Butterfly valves

[srisua]

Dear Seniors,

Greetings for the day. Thanks in advance for your support on my query. We are doing detailed engineering for fuel system for 660MW power plant. There are two fuels to be used for lighting up the boiler and for initial heating. They are Heavy fuel oil and light diesel oil. In our scope only fuel oil unloading system alone is there. System to be designed for pressure of 3.5kg/cm2,100cum/hr flow and operating temperature is 50degC. There are two pumps for each fuel system in which one is working and one is standby. Generally we use ball valves for isolation purpose. Now my question is as the pressure and temperature is less, "can we use butterfly valves instead of ball valves for this oil application?".

 

[Danlap]

Hi srisua,

For isolation purpose, you can use most type of valves for this application. With some advantage and disadvantage of course.
However it would not be the same case, shall for controlling flow purpose.

Where do you want to isolate it? Suction or discharge or both? And what is the acceptable leakage rate (from your process / pump guy point of view)?
Shall you only deliver P&T and service information to valve manufacturer, and ask the moderate price solution. There are good chances that they will deliver Double offset Butterfly valve with Rubber seating.
Rubber (range from NBR to EPDM) have a risk of reaction with the 'Oil'. Thus leaking and so on. Its not so simple to be refurbished.

Not my place to generalize answer:
- If you have maintenance / replacement schedule within 3 years to replace the sleeve (liner of Butterfly valve). PTFE liner Butterfly Valve can be an option
- If strictly this is a critical pump with no leakage or whatsoever (theoretically), and you have the money. Triple offset BV (metal to metal) can be an option as well.

Else probably have different view.
Regards,
MR



Greenfield and Brownfield have one thing in common; Valve(s) is deemed to "run to fail" earlier shall compared to other equipments

 

[srisua]

Dear Mr. Muktiadi

Thankyou very much for the information. As you guessed, isolation is suction and discharge side of pump only. We have selected EPDM seat as this will be withstand the temperature of 150 deg C whereas my operating temperature is just 50 deg C.

As it is oil application, no leakage is allowed. I have asked three manufacturers of butterfly valve and they suggested to use normal wafer type butterfly valve for oil application. myself is not satisfied and hence approached this forum.

You said there will be a reaction of EPDM with oil. can u please elaborate this?

As per my experience triple offset butterfly is suitable to oil even for steam. But the question now is normal wafer type butterfly valve can be used in oil line or not.

Regards

 

[Danlap]

Hi Srisua,

Elastomer application and interpretation is depending on the services, best practice (of manufacturer and end user) and lesson learned (especially for refinery which has the longer life expectancy).

EPDM has a good resistance to hot water, steam, dry heat, ozone and vegetable based hydraulic oils. However, it has a poor resistance against hydrocarbons. It is not recommended for mineral oil lubricants and greases.
See JamesWalker website or similar to understand the material selection matrix better.

As for Wafer type, I am not in favor of it.
Wafer --> Exposed bolts to the environment and susceptible for thermal-cold expansion (in extreme case:fire occurs). And shall expands, leakage will occurs and further feed the fire.
It really requires the right bolts/nuts material, proper flange management, and quite robust environmental temperature (not too hot and not too cold - relative).
With one exception: Water service (and sometimes instrument air).
If you see wafer type for oil in some plants, most likely it is either: an Old plant and or Plant with spatial/dimension constraint however they have calculate the risk and mitigation.

The advantage of wafer only are: fast to install into the line, relatively cheap and light (without flange)

Regards,
MR

Greenfield and Brownfield have one thing in common; Valve(s) is deemed to "run to fail" earlier shall compared to other equipments

 

[gerhardl]

I fully agree with Muktiadi's comments.

From the discusssion here it seems obvious that the reason to discuss BFL valves is mainly to come down on the total buying cost of investment (buying, freight and installing). By suggesting EPDM for the installation, it also seems that some of the engineers involved needs additional information on detailed problems and cost of longtime operation of this type of pipeline systems.

