Relief valve on main steam oulet nozzle

[arvi]

Friends,

We have recd. a rental boiler for emergency heating steam requirements during the winter period. Boiler supplied is 300 psig rating and our existing system is 150 psig. Vender has offered to put a relief valve @150 psig on the steam outlet nozzle before the stop valve by providing a tee on the outlet nozzle. Is it acceptable from code point of view.

Boiler is designed to section I. As per ASME section I, PG-71.2 and PG-71.7 an independent connection is required for RVs. Can this be considered as an independent connection because as such there is no obstruction in the steam path to RV.

De-rating the boiler to 150 psi was the first option we thought of but since that requires re-registration we are trying to avoid that.

Two PSVs @300 will stay. Additional RV at 150 is to protect the existing system.

The boiler is oil fired (start up with propane).

My thoughts were that if we install the additional RV after the stop valve then we have to follow 31.1 which means 1 RV at 150 psi for the maximum flow is enough (Max capacity would be with the steaming capacity at 150 psi which will be more than the steamning capacity at 300 psi which can be calculated). BUT if the RV is before the stop valve probably we have to follow the rules of sec I which means 2 RVs (As per ASME section I, PG-67.1) and again if adding the RV on the outlet of main steam is acceptable.

This boiler is for Ontario, Canada.

Thanks a lot in advance for your advise.

Arvi

 

[ExAI]

Arvi,
2 thoughts.
1) the boiler your installing is specifically intended for temporary service. The Jurisdictional Authority should be consulted regarding all matters involving this boiler. I would presume that temporary units are not subject to the same rules as perminent units.
2) The RV's discussed in ASME sec 1 are intended to prevent catastrophic failure of the boiler itself and do not consider system limitations. The RV's provided on the boiler (Set for 300psi?) should remain in place. Protection of your system should be performed by Alternate means including provision of outboard relief. B31 rules should apply if considered relevant by the Jurisdiction, other wise use good engineering practices. I would not even consider affecting the ASME I boundary.

Lane Baker
Baker Quality Services
LaneBQS@att.net

 

[arvi]

Thanks Lane for your advise.

Yes that is we have decided now after discussing with the boiler supplier. To keep the boiler registered as 300 psi and design the piping with additional RVs at 150 psig with full capacity (based on the maximum steaming capacity at 150 psig).

We intend to provide One (or two RVs) after the boiler nozzle and then provide the steam stop valve.

Another alternate we are thinking is to provide the steam stop valves first and then provide the RVs after the valves but then we have to consider design pr. up to stop vales at 300 psig.

Any suggestions

Thanks

 

[ExAI]

I guess I'm surprized to hear that you are responsible for the steam stops...I've never heard of a rental boiler provided without them...In addition.....I've never heard of a rental boiler supplier that is not responsible for connecting his equipment to yours. The RV's you need should be outside the ASME Sec I boundary (i.e. beyond the stop valves)and perhaps under your control (not provided by rental company). The 300# safeties should be left alone but the pressure controls should be adjusted down to 150 psi max, lower if practical.

Lane Baker
Baker Quality Services
LaneBQS@att.net

 

[arvi]

You are right, Lane. Normally stop valve is provided by the boiler supplier particularly in case of rental boiler. But this case is different. Somehow someone from our side placed wrong order (300#). When we (design) were told to support the installation, we raised all concerns. Supplier initally agreed to de-rate the boiler to 150 psig but withdrew later on and our management has agreed to take the control.

Having said all that now we need to meet all code requirements sine we are hooking up with a system which is at 150 psig syste.

Reg. sec I boundary, my understanding is that the boundary is boiler nozzle (not the stop valve). Although upto stop valve sec I is administratively responsible but technical requirements are as per 31.1.

Thanks