Thursday, September 18, 2008
Three Way Valve Interlocking.
In addition to our earlier discussion on the subject, I verified with operations people and that an additional reasoning based on their practice in dual safety valve, is that the situation is, the PSV is gone for maintenance or inline/cutoff from the system. And the same status is to be known at the key cabinet. So if the PSV-2 outlet LO key is in cabinet it is understood that the PSV is in maintenance. if it is in the inlet valve of the PSV-2 along with the second key which is used to unlock and close, it is to be understood as that it is only a cutoff. Also during maintenance the pipe spool is placed to replace the PSV and incase of any leak in the closed inlet valve, the pressure build-up is avoided by keeping the outlet LO.
As per the operation person it is important to know the PSV status in cabinet to verify the maintenance records.
So LO of outlets has to be interlocked with inlet and not independently LO as a GEP.
In addition I understand Netherlocks has recently comeup with new locking devices in which some valves which are not reachable as in your case, can be controlled by the flexible metal wire covered in plastic sheath like an electrical cable and can be located anywhere and can operate a raising stem valve. And the key can be removed or inserted using the extension rods. It looks quit neat and without any disturbance to any piping.
Smithflow guys say as per thier experience they do not have a better solution than the same wire cable for such changeover valves.
One more news is that all big oil and gas vendors are presenting themselves in Dubai trade fair. So any one in the region could benefit.
With regards,
Kannan.
Friday, September 12, 2008
RE: [piping_valves] Three Way Valve Interlocking.
Netherlock always expects and replies only for big orders. If the order is more than Euro 1million, the founder of the company will reply you back. It is not a good approach though.
Anyway. coming to your email, the observation of your PID snap shows a FG/FS, possibly fuel gas with insulation/heat traced. But the No pocket note is strange there being a gas. So definetly we cannot bring the arrangement at floor level of the vessel. So operating the valve at such height without a platform, going to be a special task. However as the top nozzle of the vessel has a fig.8. and a manhole and I expect some arrangement to reach the top. And the change over valve being a raising stem, and the simultaneous operation is required of both the valves, chain-wheel is the best cheap solution. Have a look at the below snap of Netherlock where the long rod also is available to handle the key.
With regards,
Kannan
| "Bagesh Kumar" <bagesh.kmr@gmail.com> Sent by: piping_valves@yahoogroups.com 12/09/2008 13:51
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If you can throw some light for the interlocking between these Two Change over Valves , Although a vendor has suggested a chain interlocking, which is not looking suitable at this kind of application, I have tried to contact the Netherlock but didn’t recd any reply.
Thank u once again for your suggestion.
Kumar Bagesh
Three Way Valve Interlocking.
Sorry I overlooked the three way valve you had mentioned.
Here I would like to draw a similarity, though the valve constr. and design are different, in ethylene cracking a changeover valve is used to switch from cracking to decoking mode. I happed to observe that flow pressure condition during the change over is significantly affected by the changeover valve and the downstream valves were required to achieve the right condition. Similarly, if you observe the various scenarios of the inlet flow condition under which a safety valve is designed for, the functioning will be affected, like chattering and the availability of the 3% margin.
But even with the two way valves at a transition point both the valves are 100% open and both the PSVs are available and will start chattering, but you have the advantage that the 100% relieving is available at any point of time. But in a changeover valve the 100% relieving is not there as at 50 % open condition the flow is split at 50%, compounded with a situation where one safety valve is malfunctioning, you are at more risk. But you have a bargain that the transition is shorter and easier operation than a two way valve. But if the upstream vessel is of large volume and you expect the PSV size to be in the range of 1" to 3", the 3way could be used.
But again, the outlet and inlet has to be interlocked even in case of the 3way valve, if the PSV-1 inlet side is open, PSV-2 inlet side closed and the outlet side of PSV-1 is closed and PSV-2 outlet side is open, which is possible without an interlock.
