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SteveDixey
07-10-2006, 05:36 PM
Howden WRV 255 is chucking out its oil into the system - 5 litres a day.

Visual checks on mesh in the oil separator that can be seen seem to indicate no serious contamination but obviously can't check in the body of the mesh. Can the oil sep be flushed out to clean out crud that may be blocking the mesh?

No bits of mesh in the bottom of the oil receiver so I'm assuming the mesh isn't breaking up.

Someone had wound open the valve on the small bleed line onto the compressor suction at some stage, maybe hoping to clear the issue. Other machines were only open a half-turn.

Otherwise machine seems OK. Machine has not been worked on recently so I am assuming no-one has left bits out of, (or left bits in) the oil circ system.

Correct oil is being used. Machine temps appear OK.

Is it just that the oil sep has reached the end of its life??

Steve

Andy P
07-10-2006, 06:17 PM
Hi Steve,

As usual there are more questions than answers:

Do you know the make and type of oil separator?

Where does the small line into the suction connect to?

What age is the unit?

What are the suction and discharge conditions?

Is it knitmesh type pad?

Does it stop and start through the day?

There are four possible reasons for the oil carryover: perhaps a baffle inside the separator has been dislodged and is allowing oil-rich gas to blow past the pad; perhaps the oil level has been high at some point and the pad has been saturated; perhaps the oil separator is OK, but the non-return valve is sticking and letting the compressor run backwards when it stops - throwing oil back up the suction line; or perhaps the compressor is running on minimum load at low suction pressure, which would also possibly throw oil back up the suction line.

Do any of these make sense?

Cheers
Andy P

SteveDixey
07-10-2006, 11:06 PM
Do you know the make and type of oil separator?
It was supplied with the machine, but will need to hack off a few layers of paint to tell you exactly. The main body of the separator is around 1.8 metres high by 450mm diameter.


Where does the small line into the suction connect to?
The small line connects the base of the larger diameter of the separator, (before it reduces down to the connection flange on the oil receiver), to the underside of the suction pipe on the machine.


What age is the unit?
20 years old


What are the suction and discharge conditions?
It is a low side machine, 0.75 bar(a) suction, (freezer @ -40c) and around 27c 11 bar delivery.


Is it knitmesh type pad?
Yes, the gas makes two passes, up through one mesh pad, through a drilled plate, then diverted down through another mesh screen and into the oil receiver.


Does it stop and start through the day?
Some off-loads and stops, but not frequent. More to do with production changes than plant off-loads through varying product loads.


There are four possible reasons for the oil carryover: perhaps a baffle inside the separator has been dislodged and is allowing oil-rich gas to blow past the pad; perhaps the oil level has been high at some point and the pad has been saturated; perhaps the oil separator is OK, but the non-return valve is sticking and letting the compressor run backwards when it stops - throwing oil back up the suction line; or perhaps the compressor is running on minimum load at low suction pressure, which would also possibly throw oil back up the suction line.

As far as I can see there is nothing that has fell off. The unit was removed and internal inspections were made. NRV's possibly. Another machine had the guts taken out of its NRV so can't rule it out.

Machine will run at minimum load at low suction pressure if plant off-loads instead of stopping. I'd normally issue a stop command after 5 minutes of off-load running. There are no recips to take up varying load however. As they are driven by 200kW motors, stop \ starts are not a desirable action.


Steve

Andy P
08-10-2006, 12:34 AM
Machine will run at minimum load at low suction pressure if plant off-loads instead of stopping. I'd normally issue a stop command after 5 minutes of off-load running. There are no recips to take up varying load however. As they are driven by 200kW motors, stop \ starts are not a desirable action.


Hi Steve,

The position indicator on a screw doesn't give an accurate indication of % capacity being supplied and the actual capacity depends on the suction pressure. At low back pressure the machine can offload to 0% actual load which means that gas can blow from discharge to suction taking oil with it. If the NRV doesn't shut tight then the oil will end up in the suction side. I used to have a graph from Howden showing actual minimum capacity vs suction pressure, but I don't know where it is now.

