I'm revaliding a PHA for a med/high (100-500cp) plant.
We are going through the cases and taking credit for the positive displacement pumps spill back valves for preventing down stream vessel damage in a lock in case.
The problem I encounter is that almost all of them on the high viscosity...
What is other users experience for gas phase pressure drop in Aspen using the pipe block. And, under deep vacuum ?
We have a system with HX's and Pipework under deep vacuum so the condensation thermo impacts the flow rates etc.. so using aspen is very attrative.
Aspen users the darcy...
I’ve been made aware of a paper on Flash point predictions for binary mixtures. Which describes systems with mixture flash points that can be 10-15 C lower than the pure components within the mixtures. These are for non-reacting systems, I am aware of systems which react with air and then form...
All,
maybe this sounds a daft question but i'd like some feedback on the following..
if you are using 150psig steam on a reboiler, usually you control flow to the reboiler with a CV, then the pressure drops on the steam, velocity rises..
so, if you assume 150 psig for all these case you dont...
Thanks Don,
This is very helpful. I have come accross many vessels that fire is the only case.
So, have you seen vessels in the fire zone (gas filled) that dont have a relief valve and this is allowed under codes ?
Don,
Thanks for the email.
Ok, so it is arbitary, for most EPC firms they do use this equation to generate a relief rate so it is used fairly widely i believe (and have seen).
So if you have a gas filled surge drum what basis do you assume for the relief valve, and how do you prove it is...
If you work through the formulas you find it does impact the sizing.
• Step 1: Calculation of maximum Pressure rise from gas expansion. (is a relief valve required for gas expansion)
Pmax = Pop *(Tw/Top)
• Step 2: Determine the area required to pressure relief in a fire
o Calculate vessel...
The purpose of this question is to understand partices used for operating pressure Management of change and relief load evaluations.
For a gas filled vessel the relief rate / ultimate pressure rise depends on the start pressure (e.g.) how much gas is present at the start. So. From a relief...
The purpsoe of this is to understand peoples conventions on this.. generally it does'nt impact the calcs but on a revalidation i'm doing it is close to needing a new valve.. so i'd like some input please..
So, when you size for the fire case
Q= FA^0.82 : Fire duty = Q/ Latent heat.
Is the...
I'm looking for some standard pratice or recommendations for handling relief cases when we have a utility which could over pressure the process side from leakage inwards.. but it is not a shell and tube...
so for a spiral HX on process water , or a carbon block are there any guidelines for...
Thanks,
I'm embarrised to say that rather than one anti syphon hole we have two, it was drilled straight through.. I dont think its an issue becuase i think the flow is govered as below.
Point 1: Bottom of tank / dip pipe
Point 2 : Dip pipe hole above liquid surface
h1= height from liquid...
Dear all,
sounds an odd question..
what is the guidance for min distance to avoid erroision from an anti suphon hole to the vessel wall? i've heard of an incident in the 90's at my site that at vessel failed after 20 years service from this but unfortunatly we have lost the incident and...
I'm looking for a reference for typical civil design codes and why vessels at certain location use an SG of 1.5 when the process fluids are typcially 1 or much less than that...
When we have tracked back in our records 1.5 seems to have been what we have always used and probably for good...
sorry for a short question.. I'm struggling for a decent reference for the L/D for standard 3 way valves..
I normally use 1 eblow and a valve, which is conservative but on a recent calc I exceed 3% inlet line losses on an RV. So I'd prefer the calculations to show less than 3% so I dont need...
I'm looking for some overall reference for guideance for when it is economic to split a column into two or when you just make the design MUCH taller..
For example when you have a 1.8 meter 60 meter tall and want many more stages:
> is it still economic to go for 80 meters by 1.8...
Thanks RaRo,
I've never seen a factor of 1 used. And, I've looked at calcs for square vessels a factor of A0.82 (A^0.82) was used.
Is it common to use a factor of 1 for sqaure vessels and is that documented in API521 - I've reviewed API 521 several times to update project standards and not...
Dear sirs,
Running the heat exchanger sizing program to increase flow to an operating BEM Exchanger I've noted that if we increase the flow beyond a set range it exceeds TEMA rho v2 values on the shell side.
I've looked at the mechanical design and it is not possible to fit A large inlet...
Thanks for your posts.
Agree is is an empirical formula and the adding of pipework area is equally a judgement call some places do this and others don't I've not seen specific guidance on this either.
I'd like a quick check on methods for fire area that should be used under API521 to get overall duty..
I believe if we have a system with two vessels the correct way to consider fire load is as below.
method 1: Q (Total) = 43.2 * F* A1 ^0.82 + 43.2 * F* A2 ^0.82
method 2: i believe this is...
Your requirement is to ensure your downstream system is adequatly protected from an over pressure event. And, that you suitably maintain and managed your relief valve.
I've seen systems that are unsuitable for Pressure reliefs on positive displacement pumps becuase they are carrying solids...
