P & ID's in HVAC Industry 5

[pmover]

for those experienced in hvac industry design activities.

lately, i've reviewed several hvac design dwgs - plot / plan / elevation - and not a single detailed p & id! although my background is the oil & gas industry, where detailed p&id's are the standard, why is it that p&id's are not created for hvac systems to the detailed level that the o&g eng firms generate?

i can understand client requests for not generating p&id's, but does the hvac design industry, as a general rule, create effective p&id's in which to build from?

references or documentation relating to p&id generation in hvac designs are appreciated.
thanks!
-pmover

 

[ChrisConley]

I work in a multi-disciplinary office and often get called to do industrial work in addition to standard HVAC and I've also wondered about why P&ID's aren't developed for HVAC systems as a general rule.

Having said that I tend to create control, air and water schematics, which are very similar to P&ID's myself.

I've been told that it is a cost and time issue, that and because the industry doesn't expect it, we shouldn't provide it.

 

[quark]

I can't say they are exactly PIDs. But we, in Pharmaceutical companies, prepare single line diagrams of HVAC Systems. They consist of schematic diagram of AHUs and their components (viz., cooling coils, heating coils, VCDs, FCDs, Filtration Systems etc.) which show in and out flowrates of air through each controlled space with pressures indicated.

Control points like pressure gauges, temperature sensors, RH sensors and manometers are also indicated.

System description with schematic diagrams is compulsory and I knew USFDA issuing a 483(non compliance) to a Pharma company which didn't have this information.

Regards,


Believe it or not : Though human body is made up of intricate and subtle mechanism, it is very poor in energy conversion. The maximum efficiency is 20% during cycling. During under water swimming it is just 4%.

 

[lilliput1]

It saves everbody time & money not to do P&ID drawings for typical HVAC systems. Instead the design engineer concentrates on describing the sequences of operation. It is up to the winning control system vendor to provide control equipment and control diagrams (which may or may not be in P&ID format depending on how shop & as built drawings are required). Typical HVAC controls are not like process controls that would need special PLC type controls and accurate diagram for all to check the control logic out. Instead typical control vendors have DDC system design that incorporates numerous software & hardware enhancements built in. Shop drawings & equipment data are submitted for the engineer to check prior to fabrication.

 

[VSSriram]

Talking of controls, the controls or BMS guy does what's known as an Input/Output Summary which helps him to select controllers, sensors, etc. Typical single line flow diagrams are also made in many projects, but not like what's made in the process industry. I have never felt the need to do a P&ID for HVAC requirements, though many times I have been asked for the same by consultants who are primarily into process consultancy. Once a shop drawing is made with sections taken out at critical areas, they become self sufficient. The HVAC industry is part of Building Services and I feel that P&ID is not really a must.

 

[pmover]

Sorry guys, not buying that bs of saving time and money. i believe that by generating p&id's you will be saving time and money, especially during construction, if a master set of p&id's are generated by the design firm. we all know of the problems with generalized, ambiguous, and conflicting schematics or drawings that are issued before construction. a common laborer, superintendent, or foreman may review the dwgs, note the anomalies, and then apply their own corrections rather than contacting the engineer of record (shame of those who do). if a decent set of p&id's are generated, then the piping plan/elevation dwgs and related dwgs will be simpler to generate as the required equipment (i.e. instrumentation, fittings, valves, ets.) are all on the p&id. there must (ought) be a set of drawings that are the defining record of design and contain any record of changes to the design (i.e. as-built dwgs).
-pmover

 

[VSSriram]

What you call as P&IDs are generated as schematic piping drawings and form part of the drawings issued for piping. Maybe, the terminology of P&ID is not normally used in the HVAC industry. Nevertheless, there are schematics, flow diagrams, made and issued in most cases. Many times, typical connection details at AHUs, Chillers, pumps, etc., are issued as part of a standard detail and coupled with the schematic piping drawing and flow diagram for ducting is already probably doing the function of the so called P&ID drawings.

 

[ChasBean1]

pm - The typical HVAC construction set is the design without the design intent. I agree with you in that regard. There is a continuous reliance on the automatic temperature controls (ATC) submittal process to give the system "life" and to carry out the designer's intent.

When it comes time to review those detailed submittals, the designer holding that intent is too busy designing something else, so it is delegated to a subordinate not fully aware of the designer's intent, and the ATC submittal becomes stamped "approved" with legalese.

On occasion, the building owner is aware of these issues and pays the designer sufficiently to actually design the controls which help carry out the intent.

For a construction project, developing a set of process and instrumentation diagrams for HVAC in a detailed, 3-D type fashion will quickly become nullified with the required rain leader, sprinkler, electrical, and plumbing work; not to mentioned varying ceiling heights suggested by the user to the architect. Carrying out this work is a coordination effort that cannot be planned fully in advance. Making everything work by design, in advance, would require extensive knowledge of the ATC system, the latest Cleaver Brooks boiler control package (as an example), the latest ABB drive technology, the latest air compressor vendor's interface, and maybe the Simplex fire alarm interfaces.

