Monel Trim

[hasanmoulana]

My client requires gate valve with Monel trim. What my principal offered is stem in monel, wedge in CF8M with monel overlay on seating area, Seat ring in SS 316 with monel overlay on seating area & bonnet bush in SS 316. My client has rejected the above prposal & asked me to offer trim as per API600. My principal is informing me that his above offer will work fine & there will be no problem, but he does not know how to convince my client technically. Can any one help us by giving suggestions technically.

 

[gerhardl]

As always the use and experience on how trim behaves over time is a result of the actual conditions at site: fluid, chemical composition of fluid, temperature, impurities, layout in pipeline etc.

If the end user has good experience with 'pure' monel trim, and this exists on the market at a 'reasonable' price as deemed by your customer, you have very little chance to convince the end user.

As a buyer I would only accept anything else as a replacement from a well-known valvetrim if the known product had obtained 'disadvantages' over time, mainly perhaps to high price or too long deliverytime.

If a replacement is to be considered I would at least have required references from the producer/principal for (exact) equal installations in long-time use. Your customer should be free to contact the references/existing users.

What about long-term guarantee from your customer, free trial (long-term) or free replacing with required product after trial if not so good as expected? (In short: how far will your principal be willing to back up what he is saying? This question will often reveal 'the truth', by turning your question in reality over to the construction department at your principal, in stead to a sales organization....)

In addition it would be sensible to compare in detail your constructional details to installed and described products.

But chemical reasoning? SS316 is not monel, and will have disadvantages for some fluids, an overlay might be worn away, or construction details could expose bare SS316.

 

[ValveSteve]

I've never had a customer request Monel trim and have never used it. What are the advantages/disadvantages of using it instead of 316? How do you apply it to the seat ring, by welding and machining?

Sorry for all the questions, I've never spec'd it and am curious.

 

[geos44]

Steve -

To answer your question, one application for monel is saltwater service, where it is much more resistant to corrosion than 316SS. It is a nickel-copper alloy with a very high percentage of nickel (more than 60%), compared to 316 which is a chrome-nickel alloy (~17% Cr., ~12% Ni.). Monel can be applied as an overlay, but if the base 316SS is exposed it could be attacked. A better procedure is to fabricate the trim using bar stock and/or plate. With your background you are probably familiar with that procedure, although monel is much more difficult to weld and machine than 300 series SS.

 

[ValveSteve]

Thanks geos44 for the good info!

Many of the valves I've designed before called for tungsten carbide and chrome carbide overlays inside the ports, on the seating surface of replaceable seat rings, and sometimes on the gates. They've been welding the overlays, but the welding time & wire costs are significant. (not to mention the grinding and machining time and costs) So, I'm working on better ways to deal with this.

Another challenge with the welded carbide overlays is that it doesn't adhere well to mild steel. I'd like to either find an alternate method to applying the carbide, or find a viable replacement.

 

[hasanmoulana]

Dear geos44,

Reference your comment, I request your help. We have valves manufactured with Monel overlay on CF8. My client is not accepting this. Could you please gie me some good technical point to convince my client.

 

[bcd]

You must know the media inside the valve before you can discuss what trim material is acceptable or not. There is some where solid Monel is absolutely necessary. For example, Chlorine or Oxygen are situtation where solid Monel may be required.