, pump discharge nozzle and the destination.

2. Do not re-invent the wheel. If your company has design software duly approved for doing any design calculations, use the same. You don't need to spend time developingyour own calculation procedure. Make sure that the software you are using is current andapproved by the company and / or the client.

3. If your company maintains a good reference database of past projects, use it to savetime in preparing engineering documents for similar types of projects.

4. Do not take up any engineering activity which you are unsure of. Spending time on anyactivity where there are a lot of if's and but's will lead to only unproductive work andfrustration. Take up the activity only when the minimum required input data is availableto produce a valid and correct design document.

8/6/2019 Time Saving Golden Rules

http://slidepdf.com/reader/full/time-saving-golden-rules 2/5

5. If you are doing a project of similar nature with only capacity changes then it isrecommended that the PFDs (Process Flow Diagrams) and P&IDs should first beconverted to the project format first before attempting any engineering mark-up. The task of changing the title block of the drawing should be left to the CAD operator. Remember,

the man-hours of a CAD operator cost much less than that of an engineer. Maximize theutilization of the CAD operator by assigning him the conversion of the drawing to thecurrent project format to the maximum possible extent.

6. A lot of process engineering documents are deliverables to other disciplines. For example, process data sheets for instruments are generally an input to the instrumentationdiscipline to prepare their purchase requisitions. The instrument purchase requisition is anextensive document which has one section for process data. A time saving measure could

be to directly fill the process data in the purchase requisition instead of generating aseparate process datasheet and issuing it to the instrument discipline, which subsequentlywould require transferring the data from the process datasheet to the purchase requisition.

7. If you are preparing a descriptive word document which requires a lot of attention tothe contents and requires tremendous powers of concentration, then just write by hand on

paper before getting it typed and formatted. If secretarial staff is available to do thetyping and formatting, utilize them. Avoid spending time on typing and formatting aword document in case competent secretarial staff is available. Again, the man-hour costof a secretary is far less than that of an engineer.

8. Avoid re-work. It is totally unproductive and you end up spending more time thanexpected as well as not doing it right. If you are anticipating that the input data providedto you is not firm and can change, don't work on that deliverable till firm input data isavailable.

9. Ensure proper coordination with other disciplines. Lack of coordination can provedisastrous. For example, if the piping discipline decides a planometric change (e.g.sequence of connecting various tappings on a header) in the piping GA drawing it should

be with the consultation and concurrence of the process discipline. Most piping engineersare unlikely to know the consequence on the process if they change the sequence of tappings on a header and only the process engineer is likely to know it.

10. Don't leave documents of other disciplines sent to you for review and checking lyingon your desk indefinitely. Other people are depending on your inputs and comments for their work to progress. Follow the schedule for checking and returning. If you cancomplete it before time, believe me you will earn a lot of friends and admirers.

11. Sometimes engineering documents are sent to you for review and checking which is beyond your capability. Don't be ashamed of your inability to review the document. Youare not supposed to be a know-it-all. Tell the concerned person that you are unable toreview the document sent by him or her because you are not the right person to review

8/6/2019 Time Saving Golden Rules

http://slidepdf.com/reader/full/time-saving-golden-rules 3/5

the document. Return the document immediately without reviewing, because allowing itto lie on your desk is unproductive and a waste of precious project man-hours.

12. Don't make frivolous changes. Engineering is serious business and not a personal egotrip. Changes for the sake of change don't serve any purpose. Review carefully the impact

of the change on the cost, project schedule, safety and functionality. However, remember that if by not changing you are hiding a design mistake than you are being dishonest.Mistakes have to be corrected no matter what the cost is.

These are just a few rules that I have mentioned. Would be happy to know some moreexperiences of readers of the forum regarding engineering design activities

A very good checklist Ankur! I have been working in process engineering for 40 yearsand at some time have made many of the mistakes you identify. Thanks for keeping ushonest.I would add:

Don't trust formulae where you do not know the origin or cannot understand the basis.If you are stuck - its usually because you need more data - so find it, or ask colleagues /supervisor.When trouble-shooting trust basic principles of physics and thermodynamics. If you arerusty on these - refresh your understanding - its a good investment.Don't be afraid to challenge what is not clear - but don't be defensive if you can see youhave gone down the wrong track. Admit it and move on, you will be respected for this.Keep your copy of project documents up to date and mark superseded documents as such- as soon as you get a revision.When developing a complex simulation model you will make mistakes while debuggingit - so keep a log of changes made to each revision - retaining the older models which youmight want / or have to revert to.