I agree with your thoughts on this issue, but it would require:

a. All trades to coordinate fully and not be obstructed by small mitigating factors such as building support beams,
b. All trade practices to become standardized (in measurement and terminology),
c. Owners to become realistic about prices for a real design versus CAD draftsmanship, and
c. The world to be perfect...

 

[rajeshbidani]

Iagree with pmover. D&ID (not P&ID) are a must for clear understanding of HVAC System operation, controls and shutdown philosophy. I am working in offshore industry and find Damper & Instrumentation Diagrams (D&IDs) very useful. D&ID is a standard document in offshore industry and forms the basis for detail HVAC design. But yes, you are correct that these documents are not produced by HVAC designer working of onshore projects on comfort application. The reason can be that the dependence and interface with BMS is very limited when compare to oil and gas or offshore project.

 

[imok2]

Gentleman I read with great interest your comments about PID in HVAC I think I have an article that might interest you about how we in the hvac industry feel about PID title "Out with the old and in with the new" I would be interested in you comments.

http://www.hpac.com/member/archive/0208freaks.htm

 

[pmover]

imok2,

thanks for your input; however, the meaning of P&ID is "Process and Instrumentation Diagram". P&IDs are a clear & concise representation of the process piping, fittings, valves, and associated instrumentation of the facility's process.

in other words, in the hvac industry, the process can be condition air, steam, water, compressed air, vacuum systems, etc. schematics are acceptable to gain an understanding of system components, but not to use for construction purposes.
-pmover

 

[lilliput1]

P&ID for general HVAC will be over engineering. This is no bs. It is a fact of life. We have to make profit to survive & finish work within budget and on time. We have been able to communicate our design intent using written description of sequences of operation. Translating this to P&ID would be mere duplication of work. After installaion, it will be the control vendors shop drawing submission that will be finalized for as built & the P&ID drawing will not be used. The building operator would use and understand a written sequence of operation instead of P&ID. Try to do P&ID for HVAC other than that for process or pharmaceutical and you will incur the ire of your boss for inefficient use of manhours.

 

[imok2]

pmover, Thanks I stand corrected.

 

[maxoverdrive]

Just looking for some clarification. My knowledge of P&ID's is piping and valve identification including National Board numbers for vessels over 3 ft3. Somewhere I think the conversation went askew and we are arguing PLC and their documentation. I can only assume by PMover's original query that he is referring to the former (being an API type person). Please help me in directing/redirecting.

TIA

 

[imok2]

pmover,
You may find this mickey mouse but I swear it worked very good. I was at one time an application engineer in HVACR with civil Service My job was to go out and survey older buildings and try to come up with a plan to replace inefficient equipment, and improve energy eff. When I gathered all the info I required, it then was my job to determine what and who's equipment to buy, estimate the entire project, make up a material list, figure man hours, and make single line drawings with all required call outs of sizes, HP, HD,etc. and finally to write out the instructions in an unstandable manner. Then I was responsile for managing the installation with the craft people. All my projects worked,some with minor revision. Most work was less then $1,000,000, and all of the work was retrofit. I bring this to your attention because I realized how much a (1) person can do if given the support and authority to do a job, however, you have to be willing to put your ass on the line and take the flack. The whole process was fast, simple and no politics only wanted results. It was the best job I ever had and I worked there 28 years

 

[ChasBean1]

I guess in a multilingual world, Step 1 is to define P&ID: P&ID is "process and information diagrams", where PID in HVAC relates to how the control system works, in "proportional-integral-derivative" fashion...

Is this post shallow and lame? Now I guarantee many people are saying OOOHHHH! That's what it means...

 

[VSSriram]

I thought P&ID stood for Process & Instrumentation Diagram !!!

 

[imok2]

This is a good example of the inportance of good communication. Many of us have a different understanding of many various terms and semantics. Wasn't this
a problem recently with an orbital rover that never made the destination it was programmed for, because of a misinterpretation of some engineering stats? Any way it should remind us to be as descriptive as possible in what we write. I don't know about you, but I always have problems with (acronems)? especially with other engineering professions.

 

[chims]

Amen to what Lilliput1 said. When you're in the oil and gas business, you're dealing with millions of lost dollars per day if the system doesn't work. O&G companies are willing to put the money into the design up front rather than field fixes. In the HVAC business, we're quite often dealing with developers and owners who want it quick and cheap. Hence, the "bs of saving time and money". I've had to deal with people coming from the O&G industry into the commercial industry. They learn pretty quick that engineering firms are run by accountants, not engineers. Reality sucks!

 

[DouginMB]

This entire thread has me snickering. Being in the HVAC side, I thought the original post was related to proportional-derivitive control as well. I was thinking: "Who in the hell has time to design a control feedback loop?!"

After being enlightended to the original poster's meaning of P&ID, I have agree with lilliput as well. My understanding of industrial work is there isn't much in the way of a bid process. Your construction budget is such that you dictate on your plans which manufacturer's products will be used without exception. In the "bid & spec" market we don't have that luxury. This is especially true for government projects where you can't even list a manufacturer you prefer. And it is a paradox: while it would seem to be beneficial to have a P&ID drawing in these cases where you're at the mercy of the lowest bidder, if a P&ID were drawn based on Product A and Product B wins the project, you've completely wasted your time designing around product A.