NON RETURN VALVE LEAKING 2

[puresteam]

AT MY PLANT WE HAVE 2 500HP STEAM BOILERS AND ON ONE OF THEM THE NON RETURN VALVE IS LEAKING WHICH IS CAUSING THE PRESSURE GAUGE NOT TO GO DOWN ONCE THE BOILER IS SWITCHED FROM LEAD TO LAG.I AM NEW TO STEAM AND DON'T KNOW THAT MUCH YET BUT AM VERY EAGER TO LEARN. BY THIS VALVE BEING LEAKY CAN THIS HAVE A MAJOR EFFECT ON THE OPERATION OF THE BOILER. THE MANAGER DOES'NT WANT TO CHANGE IT OUT BECAUSE OF THE WORK INVOLVED,BUT I'M THINKING IF IT WILL CAUSE DAMAGE TO THE SYSTEM LET'S GET IT DONE.WHAT ADVICE CAN U SHARE WITH ME.

 

[pmover]

the lag boiler pressure may very well remain at steam piping pressure and the boiler will remain warm. however, for the lag boiler to remain in that state for a long time, there is a possibility of the steam condensing, thus raising the water level in the boiler. before any work is done on boiler internals, the boiler must be isolated from the steam piping system. hopefully, there is a main stop valve for that purpose.

hope this helps.
-pmover

 

[insult2injury]

I'd prefer to see two stop valves with a drain in-between.

I2I

 

[BenThayer]

explain what you mean by lead vs. lag.

typically when there are more than one boiler, both are running at some % of load. do you load the lead boiler to 100% of capacity and then start loading the lagging boiler?

don't you want to have a bias of something like 70% load on the lead boiler and 30% load on the lagging boiler?

the reason for having a bias split the load is to have the lagging boiler operational. if you load to 100% and then start loading the lagging boiler, that sounds like you will be upsetting the site header pressure.

 

[Mopar71]

If I am not mistaken,there should be a drain valve at the bottom of the non return valve,this is used to bleed any accumulating condensate.we used to open it at startup of the boiler till it reached full pressure then shut it. also at shutdown open it and leave it open.

 

[unclesyd]

Does your non-return valve have a impact hammer handwheel?

Does your non-return valve act like a lift check when in the open position?

 

[CaptainKvar]

Puresteam,

When you switch from lead to lag boiler is the steam pressure equalized on both boilers? Is the steam rate (capacity)the same on both boilers?

Why not run both boilers together in battery and run the lead boiler with more load and the lag boiler with minimu load?

A non-return valve is basically a stop and check valve.
You can manually re-seat the valve with the handwheel and then try re-opening the valve to see if the valve re-seats.

With the non-return leaking you wont really harm the boiler and it will stay warm (which is good for stand-by purposes)but you will go high water so you will continuing blowing down the boiler and wasting chemicals.

CaptainKvar