Danfoss solenoid valves not opening fully.

[RANGER1]

Have a weird one with Danfoss solenoid valves in Nh3 plant.

EVRA 25 & EVRAT20 on liquid makeup to vessels not opening properly.

High pressure liquid from liquid receiver 1000 to 1250 kpa.
Liquid makeup to 2 seperate accumulators 1 at 120 kpa & 1 at 180 kpa.
Solenoid & hand reg valve.
Liquid trickles through as valve does not open fully.
Frost between solenoid valve & upstream of reg valve.
Close stop valve upstream, then open, all good, frost disappears between solenoid & reg valve, can hear good refrigerant flow until solenoid closes, then has to open again.
EVRA25 & EVRAT20 new valves.
Solenoid coils 11 Watt 240 Volt.

Any ideas anyone?
Thanks

[Glenn Moore]

1) Is there a filter before the solenoid valve
2) what is the code no of the solenoid coils fitted
3) have the valves been stripped and checked for system debris
4) what are the valve capacity’s at design

[Brian_UK]

Is this a fault on a new system or a new fault on an old system?

[Tycho]

Oh this is like a blue print of a problem I had some years back...
I never could figure it out.
the price goes to the ships engineer.

I'm going to tell you the entire story of how I struggled, to make you appreciate how easy the solution is

I supervised and built a NH3 freezing plant on a Crab fishing vessel, plant had:
Pump circulated:
1 tunnel
3 plate freezers

Supplied by HP liquid:
1 RSW chiller working at -5C
1 Brine chiller working at -18C

The brine and RSW chiller are fed from the bottom of the pilot receiver, to ensure they have a feed of HP liquid.

During commissioning, I noticed that as long as the RSW chiller was working alone, everything was fine.
When I started the Brine chiller, which was fed from the same liquid line, both the RSW and Brine chiller would loose liquid supply.

Both chillers were supplied from the pilot receiver, the pilot receiver had liquid level, so the level in the pilot is not the issue.

Both chillers were supplied through a danfoss PMFL valve combined with a float valve, so if the liquid level dropped, the valve would open and allow more liquid in right? easy peasy!

Once I had the system up and running, I noticed that the RSW chiller was working, but the brine chiller seemed to be constantly starved of liquid.

I did a test, so I shut of the liquid valve feeding the brine chiller, and the RSW chiller was working just fine.
Then I had a stethoscope mounted on the brine chiller liquid line while I opened the liquid line, and I heard a *ssssssh thud*

and to me, it sounded like the spring in the PMFL valve was too strong and couldn't handle the pressure difference.

so I ordered a new weaker spring sent from china and got it to work somewhat, it was still kind of on and off.

And then after the ship had been at sea for 3 weeks I got an e-mail from the onboard engineer, that he had "forced open" the quick closing valve, and now the RSW and Brine worked perfectly.

The quick closing valve was a danfoss EVRA 25...

The danfoss EVRA 25 handles pressure difference very well..

What it does not handle is flow...

An EVRA valve works very well on smaller applications, but on larger applications, especially on the liquid line, because of the increased flow, it struggles.
High pressure difference, higher mass flow, we can now introduce the Coanda effect.

What is the coanda effect?
the coanda effect is the the "tendency of a liquid to stay attached to a convex surface" and this happens inside a solenoid valve that has a bellow, and if the flow of liquid through the valve is faster/higher than the valve is designed for, it will close.

-----------------------------

So Ranger1, what you are looking at here is an undermentioned valve or some desk rider choosing valve size from pipe size and not function

[RANGER1]

1) Is there a filter before the solenoid valve
2) what is the code no of the solenoid coils fitted
3) have the valves been stripped and checked for system debris
4) what are the valve capacity’s at design

Glenn, not a plant we work on, just trying to help solve what seems a basic problem, but not working out.
For whatever reason appears flash gas in pilot area not allowing valve to open.
Valves I would say are to big under current load, but at same time they only need to open to maintain a liquid level.
Suggested he gets power from power point & see if it opens valves, but have not heard back.

1/ Yes but client removed for whatever reason
2/ would have to wait to get it
3/yes have been stripped & checked
4/ don’t know , plant has been altered & very lightly loaded.

Plant net is not new, has worked before, but probably under much different than design.

[RANGER1]

Brian,
Old system that has been altered a bit, equipment moved a few metres for upgrades.
Plant just holding room temperatures ready for production.
Not a plant we work on, just trying to help a bit ( now getting to hard).

[RANGER1]

Oh this is like a blue print of a problem I had some years back...
I never could figure it out.
the price goes to the ships engineer.

