B16.5 Flanged fittings 1

[DGStavlas]

Hi all,

My customer requests to design its pumping station connections with rubber lined flanged fittings. Though the flanged fittings in accordance with B16.5 are tabulated and dimensions are given I don't know whether there are suppliers that fabricate them. The other solution I was thinking was B16.9 fitting with B16.5 at both ends but then another question arises.which of the code would essentially govern the fabrication of flanged fittings as I described above. In case I'm wrong and B16.5 flanged fittings are easily fabricated and supplied which is the most economical solution ?

Thanks in advance

 

[pennpiper]

DGS,
Look here:

http://www.piping-engineering.com/rubber-lined-piping-solution-to-corrosion-resistance.html

And here:

https://www.google.com/search?q=rub...0ahUKEwiwpueWj8PMAhVI2R4KHW-9C-kQsAQIPA&dpr=1

Sometimes its possible to do all the right things and still get bad results

 

[DGStavlas]

Dear pennpiper,
First of all thank you for your quick response. I've seen some of the suppliers of rubber lined fittings but I wasn't able to understand which code they use. As I'm not responsible for the supply of the fittings I need only to deliver an iso of the piping connections and the respective parts drawings. Let me be more specific. Should I use b16.5 dimensions or "create" a flanged fitting from a b16.9 and two flanges at the end ?

 

[pennpiper]

DGStavlas:
You wrote the following (My comments in red):
1. I've seen some of the suppliers of rubber lined fittings but I wasn't able to understand which code they use.
There are so many ways to make Rubber-Lined piping and fittings. I do not know which code or which method your fabricator will use.

2. As I'm not responsible for the supply of the fittings I need only to deliver an iso of the piping connections and the respective parts drawings.
I suggest you use only overall dimensions on your Isometrics such as center to center of runs between direction changes, face of flange of valves or nozzle connections. Let the Fabricator/Liner workout the dimensions based in your Isometric and their method of making the fittings. As you can see on the Rubber Lined Fitting Images, there are different ways to fabricate the piping and fittings.

3. Should I use b16.5 dimensions or "create" a flanged fitting from a b16.9 and two flanges at the end?
You need to consult with your Fabricator on this. It will depend on the Pressure and temperature of the commodity. They could make the Lined fittings and pipe from Cast-Iron or Carbon Steel. The Cast Iron Fittings would/could be one piece, the dimensions for this would not be B16.5. If made out of Carbon Steel they could be made out of B16.5 Fittings but which ones. Example: some of the CS fittings (Tee) may need to have Weld-Neck flanges and others (90 degree Ell) may be able to use the cheaper Slip-On flange.

Sometimes its possible to do all the right things and still get bad results

 

[DGStavlas]

Pennpiper,
The problem is that my customer wants workshop drawings for each fitting. Let me ask you one more question
You wrote "It will depend on the Pressure and temperature of the commodity". Is there a problem using B16.9 and two flanges at the end? You mean that the working pressure of the fitting will be different than of each separate element? Probably I'm asking for the fundamendals but due to my lack of experience I'm forced to. Let me tell what I'm thinking. Because here in the local market b16.9 fittings and b16.5 flanges can be found easily, I was thinking to combine them so as to create the required fittings.

 

[pennpiper]

DGStavlas,
We need to start over.
1. What is the Commodity?
2. What is the maximum Operating Temperature?
3. What is the maximum Operating Pressure?
4. What is the Nominal Pipe size?
5. Who is going to do the Rubber Lining?
6. Why does your Client want Drawings for each Fitting?
7. What about the Straight Run Piping, does the Client want drawings of that too?
8. If the piping system is NOT Rubber Lined does the Client still require drawings of each fitting?


Sometimes its possible to do all the right things and still get bad results

 

[DGStavlas]

Penpipper,

First of all thanks again for your valuable help.