I would also like to add that standardization of similar equipment would save lot of time.

Assumptions – Their Necessity And Their Pitfalls InEngineering Design

03 October 20101 Comments Posted by ankur2061 When I first started working in engineering design I came to know the real significanceof the word "assume".But can we avoid assumptions? The practical view point is that you cannot avoidassumptions during the initial phase of engineering design. Let us understand why it isnecessary to assume during the initial stages of engineering design.

8/6/2019 Time Saving Golden Rules

http://slidepdf.com/reader/full/time-saving-golden-rules 4/5

When engineering of any project is started one of the main tasks is to get thespecifications / datasheets of long-lead items sent to the manufacturers as soon as

possible. The long-lead items are the ones which require a long duration (typically 12-18months) to engineer, manufacture and transport and without which the plant / unit being

constructed cannot be commissioned or started up. Essentially it means that these itemsneed to be given top priority during the engineering design phase by the engineeringconsultant / contractor. Any delays in procurement of the long-lead items could provedisastrous for the financial viability and profitability of the project and thus a delay or hitch in their procurement is a strict no-no.

Why assumptions are required? At the start of the project a lot of input data required to perform engineering calculations is not available. For example, if the layout of the proposed plant / unit and the various equipments in it is not frozen and still under debateand you need to prepare a datasheet of a pump which is a long-lead item, then hydrauliccalculations (e.g. NPSHa, rated discharge pressure, differential head) need to be

performed irrespective of the fact that no line routing (suction / discharge) data isavailable. A tentative location for the pump suction source, pump and the pumpdestination and pipe routing need to be assumed. The hydraulic calculations need to bedone based on the above-mentioned assumptions.

What happens if the pump and its suction and discharge layout changes drastically fromthe assumed layout and pipe routing? Your hydraulic calculations become totally uselessand you are back to square one.

Another example of an assumption would be the assumption of physical properties of achemical for which information is available for a single set of conditions. Manychemicals are sold by trade names and many of the manufacturers provide data such asvapor pressure, specific gravity, viscosity for a single temperature value. If that chemicalis being pumped at a different temperature then the one provided in the manufacturer'sdatasheet, then can you assume the properties for a different operating temperature? Anyexperienced engineer would tell you that this is being foolhardy.

With lack of data at the initial stage of the project, how does one proceed to doengineering? This is where the well established and bigger engineering consultants /contractors come into the picture. A lot of these reputed engineering consultants have awell established reference database of similar past projects and vendor data to kick-start the project on a satisfactory note. The assumptions in such cases are not just pureassumptions conjured out of thin air but are based on previous data of a similar natureand are much more reasonable then any random assumption. These engineeringconsultants also have direct contact with the equipment manufacturers whereby anyunforeseen changes in engineering data at a later stage can be absorbed without muchimpact on the equipment delivery schedule.

One of the often neglected but very important aspects in engineering is maintaining adatabase of past projects and vendor database.

8/6/2019 Time Saving Golden Rules

http://slidepdf.com/reader/full/time-saving-golden-rules 5/5

The reputed engineering consultants in the chemical process industry have developedtheir own internal engineering design standards for engineering based on acceptedinternational standards and good engineering practices. This helps these companies toexecute any project better and faster.

To conclude, assumptions are unavoidable during the initial phase of the project.However, the assumptions made need to be based on past experience and soundengineering logic and cannot be random assumptions. Unsound assumptions can havedisastrous consequences on the project in terms of implementation, operation and safetyof the plant / unit.

Another challenging "assumption" is with regard to Heat exchanger design pressures inthe Pump Circuit. The pump curves would not be available in the initial stages of Datasheet preparation and many times young Process engineers will put "Hold" on thedesign pressures of Tube and Shell. This is not acceptable to the heat exchanger designer

of mechanical discipline.To overcome this problem, it is better to look for a similar pump both with respect toHead and Flow rates and use the pump curves to look at the Shutoff Pressure. This witha factor of safety should be able to solve the problem.