If you've got more than one compressor how about trying this one as lead so it doesn't offload as much?

Alternatively move the minimum cam switch so that "minimum" is at about 30% indicated - this should be a lot less than 30% of full load for the reasons given above, and will prevent the possible back flow. Hopefully this will reduce the oil loss, and will suggest a closer look at the NRV

I hope this help

cheer
Andy P

US Iceman
08-10-2006, 12:50 AM
Howden WRV 255 is chucking out its oil into the system - 5 litres a day.


Is this something that just started recently, or become increasingly worse as time passes?

Also, with the oil loss you mentioned... does the oil level in the separator tend to reestablish itself after some period of running time, or just continue to decrease if left unattended?

One last question. Has the mist eliminator pad been replaced recently, say before the carryover problem was noticed?

Josip
08-10-2006, 01:30 PM
Hi, SteveDixey :)


It was supplied with the machine, but will need to hack off a few layers of paint to tell you exactly. The main body of the separator is around 1.8 metres high by 450mm diameter.

The small line connects the base of the larger diameter of the separator, (before it reduces down to the connection flange on the oil receiver), to the underside of the suction pipe on the machine.

20 years old


It is a low side machine, 0.75 bar(a) suction, (freezer @ -40c) and around 27c 11 bar delivery.

Yes, the gas makes two passes, up through one mesh pad, through a drilled plate, then diverted down through another mesh screen and into the oil receiver.

Some off-loads and stops, but not frequent. More to do with production changes than plant off-loads through varying product loads.

As far as I can see there is nothing that has fell off. The unit was removed and internal inspections were made. NRV's possibly. Another machine had the guts taken out of its NRV so can't rule it out.

Machine will run at minimum load at low suction pressure if plant off-loads instead of stopping. I'd normally issue a stop command after 5 minutes of off-load running. There are no recips to take up varying load however. As they are driven by 200kW motors, stop \ starts are not a desirable action.

Steve

One more question;)

Oil cooling is indirect or direct with refrigerant?

Best regards, Josip :)

SteveDixey
08-10-2006, 02:43 PM
Is this something that just started recently, or become increasingly worse as time passes?

Fairly recent event, with no previous history as far as we know. However, the previous plant operator tended to keep secrets and not tell anyone things. That is now starting to tell....


Also, with the oil loss you mentioned... does the oil level in the separator tend to reestablish itself after some period of running time, or just continue to decrease if left unattended?

Just empties and empties. It does not re-appear, or at least not soon enough to stop oil level trips.


One last question. Has the mist eliminator pad been replaced recently, say before the carryover problem was noticed?

As far as I know, no pads have been touched. The guys who inspected the separator internals did not disturb anything as they were not sure if the mesh was removable or not. I might be able to get some photos they took of the internals though.

Steve

SteveDixey
08-10-2006, 02:50 PM
Hi Steve,

The position indicator on a screw doesn't give an accurate indication of % capacity being supplied and the actual capacity depends on the suction pressure.

Alternatively move the minimum cam switch so that "minimum" is at about 30% indicated - this should be a lot less than 30% of full load for the reasons given above, and will prevent the possible back flow. Hopefully this will reduce the oil loss, and will suggest a closer look at the NRV

I hope this help

cheer
Andy P

The loading system was my next target given it is easy to get at and check. There have been a few problems with the Danfoss controllers on this plant and from other posts on this forum I understand that in the past they have not been the most robust industrial grade controllers.

I now know that another NRV on the plant is known to be passing back, but on the high-side, so it maybe indicates that the NRV's are getting past their best.

Steve

SteveDixey
08-10-2006, 02:54 PM
Hi, SteveDixey :)



One more question;)

Oil cooling is indirect or direct with refrigerant?