1. What is the Commodity?
The design has to do with a pumping station of a tailings management facility seepage collection pond.
2. What is the maximum Operating Temperature?
40°C
3. What is the maximum Operating Pressure?
16 bar
4. What is the Nominal Pipe size?
14"
5. Who is going to do the Rubber Lining?
Don't know my customer has its own procurement department.
6. Why does your Client want Drawings for each Fitting?
Because he has the possibility to manufacture the fittings by himself.
7. What about the Straight Run Piping, does the Client want drawings of that too?
Only the parts placed inside the pumping station.
8. If the piping system is NOT Rubber Lined does the Client still require drawings of each fitting?
It is the customer's demand that all piping should be rubber lined.

 

[pennpiper]

DGStavlas,
So, lets see if we can bring this to a close.
Your answers to my questions.
1. What is the Commodity?
The design has to do with a pumping station of a tailing management facility seepage collection pond. Its just warm dirty water
2. What is the maximum Operating Temperature?
40°C That's 104 degrees F, are you sure this is not the Design temperature?
3. What is the maximum Operating Pressure?
16 bar That's 230+ PSI are you sure this is not the Design Pressure?
4. What is the Nominal Pipe size?
14" Okay, but are there any Reducers to change the diameter?
5. Who is going to do the Rubber Lining?
Don't know my customer has its own procurement department. Okay, but you should find out who will be doing the lining because it may make a difference
6. Why does your Client want Drawings for each Fitting?
Because he has the possibility to manufacture the fittings by himself. Okay
7. What about the Straight Run Piping, does the Client want drawings of that too?
Only the parts placed inside the pumping station. Is that a Yes?
8. If the piping system is NOT Rubber Lined does the Client still require drawings of each fitting?
It is the customer's demand that all piping should be rubber lined. Okay

Now my recommendation.
1. You need to determine the thickness of the proposed lining. Ask the Client, The proposed Lining Company, somebody must know what the thickness will be. You ask, why do you need this. Because the flanged ends of all pipe runs and flanged fitting will have the flange face covered with the rubber lining. This system will not use the conventional "Gasket" as found on all other non-lined piping systems. On this system the rubber lining will be extended beyond the end of the flange face and then be folded flat over the flange face. This result in two times the rubber thickness at each flange joint. If your lining is 1/4 inch then you end up with the equivalent of a 1/2 inch thick gasket. That may not seem like an important issue but if you multiple flanged joints in a pipe run it could add up.

2. Design your piping system and make your Isometrics using the normal ASME B31.3 Code piping rules and practices. Use Standard Carbon Steel class 150 B16.5 Flanges and Carbon Steel, Schedule 40, B16.9 Fitting dimensions for your Elbows, Tees, and Reducers. Remember, allow for the thickness of the Lining as the "Gasket" dimension at each Flange face (two flanges face-to-face, two rubber thicknesses face-to-face).


Sometimes its possible to do all the right things and still get bad results

 

[Gator]

Also check if the lining requires venting between the pipe inner wall and the outer surface of the lining itself. This is often the case and if so, then the manufacturing standards for the fittings and pipe are not the limiting factor.

 

[DGStavlas]

Penpipper,

Yes my mistake, the maximum operating pressure is 25 bar but still the maximum operating temperature is 40°C. Regarding your recommendations, I think that this is the best solution. Still I have one last question.
Because of the low pressure I'm thinking to use slip-on flanges. Are there any limitations? I think this is a more economic solution than using welding neck. Do you agree ?

Gator,
Could you be more specific because I think I'm missing something here ?

 

[LittleInch]

Usually with rubber lined flanges there is a requirement to internally radius the flange to prevent a sharp edge which is difficult to coat and risks creating a tear. Doing this for a slip on flange risks removing some of the weld. Machining of the flanges before you install them will give a much better and more exact profile and can be done much more cheaply than trying to do the same for slip on flanges.

Slip on flanges are not great and should be avoided wherever possible IMHO. There has been much discussion on the issues with slip on flanges. Given you have to do two welds, why do you think this is the cheaper option?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[DGStavlas]

LittleInch,
First of all thanks for the reply. I was thinking that slip on flanges are the cheaper option because my client wishes to manufacture the fittings by himself and at this case, after his demand, labour cost is not included in the budget. So in terms of capital cost only slip on are cheaper than weld neck.

