Howden compressor questions

Recentally i have been working with a project using the howden compressors WRVi321/1.65,the swept volune is 4790m3/hr, the condition for this project is at suction/discharge temperature -35℃/40℃, with refrigerant R22.
It's my first time to deal with Howden compressors, There are two questions i'm not very sure and need your help.
1. For the oil system design, there are two lubrication methods, one is Fully Pumped Lubrication System and the other is Partially Pumped Lubrication System. The cost of the Fully System is much higher than the Partially System, so we plan to take Partially Pumped Lubrication System. But I don’t know whether this system can work properly and how to calculate the volume flow of the part supplying to the bearings (flow from the oil pump,for pump selection), and are there any other notes making the system run stablely for this design?
2.For this project with WRV321/1.65, the size of the horizontal oil separator which I calculated is DN1100,is it ok?
and who can tell me the oil charge?

thanks

cygbob

Hi cygbob its minimum of 114 litres of oil or 1/2 the capacity of oil pump per minute which ever is greater,speak to howdens and i am sure theyll help you out

hello cybog,
I think partial pumped lubrication system will create lot of problems at later stage because the Oil separator elevation has to be more than oil cooler elevation so that oil can flow to oil cooler,and we need to have sufficient head available for oil pumps also.Though this system is cheaper than other but maintenance and location wise ,fully pumped system will be better. Oil charge will be calculated on the basis of volume occupied by the oil in lube oil console skid. You should keep sufficeint margin for flushing the circuit with oil ,at later stage.

There are a large number of systems with partial pumped lube system .
If oil cooler is installed all oil would go through it and tee off to oil pump and oil injection . Oil injection is differential feed into rotors . With your system operating -35 / 40 deg C i see no problem . This reduces size of oil pump by more than half .
Would instal a non return valve in oil injection line to avoid pump probs at start up .

I just want to highlight the problems that one has to face while installing Oil seperator and oil cooler.You have to lift up the compressor because oil separator will be at higher elevation. Check the available space and decide tentative piping before opting for such system.You will definetly save money on Pump and oil piping, if you are opting for partial pump lubrication sytem, but check the points which i have highlighted.

thank you all for the helpful informations!
one thing you mentioned a lot is that the elevation between the oil seperator and oil cooler, if the height need to suppy the oil cooler pressure drop(say 0.5bar),then i think the height need to be more than 5 metres? so high?? i must be wrong, but where?

thanks again

cygbob

Well the discharge pressure will be enough to push the oil once the system is running, but at the start one has to ensure the supply of oil through oil pump to casing etc. I think u should maintain sufficient elevation so that oil can flow through gravity to oil cooler . Velocity of 1 m/s will be safe enough for reducing the pressure drop. I could not understand your query regarding pressure drop.??

sorry, i'm confused by the concept 'conquer the resistence':(
thanks

Hello,

NEVER run a Howden WRV whitout an absolute minimum of 1.0 bar over the discharge pressure. 2.0 bars is the best and 2.7 bars for a "H" designed compressor.
You will allways have to use an oil pump on this types of compressor.

Gerben
www.rm-support.nl

Someone may correct me, but I think the net oil pressure to the compressor is: Net oil pump discharge pressure - compressor discharge pressure.

The net oil pressure is after the losses are accounted for in the oil piping, oil cooler, and oil filters.

US ice man , you are correct. Oil pressure in partially pumped system is equal to to "Net oil pump discharge pressure - compressor discharge - pressure drop in oil cooler and connecting lineviz" Here we consider pressure drops in oil cooler , strainers, lube oil filter etc and then we calculate the net pressure with which oil will enter into the compressor bearing etc.