Best regards, Josip :)

Thermosyphon fed from a HP receiver on the plant room roof, on a shell and tube heat exchanger. No refrigerant injection into the rotors or discharge pipe.

Steve

US Iceman
08-10-2006, 06:05 PM
Hi Steve,

Thanks for the replies.

My reason for asking about the mesh pad being recently replaced was based on an observation I made years ago.

If you look closely at the wire mesh you will see that it is basically a corrugated pattern laid down down in layers. Flow through the pad with the mesh being aligned in a perpendicular flow path provides many impingement locations.

In the case I observed the correct pad was used, but the mesh was installed such that the corrugations in the pad were parallel to the flow. Installed in the wrong manner the mesh pads becomes very ineffective.



Is this something that just started recently, or become increasingly worse as time passes?




Fairly recent event, with no previous history as far as we know.


That tends to point to one of several possibilities. This oil loss problem has either become recently public, something in the operation of the system has recently changed, or a component is experiencing periodic or potenital failure.

If the engine room log book was kept current that might shed some light on the time frame of the oil carryover. It might not also, since you said the former operator tended to be secretive.

Since the compressor is operating in a single stage manner, have you noticed any recent fluctuations in the discharge pressure? Say, either the discharge pressure control or during onset of a hot gas defrost cycle?

Large reductions in discharge pressure can cause the oil separator velocity to dramatically increase and result in oil carryover.

Conversely, if the suction pressure is also seen to fluctuate through large pressure swings, the increase in suction pressure results in higher mass flow through the oil separator. This can also overload the separator and cause oil carryover.

Last question... Did this problem start to be noticable when the weather started to change?

Andy
08-10-2006, 09:37 PM
Hi Steve:)

You mentioned an oil return to suction, this to me would normally be the coalecent filter oil return.
Are the coalecent filters blocking up or is the oil return line partially blocked.

Also is there a possibility of liquid being carried into the compressor, that would explain a sudden increase in oil usage.

Kind Regards Andy:)

SteveDixey
08-10-2006, 11:00 PM
That tends to point to one of several possibilities. This oil loss problem has either become recently public, something in the operation of the system has recently changed, or a component is experiencing periodic or potenital failure.

Since the compressor is operating in a single stage manner, have you noticed any recent fluctuations in the discharge pressure? Say, either the discharge pressure control or during onset of a hot gas defrost cycle?


Last question... Did this problem start to be noticable when the weather started to change?

There is no hot gas defrost cycle on the freezers. The operators have not noticed any pressure readings that are irregular. The load seems to be quite constant when they put the freezers on and there have been no changes to operating procedures on the freezer side.

The weather hasn't changed here. We are still running around in shorts and t-shirts :)

Steve

SteveDixey
08-10-2006, 11:09 PM
Hi Steve:)

You mentioned an oil return to suction, this to me would normally be the coalecent filter oil return.
Are the coalecent filters blocking up or is the oil return line partially blocked.

The oil return line appears to be clear. The line is hot if you open up the valve, enough to melt a 50mm circle into the ice on the suction stop valve. That seems to point to gas whistling thorough quite nicely. I am talking them around to putting a sight glass into the oil return line to check what is going on. Might be a good investment seeing as £19k is the going price for fitting a new separator:eek:


Also is there a possibility of liquid being carried into the compressor, that would explain a sudden increase in oil usage.

No reports of that to be honest. Superheats seem OK but the gauges need replacing to be sure of that. Oil has not been frothy, just a good colour and steady in the sight glasses

Kind Regards Andy:)[/QUOTE]

US Iceman
08-10-2006, 11:37 PM
Since the system operation is stable, then I believe we are looking at some fault in the components.



The line is hot if you open up the valve, enough to melt a 50mm circle into the ice on the suction stop valve. That seems to point to gas whistling thorough quite nicely.


Typcially, I would expect this line to be about the same temperature as the oil injection temperature. If the valve is open all of the way, then a lot of hot gas would be flowing through this line.