Most of the vendors who manufacture such changeover three way valves do guarantee the flow area remaining constant during the transition but in case one PSV has failed the vessel is in high risk for the short duration of the 3way valve operation.
With regards,
Kannan
| "Bagesh Kumar" <bagesh.kmr@gmail.com> Sent by: piping_valves@yahoogroups.com 12/09/2008 10:45
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|
But the Valve is not simple Three way, It’s a change over Valve, I agree with your answer for interlock, but the change over valve working principle explains clearly that It is not possible to block the flow, i.e if one closes other side opens simultaneously and in any case the inlet side is always open.
Kumar Bagesh_._,___
Three Way Valve Interlocking.
The answer is simple.
Imagine if someone mistakenly closes the PSV outlet block valve, what would be the scenario. To avoid that, the interlock should be there between the inlet side and the outlet side of the dual PSVs.
The sequence goes like this....the outlet valve of PSV-1 which is in locked open using first key and the key is removable only if the valve is in open position and for closing that valve the first key is required and the inlet valve of PSV-1 which is LC to be unlocked and with that first key and is opened and LO using second key and this key will be removed after locking and will be used to unlock the inlet valve of PSV-2 and the valve is closed and locked using third key and this key is removed and inserted to lock open the outlet valve of PSV-2 and this means the third key stays there in LO and that the outlet valve cannot be closed.
The core purpose is that both the outlet valves are open irrespective of the respective inlet open/close positions and that it can never be closed and to enable one stream to be opened before closing the other stream. So interlocking will be required either in three valve system or two way valve system.
Even your first initial PID is also incorrect. It should have the PSV outlet side valves also interlocked.
Additionally, my recommendation is that never use a three way valve for a safety valve as the reason for two valves and two streams is for safety reasons that even if one stream is having a problem the other one is available. It is not a matter of cost saving but a safety matter.
With regards,
Kannan
| "Bagesh Kumar" <bagesh.kmr@gmail.com> Sent by: piping_valves@yahoogroups.com 12/09/2008 03:18
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Dear All,
Please suggest me why interlocking is necessary in Dual relieve Safety Valve, My issue is like this,
In a Russian project the Licensor PID specified the single relief valve diagram. After detailing our process team found that Dual relief Valves are required, As the detailing went on they generated the scheme for Dual relief Valves with Two Gate Valve in inlet and Two in Outlet by single operation scheme, i.e. One Lock Open and one Lock Closed, Process team wanted to purchase an interlock system between both Gate Valves, Then it came for material parts, I suggested them to use two Three way Valves in dual relief operation, because I had used it earlier in a plant of Zimmer licensed, and the operation of these valves are similar to my project requirement, after that our PID with both diagrams went for an approval to PMC, now PMC wanted to use this Change-over Valve system, but interlocking to be done between Inlet three way Valve and Outlet three way Valve, I remember previously I have not used any interlocking between these.
My question remains,
Why Interlocking is necessary between these two changeover valves in Dual relief Safety Valve operation, Although Vendor is ready to provide interlocks between these.
I request member suggestion.
Attached is the scheme suggested by me, after that PMC added interlocking provision.
Earlier it was like this.
Regards
Kumar Bagesh
Thursday, September 11, 2008
Use of DIN material in B31.8 design practice.
ST52.0 which is equivalent to 1.0421 / A519 and ST52-3N which is equivalent to 1.0570/1.0576 / A516, A572 can be used for the purpose inline with B31.8 para 811.221 being an official equivalent of ASTM material.
With regards,
Kannan
| "Mohammad Yaghoubi" <yaghoubi_m@nigc.ir> Sent by: materials-welding@googlegroups.com 11/09/2008 12:07
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DEAR SIR
CAN WE USE PLATES OF DIN1629 ST 52.0 OR DIN17121 ST52.3N TO MANUFACTURE
SPLIT TEE ACCORDING TO ASME B31.8
BEST REGARDS
MOHAMMAD YAGHOUBI
----------------------------------------------
National Iranian Gas Company
http://www.nigc.ir
Copper gasket.
