RE: Query

From: <Steve>
Date: Tue May 28 2002 - 19:08:00 EDT

Hi Mr Joshi

the cheapest solution is the best, assuming equal design quality and performance.

Rigid structures and flexible piping is by tradition the cheapest solution in most cases.

The question is a little difficult to answer definitively, however for the following reasons:

1. Suppose we have a structure supporting a pipe on a roller guide to permit thermal growth. The roller guide is clearly flexible in one direction. Does this mean we have a flexible pipe or a flexible structure? A similar question arises with expansion joints. I will assume the structure/guide case is flexible pipe/rigid structure as it is the pipe and not the structure that moves.
2. In order to prevent excessive terminal load transfer at pump connections, vessels etc, often necessary to have pipe anchors. A pipe anchor should be rigid and is normally classed as a structure. This means that least one pipe support must be rigid, in the majority of cases. In turn, in this case the solution would be a compound of rigid and flexible structures, if the latter was decided upon as the ruling philosophy.

The criticality of a service should reflect on safety/design factors and extent of design input. It should not favour one philosophy over another. Your question 6 would tend to favour the flexible pipe option, but only on these grounds of perceived costs.
For underslung pipes, dual rod pipe hangers are cheap and permit thermal growth while providing reasonable lateral resistance. If the hanger is considered to be the structure then it is clearly a flexible structure. However the structure that the hanger is attached to is normally considered rigid. Which one is the "structure"?

If you have a case where you feel flexible structure design could be cheaper than a rigid structure, do a preliminary design and costing on both, and go with the cleaper. I have a feeling the flexible structure preliminary design will reveal a number of costly details which need to be included, if the entire structure is to be flexible.

I feel that in most cases the flexibility of structures is a largely unwanted byproduct which must be analysed for interaction with the piping system, and adjusted accordingly.

Interesting question.

I fell there may be some differing opinions on this one.

Cheers

Steve Mckenzie

-----Original Message-----

From: KAUSTUBH JOSHI [mailto:kvj@epc.ltindia.com] Sent: Tuesday, May 28, 2002 11:37 PM
To: PipingDesign@yahoogroups.com
Subject: [PipingDesign] Query

Hi all,

When designing the piping and support structure, what is better:

1) To have a rigid piping and flexible support structure?
2) To have a flexible piping and rigid support structure?
3) To have a rigid piping and rigid support structure?
4) To have flexible piping and flexible support structure?

5) Does this philosophy depends on criticality of system? if yes, how? 6) How this philosophy differentiates with the dynamically loaded and statically loaded system?

waiting for replies,
Kaustubh

---

Unsubscribe: PipingDesign-unsubscribe@yahoogroups.com

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

---

Incoming mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.363 / Virus Database: 201 - Release Date: 5/21/2002

---

Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.363 / Virus Database: 201 - Release Date: 5/21/2002 Received on Tue May 28 19:08:00 2002