If this valve was opened all of the way up because somone thought the excessive oil carryover (to the system) could be minimized, then it sounds like this points to a possible coalescing filter problem as Andy suggested. Possible gaskets or O-rings leaking or the element itself.

Has this compressor experienced any liquid slugging recently? Perhaps before this problem was noticed?

Of course it could also be the NRV's too, if the compressor starts and stops on a somewhat regular basis. Is there a valve installed that bypasses the suction NRV to allow the package to equalize with suction pressure?

SteveDixey
09-10-2006, 06:57 PM
Possible gaskets or O-rings leaking or the element itself.

Has this compressor experienced any liquid slugging recently? Perhaps before this problem was noticed?

Of course it could also be the NRV's too, if the compressor starts and stops on a somewhat regular basis. Is there a valve installed that bypasses the suction NRV to allow the package to equalize with suction pressure?

The separator appears to be a sealed unit. The mesh is built into the large diameter shell, and the end caps and flanges welded on.

No by-pass NRV. Liquid slugging, possibly but isolated instances. Nothing has occured during the time I have spent in the engine room and it is pretty much continuously manned as control is quite basic (radio controlled human).

I am looking at double checking the levels. There has been no records kept of refrigerant added and it is entirely possible that in response to another "problem" someone has added a tank or two.

Steve

aawood1
09-10-2006, 08:18 PM
Hi Steve, I have one question you say that it is a low side machine and that the suction is -.75bar. and the delivery is 11bar. what are the high side machines working at ?. On the WRV255 howdens that we use on our low side of the plants run at -.5 bar on the suction and have a delivery of 2.5 to 3 bar. but when the oil separator filter was blocked the delivery pressure whent up and the oil level whent down. I will say that the howdens had been fitted inplace of Grasso MS 1034 units but we used the Grasso two stage oil separator with a filter in the 2nd unit that could be replaced. The high side of our plant runs at a suction of 2.5 bar and a delivery of 11 bar to 13.5 bar. The only thing that we had was the oil was sucked back into the compressor heads when they stoped. ( did say this in a old thread with Andy.)
Arthur

Andy
09-10-2006, 09:15 PM
Hi Steve:)

with a return line to the suction, this has to be the secondary oil return. A sight glass is near an essential on this line (grasso do one for 8mm pipe that is used on their screws).
I would fit the SG and throttle back the oil return. If the primary separation is the problem you should have oil flowing through the oil secodary return line matter how far the throttle valve is open.
If the problem is o-rings ect on the secondary separtion elements there will be little or no oil return matter what the valve opening degree is.

I suppose a temperature logger on the discharge line would be an easy way of picking up low suction superheat, the only other way that this type of excessive oil useage would happen.


There must be coalecent elements fitted on this plant, if it's a Howden built (Holima) there is a plate 1" thick round plate on the top of the seporator, the discharge line comes off the top and the round plate is at a tangent to this.

Hope this helps:)

Kind Regards Andy:)

SteveDixey
09-10-2006, 09:44 PM
Hi Steve, I have one question you say that it is a low side machine and that the suction is -.75bar. and the delivery is 11bar. what are the high side machines working at ?Arthur

The low side is -0.25 barg (0.75 absolute) and intermediate runs 2 to 2.5 bar (runs chillers evaporating at -6c) and high sides run to those pressures you described.

I've asked for some more detailed monitoring to be done by the plant ops, and to get a few dodgy gauges changed so they can make some meaningful plant readings.

Steve

SteveDixey
09-10-2006, 09:59 PM
Hi Steve:)

with a return line to the suction, this has to be the secondary oil return. A sight glass is near an essential on this line (grasso do one for 8mm pipe that is used on their screws).

Sabroe do it as well.


I would fit the SG and throttle back the oil return. If the primary separation is the problem you should have oil flowing through the oil secodary return line matter how far the throttle valve is open.

I've asked them to consider it..



I suppose a temperature logger on the discharge line would be an easy way of picking up low suction superheat, the only other way that this type of excessive oil useage would happen.

