Auto Layout Technical Note

PIPENETA UTOLAYOUT A N EW T OOL FOR THE S PRAY /S PRINKLER M ODULE — T ECHNICAL N OTE © SUNRISE SYSTEMS LIMITED, MAY 2008 May 2008 Page 2 COMMERCIAL IN CONFIDENCE . 3 STATEMENT OF PROBLEM Given the size and shape of a plant vessel or area. Automating part of this design process will not only save time and effort. The design must either comply with applicable fire-authority standards. such as those laid down in NFPA 15.1 SUMMARY This note describes a new tool for the PIPENET Spray/Sprinkler module. This note begins with a statement of the problem and a discussion of an illustrative example. areas or other objects/locations from the effects of fire. some details concerning the variations in spray and rundown density for vessel protection are discussed. Finally. May 2008 Page 3 COMMERCIAL IN CONFIDENCE . then goes on to give a brief description of the prototype autolayout tool. or else satisfy a user-defined areal flowrate and spray distribution specification. The tool’s purpose is to automate part of the task of designing sprinkler systems for protecting storage/process vessels. it will also allow fire-protection rules to be encapsulated within the software and thus help to ensure that the resulting design is compliant with fire-authority standards. 2 INTRODUCTION Defining the layout of a sprinkler system for a large vessel or area can be laborious even with the aid of a graphical tool such as PIPENET. design a sprinkler system to protect it from fire. 2 (L/min)/m2].2. By way of illustration.4. shall not exceed 12ft (3.) will obstruct water spray coverage.4 Spherical or horizontal cylindrical surfaces below the vessel equator shall not be considered wettable from rundown. the distance between nozzles at different levels or elevations.25 gpm/ft2 [10.1 Example: NFPA 15 Applied To Vessel Protection The following standards from NFPA 15 are applicable to the protection of plant vessels (reproduced from NFPA 15 Standard for Water Spray Fixed Systems for Fire Protection.6 All uninsulated vessel skirts and any uninsulated steel saddles greater than 12in. 7. 7. additional nozzles shall be installed around the projections to maintain the wetting pattern that otherwise would be seriously interrupted.2* Vessels.25 gpm/ft2 [10. protecting vertical or inclined surfaces.2 (L/min)/m2] of exposed surface. A system for exposure protection shall operate as intended for the anticipated duration of the exposure fire. 7.4 Exposure Protection. 7.1 Water spray shall be applied to vessel surfaces (including top and bottom surfaces of vertical vessels) at a net rate of not less than 0. 7.4. (305mm) high at the lowest point shall have water spray applied on one exposed (uninsulated) side.2. the application of NFPA 15 to the design of a vessel protection system is used as an example. 7.2. at a net rate of not less than 0.5 Where projections (manhole flanges.1* General.2.4. including rundown on vertical surfaces. pipe flanges. 2007 Edition) – 7.3* The horizontal distance between nozzles shall be such that spray patterns meet or overlap at the protected surface.4.4. 7.7m) as measured along the surface. etc. relief valves.4.4 FIRE-AUTHORITY STANDARDS The autolayout tool is intended to handle a variety of fire authorities' standards and protection scenarios.4. 4. 7. support brackets.4.2* Where rundown is contemplated.2. May 2008 Page 4 COMMERCIAL IN CONFIDENCE .2. based on some design information provided by the user. the proposal for the autolayout tool is that. May 2008 Page 5 COMMERCIAL IN CONFIDENCE . the water is “depleted” on its way down. from rundown.4.5 and 7. Since this is unlikely to be achievable without overlapping spray patterns.4.2. ie the same litre of water cannot be considered to contribute to the minimum required areal flow for every square metre of surface that it runs down.4. Standard 7.2 Interpretation For the purposes of this application. b) For those surfaces which are considered wettable from rundown.1 to 7. while 7. c) With rundown. 4. it will generate a sprinkler layout which is compliant with standards 7.2. the system must be such that there is no part of the surface which receives less than the minimum flow directly from one or more nozzles. the following assumptions are made – a) For those surfaces which are not considered wettable from rundown.2. Again.4. practical considerations imply that the average flow will need to be somewhat greater than the specified minimum. the average areal flow rate on such surfaces will generally need to be greater than the specified minimum.4.4.2.1 can be handled by constraining the choice of pipe material.6 are addressed by allowing the user to change the design manually once the basic layout has been generated.4. the spray pattern must be such that there is no part of the surface which receives less than the specified minimum areal flow directly from one or more nozzles.3 Fulfilling NFPA 15 In the context of the above standards. or from a combination of the two. 5. it will offer to join the new sub-network which is about to be generated to that node. the user selects Autolayout from the Tools menubar item: If an existing node is selected when the tool it launched. May 2008 Page 6 COMMERCIAL IN CONFIDENCE .5 USE OF THE AUTOLAYOUT TOOL Use of the prototype autolayout