WHITE PAPER ON EXCEUTION OF UNDERGROUND PIPING DESIGN FROM NDEU FOR P&C JOBS

Purpose

Purpose of this white paper is to define the work process to carry out underground pipe design for P&C jobs. It is also intended to brought out the involvement and responsibilities of the Engineering discipline to complete this job from NDEU.

Work Process of Underground Pipe Design

Presently NDEU (Plant design) personals on power jobs are responsible for design of most of underground piping systems with the exception of plant storm water system. Which normally is being done by FREU (Civil). This philosophy is in line with the division of work followed at FREU. However, for P&C jobs at HOUE under ground piping design (including storm water management) is the responsibility of a separate team formed by Engineers and designers from Civil and Piping disciplines.

Attached are the 2 Annexures showing work processes being followed at HOUE for carrying out detailed design of underground piping. Annexure- A defines the work process for Storm water/drain piping design. Annexure- B indicates the work process for other utility piping and Fire Protection piping.

It is clear that there is no additional expertise required for plant design personal to complete the design for utility piping except that they will interface with civil for requirement of frost depth, how deep/far piping could be routed underneath/nearer to equipment foundation. Interference with reference to underground storm water piping also needs to be thoroughly reviewed.

For underground storm water piping and floor drain piping, following additional activities are involved:

Compute rainfall and Fire Protection deluge valve water quantities.

Finalized Grade paving/slope concepts. Select type of manholes/catch basins. Decide on preliminary locations of Catch basins and

underground piping net wok considering equipment layout/access areas and paving details.

Calculate pipe sizes. 3D Model of piping and Catch basins. Prepare Schedule (quantities, type) for Catch basins/Manholes

and finalize the vendor. Review of Catch basin/manhole fabrication drawings. Extract Piping MTO and isos for fabrication.

Common activity covers development of composite Orthographic drawings for complete underground piping.

It is clear from above mentioned work-process that there is a need for the participation of civil engineers/designers for activities like clear understanding on site grading/paving details, catch basin selection and its fabrication details. However, considerable time needs to be spent on 3D modeling and associated activities of piping design. Plant design personals are also better equipped and trained for understanding on pipes, fittings, their materials, MTO/Iso extraction and Orthographic drawing generation.

Piping Quantities and Job-hours

For Typical P&C Job, given below are the piping quantities and job-hours associated with underground pipe design activities:

Utilities, off site and Fire Protection Piping: ----- Feet

Storm Water and drain piping : -------- Feet

Type of Manhoels (Average): ------ Number

Number of Manhole:

Job-hours allocated for all underground design activities: 1000 hrs

Appx 10% hours are spent on calculations and selection of piping material etc.

Appx 30% hours are spent on finalizing paving area drawings, selection of catch basins/Man holes, review of catch basin fabrication drawings etc.

Rest of the time is being used for modeling and preparation of deliverables (Isos or Orthographic drawings)

Normal time schedule to complete this job is 6 to 7 month in each project.

(Note : Data above is used from Equiva Project)

Conclusion

Since this being considered as expertise job and needs close co-ordibnation between Plant Design and Civil disciplines, it is proposed to form a separate group under the Administrative control of Plant Design chief at NDEU. This group would consists of 2-3 Plant design designers and 1-2 Civil Engineers. Overall responsibility at project level lies with the PD EGS.