Piping Design Questionaire Feedback

Here are some recent comments from Mike at www.pipedesign.com:

First of all, I thoroughly enjoyed reading the Piping Design Questionaire by K. Rudra, R. Patil & J. Thinakaran. It has given me a lot of useful information that I can apply to my piping designs. However, I find that I have several questions about the answers posted as being the correct answers:

In Question #1, the "ASME code followed for design of piping systems in Process pipings (Refineries & Chemical Industries)" should be (ii)... B31.3, not (iii)... B31.5. B31.5 is Refrigeration Piping and Heat Transfer Components. That answer "ii" is the correct answer is verified in the questionaire's Question #36.

In Question #4, by looking at the sketch, it appears that "stub-ons" are dummy welds to piping systems, like dummy leg supports, trunnions, etc. But then the questionaire states that "For branching of one size lesser of run pipe, Stub On is preferred". If this is the case, there should be a penetration shown through the run pipe in the sketch.

In Question #7, the OD of 14 NPS pipe is 355.6mm, not 355mm (I know, this isn't a biggie... smiling).

In Question #11, TIG stands for Tungsten Inert Gas welding, not Tungsten Inter Gas welding. The prefix letters for SMAW should be "i" (not "ii") and for TIG the letters should be "ii" (not "iii").

In Question #12, the calculated rise for a 5000 unit run using a 1:100 slope is 50. Therefore, -100.050 + 50 + 50 yields -0.050 at point "A"...not 100.050. (am I doing something wrong?)

In Question #15, eccentric reducers are used in "side suction" centrifugal pumps (not top suction pumps). It is commonly believed that the flat side up will prevent a cavity in which air bubbles will collect before entering the pump volute. Another philosophy maintains that by using eccentric reducers right at the pump horizontal suction connection will make the fluid suddenly "ramp up" into the pump impeller like a ski jump, causing turbulence and consequent air bubbles... so some plants are in favor of using concentric reducers at their horizontal pump suctions (and do so without the harmful effects of cavitation)... hhmmmmm....

In Question #40, the required upstream and downstream straight runs of pipe are calculated by using the beta ratio (orifice diameter divided by the inside diameter of the pipe) and by the piping configuration. Some multi-plane piping configurations require greater straight runs (both upstream and downstream of the orifice meter). I've seen as many as 38 pipe diameters required upstream of an orifice meter to maintain a .7 beta ratio.

Question #47 is a favorite of mine... it is a common error for piping designers to locate branch connections too close together. The HAZ's (or Heat-Affected Zones) are not considered by most... GOOD INFORMATION! Received on Tue Mar 13 22:37:00 2007