the quality of valve manufactures

This is not a quality issue. It is a combination of incorrect trim specification and/or poor water treatment. A stainless steel or bronze disc should have been specified for this application.

Good day,

Been in valve industry for 20 years, I barely have any experience with Siemens. So cannot say they are bad or good.
It is quite common in certain system and/or skid to buy a bundle of equipment from single source supplier, so let say we buy Flowserve pump, then skid components (valve, etc.) surrounding it will be kind of black box for end user. Not necessarily for example the ½” – 150# ball valve supplied by them will have inferior quality (FS don’t make small, relatively low engineering ball valve).

Before jumping to quality of certain (not commonly known as) valve supplier, would suggest performing more elaborative root cause analysis:
-What sort of butterfly valve? Metal seated triple offset or rubber seated double or even zero offset.
-If replaceable rubber seat butterfly valve, then who installed it? Please note that this kind of valve should be in open position during flange tightening. Risk (tightened in close position) will make the seat bulging, and block valve movement. Eventually will torn the seat as well.
-Motorized valve got stuck at 5% when signal given is 0% (fully close) ? Isn’t this going to trigger some alarm? What sort of response did you do e.g. manual override it, increase the torque, etc.?
-What material is the disc/seat? Did Siemens specify the material or is this the End user part?
-Pitting corrosion remarks in comparison with cavitation can be quite subtle for common eyes. Is your cavitation theory has been verified by metallurgist?
-Corrosion on disc usually not causing valve to get stuck. Stuck on butterfly valve is more corrosion on bottom/top bearing and or bulging on rubber seat

Agree with TugboatEng, the contributing factors can be design and material specifications issue.

Please note that it is harder and more expensive to find pure metal ore. By that respect for the last 10+ years, we are already entering the era of renewable metal, which has lower nickel and molybdenum content. More susceptible to pitting corrosion.

Excuse my grammar.
Regards,
D

@ TugboatEng: thank sir for the response. A third-party contractor routinely treats the chilled water system. According to my understanding, the trim specification relates to the internal condition of the valve. In this instance, however, the valve is not closing properly; rather than a single valve, six valves are functioning identically in the same plant room. Overriding the disc and closing down are ineffective. What I've found is that the problem is mechanically and not related to the actuator. Recently, it was sent to an outside service, where the defects were rectified. However, because the near-closed operation may cause cavitation, the side of the disc has already corroded with pits. I classified it as a manufacturing defect for this reason.
Is it true that Siemens does not have a factory to produce its own brand of valves?


The problem with the world is that intelligent people are full of doubts, while stupid ones are full of confidence.
-Charles Bukowski-

@Danlap, Thanks for taking time to explain more about it.the datasheet for the concerned valve is attached. The specification is not shown as a triple or zero offset. The identical valve proposed for a new project for the motorised isolation purpose for the plate heat exchanger! I came upon the identical info sheet. “The project consultant advises that the butterfly valve in the ETS room be double eccentric." I reviewed the datasheet for the exact word; it is not listed.
“Pitting corrosion remarks in comparison with cavitation can be quite subtle for common eyes. Is your cavitation theory has been verified by metallurgist?
There is no third-party confirmation; I assumed it was cavitation.


The problem with the world is that intelligent people are full of doubts, while stupid ones are full of confidence.
-Charles Bukowski-

Hello moideen,

This is a classical example : everything is OK but the end result. As mentioned by others (I do agre with the posts above) several things might be wrong. With stainless steel as spcified for the disc, it is more likely that the pistting is cavitation corrosion. This should however be easy to spot for engineers familiar with cavity damage by the cavitations 'non smooth' pitting grooves, and likely similar damage for all six valves.

Further, if we assume cavitation, it could be mannufacturing faults (outside tolerence limits for disc, sealing or positioning), but most common are unprecise adjustments of actuators limit switches.

I doubt that a well renowned German company as Siemens could have slipped on product quality control, and would suspect bad adjustment of control devices/limit switches and/or false mounting/support for the valves with actuators.

The mechanical faults mentioned I would have liked more specified, with photos of damage and pipeline installations.

As mentioned lugged or flanged valves with double eccentric closing would have been better. As a tip for this size of valves, closing and opening time can often be doubled (or more) giving smaller elecrtical actuaters with gear, at lower total cost.

Good luck with your investigations!

I doubt that a well renowned German company as Siemens could have slipped on product quality control

Click to expand...

Don't get me started on ZF azimuthing thrusters... Country of origin is not a determination of quality.

TugboatEng, You caught me there....I stand corrected!