Stephen Mitschke
August 12th, 2003, 12:28 PM
Jim has asked that any interested parties on this list review and comment.Please do so to the list so we can all learn from each others experiences.Thanks.Ian-----Original Message-----For interest, here's a FOUNDATION Fieldbus project spec that Ralph Hartmanand I generated for a gas compression expansion project Aramco's got comingup. Since the project is using DeltaV, we left out most of the FF/Hostrequirements that we know DeltaV already gives us. The intent of the specis to instruct a lump sum turn key (LSTK) contractor and DeltaV vendor onour FF system design requirements. Any comments? Things we should add/takeout?Jim SpragueE-2550, Engineering BldgDhahran, 31311Saudi Arabiatel: 966-3-874-6414fax: 966-3-873-0037spragujl@aramco.com.sa<<BE391x-4.doc>> - - - - - - thread starts - - - - Two things that I would add.Segment loading should include a VCR calculation. I understand that you areusing a Delta V and you have included their limitations as far as maxfunction blocks. However to really size the segment loading a good measureof bandwidth usage on the segment is by doing a VCR loading calc. You should add a spec to include proper grounding techniques for a fieldbussegment. I have been to numerous sites where good wiring practices were usedhowever there was tremendous noise on the network making the fieldbusinoperable.Good luck!Raj KhemchandaniFieldbus Knowledge ManagerHoneywell Ltd.- - - - - - - re failure mode, as written in spec below, my question is: how do youindicate on the P&ID the two modes. We in the past have just shown themechanical failure state, and then had the "electronic" failure state in thescope of work somewhere, however I have always been a little uneasy aboutthis, especially as the maintenance instrument technicians can not easilysee the mode required.This may be a standard instrumentation question, but it equally applies to afieldbus system. rm The valve has two different fail states depending on failure mode: 1)configured fail state 2) mechanical fail-state. For example, on loss ofcommunication, the valve can be configured to hold last position. Loss ofcommunication can be caused by:· H1 card failure, if a backup LAS isnot used. · Accidental removal of terminator · Loss of input signal to the valve (i.e. AIfunction block). The valve will go to its mechanicalfail-state position (i.e. spring return position) on loss of power. Loss ofpower can be caused by:· Broken wire · Shorted wire · Failed power conditioner · Loss of DC supply voltage to powerconditioner - - - - -A very nice document Jim. Of course, I too have a few comments if I may.Section 4.1.6 - Spare Capacity. Do you want to specify a maximum macrocycleloading level (i.e. 70%)Section 4.3.1 - PID Control in Segment. I did not catch what your preferenceis in the case of a single loop that execution should be in the analogoutput device.Figure 2 - I would suggest you show the terminator location in eachinstance.Section 5.8.3 Add another bullet - Segment capacitance. Refer to the Relcomdesign guide at http://www.relcominc.com to see how this should be done.Section 7.2.2 - Terminators. What about in the case of spurs?Section 9.1.1 - P&ID Symbols. ISA 5.1 is leaning towards use of a closedbubble.Thanks again for the chance to look this over.Ian- - - - -You can also specify the mode shedding configuration of the Function Blocks.Thestatus of the signals (e.g. PV) can affect the mode of a control functionblock. The default configuration may be device vendor specific.FF-Device Description is a mandatory part of a registered device. Is theirsomeadditional requirement for Aramco project (software wizard) and if so, whatisthe reason?Kari HartikainenMetso Endress+Hauser Technology AG- - - - - - Thanks for the feedback on the DeltaV FF Spec. Here's a few replies back onthe comments and a scanned version of our segment diagram:====================== Raj, We've been assuming that segment communication loading is handled bythe DeltaV inherently by limiting H1 cards to 64 function blocks and how itcalcs the macrocycle time. Is there something else we should be watching,e.g. VCR calculations? Can you educate us what to calculate and why?We are using our existing wiring standard that does a pretty good job indefining shield grounding, signal separation, wire routing and support, ect.We're assuming traditional shield grounding techniques are sufficient forFF.We only show mechanical fail state on the P&ID. We consider the electronicor soft fail state part of configuration, which is identified elsewhere.