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  1. meanderson3d

    Vacuum Relief on an API 12D Tank

    I have an some API 12D tanks (10,000 barrels). According to API 12D, the design pressure of the tank is 3 oz., and the allowable emergency relieving pressure is 4.5 oz. When it comes to vacuum, API 12D is not so clear. It states that the design vacuum is 0.5 oz., but unlike the pressure...
  2. meanderson3d

    Sizing PSV Header Piping

    polyroly, You need to determine what your maximum relief rate will be for each valve and then calculate your back pressure backwards from your vent or flare. This will give you the pressure at each point in the header, which will tell you what the superimposed pressure is at each valve. Note...
  3. meanderson3d

    Blanketing

    My understanding is that diesel is classified as a combustible material and therefore does require an area classification. It would just be a smaller area than a flammable material like gasoline. It's true that if you blanket the tank with fuel gas, that will add a Class 1 Div 1 area where...
  4. meanderson3d

    Natural gas composition

    Natural gas is simply a mixture of hydrocarbons that happen to be in the gaseous state at the operating temperature and pressure you're looking at. Coming out of a wellhead, you usually have a natural gas phase in equilibrium with a crude oil or condensate phase, with a water phase (liquid)...
  5. meanderson3d

    PSV Discharge Line Choking

    buelowj, When I design relief systems, I am generally less concerned with whether or not there is choked flow in the pipe than what the actual back-pressure at the valve is. For a balanced bellows or pilot operated valve, this is not usually an issue, but it still needs to be checked. I agree...
  6. meanderson3d

    Determine Flow Capacity for Safety Relief Valve

    One thing you have to be careful of is your reducing valve being able to have more than one trim size. If you currently have a trim size that is smaller than maximum, someone can go in there later and install a larger trim if they decide they need more flow. Then your relief valve will be...
  7. meanderson3d

    2 PSV's - 2 Vessels but 1 flame arrestor

    It is never recommended to install a flame arrester in a PSV discharge line. At best, they impose a restriction. At worst, they can get plugged. Relief valve discharge piping should be sized to limit built-up back pressure at the relieving valve and super-imposed back pressure at all other...
  8. meanderson3d

    Vent / Flare Stack Question

    I am designing a NGL processing facility and need some help with the vent system design. Since the facility is essentially liquid packed, purge gas is not available to keep a positive pressure on the vent system to prevent air ingress. The only time the vent system will see a flow is in the...
  9. meanderson3d

    Gas Sweetening Plant Design

    I am looking for help designing a gas sweetening plant. We're just in the conceptual stage right now. The flow rate is about 15 MMSCFD of gas with 20 ppm H2S and 4% CO2. I'm familiar with amine units from a process flow standpoint having worked at a gas plant that had one specifically for CO2...
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