I'm going to tell you the entire story of how I struggled, to make you appreciate how easy the solution is

I supervised and built a NH3 freezing plant on a Crab fishing vessel, plant had:
Pump circulated:
1 tunnel
3 plate freezers

Supplied by HP liquid:
1 RSW chiller working at -5C
1 Brine chiller working at -18C

The brine and RSW chiller are fed from the bottom of the pilot receiver, to ensure they have a feed of HP liquid.

During commissioning, I noticed that as long as the RSW chiller was working alone, everything was fine.
When I started the Brine chiller, which was fed from the same liquid line, both the RSW and Brine chiller would loose liquid supply.

Both chillers were supplied from the pilot receiver, the pilot receiver had liquid level, so the level in the pilot is not the issue.

Both chillers were supplied through a danfoss PMFL valve combined with a float valve, so if the liquid level dropped, the valve would open and allow more liquid in right? easy peasy!

Once I had the system up and running, I noticed that the RSW chiller was working, but the brine chiller seemed to be constantly starved of liquid.

I did a test, so I shut of the liquid valve feeding the brine chiller, and the RSW chiller was working just fine.
Then I had a stethoscope mounted on the brine chiller liquid line while I opened the liquid line, and I heard a *ssssssh thud*

and to me, it sounded like the spring in the PMFL valve was too strong and couldn't handle the pressure difference.

so I ordered a new weaker spring sent from china and got it to work somewhat, it was still kind of on and off.

And then after the ship had been at sea for 3 weeks I got an e-mail from the onboard engineer, that he had "forced open" the quick closing valve, and now the RSW and Brine worked perfectly.

The quick closing valve was a danfoss EVRA 25...

The danfoss EVRA 25 handles pressure difference very well..

What it does not handle is flow...

An EVRA valve works very well on smaller applications, but on larger applications, especially on the liquid line, because of the increased flow, it struggles.
High pressure difference, higher mass flow, we can now introduce the Coanda effect.

What is the coanda effect?
the coanda effect is the the "tendency of a liquid to stay attached to a convex surface" and this happens inside a solenoid valve that has a bellow, and if the flow of liquid through the valve is faster/higher than the valve is designed for, it will close.

-----------------------------

So Ranger1, what you are looking at here is an undermentioned valve or some desk rider choosing valve size from pipe size and not function

Tycho,
If we closed regulating valve downstream, would that not help situation?
Valve probably to big at the moment.
You mention quick closing valve EVRA25, what do you refer to?

[Glenn Moore]

Let’s start with the EVRA 25 valve
The EVRA 25 valve needs approx 2 psi / 0.15 Bar Pressure drop across it to be fully open , a lower mopd would cause the valve to only partially open.
When the old EVJDA 25 was upgraded to the EVRA25 it caused many problems due to it failing to open. I spent many days running round to NH3 sites due to the valves poor performance. There were several issues with the valve , partly due to the pilot flow , but mainly due to the piston. The early piston was an extruded type which had labrynth seals (grooves) around the piston to act as a seal. These pistons often were out of round causeing leakage past the piston causing the servo function to mal function. After a few months the steel piston was changed to a cast iron piston with a piston ring plus mods to the pilot system. This solved the problem completely. The only issues after this modification was caused by system debris causing the piston ring to jam in the piston groove , simply cleaning the valve and freeing the piston in the groove gets it working again.
But if the valve is oversized for the duty required it will struggle to go fully open .The EVRA 25 can do approx 1100 kw liquid line capacity on NH3. The coil for this valve is the standard 10 watt 068F6702 coil for 240 volt 50 Hz.
The EVRAT 20 valve as you know is an assisted lift valve with a diaphragm. This valve doesn’t need a pressure drop to keep it open as the assisted lift spring connector does this via the armature. But the EVRAT valves need a bigger coil to open the valve due the the weight of the spring a diaphragm connected to the armature. This valve should have a minimum 12 watt coil fitted to give the coil extra pulling power. The coil code no is 068F6802 for 240 volt 50hz. Often using a weaker coil with these valves causes problems. Always check the diaphragm material ,this should be flat , if the diaphragm has ripples in the diaphragm it must be changed as instead of it simply deflecting open and closed it tends to click open to close which can take a few seconds due to the diaphragm having to overcome the stretched diaphragm material.
In this instance If necessary change the EVRA25 to a EVRAT 20 as it will fit into the same flanges and with its reduced capacity should open without problems