=======================================A ttached is a scanned version of our 'segment diagram' go-by, from appendixA in the FF spec (note that it's not perfect - more like quick and dirty). On the data sheet, our intent is to show only what was purchased, e.g. whichfunction blocks are available with that instrument. We figure use of thefunction blocks is part of configuration and will change. Hi Ian, Thanks for your comments. Here's a couple reply's:>Section 4.1.6 - Spare Capacity. Do you want to specify a maximum macrocycle>loading level (i.e. 70%)We've been assuming the way DeltaV inherently allocates cyclic to acyclicmacrocycle time is conservative and adequate (I think 30%/70% ?). I hope itis....>Section 4.3.1 - PID Control in Segment. I did not catch what yourpreference>is in the case of a single loop that execution should be in the analog>output device.Yeah, the commentary after section 4.3.1 is a bit cryptic. Our intent isthat segment PID be in the final element. If the designer wants itelsewhere, he'll have to convince us.>Figure 2 - I would suggest you show the terminator location in each>instance.Thanks, we'll consider it.>Section 5.8.3 Add another bullet - Segment capacitance. Refer to the Relcom>design guide at http://www.relcominc.com to see how this should be done.Hmmmm, we'll consider it. Interesting, but I don't think theFisher-Rosemount segment Excel based engineering tool includes capacitancecalcs..? (97Eng_FBSegTool.xls)>Section 7.2.2 - Terminators. What about in the case of spurs?We're only putting terminators at each end of our trunks, e.g. in our FFpower supply (FFPS) and at the far end of the trunk in the JB. Nointermediate spurs have terminators.>Section 9.1.1 - P&ID Symbols. ISA 5.1 is leaning towards use of a closed>bubble.We really think the double dash with an open bubble is too congested. Butfor now, we're going with it. Can you imagine a P&ID with double dashclosed bubble!? It would an eyesore & VERY congested. I hope they staywith the open bubble (or something even simpler....?).>Thanks again for the chance to look this over.>>Ian>Syncrude Canada Ltd.>PO Bag 4009, MD 0032>Fort McMurray, AB T9H 3L1>P 780 790-4079, Cell -799-6017>F 780 799-5190>verhappen.ian@syncrude.com======================== ============We really don't want our instrument techs to have to modify transducer blockmodes and parameters to do transmitter/positioner setup, reranging, andzeroing. For this reason, we've asked for software 'wizards' to help walkthe techs through these standard procedures. We really want all vendor'sinstruments to have wizards, but at present, DeltaV AMS inside only provideswizards for their own FR products. > FF-Device Description is a mandatory part of a registered device. Is their> some> additional requirement for Aramco project (software wizard) and if so,> what is> the reason?> > Kari Hartikainen> Metso Endress+Hauser Technology AG> <<Segment.exe>> - - - -Raj, We've been assuming that segment communication loading is handled by> the DeltaV inherently by limiting H1 cards to 64 function blocks and how> it> calcs the macrocycle time. Is there something else we should be watching,> e.g. VCR calculations? Can you educate us what to calculate and why?A Fieldbus device is divided into two or more Logical Field devices:A Management Virtual Field Device (Management VFD)One or more Function Block Application Processes (FBAP VFD). The Management VFD contains the device's Physical and Resource dataResource data includes the virtual communications resources (VCR's).Each device has a set number of available VCRs and each host system has aset number of available VCRs. Depending on your individual fieldbus controlstrategy each strategy will utilize a set number of VCRs. Each publish andsubscribe link to another device consumes one VCR.Determine your control strategies, determine how many VCRs those controlstrategies will consume on the segment. There is a limit on the number ofallowable VCRs per segment, get that specification from your controlmanufacturer. Now compare the two numbers, if your control strategies consume 88 VCRs andthe controller has only 50 VCRs allowed per segment then you have a problem.Either reduce the number of devices or the number of publish/subscribesbetween devices to reduce the VCR count.I compare VCR calculations to the segment bandwidth calculation. Essentiallythat is one reason why you try to limit the number of connections betweendevices by reducing the bandwidth or the number of VCRs. Cheers!Raj K P.S if someone has a better explanation I would appreciate some feedback.