 

[pennpiper]

DGStavlas,
You asked the following:
1. Because of the low pressure I'm thinking to use slip-on flanges. This is acceptable
2. Are there any limitations? Make sure you put a clause in your Fabrication Specification that the inside weld for each Slip-On Flange is ground smooth. Sharp edges can damage the Rubber Lining.
3. I think this is a more economic solution than using welding neck. This has been a subject of discussion for many years and we do not need to bring it up again for just your project.
4. Do you agree? Yes and No, I would prefer to leave it up to your Fabricator.

Other issues:
a. Gator is correct about the Vent holes and I will let him give the reason.
b. Make sure you require the Fabricator to sand blast the out side of the finished lined pipe. They should then Prime and finish paint each lined piece. They should then paint warning signs on each piece stating "RUBBER LINED PIPE, NO WELDING ALLOWED".
These signs should be stenciled at least once on all smaller spool pieces and not less than once every ten feet on longer spool pieces.



Sometimes its possible to do all the right things and still get bad results

 

[Gator]

Perhaps this doesn't apply in your case:

"Venting is a primary element of lined piping systems, its absence can be dangerous, but it is little understood. All PTFE and PFA lined equipment should have a venting system, most usually 3mm holes in the steel pipe. This serves two purposes. First, without venting, any gas trapped between the lining and the steelwork will expand with an increase of temperature. Such gas can arise by permeation through the lining. If it has nowhere to go the pressure on the back of the lining can cause it to collapse. Secondly, if for any reason the lining is damaged and leaks, the presence of a vent hole will provide an early warning of leakage and avoid the catastrophic failure of the piping."

From

http://www.crp.co.uk/technical.aspx

Corrosion Resistant Products Ltd.

 

[racookpe1978]

Would not lapped flanges provide that smooth inside surface to the flange face from the inside of the pipe, while still providing a workable (far easier, quicker than but joints for lined pipe) flange positioning method for field fitup and welding?

(Now usually I prefer slip on flanges over lap joints, but here ?? Seems like the lap joint has a lot going for it. )

 

[pennpiper]

racookpe1978,
Yes there are some minor technical advantages for the Lap-Joint flange method but it is normally more complex and more expensive. You must purchase two items, the "Stub-end" part and the "Lap Joint Flange" part.
The complexity comes in when you must consider the Short Pattern (stub-End) or the Long Pattern (Stub end) and then get all the dimensions correct.
There are apparently two other issues here: (a)the Cost, the Client is trying to do this job on the cheap. and (b) the Designer seems to be new to this issue of Lined piping so I was trying to keep it simple.

Sometimes its possible to do all the right things and still get bad results

 

[moltenmetal]

Bonded or spray-applied linings don't require vent holes. Loose linings do, even if they are "locked" by circumferential swaging of the pipe or other clever means.

Linings that are formed in place and/or baked to cure afterward, require very good quality surfaces on all the interior welds, generally requiring grinding the roots flush or smooth followed by inspection of the weld roots by dye penetrant examination. Porosity generates defects in the cured lining. In many cases, the cost of the lining once installed exceeds the cost of the components and labour used to make the flanged fitting, so you want to make sure you get this right.

Most linings either require, or their durability can greatly benefit from, radiusing of all sharp edges INCLUDING between flange faces and flange bores. The degree of radiusing required varies by the thickness and nature of the lining used.

Many linings PREFER, for this reason and others, that the flanges used be slip-on flanges rather than either weld neck or lap joint. For some linings, this is more of a want than a need, but for others it can matter a lot (centrifugally molded linings are one example where SOs are required rather than merely being suggested). Note that unless you buy special butt-welding fittings with extra long straight lands on them, you will need to butt weld a pup piece of pipe onto the fittings at each flange location, so you will be doing three welds per flange (one butt plus two fillets) instead of one. Most liners also require, or strongly suggest, that a hole be drilled on an angle to vent the cavity between the OD of the pipe and the SO flange exterior, which is a cavity trapped between the two fillet welds of the slip-on assembly. And generally, the exterior weld should be done last, to give a better likelihood that you deposit a porosity-free interior weld where it matters most to the quality of the finished assembly.