Valve Manufacturer Advice

[JoeChem]

Greetings,

I am designing a small batch chemical plant and for the first time ever getting into the real details of piping costs. The piping systems I am considering are 2 in dia or less and low pressure/temperature where stainless steel is more than adequate corrosion protection. Right now I am looking at basic hand valves for the lines (ball, gate, globe, and maybe a butterfly or two) and am amazed at how many valve manufacturers there are out there. I am also very surprized at the huge variation in cost for the same size/type of valve in the same "class" of service. The valve descriptions do not offer any explaination for the cost differences.

I know this may be a difficult question but can anyone offer some manufacturer advice for basic hand valves for low pressure mildly corrosive service (316/304 SS). I am just looking to narrow the playing field here and not choose somthing very cheap or very expensive without a good reason.

Any experience passed along will be greatly appreciated.

JoeChem

 

[BigInch]

Its pretty basic. Although there is some brand loyalty, you generally get what you pay for. Higher end valves will almost always have better sales and engineering support, more quality controlled manufacturing and testing procedures, better after sales service, better warranties and with that, better reliability. A choice between several high end mfgrs often boils down to delivery time, although on 2" items, you will be able to buy off the shelf in most cases.

"If stupidity got us into this mess, then why can't it get us out?" - Will Rogers (1879-1935) ***************

http://virtualpipeline.spaces.live.com/

 

[gerhardl]

Think also a bit about getting a supplier that can supply threaded, buttweld (long and short) and flanged at choice, and valves that are easily adaptive or complete for mounting of pneumatic or electric actuators.

If the supplier also can offer 2 pices-valves as well as 3 pieces (middle piece with ball demountable by 4 through- going bolts to the two end-parts) for easier inspection, change and cleaning of ball and sealings, while (ends) mounted in pipeline, you will have a good start.

 

[moltenmetal]

Oh come on- you ALWAYS get LESS than you pay for, or else someone isn't making a profit!

You're experiencing to some degree the phoney diversity offered by the marketplace.

Low pressure/temperature, small size (< 2"), and either 304 OR 316 are acceptable? Investment cast commodity ball valves are the usual solution for blocking, and cast globe valves for throttling. These are COMMODITY valves, and dirt cheap. Literally hundreds of "brands"- every stainless piping supplier name-brands some in this part of the world.

Butt weld or flanged are going to be overkill. You're looking at either threaded or socket welded, unless there's something about your process you're not telling us.

Need the connections to be welded? Three-piece construction is the norm, so you can easily disassemble prior to welding, and later for maintenance. Threaded is OK? Then you may save a few bucks with 2 pc for valves you don't expect to service/repair frequently. Really trivial services like instrument air blocks etc.? One piece reduced port (end entry) saves a few bucks more.

Most of the cast valves are CF8M, which is a cast 316 grade. If you get these valves with socket-welded ends, you will get a threaded valve with threads removed- the same for the 150# fittings typically used up to 2" in these services. Note that CF8M is NOT 316L- it is NOT low carbon! If you weld it, you may have carbide precipitation and lose corrosion resistance in the HAZ. The low carbon grade CF3M is MUCH less readily available.

Cycling a lot? Then you may want live loaded packing. This can double the cost of the normal el-cheapo three-piece ball valve, but may be worth it depending on your cost of down-time to do repairs/replacement.

These are a commodity product, which means they're pretty much all the same within reasonable expectations of performance. Yes, there are some 1000 WOG and some 2000 WOG versions (makes no difference to you, though!), some with through-body bolts and some with only bolt tabs on the body etc. Some with proper actuator mounts, handle extensions available etc., and others without. Some even offer more than one seat material. But for your service it probably doesn't make a hill of beans difference which of these you choose. Sure, they all try to differentiate themselves from one another by some subtleties, and some brands may actually have more quality control than others, but how you'd ever really know the truth from the sales bum-fodder is tough to determine.

 

[belowzero]

I really wouldn't bother with 2" butterfly, stick to ball valves as these will remian the most competetive for the performance they offer. A 2" butterfly blocks most of the pipe and the CV is terrible. 2" reduced bore or full bore offer the best flow and opening characteristics for manual valves.
Very low cost valves will almost be throw away as they are just designed for cost and speed of manufacture rather than servicability.
B

 

[BillBirch]

Well Joe,
This is a reassuring request to my mechanical colleagues from one of our arch-enemies, the process hotshots! Perhaps you now understand what we do?

Jokes aside, the difference would be largely due to whether compliance is needed with the major equipment standards such as API, ASME or BS (which have very good, but rigorous standards for small bore valves).

As you would know, the requirement for these standards is given in the particular piping code to which your plant is, or will be built.

I have known instances where vendors have been trying to peddle half inch ball valves in stainless steel (well they do look silver), but don't expect to see any reference to a design standard. These, and bronze equivalent valves will sometimes go for as low as five bucks each, but don't expect to use them on anything more hazardous than mains pressure water.

In short, specify an applicable standard and ask to see certification if in doubt.

 

[moltenmetal]

BillBirch: JoeChem's building a small batch chemical plant. The requirement under B31.3 to use ASME B16.34 "listed" valves for normal fluid service is not written as a hard prohibition against using non-listed valves. There is freedom under this code to use non-listed components (including valves) for normal fluid service, within some very reasonable limits. That does not mean that the ASME, API, BS etc. standards aren't an excellent resource- nor does it mean that the piping code is the only applicable standard. Owner preferences and standards, underwriters' requirements, other related standards such as fire regulations (ie. requiring API 607 fire safety), or over-arching regulations such as CSA B51 that impose some requirements beyond the piping code itself, may apply. The designer has to be aware of the entire regulatory and customer requirement framework in order to do their job properly.

Mind you, I've seen plenty of truly "BS" standards for valves from all sorts of sources. Specs that are a wish list of mutually exclusive requirements that no one real valve could achieve- containing requirements that nobody in the owner's company remembers why they were put in there in the first place, much less whether or not the concern is still valid! Specs like this are too often used to substitute for, rather than supplement to, good engineering judgment on the part of the people designing the piping system.

We use commodity ball valves- the ones you refer to as "bronze equivalent", successfully in all sorts of services- not just in Category D services. Many of these valves have Canadian Registry Numbers (CRN), so we know we're not alone.