You can buy a 4 channel datalogger for £125 now, again suggested to the powers that be



There must be coalecent elements fitted on this plant, if it's a Howden built (Holima) there is a plate 1" thick round plate on the top of the seporator, the discharge line comes off the top and the round plate is at a tangent to this.

I'll see if i can post up the photos they took so we know we are all talking about the same lumps of metal. The fact that a new separator was supposedly deemed neccessary by one supplier makes me wonder if it is really a sealed non-serviceable item like the oil seps on Sabroe recips. When the mesh went, you had to buy a new separator. Other Howdens on the plant have different separators. Maybe need to do bit more digging on that score.

Steve

US Iceman
09-10-2006, 11:08 PM
Based on what I have read so far, this is beginning to sound like the coalescing elements have partially lost their separation capacity.

As Andy said, if there is a return line there has to be an element in the separator. If there were no coalescers you would not need the return line.

One thing I have seen where the oil carryover rate is high is when the compressors have been flooded out at one time or another (or several times). The flooding washes all sorts of junk out of the system and into the oil filters and coalescing elements.

I've seen some cases where solids cut holes in the elements and once this happens the oil carryover rate really goes up.

To be sure, you really need the separator drawings to see the vessel internals. Hopefully, it's not one of those separators that has coalescing elements that are permanent.

SteveDixey
09-10-2006, 11:21 PM
Hopefully, it's not one of those separators that has coalescing elements that are permanent.

That is what we think we have.... hence a price of £19000 for a new separator being quoted.

I've asked for more details taken off nameplates, etc to be sent over. As these are quite old machines, I am beginning to doubt if they had the benefit of newer coalescing type filters such as fitted to the SAB Sabroe screws.

Anyway, should see before the weekend.

Steve

TXiceman
10-10-2006, 03:19 AM
Are the mesh pads replacable and are they the coalescing type? Generally oil loss/carry over prblems with a screw are attributed to the following.

Liquid carry over to the suction
bad oil separator pads
Bypassing pads (o-rings in a coalescing type)
Incorrect or incompatible oil type.
Mixed oils
blocked oil return line.
Low head pressure, especially a sudden reduciton in head pressure. Often a bad or inmproperly adjusted pressure control switch.

A few starting points.

I have fitted a secondary oil separator (coalescing type) when we have a poor performing primary separator. Saves all of the rework cost to replace a primary separator.

Ken

US Iceman
10-10-2006, 03:31 AM
Steve,

To expand on my comments about flooding...

Has there been any noticable increase in oil filter replacements? This is usually the first thing that happens after a screw floods out. All of the junk plugs up the filters.

Unfortunately, all of this junk goes through the compressor and oil separator before it gets into the oil filter elements.

Depending on the discharge pipe location and orientation to the mesh pad, the gas velocity coming out of the discharge pipe can be quite high.

Absolutely anything in this gas stream is a high velocity projectile.

It does not take much for these pads to really start bypassing from what I've seen.

Josip
10-10-2006, 02:53 PM
Hi,

Once we had a problem regarding STAL screw with vertical oil separator (TAS).

It was a big discusion because oil loosing started after replacing the unit from one engine room to another and before everything was OK :eek: .

Finally found the reason: TAS was not in vertical position (fast installation over weekend:rolleyes: ), it was inclined in opposite side from where is connection for oil return into suction of compressor. Hope that is not a case here;)

Another problem with the same type of oil separator was the horizontal plate with coalescent filter elements was not welded all the way around to shell. Small leak but a lot of oil pushed into dicharge line.

Best regards, Josip :)

US Iceman
10-10-2006, 05:03 PM
Hi Josip,

Your comments were a helpful reminder...:)



Another problem with the same type of oil separator was the horizontal plate with coalescent filter elements was not welded all the way around to shell. Small leak but a lot of oil pushed into dicharge line.


