Temporarily ignoring the subject of expanding flange as being not covered under B16.5,
considering your pipe thk as sch160 for 2", doing a small check, the SPW gasket inner dia is 58.68mm for 2" and outer is 85.85mm. The pipe inner dia is 42.82mm for 2" and 53.94mm for 2.5". So using a SPW gasket without inner ring, the protrusion/obstruction of gasket is not going to be there. And the flange and blind flange are 2" and will not have problem in diff of RF facing dia. Also the step of hole dia change is 5.56mm which is not an issue for any instrument item for sure. So you can use SPW without inner ring, however for the service indicated by you it will definitely be required frequent replacement than with a inner ring.
Speaking in general of the use of copper gasket, yes what the vendor says is true in case of cyclic loading, else it can be used. I do not feel any cyclic loading is going to be there for the service mentioned by you. After every maintenance it will have to be replaced like the soft rubber or metal ring gaskets.And you can never apply the SPW torquing for it. For your info even Aluminium gasket are used.
Now the solution as copper gasket for your situation is not suitable and you have to go soft iron. But not as a flat one but as o-ring gaskets on a V-groove flange. This could be an alternative solution for you. You could use 90 deg. V groove of 2.1 mm depth on the RF at 80mm diameter which is near to the outer dia of a SPW gasket and use a soft iron of 5mm dia. Finish/tolerance of the groove shall be similar to a ring joint flange. This innovative site solution is used in normal 125 to 250 AARH, RF, B16.5 flanges and have been a proven solution. But you have to calc. your torquing table for these joints. But the torquing data is very similar to the ring joints. In case of 2" it would coincide, but verify from your end. Moreover your services would go well with soft iron.
For the SPW gasket property info the best resource would be the inventors of SPW gaskets, the flexitallic (http://www.flexitallic.com/pro_semi_spiral.html) Also they do give reply in a day or two.
Coming to B16.5 compliance, the other alternative, if it is few points in the plant, replace the 2" flange with 2.5" x 2" reducing WN flange, and with 2.5" bored blind flange, this will ensure you are in line with B16.5.
With regards,
Kannan
| yogesh modak <yogeshm28@yahoo.com> Sent by: piping_valves@yahoogroups.com 04/09/2008 09:55
|
|
Thanks for your mail.
Will go through the tables and other material mentioned by you.
However another query regarding mechanical properties of copper under compression. Can we use standard bolting torques while using copper gasket?
Any informatino on mechanical properties of Spiral wound gaskets?
thanks & regards
yogesh
----- Original Message ----
From: "Bhattacharyya_Bibekananda@ke0.grp.kaneka.co.jp" <Bhattacharyya_Bibekananda@ke0.grp.kaneka.co.jp>
To: piping_valves@yahoogroups.com
Sent: Thursday, September 4, 2008 2:21:10 AM
Subject: Re: [piping_valves] Copper gasket.
Hi! Yogesh,
Thanks for the input.
I understand the situation. And it is a straightforward case indeed!
Please refer ASME B16.5 Table 6 or Table 7 (I do not have it in front of me
right now.) with title as “Reducing … Flanges for Classes … “. Please read
the table and notes very carefully.
The case of modified flange (as indicated by you) is basically an
“Expanding Flange”. Code only permits reducing flanges with boring size
limits. Please read the table.
I hope that it will be clear to you.
For non-Code and poor engineering practice cases, finding a solution is
like “re-inventing wheels”.
I am sorry that I cannot help you in this case.
For additional reading, you can refer ASME B31.3 paragraph 304.4, 305 and
306, which talk about listed and unlisted components.
I think that you should also similarly respond to site, without breaking
your head.
Kind regards,
Bhatta.
yogesh modak
<yogeshm28@yahoo.
com> To
Sent by: piping_valves@ yahoogroups. com
piping_valves@ yah cc
oogroups.com
Subject
Re: [piping_valves] Copper gasket.
09/03/2008 11:38
PM
Please respond to
piping_valves@ yah
oogroups.com
Requested parameters:
1. #1500
2. design temp. 100°C
3. Fluid type - Glycol / De-Emulsifier (De-oiler) / Nitrogen Gas
Flange details
Piping side is having standard 16.5 raise face flange.
Instrument side is having Modified blind flange. 2" blind flange bored to
accomodate approx 2.5" instrument meter pipe. Due to this the raise face width at
instrument side is reduced and so standard 16.20 dimension gasket does not fit.
The flange type based on the drawing of vedor is similar to fig. 4a
ASME SECTION VIII DIV 1 appendix 2.
I have done the stress calculations as per ASME but that does not answer the point
raised by vendor i.e copper work-hardens and hence after
couple of cycles leak proof joint cannot be guranteed. As against spiral wound
gasket which has springing property and hence good for cyclic loadings.
Also the required torque calculated using the Min design seating stress required
for flat copper metal gasket (Table 2-5.1 of ASME) is very low as compared to the
standard torque values used for bolting. And if that values are used than the
initial stress on copper gasket goes beyond UTS. Since gasket will always in
compression comparing with UTS may not be correct. Is there any value fo copper
gaskets upto which the copper gaskets can be initially compressed?
Also would like to know if available, mechanical properties of sprial wound
gakset.
Regards
Yogesh
----- Original Message ----
From: "Bhattacharyya_ Bibekananda@ ke0.grp.kaneka. co.jp"
<Bhattacharyya_ Bibekananda@ ke0.grp.kaneka. co.jp>
To: piping_valves@ yahoogroups. com
Sent: Wednesday, September 3, 2008 9:12:33 AM
Subject: Re: [piping_valves] Copper gasket.
Dear Yogesh,
Request you to indicate the following parameters please ...
1) Pressure Rating of the Flanges, in question;
2) Temperature of fluid, which will be wetting the flanges and gasket;
3) Name of fluid, which will be wetting the flanges and gasket;
4) Both flanges' facing details, like type, RF dimension, finish etc.
All these parameters are needed to do a quick check for the flanged joint's
integrity.
Guessing: What is the problem, if soft iron is used?
Kind Regards,
Bhatta.
yogesh modak
<yogeshm28@yahoo.
com> To
Sent by: piping_valves@ yahoogroups. com
piping_valves@ yah cc
oogroups.com
Subject
Re: [piping_valves] Copper gasket.
09/03/2008 01:22
AM
Please respond to
piping_valves@ yah
oogroups.com
At site on one of the flow meters flange facings of flowmeter flange and standard
piping flange do not match for the raise face dimension.
The raise face width at flowmeter end is less than standard flange. Hence
standard spiral wound gasket does not fit. Site came up with option of using
copper gasket. We enquired with gasket vendor and one of them said that copper is
not suitable for cyclic loading. He say's copper work-hardens and hence after
couple of cycles leak proof joint cannot be guranteed. As against spiral wound
gasket which has springing property and hence good for cyclic loadings.
Also for copper, can we use standard bolt torque for tightening?
Regards
Yogesh _,___
No comments:
Post a Comment