Regards to Tycho,s problem with the PMFL level control system , these level systems were always a pain to set up whether it was an PMFL or PMFH. The main valve was fine but the SV float had to be set correctly via its small throttle valve and then tuned with the feedback springs in the main valve.
The HP system was the biggest problem due to the SV float fitted upside down in the HPmode. This caused the pilot signal to be erratic as it could be either flash gas, saturated or sub cooled liquid in the pilot line. I built “special SV float assemblies” for the HP flooded systems fitted in a well known departmental store in London as the standard SV1 parts just could not control the level. I later found out that the factory made identical SV assemblies to my design and called them the British version which became a Danfoss spare part for the SV1
The LP float system with the PMFL+SV1works quite well but it needs tuning with the pilot flow throttle needle approx 1 turn open , and the feedback springs on the PMFL adjusted to give a proportional flow . Sometimes fitting the SV3 nozzle into the SV1 float as it reduces the PMFL p band .
An even better solution is to use the SV4 float which is the old GRAM float as it has a better float movement and operating P band with the PMFL valve than the SV1 or 3 due to limited float movement

[RANGER1]

Thanks Glenn for very detailed response.
Will check what you suggest & see if improves.

[Tycho]

Tycho,
If we closed regulating valve downstream, would that not help situation?
Valve probably to big at the moment.
You mention quick closing valve EVRA25, what do you refer to?

I did get it to work when I throttled the downstream valve, but it was a SVA, not a reg, so it was a right pain to set it just right. but with the SVA valve throttled there wasn't enough liquid to feed the two chillers.

The valve was used as the "emergency quick closing valve" on the HP liquid supply line to two chillers.
it was an danfoss EVRA 20, just checked the drawings, the line was DN25.

Brand new system, we ended up switching the valve for a PM1-25.

The chief engineer had a stethoscope that could be attached to the pipe, so while opening the SVA valve I could hear the flow of liquid and then a *thunk* as the EVRA pulled shut. I thought the sound was from the PMFL closing, but it was the EVRA.

Only Other time I've seen this happening was with a BML valve on a R-22 system some 20 years ago.
Same thing would happen, start opening the valve and then *thunk* it would pull closed.

[Tycho]

Let’s start with the EVRA 25 valve
The EVRA 25 valve needs approx 2 psi / 0.15 Bar Pressure drop across it to be fully open , a lower mopd would cause the valve to only partially open.
When the old EVJDA 25 was upgraded to the EVRA25 it caused many problems due to it failing to open. I spent many days running round to NH3 sites due to the valves poor performance. There were several issues with the valve , partly due to the pilot flow , but mainly due to the piston. The early piston was an extruded type which had labrynth seals (grooves) around the piston to act as a seal. These pistons often were out of round causeing leakage past the piston causing the servo function to mal function. After a few months the steel piston was changed to a cast iron piston with a piston ring plus mods to the pilot system. This solved the problem completely. The only issues after this modification was caused by system debris causing the piston ring to jam in the piston groove , simply cleaning the valve and freeing the piston in the groove gets it working again.
But if the valve is oversized for the duty required it will struggle to go fully open .The EVRA 25 can do approx 1100 kw liquid line capacity on NH3. The coil for this valve is the standard 10 watt 068F6702 coil for 240 volt 50 Hz.
The EVRAT 20 valve as you know is an assisted lift valve with a diaphragm. This valve doesn’t need a pressure drop to keep it open as the assisted lift spring connector does this via the armature. But the EVRAT valves need a bigger coil to open the valve due the the weight of the spring a diaphragm connected to the armature. This valve should have a minimum 12 watt coil fitted to give the coil extra pulling power. The coil code no is 068F6802 for 240 volt 50hz. Often using a weaker coil with these valves causes problems. Always check the diaphragm material ,this should be flat , if the diaphragm has ripples in the diaphragm it must be changed as instead of it simply deflecting open and closed it tends to click open to close which can take a few seconds due to the diaphragm having to overcome the stretched diaphragm material.
In this instance If necessary change the EVRA25 to a EVRAT 20 as it will fit into the same flanges and with its reduced capacity should open without problems

Regards to Tycho,s problem with the PMFL level control system , these level systems were always a pain to set up whether it was an PMFL or PMFH. The main valve was fine but the SV float had to be set correctly via its small throttle valve and then tuned with the feedback springs in the main valve.
The HP system was the biggest problem due to the SV float fitted upside down in the HPmode. This caused the pilot signal to be erratic as it could be either flash gas, saturated or sub cooled liquid in the pilot line. I built “special SV float assemblies” for the HP flooded systems fitted in a well known departmental store in London as the standard SV1 parts just could not control the level. I later found out that the factory made identical SV assemblies to my design and called them the British version which became a Danfoss spare part for the SV1
The LP float system with the PMFL+SV1works quite well but it needs tuning with the pilot flow throttle needle approx 1 turn open , and the feedback springs on the PMFL adjusted to give a proportional flow . Sometimes fitting the SV3 nozzle into the SV1 float as it reduces the PMFL p band .
An even better solution is to use the SV4 float which is the old GRAM float as it has a better float movement and operating P band with the PMFL valve than the SV1 or 3 due to limited float movement