I saw one of those recently on some old Sullair booster compressors. The weld had cracked in several areas around the perimeter of the element support plate.

Andy P
11-10-2006, 12:29 AM
Dear Steve,

I'm still keen to know whether you have coalescer elements or not - if so then it is quite possible that they have fouled up, but if not then I doubt that the knitmesh has just stopped working (although it is possible). We also had a cracked weld on a support plate, but it happened when the unit was only a few months old. You could tell where the crack was with an infra-red thermometer on the outside of the separator shell - it was hotter where the gas was passing through the cracks

I still think your NRV is suspect. Depending on the L/D ratio of the compressor you can put a longer slide valve stop ring into the capacity cylinder to prevent it offloading so much - for example put the ring for a 1.93 into the 1.65 and so on.

cheers
Andy P

Josip
11-10-2006, 10:32 AM
Hi, all :)


Dear Steve,

I'm still keen to know whether you have coalescer elements or not - if so then it is quite possible that they have fouled up, but if not then I doubt that the knitmesh has just stopped working (although it is possible). We also had a cracked weld on a support plate, but it happened when the unit was only a few months old. You could tell where the crack was with an infra-red thermometer on the outside of the separator shell - it was hotter where the gas was passing through the cracks


cheers
Andy P

I forget to mention this in my post but, yes, it is possible to have a problem with coalescent inserts but it is not possible to determine which one is broken-simply replace them all together with O-rings/gaskets (can be broken too;) ) This problem with gasket I had in Saudi Arabia, loosing of oil about 30-40 lit/week close to 5lit/day;)

Best regards, Josip :)

refteach
11-10-2006, 02:59 PM
I agree with Josip it is very hard to visually see if a coalesing element is bad unless it actually blows out and you have the glass fibers to contend with. The coalesing elements act as big filters on systems and have a tendency to collect dirt on the fibers, once they start to get dirty they lose surface area and the velocity through the remaining element increases. If the velocity increase too much the oil can be stripped off the fibers by the higher than normal gas velocity. Eventually you can plug it up to the point of blowing out the glass fibers. Sometimes you may be able to check if an element is dirty by taking a drop light and putting it in the element and looking for dark and light spots.

I have seen similar issue on demister pad type separators but these were used on recip compressors that had problems with carbonized oil and sludge partially plugging them causing them to lose efficiency.

SteveDixey
11-10-2006, 05:07 PM
Dear Steve,

I'm still keen to know whether you have coalescer elements or not

So am I....

The guys who did the internal inspection of the vertical separator are on rota days off at the moment. I have requested they forward the pics they took as soon as they get back so I can recheck things in the light of points made here.

Steve

Gerben
12-10-2006, 10:07 AM
Hi Steve,

I'm working on Howden units for a long time now, and used to work at SES, the Howden package constructor in Delden , the Netherlands.

Could you send me a list with temps and pressures?
A picture would also help, maybe I can see more about manufacturer and type.
When did you change oil last time, and did the problem occur since then, or before.

Regards,

Gerben Beltman
gerben@rm-support.nl

SteveDixey
12-10-2006, 06:23 PM
When did you change oil last time,


The oil is currently being "changed" every three weeks so to speak, as in it consumes the volume of the oil receiver within that period.

The problem has not co-incided with an oil change however.

They have promised to send me over the data, but as they write it manually into a logbook, rather than onto photocopied sheets, someone will have to copy out the book page by page manually on a photcopier.....

However, many pressure gauges have probably never been checked changes since the machines were built, and a number of thermometers do not work, including the discharge temp on this one. So the data may be either incomplete of inaccurate.

