Replacebale seats or Intergral seats

[CKchi]

Recently i faced a case on 3/4 inch forged steel valve (ISO157160 . The client is insisting to have replacebale seat inserts, but our supplied forged globe valve is interal body seats with stellite 6 overlay.

Referrign back to ISO15716
Section 5.4.6.1 “Integral body seats are permitted in austenitic stainless steel bodies. An austenitic stainless steel or a hard facing material may be weld-deposited either directly on a valve body or on a separate body seat ring.
Section 5.4.6.2 “Except as provided in 5.4.6.1, valve bodies shall have separate removable seat rings that are threaded, rolled or pressed in place...

While if you refer to 5.6.1 - Seating surface, Obturator seating surfaces shall be intergral or have a facing or weld metal.

Seems like 5.6.1 and 5.4.6 are somewhat in conflict. i was trying to convince the client using section 5.6.1 but he told me should refer to section 5.4.6

Can anybody give some advice?

 

[Danlap]

The word except generally translated, "for some good reason defined by end user, the small sizes globe may also have separate removable seat rings".

Maybe I am wrong, but my analysis of your condition are:
[ul]
[li]Your preferred supplier have a robust design and manufacturing process. Making an extra effort (design change, fabricate replaceable seat) for small quantity is not economically efficient.[/li]
[li]Your customer have either a good reason / experience. In combination with they also have their maintenance team and strategy. Therefore in the next 3-5 years they have idea to change only the Seat whenever required by themselves.[/li]
[/ul]

Personally I would prefer also integrated Seat for sizes 3/4 and or smaller for most cases.
Removable seat susceptible for crevices between Seat and Body. For corrosive medium (let say acidic steam) or light medium (Hydrogen, etc.) may penetrate these crevices and then become internally passing or corrosion occurs.

Advice: Offer Open / win-win solution for your end user and Manufacturer:
- Valve with integrated seat price is x
- Valve with removable seat price is y
- Removable seat price is z
- x < y + z + projected maintenance cost
If your customer choose still the removable seat scenario, then he probably have a really good reason. And there are manufacturers which can provide this service

Regards,
MR


All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

 

[moltenmetal]

If your client REALLY wants replaceable seats (and plugs) for this valve, they may be better served with a control valve with manual actuator than with a globe valve. A 3/4" commodity globe valve is a throwaway item.

 

[Danlap]

Agree with moltenmetal comment,
this is normally commodity valve.

Only 2 scenario (3/4" Globe valve - manual) that I've ever experience which are not:
- Oxygen/nuclear valve with Monel material. It cost my company a fortune per piece, so replaceable seat preferred.
- High temperature Butt-weld valve (normally downstream/refinery) which requires F22 (low alloy), F11, etc material. Indeed also classified as commodity valve, however due to relatively longer lead time (shall it suddenly passing beyond tolerance) compare to standard material, we've kept some of the trim replacement in-house. And no additional PWHT required (shall remove the whole valve and re-install new one).

Maybe others have different approach

Regards,
MR

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected