Estimate Clean Pressure Drop in Cone Strainer
Estimate Clean Pressure Drop in Cone Strainer
(OP)
We are installing some specially designed cone strainers at the outlet of a reactor to catch any catalyst pellets which might break through. This is vapor service (H2 and vaporized hydrocarbons) at 900F and 40psig. I would like to estimate in advance the pressure drop of the proposed design (designed by others).
The strainer is the surface of a circular cone fustum built into a spool of 24"dia pipe (ID=23.25"). The cone shaped support plate is lined with wire mesh..
This is my geometry:
R1=19.25" (note: there is a 1/2" thick solid support ring holding the cone away from wall so the effective pipe cross-section at this point is 19.25" dia)
R2=5" (note: this is a flat steel plate at small end of cone)
H=47.75" (distance between base and top faces of cone)
Support plate open area=40% (as 1/8" perforations)
mesh wire size=0.025" (layed inside, flow is inside to out)
wires/inch=16 (note: this gives 40% open area in mesh)
I get the surface area of the cone part from the formula:
A = pi*(R1+R2)*(H^2+(R1-R2)^2))^.5 = 26.4sqft
with a clean open area of
26.4*0.4*0.4 = 4.2 sqft (vs 2.9 sqft cross-section area of pipe)
which all looks reasonable.
Now I am wondering if anyone can tell me how to relate the pressure drop of this spool in terms of equivalent length of 24" pipe? A bonus would be a method which can also estimate the pressure drop as the open area is reduced by plugage.
Any help is appreciated.
best wishes,
sshep
The strainer is the surface of a circular cone fustum built into a spool of 24"dia pipe (ID=23.25"). The cone shaped support plate is lined with wire mesh..
This is my geometry:
R1=19.25" (note: there is a 1/2" thick solid support ring holding the cone away from wall so the effective pipe cross-section at this point is 19.25" dia)
R2=5" (note: this is a flat steel plate at small end of cone)
H=47.75" (distance between base and top faces of cone)
Support plate open area=40% (as 1/8" perforations)
mesh wire size=0.025" (layed inside, flow is inside to out)
wires/inch=16 (note: this gives 40% open area in mesh)
I get the surface area of the cone part from the formula:
A = pi*(R1+R2)*(H^2+(R1-R2)^2))^.5 = 26.4sqft
with a clean open area of
26.4*0.4*0.4 = 4.2 sqft (vs 2.9 sqft cross-section area of pipe)
which all looks reasonable.
Now I am wondering if anyone can tell me how to relate the pressure drop of this spool in terms of equivalent length of 24" pipe? A bonus would be a method which can also estimate the pressure drop as the open area is reduced by plugage.
Any help is appreciated.
best wishes,
sshep





RE: Estimate Clean Pressure Drop in Cone Strainer
Pressure Drop (psi)= .0005*P*V^2
P= density = #/ft^3
V=fluid velocity of approach in ft/sec
This is taken from an old Mack Iron Works Chart
RE: Estimate Clean Pressure Drop in Cone Strainer
However, when you line the perf cone with wire mesh, the wires have to occlude the perf holes, in a way that simple tools can't hope to model.
Since you have, or could soon have, a physical manifestation, how about setting it up in a standpipe and doing a water flow test?
Mike Halloran
Pembroke Pines, FL, USA
RE: Estimate Clean Pressure Drop in Cone Strainer
And, as MikeHalloran suggests, if you do set it up in a standpipe and do a water flow test, you may please post your observations and recordings on this forum for the benefit of all of us.
Thanks.
RE: Estimate Clean Pressure Drop in Cone Strainer
A test stand probably won't be practical, but I should be able to get clean dP data under recycle gas circulation as a prestart-up activity- i.e. before hydrocarbons are introduced and things get dirty. We have some instruments to monitor which will be calibrated to give good resolution since each 1psid = at least $50k/yr electrical cost.
Unclesyd, your formula doesn't reference the strainer open area but may prove a useful for predicting other conditions once a reference data point is known.
I'll let you know if anything interesting is found in September when these changes come on line as part of a larger project.
Thanks,
Sean
RE: Estimate Clean Pressure Drop in Cone Strainer
Truncated cone 175% vol; 150% area; 80% pressure drop at length L
Inverted cone 150% vol; 200% area; 95% pressure drop at length L
Cylinder 300% vol; 200% area; 20% pressure drop at length L
RE: Estimate Clean Pressure Drop in Cone Strainer
I contacted the designer to give me an estimated pressure drop for this service. His answer was 2 to 3psid clean pressure drop for the normal flow condition. FYI, the specs I wrote were 276000pph, MW=30, 920F, 45psig, 0.03cP. I called for 0.2psid clean, and 1psid dirty (30% or more plugged), but the available length of piping we allowed was apparently too short for a design meeting my specs.
Now I will take suggestions for possible mitigations. Again thanks to all.
best wishes,
sshep