Like many who run factories and the like, if something breaks but doesn't stop the compressor working, it tends to get ignored:mad:

Steve

TXiceman
13-10-2006, 01:20 AM
A lot of things to be checked as far as I can tell. Steve you need to get some hard data back to everyone here. I did not see that you ever addressed the issue of low or suddenly dropping discharge pressure. Low discharge pressure increases the volume flow and if it is beyond the CFM limits on the separator, the elements can be overloaded and you will get carry over. You can also permanately damage an element with excessive flow.

recently we had a unit that had several years of operation start loosing oil badly. we had to open the separator to check the condition, expecting to find aa blown element. One of the coalescing elements clamping rods had sheared and waas not holding the element in postion to seal. After clearing the separator, we reattached the rod and installed all new elements. Problem was corrected. First unit we have had to have this problem.

Ken

SteveDixey
13-10-2006, 04:44 PM
The vertical oil sep vessel is manufactured by Stanref according to the plant register.

Steve

Tycho
13-10-2006, 06:18 PM
does the oilseperator have two heating elements?
The HP line goes under the compressor, under the motor and enters the oilsep. low to the ground, HP outlet from the oilsep is high up. There is a level sightglas on the separator on the left side inside the frame if seen from the compressor side.

unit looks somewhat like this: (oilsep on the other side from what it shows in the drawing)

http://www.pbase.com/kimmo98/image/68493639.jpg

TXiceman
14-10-2006, 02:26 AM
How old is this system? I don't know the last time I saw one with the "muffler" on the diacharge in the separator. As far as I could tell, the "muffler" which was supposed to start the oil coalescing, just made a tremendous atomizer.

This type separator tends to be very sensitive to oil type and foaming. Are the sight ports clear or reflex type. If clear, how much foaming action do you see in the glass...just a little on top of the oil or is it foamy well below the surface.

Since this appears to be a sealed design, the best solutionis the addition of a secondary oil separator down stream of the first and make a replacable core coalescing type. I have used this approach on several jobs with oil pumpers. Elevated the secondary on and return oil to the screw side port with a simple float drainer.

Ken

Tycho
14-10-2006, 05:13 AM
How old is this system? I don't know the last time I saw one with the "muffler" on the diacharge in the separator. As far as I could tell, the "muffler" which was supposed to start the oil coalescing, just made a tremendous atomizer.

This type separator tends to be very sensitive to oil type and foaming. Are the sight ports clear or reflex type. If clear, how much foaming action do you see in the glass...just a little on top of the oil or is it foamy well below the surface.

Since this appears to be a sealed design, the best solutionis the addition of a secondary oil separator down stream of the first and make a replacable core coalescing type. I have used this approach on several jobs with oil pumpers. Elevated the secondary on and return oil to the screw side port with a simple float drainer.

Ken

He said "atleast 20 years old" thats why I brought up this, at least 30 years old design, there is no coalescent section on this type of seperator tho...

SteveDixey
23-10-2006, 09:04 PM
Tycho is right, no coalescent type filter and......ta raaa.. we look to have a cracked weld around the baffle plate by the looks of it so looks like a new separator vessel.

Somehow, they are going to have to convince the owners to cough up a fair chunk of cash that hinges on this phrase "looks like..."

Now, if we x-ray it, would it show up behind the other bits and bobs welded in there? I'd assume we would need a detailed drawing to help the NDT guy postion his kit for best effect?

Steve

Andy
23-10-2006, 09:53 PM
Now, if we x-ray it, would it show up behind the other bits and bobs welded in there? I'd assume we would need a detailed drawing to help the NDT guy postion his kit for best effect?

Steve

Hi Steve:)
your making progress:) what about AndyP suggestion, use thermal imaging to show up the crack.

Kind Regards Andy:)

SteveDixey
23-10-2006, 09:58 PM
I'll have to make some enquiries about what services are available in the area. Plenty of NDT available as the Humber refineries are just up the road but thermal imaging might be a cheaper option to start with.

Steve

US Iceman
24-10-2006, 01:05 AM
we look to have a cracked weld around the baffle plate...


If there are no coalescing elements, where is the baffle plate? If the separator is anywhere close to the picture Tycho posted, the demister pad is probably mounted on clips inside the separator.

The separators I have seen similar to this don't have baffle plates.