Even the nonstandard solution is being adapted and in most cases the site personnel do violate the codes and standards to find some solutions specifically without even consulting the engg. office.
So I go by what Bhattaji says as, it does pose serious hazard being a 1500# rating and with a gas service. A big potential for a high speed accident. The reasoning for this is simple. The B16.5 flanges does increase in the OD and thickness of the flange and the hub as the size increases and does have the backing for those dimensions under those Max. Working Pressures. Already it is a weak point in a piping system and if you are prescribing a flange dimensioned for 2" and going to use as a 2.5" connection, moreover a bored flange without a hub, which makes it the most weakest point. A 6mm fillet weld cannot substitute a hub.
So use of SPW / copper gasket can be at the descretion of site and if from engg. office it is to be replaced with a 2.5" reducing flange. As Bhatta refered the bore dim., which is a purchased defined parameter and the para 6.8 very well says that the hub will be as per 2" and thk/od as per 2.5". So I do not find any problem in going for it.
Sometimes such decision is like being with angel / devil.
With regard to your other query, in ethylene plant copper is used only in some cold fraction part and not as a flat gasket but as a V groove O-ring gasket. Aluminium and copper are also used in air seperation units . The torquing calc is the standard procedure and same as the ring joints. But I remember some posting was there by Raghuram some time back on the subject. Pl. check the group's archive.
You can also check http://www.futek.com/boltcalc.aspx
With regards,
Kannan
Thanks Kannan,
Kannan, please ignor questions in earlier mail.
As you said the comparision of diameters was done and we were able to eleminate most of the cases which were originally thought to be problematic. On most of the cases comparing the gaskets ID and instrument tube OD, it was found that standard 16.20 spiral wound gasket can be used. So the problem was reduced down to small numbers.
As you have said that standard SPW gasket torquing cannot be used for copper gaskets. Is there any reference to calculate the required torque?
regards
yogesh
Copper gasket.
Dear Kannan,
Good Morning!
I do repeat again that the problem case is a simple SPW gasket case.
I find it difficult to convince myself while wasting my effort on
somebody's fertile idea of using copper gasket.
Regarding your sportive comment, please do appreciate it is a non-code
example of using expanding flange. Such type of flange is indeed a safety
hazard for higher pressure rating.
I can do the "re-inventing of wheels", if I have time and certainly not in
this unsafe case.
Pertaining to your alternative solution "...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" ...", kindly ckeck the boring size limit in the B16.5 table.
Thank you again.
Kind Regards,
Bhatta.
*********
Additionally, for our Bhattaji as quoted below,
"I think that you should also similarly respond to site, without breaking your
head."
These problems do occur due to the negligence of the white color engineers siting
in A/C office and doing poor engineering. So white colors do have to break thier
heads to find solutions to thier mistakes as we are called as engineers by our
site colleagues. So we have to engineer it.
This problem is a well known purposeful ignorance by the piping material engineer
who does not co-ordinate with the instrumentation specialist. And he ignores to
comment or talk to piping material engineer. The big excuse and a fact is that the
orders of the intruments are placed after the instrument assembly specification
prepared by the piping material engineer is closed and forgotten and IFC
isometrics is in progression.
So the site can be spared only at the will of the two colleagues involved.
Just a sportive reply dear bhatta.
Happy piping.
Kannan.
Wednesday, September 10, 2008
Copper gasket.
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
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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 _,___
locking devices
In continuation of the earlier email on the subject, the following companies are few prominent manufacturers.
http://www.smithflowcontrol.com/new/wheel-valves.htm
http://www.gst-systeme.de/Steuertechnik%20Download%20englisch.htm
http://www.netherlocks.com/
Check out the animation also.
With regards,
Kannan
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