Recommendation and sizing basis for Footvalve/strainer on a gear pump

[juanon]

Friends,


I have a rotary gear pump for lube oil pumping having a negative suction lift of 20". A strainer /footvalve arrangement is proposed a the suction to remove particulates and maintain the suction line primed.

Do you recommend this configuration ? If so any design guidelines ( recommended standards/ publications) available for sizing this component ?

Response much appreciated

 

[pardal]

Hi Juanon :

When asking be more specific.
Flow to handle:
Kind of oil:
It´s
specific weight:
sepecific viscosity:
Tank temperature:
mean size of the particulate to be filtered:

Pardal

 

[juanon]

Pardal,

FYI

Flow to handle: 26USGPM
Kind of oil:Lube Oil(superturbolfo 32)
It´s
specific weight:0.87
sepecific viscosity:33.4
Tank temperature:40 deg c
mean size of the particulate to be filtered:30-50 micron

Thanks

 

[pardal]

For this flow you will shall run the flow on a about 34 mm internal diameter.
For this kind of pumps, if are new, you only will need to prime at the first star up.
You shall follow this rule:
" let the suction as free as possible" the sole warning is to locate a strain filter 200-300 mesh just to avoid the incoming of a huge debris, or a cleaning cloth left inside the tank.
For that particulate size you shall use a cartridge filter on the presure line , it could be full flow or derivated flow.
Ask to any hydraulic service vendor and they sure will supply with such elements.
I forgot to ask the max pressure on the line.
At the first start up time , just let the out flange free, drop oil over the out side chamber, then run a hose back to tank, fill with new oil from the hose free end , make a few short pulse starts until the pump is primed , after it reconetc the supply line, after it the pump will be still primed if used frequently.
If the prime is lost easy, check for leakgeage on the pump.
If you did not get a satisfactory result , you will need to use a check valve , choose a 2 or 3 diameter up than pipe.
For this case should be a 2" inch as the pipe for this case will be a 1.250 inc Schedule 40 .
Care must be taken to use a check valve with a small weigth poppet.
But does not matter if the check valve is used, you shall fill all the suction pipe, before fiting it to the pump "in port" , then do the same procedure as stated before.
Hope it help.

If you want, contact me at
k281969@hotmail.com











Optimal pipe diameter about: 34 mm
Possible diameter: DN 32 ==> Velocity 2.04 m/s
Possible diameter: DN 40 ==> Velocity 1.31 m/s Pardal

 

[juanon]

Pardal,

sorry to be late in responding. I appreciate your help. It is obvious you are talking real life experience. To summarize your thoughtful email.

a) STRAINER

Let the suction be as free as possible :

Avoid any restrictive device at the inlet. In fact, their is a provision at the discharge to filter it with a 40 micron filter.

A coarse strainer 200-300 mesh is recommended at the suction
but considering the negative suction lift I would prefer to avoid. The NPSH req for Flowserve (wothington) 4GAFM1D0 is 15.95 ft.

b) PRIMING

For the first time the priming is ensured by filling the pump casing from the discharge flange with a few short pulses. Air in the suction line will be displaced and released through the broken flange connection.

This pump is on a continuous duty for lubrication purpose
so in absence of any leakage the priming shall be maintaned( oil shall not drain out from the gear mesh and separation of the inlet and outlet is expected to be maintained even the pump stop and the suction line gets drained.)

In case the priming is eaily lost a poppet type check valve is requied at the inlet suction line 2-3 diameter

CONCLUSION

The proposed modification is only required if priming is easily lost and there is apossibility of big debris in the tank.

 

[pardal]

Hi Juanon:
Where are you ?

Let me know how it work, if it work of course.

Feel free to be in contac any time you want to.

Pardal. Pardal