tool is described in the following sections.1 Tool Selection Having selected pipe types and nozzle libraries. pipe parameters and component labels: In this example the diameter and height of the vessel have been entered but all other parameters have been left at their default values.5. spray density and nozzle layout requirements (which can be selected to be compliant with a built-in fire-authority standard). May 2008 Page 7 COMMERCIAL IN CONFIDENCE . the user specifies the shape and size of the object to be protected.2 Dimensions And Spray Requirements In the first of two dialogue windows. values such as pressure.3 Nozzle Configuration In the second dialogue the user can adjust the nozzle configuration (within the constraints imposed by the selected standard). the user then clicks on the Finish button. Based on the information supplied together with the parameters of each nozzle in the library.5. total flowrate and overlap are displayed for each nozzle type. May 2008 Page 8 COMMERCIAL IN CONFIDENCE . Having adjusted the nozzle configuration values interactively and selected the nozzle type from the list. Fittings are included on the pipes. May 2008 Page 9 COMMERCIAL IN CONFIDENCE . and pipe-sizing can be performed in the usual way. Note that the generation of this example involved seven mouse-clicks and the entry of two numbers: a further two mouse-clicks were involved in having it joined to the existing node automatically.5.4 The Generated Layout The generated sub-network is drawn on the schematic grid ready for further editing. 5 Area Protection Example The following screen-shots show the two dialogues and generated sub-network for an area protection scenario: May 2008 Page 10 COMMERCIAL IN CONFIDENCE .5. May 2008 Page 11 COMMERCIAL IN CONFIDENCE . even with uniform spray density within the spray cone. ● the angle of incidence on the vessel surface increases.6 SPRAY DENSITY CONSIDERATIONS For surfaces which are not considered wettable from rundown. For surfaces which are considered wettable from rundown. the choice of nozzle configuration depends on whether the flowrate requirement is an average or a minimum – ● “average flow” requirement: the total required flow defines the number of nozzles. spreading the flow over a larger area of vessel. with increasing angular distance from the centre of a nozzle’s spray pattern – ● the distance to the vessel surface increases. there is an additional factor causing the rundown density to vary – the height over which rundown is accumulated decreases with increasing horizontal distance from the centre of a nozzle's spray pattern. the surface receives the correct areal flow. overall. ● “minimum flow” requirement: the nozzles are distributed in a “covering” arrangement. This is because. Note that meeting the second of these requirements is complicated by the fact that. which are then distributed in a “near-uniform” arrangement such that. The variation in rundown density is illustrated below – May 2008 Page 12 COMMERCIAL IN CONFIDENCE . the areal flow striking the vessel surface will vary with angular distance from the centre of the cone. reducing the spray density in the diverging cone. The autolayout tool will allow for either option. such that no part of the surface receives less than the minimum areal flow directly from one or more nozzles. May 2008 Page 13 COMMERCIAL IN CONFIDENCE . the choice of nozzle configuration depends on whether the flowrate requirement is an average or a minimum.Again. 1 Calculation Of Rundown The autolayout tool will calculate rundown as outlined in the following diagram. dy y = yP where Fn(x.6. y  . y  F 2  x P . May 2008 Page 14 COMMERCIAL IN CONFIDENCE . By handling the variation of spray and rundown density rigorously.y) is the areal flowrate at (x. the areal flowrate including rundown is given by – RP = 1 hP y = y P  hS ∫  F 1  x P . which shows (in elevation view) the spray patterns from nozzles N1 and N2 overlapping on the side of the vessel: In the column from the top of the area protected by these nozzles to the point P. and to do so in the most economical way (minimizing total flowrate in order to keep supply piping and pumping costs to a minimum. for example). the autolayout tool will allow the user to ensure that the minimum flowrate requirement is truly met at all points around a vessel where this is a design requirement.y) from nozzle n. certified design or to provide a substitute for the user's expertise and engineering judgement – it is primarily a productivity aid.7 CONCLUDING REMARKS ● ● ● ● ● The autolayout tool is not intended to produce a finished. of Sunrise Systems Ltd. The information contained in this note is strictly confidential and is not to be shared with third parties without the express agreement. The autolayout tool will be extended to support a variety of fire protection standards. in writing. May 2008 Page 15 COMMERCIAL IN CONFIDENCE . The purpose of this note is to gauge opinion on the way in which the autolayout tool is presented to the user. The autolayout tool will be extended to handle a variety of vessel shapes and other fire protection scenarios. with the user choosing which standard is applicable or else specifying the spray density and other requirements directly. and to invite further comments and suggestions.