Errors in new PE-Mechanical reference Handbook V1.1

[ZDG]

What is the process for exam questions that require material that is incorrect in the Reference Book? I am finding the same problem with steel pipe friction tables 3.4.2.11 . I am using reference book 1.4.

During the exam, will we be expected to use the incorrect table, or go into it memorizing the errata before hand?

 

[Tiger15]

What is the process for exam questions that require material that is incorrect in the Reference Book? I am finding the same problem with steel pipe fraction tables 3.4.2.11 . I am using reference book 1.4.

During the exam, will we be expected to use the incorrect table, or go into it memorizing the errata before hand?

That's a good question. I'd be curious to know.

 

[Slay the P.E.]

steel pipe friction tables 3.4.2.11 . I am using reference book 1.4.

What error do you see in this table?

 

[ZDG]

What error do you see in this table?

I was looking at 8 inch and 10 inch steel pipe friction head loss per 100 ft for 1000 gpm flow. seems to be off by a factor of 2 from what I found online and in the solutions for TFS PPI 6 minute problems 3rd edition section 3 question 7. I have not checked for any other values. I read head loss as 3ft/100ft for 8inch and 1ft/100ft for 10 inch in the NCEES charts. I believe the correct numbers should be about half that (1.5ft head/100ft pipe and 0.5 ft head/100ft pipe).


It appears to be the same error that someone had in version 1.2 a year ago. I can get screenshots tomorrow if people want to verify if this is an error or if I am reading it wrong. I suppose I'll use the NCEES chat support to report this, however I'm concerned that during test day I will not know what to do if I either dont realize a mistake or know there is one and am unsure of which numbers to use.

 

[Slay the P.E.]

@ZDG

For 8-inch pipe, (ID=7.981”) with Q=1000 gpm, the Hazen Williams equation with C=100 yields 3 ft head loss for a length of 100 ft, matching the value in the table.

From 3.4.2.3, Hazen-Williams for 1 foot length is:

h = 10.44 (Q^1.85)/(C^1.85*D^4.87)

If you plug in the numbers you’ll see the value in the table is correct.

This is also corroborated by the online calculator at Engineering Toolbox:

 

[ZDG]

Thank You @Slay the P.E. . I was looking at this chart Pressure Loss in Steel Pipes Schedule 40


The PPI book I have uses numbers more in line with the link above. The book calls out 8 and 10 in schedule-40 steel pipe and uses 1.56 and 0.5 . "The head loss per 100 linear feet of pipe, hf, can be found using pipe friction tables. Be sure to use the water, schedule-40 steel pipe table. Looking up hf for a 10 in pipe with a flow rate of 1000gpm, it is found that hf=0.5ft/100ft" and similarly with 1.56ft for 8in. After seeing that the reference manual had errors in the past and with 2 sources showing otherwise (albiet with no rigour put into my search), I assumed the reference manual was wrong. Ill take it as a study exercise to figure out why Hazens Williams you used and the Darcy Weisbach used in the link above differ and when to use each one.

Thank you for the insight and apologies for my misleading post. I found this old post through googling information about reference book mistakes.

 

[Slay the P.E.]

Thank You @Slay the P.E. . I was looking at this chart Pressure Loss in Steel Pipes Schedule 40


The PPI book I have uses numbers more in line with the link above. The book calls out 8 and 10 in schedule-40 steel pipe and uses 1.56 and 0.5 . "The head loss per 100 linear feet of pipe, hf, can be found using pipe friction tables. Be sure to use the water, schedule-40 steel pipe table. Looking up hf for a 10 in pipe with a flow rate of 1000gpm, it is found that hf=0.5ft/100ft" and similarly with 1.56ft for 8in. After seeing that the reference manual had errors in the past and with 2 sources showing otherwise (albiet with no rigour put into my search), I assumed the reference manual was wrong. Ill take it as a study exercise to figure out why Hazens Williams you used and the Darcy Weisbach used in the link above differ and when to use each one.

Thank you for the insight and apologies for my misleading post. I found this old post through googling information about reference book mistakes.

Ok, I see now.

As you have also noted, the table you linked uses the Darcy-Weisbach equation and the table in the reference handbook uses Hazen-Williams. One can find references recommending C=150 for Hazen-Williams in new steel pipe. Using C=150 brings the results a lot closer.

It is worth noting that the reference handbook does NOT have Darcy-Weisbach tabulated (as of version 1.4). You would have to use the actual equation.

The differences in the two approaches can be so large that the exam problem will have some unambiguous way to let you know which approach to use (for example they would give you a wall roughness or a Darcy friction factor so you would use Darcy-Weisbach since these parameters are not used in Hazen-Williams).

EDIT: By the way, Hazen-Williams only applies to ambient temperature water. Anything else (hot water, any other fluid etc) will have to be analyzed with Darcy-Weisbach.