Mechanical seal failure flow rate calculation

[humaidq]

Hi All,

I am fairly new in terms of dealing with Mechanical Seal and would like to know how I can calculate the flow rate if the seal fails. I have attached a picture of a mechanical seal that I am working with.

 

[flexibox]

you cannot calculate this. rather strange set up, you have a fixed and a floating bush? normal seal leakage is approx 5-10cc/hr. are you injecting N2 where the green arrows are? normally there is only 1 bush and this appears to be for safety because the product is not environmentally safe when it leaks. if thisi s the case then you have the wrong seal. one needs to know what the produst is, if you have a high Vapour Pressure then you will have a gas leak, if low VP then liquid leakage. so you question is not clear, do you want to know what the max leakage is in the event of a seal failure or normal leakage?
send some more information about product and what you are trying to achieve.

 

[humaidq]

I would have liquid ammonia at the red arrow if the seal failed. I would like to know the max leakage at the event of a failure.

 

[Dougt115]

Define fail. Your valve is 100% functional to 100% failed. You could calculate the flow rate without seals to determine max leak rate. Then you will know you will be between this number and zero.

 

[flexibox]

Humaidq
Max leakage in the event of failure needs to define the mode of failure. Looking at the drawing there are no pressures shown but if we assume flow through a 1/2" pipe with 1/8" orifice and 20PSI Delta P then leakage is around 1.5Gal/min. orifice area represents the bush clearance but the leakage depends on the level of damage. i think that you need to have a dual pressurised seal anyway for safety. I remember years ago getting a whiff of ammonia and it was not pleasant. if this were mine i would convert to double pressurised seals.

I now understnad why you have a double bush configeration which is rather unusual in fact this is the first time i have ever seen it. I think it is used like this to minimise any leakage to atmosphere in the event of a seal failure. not the best way to seal this if you are after safety.