If it's just the demister pad, it might be cheaper to remove the separator head and reinstall a new demister pad and weld the head back on. If there is a refinery close by, they might be able to recommend a good pressure vessel repair shop for this.

SteveDixey
24-10-2006, 10:21 PM
Finally, a picture of the layout of the separator \ receiver. The white pipe coming off the bottom left of the separator vessel goes to the underside of the suction pipe at the handwheel valve on the top left of the picture.

Steve

Andy P
25-10-2006, 08:08 PM
Now, if we x-ray it, would it show up behind the other bits and bobs welded in there? I'd assume we would need a detailed drawing to help the NDT guy postion his kit for best effect?

Steve
Hi Steve,

I suspect that radiography won't do it for you - you are asking the NDT man to shoot through a disk of about 400mm diameter edge on and make sense of something on the far side....(they all look like a foggy day in December to me anyway!)

I still think a shot of the sep in operation with a thermal camera should be enough to condemn it.

Have you asked Stanref to quote for a replacement?

cheers

Andy P

SteveDixey
25-10-2006, 09:06 PM
Have you asked Stanref to quote for a replacement?
Andy P

There has been a quote for £19k fitted, hence the exploration of other possibilities before shelling out the cash. Anyway, that is a decision for the plant owners to bite that bullet. I am not doing anymore at the moment beyond laying info at their feet.

Steve

Mike W
27-10-2006, 03:05 AM
Steve,
We had a similar problem with a screw compressor set. The cause was the discharge non return valve was leaking ( not excessily)when the compressor was off and allow high pressure gas back into the oil seperator which would them condense into a liquid or excessive ammonia to be absorded into the oil. On startup this caused to oil to foam excessively, then oil would be thrown out of the seperator. I hope this is of some help.

Regards Mike W

US Iceman
16-11-2006, 08:56 PM
Steve,

Have there been any developments on this oil separator issue recently? I'm curious about what was found.

Thanks,
US Iceman

SteveDixey
16-11-2006, 09:04 PM
Steve,

Have there been any developments on this oil separator issue recently? I'm curious about what was found.

Thanks,
US Iceman

No developments. The engineers are snowed under with other work. They are struggling to keep their legal obligations up to date at the minute, money is tight and, I suspect, unless the plant stops, there will be no real urgency.

I have left them to it and won't do anymore until they ask and then only when they replace various gauges and temp probes so I can make an informed decision on what the plant is doing.

I am as curious as you....

Steve

Magoo
01-03-2008, 01:01 AM
Check oil injection rate, as overinjecting will agrivate carryover. Check discharge temp, should be around 75'C . Differential oil pressure on Howden is nominal 35 psig or 2.5 Bar.

magoo

SESHowdenHolima
14-06-2009, 10:40 AM
No developments. The engineers are snowed under with other work. They are struggling to keep their legal obligations up to date at the minute, money is tight and, I suspect, unless the plant stops, there will be no real urgency.

I have left them to it and won't do anymore until they ask and then only when they replace various gauges and temp probes so I can make an informed decision on what the plant is doing.

I am as curious as you....

Steve

Dear Steve,
Just browsed past this thread and I was wondering if you have found the cause and sollution to the problem?
Regards Bas.

Tycho
04-06-2010, 05:53 PM
Dear Steve,
Just browsed past this thread and I was wondering if you have found the cause and sollution to the problem?
Regards Bas.

I would also like to know

bigsk
27-07-2010, 03:41 AM
Hi, gerben, could you send me some howden manuals, thanx, my emailbox: bigsk.smth@gmail.com


Hi Steve,

I'm working on Howden units for a long time now, and used to work at SES, the Howden package constructor in Delden , the Netherlands.

Could you send me a list with temps and pressures?
A picture would also help, maybe I can see more about manufacturer and type.
When did you change oil last time, and did the problem occur since then, or before.

Regards,

Gerben Beltman
gerben@rm-support.nl