Two major points of clarification for you here is:

1. Total cost over the installations planned lifetime, procurement and installation cost PLUS and including stop for maintenance, changing of valves or general maintenance, unplanned stop and disturbances (including lost income from business and compensations for downtime, if any), deliverytime cost and stocking cost of spare assortment.

2. General quality and dependabillity of valves selected, including the vastly differing cost and quality of BFL valves, if selected. Does the valves satisfy all local apllicable rules and norms for fire protection (firesafe construction/test if required), leakage to air (if any requirements) cost of later automation (if relevant), buing cost comparison between alternatives. If small valves, ball valves might be cheaaper than butterfly, if larger valves safety and standtime might be far better for ball-valves. High-quality- BFL valves will cost much more than cheaper BFL valves with longer standtime.

Too often a discussion about valves narrows down to 'what can I use to lowestbuing cost' in stead of 'what should I use to obtain the best and cheapest possible long-term operation'.

Direct answer to your original question:

As fuel quality and additives might vary I would generally go for PTFE sealings. You have consider valves allowed for end of line duty ( kept in place by bolting and allowed if pipeline is demounted on one side) or not, and piggable lines (ball valves) or not If everything else in comments above is satisfied you are free to use any (general) BFL valve. I would generally in this case go for ball-valves, especially for 'smaller' sizes, if BFL valves suited and with references for this type of service, with references for long-time , trouble-free operation.

(Sorry for the long answer, got a bit carried away here! Good luck!)

 

[srisua]

Dear Mr.Muktiyadi, Mr. Gerhardl,

Thank you very much for your valuable time and response.

I have almost got answer from the reply of Mr. Muktiyadi.

Mr. Gerhardl, you need not to say sorry for long reply and as a juniors we should always thankful to you.

Coming to point, we are doing this project for 660MW power plant in which i have selected all process valves are ball valves only. But before pump as per specification i should mount duplex strainer. This strainer containing two bodies and there is a valve mainly for isolation of two bodies. here as per strainer vendor suggestion, to optimise cost we have used butterfly valves. two top consultancies in India has approved this strainer GAD. Herewith I am attaching drawing for your information. Strainers manufacturing is also completed and now this doubt has come. As per discussions had with you, i am planning to go ahead with ball valve even for strainer instead butterfly valve. changing valve at this stage is loss to us and tedious process, but as an EPC contractor we should ensure our system performance also.

Please suggest changing of valve at this moment is good or can i continue with same butterfly valve

 

[Danlap]

Gerhardl,

Thanks. And for your footnote.

Srisua,
With all due respect, you cannot elaborate full analysis for this design selection in a simple A4 pages.
For instance, rhetorically:
- how often the inspection of these strainers will be commenced periodically
- how 'clean' does these oil with respect to the valve selection (quarter moving valve with soft material is susceptible for scratches shall dirty service after some cycle)
- assuming the operator only know how to open and close the valve, how they normally does this (behaviorally)
- What is the flow nature when its 'hit' the valve trim
- etc.
And most importantly, does the similar design (with same service) has been proven successful.

Plus, your sketch and your information is contradictory. Sketch shows lug type BFV and you mention above is Wafer?

If I understand this correctly there are three parties involved: Your consultant, you as an EPC and end user.
You guys should seat together and sparing (challenge each other). You will eventually land a decision over which type.

The answer can be as simple:
- If this is Brownfield, than your end user may already have experience either with BFV or Ball Valve
- If this is Greenfield, the answer is already in your FEED analysis (if there is any).

If this is a very clean service, I would suggest Ball Valve with periodic inspection / maintenance. But who am I to decide , I know nothing about this Plant behavior (people, service and regulation)


Greenfield and Brownfield have one thing in common; Valve(s) is deemed to "run to fail" earlier shall compared to other equipments

 

[gerhardl]

Supporting and agree with Muktiadi: This is a decision to be made locally, based on local discussed pros and cons.

Perhaps not a bad idea to present two alternatives (defined make with all details), one BFL and one ball-valve with lists of pros and cons. Then make up your mind and recommend one of them, afterwards asking for evaluation/approval of your comparison and the result from the end-user or a higher level in your own company before the final descision.