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  • Users: Justice100
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  1. Justice100

    Real or ideal cp/cv for orifice sizing

    Hello all, I am using Crane for gas orifice sizing but am wondering if the real or ideal k (cp/cv) should be used? I know for relief valves it should be the ideal but unsure for a standard orifice plate. This is a blowdown orifice so flow is choked.
  2. Justice100

    Psv inlet pressure drop 3% rule

    Hi all Just looking for some wisdom on where the 3 % psv inlet dp should be calculated from. As there are differing views internally. 1. Pressure let down - a pressure control valve lets down pressure, there is no associated vessel so the psv is located on the downstream piping. Should the...
  3. Justice100

    Blowdown of linked liquid filled vessels

    Hi all, I am looking at emergency blowdown of two liquid filled vessels that are linked via piping at the bottom. The blowdown valve is off the top of one vessel (I have attached a sketch). The liquid is hydrocarbon condensate at its bubble point. Assume for simplicity that both vessels are...
  4. Justice100

    Tube Rupture - High pressure gas into water

    Hello all, I have a shell and tube HE with dense phase HC fluid on tube side at 350 barg and hot water on the shell side at 15 barg and 150 DegC with a design pressure of 24 barg. The shell will be protected by 2 bursting discs connected to the main flare header via tail pipes and a sub header...
  5. Justice100

    API 2000 - Conversion from Nm3/h of air when tank is blanketed with fuel gas

    For API 2000 the relief rates are defined as Nm3/h of air. When looking at for example thermal inbreathing - My tank is blanketed with fuel gas with a PCV that will open up at 0.1 barg to let fuel gas in. Once I have the required flow rate in Nm3/h of air how to work out fuel gas consumption...
  6. Justice100

    Big Valve Small valve - how to size the small valve

    Hi, We are in a position where we are about to install a pressure control valve but new requirements have come in for a much lower turndown so the intention is to install a small control valve in parallel to provide the turndown. There needs to be controllability all the way from the normal...
  7. Justice100

    API 14c - other pumps - high pressure trip on discharge

    Hi all, API 14c states that a high pressure trip on the pump (others) discharge is not required if the “Maximum discharge pressure does not exceed 70pc of the maximum allowable working pressure of the discharge piping”. It also states a psv on the discharge is not required if “Maximum...
  8. Justice100

    Finger Type Slug Catcher Design

    Hi, Can anyone point to a reference which details how to design a finger type slug catcher
  9. Justice100

    ESD valve location - Guide

    Hi all, Is there a good reference document or article that discusses the location of ESD valves? E.g. ESD valves are located on the liquid outlet of vessels presumably to isolate the liquid inventory in case of a leak. Also, they will be at fire area boundaries to prevent flammable materials...
  10. Justice100

    Minimum allowable pressure drop across a control valve for a low pressure gas system

    Hello all, General advice for defining a control valve DP at design flow is 0.7 bar or 30% of total system DP, whichever is higher. For low pressure gas systems the minimum of 0.7 bar can be unachievable as it is not available. Can any one point me to guidance for defining this for low pressure...
  11. Justice100

    Admin Controls - locked open valves - API 521 Section 4.2.2

    Hello all, When considering use of API 521 Section 4.2.2 – use of admin controls. If I have a high pressure vessel feeding a lower pressure heat exchanger with locked open isolation valves then for the closed outlet case if the upstream vessel has a PAHH set at less than 1.3 x design pressure...
  12. Justice100

    Control Valve Minimum allowable Pressure Drop

    Hi there, A problem I've come across a few times and had a few different opinions so I thought I would asked here... Typical rule of thumb for allowable control valve pressure drop is 30% of the total frictional losses or a minimum of 0.7 bar. How critical is the minimum value... I have a...
  13. Justice100

    Which rated flow for DP calcs

    Hi, I have just got some vendor quotes back and looking at reviewing the inlet/outlet line sizing based on the chosen vendor. The project is in Europe with vessels to EN 13445. One vendor states an actual Kd and orifice area and then apply a de-rating factor of 0.9 to calculate the rated...
  14. Justice100

    Body Bowl choking

    Hello all, I am looking at some PSV discharge piping calculations using Hysys for choked vapour flow. One thing that I am finding is that it appears that there is choking in the outlet nozzle of the valve. Having read around this is I see it is called body bowl choking but is more of a concern...
  15. Justice100

    CS Methanol Storage Tank corrosion rates

    Hi, We are looking at using CS for a methanol storage tank and injection system at and oil and gas site. I see either CS or SS316 is suggested from various sources (e.g. ISO 21457, M-001 etc). Is it possible to calculate a corrosion rate for using CS? I have done some searching but can only...
  16. Justice100

    Required and rated flows for back pressure / header determination

    Hi all, I am trying to understand when to use required and rated relief flows for header sizing for conventional pressure relief valves. API 521 states in table 8 that for a spring loaded PRV then design for rated capacity in the tail pipe and required in the main header. My understanding is...
  17. Justice100

    Tank Emergency Vent - Capacity Charts

    I have a tank filled with cryogenic hydrocarbon. The emergency relief vent (weighted pallet with hinge, something like this - https://www.protego.com/products/detail/ER_VH.html) is set at 130 mbar with 20% allowable accumulation and there is an inlet line 10m long (required as double walled...
  18. Justice100

    Inadvertent valve opening PSV case - also include max normal operating flow from other sources?

    Hi there, I have a vessel that normally receives fluids from various sources. For the case where one of the sources has a control valve that can fail open would you consider the relief valve to be sized based on the maximum Cv of that control valve only (with the control valve pressure at the...
  19. Justice100

    Slug velocities in pipe

    Hi there, I am am looking at 2-phase flow through a ~100m line of various sizes (3",4",6" and 8"), which is mainly horizontal pipe with a few short sections of vertical pipe. Based on Perry's 2-phase flow map I have slug flow. I need to report slug velocities to check the piping support...
  20. Justice100

    Spitzglass - low pressure system DP

    Hi there, I am looking at using the Spitzglass method (as described in GPSA and others) as the system is at near atmospheric pressure. The one thing I am not sure about and none of the references I have discuss is whether the length is the pipe length or the equivalent length and if it is...

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