My biggest issue with the SV1 is people forgetting to move the little screw inside to the correct position.
and back when the SV1 and PMFL/H was the standard, that the pilot line was ran all around the engine room, creating a lag in valve operation (especially closing), that's when you could spend a whole day tuning the needlevalve and spring tension.

there were a few years around 97-99 when there was an issue with the needle that caused it to snap inside the pilot hole and block it.

Haven't checked what they are made of now, but I have spent a few late evenings on the lathe to turn out a new one from welding rods

I'm interested in hearing more about the "british version" this is truly history in the making

[Tycho]

Glenn, not a plant we work on, just trying to help solve what seems a basic problem, but not working out.
For whatever reason appears flash gas in pilot area not allowing valve to open.
Valves I would say are to big under current load, but at same time they only need to open to maintain a liquid level.
Suggested he gets power from power point & see if it opens valves, but have not heard back.

1/ Yes but client removed for whatever reason
2/ would have to wait to get it
3/yes have been stripped & checked
4/ don’t know , plant has been altered & very lightly loaded.

Plant net is not new, has worked before, but probably under much different than design.

Another thought...

On the DN20 valve, could be that the diaphragm is old and in need of replacement... over time, as Glenn said, they can get disfigured or just plain floppy. (did you open it, or someone else? if someone else, always the chance that they put it back in the wrong order )

The EVRA25 has a different design, and with a 9 bar difference that one should pop open like a champagne cork
unless the piston is seizing like Glenn mentioned. I've only seen the types with piston rings.
most issues are with the EVM controlling the pilot pressure.
but I have had a few on older system where the piston ring has gotten stuck inside the groove on the piston and this causes enough bypass to only partially open the valve.
remove the piston, pry the piston ring out and give the groove and piston ring a good dabbing with a scotch pad usually solves it in emergencies, but the best option is always to give it a new piston.

Do they have a permanent coil they can check with?

[Tycho]

Brian,
Old system that has been altered a bit, equipment moved a few metres for upgrades.
Plant just holding room temperatures ready for production.
Not a plant we work on, just trying to help a bit ( now getting to hard).

Site engineer that is a bit too friendly and eager to fix things without getting a service tech on site?

[RANGER1]

My biggest issue with the SV1 is people forgetting to move the little screw inside to the correct position.
and back when the SV1 and PMFL/H was the standard, that the pilot line was ran all around the engine room, creating a lag in valve operation (especially closing), that's when you could spend a whole day tuning the needlevalve and spring tension.


there were a few years around 97-99 when there was an issue with the needle that caused it to snap inside the pilot hole and block it.

Haven't checked what they are made of now, but I have spent a few late evenings on the lathe to turn out a new one from welding rods

I'm interested in hearing more about the "british version" this is truly history in the making

Australian history (if that means much) was to just use SV3 in series with needle valve fully open, no adjustments, just works.
Pilot line to long, diameter to small, or with pockets, no good.
They changed material several times, probably ended up with polymer seat like everything else now.
We have pulled all of them out now, all electronic controlled.

[RANGER1]

Another thought...

On the DN20 valve, could be that the diaphragm is old and in need of replacement... over time, as Glenn said, they can get disfigured or just plain floppy. (did you open it, or someone else? if someone else, always the chance that they put it back in the wrong order )

The EVRA25 has a different design, and with a 9 bar difference that one should pop open like a champagne cork
unless the piston is seizing like Glenn mentioned. I've only seen the types with piston rings.
most issues are with the EVM controlling the pilot pressure.
but I have had a few on older system where the piston ring has gotten stuck inside the groove on the piston and this causes enough bypass to only partially open the valve.
remove the piston, pry the piston ring out and give the groove and piston ring a good dabbing with a scotch pad usually solves it in emergencies, but the best option is always to give it a new piston.

Do they have a permanent coil they can check with?

Tycho,
New solenoid out of the box, buy even that makes me think these days!

[RANGER1]

Let’s start with the EVRA 25 valve
The EVRA 25 valve needs approx 2 psi / 0.15 Bar Pressure drop across it to be fully open , a lower mopd would cause the valve to only partially open.
When the old EVJDA 25 was upgraded to the EVRA25 it caused many problems due to it failing to open. I spent many days running round to NH3 sites due to the valves poor performance. There were several issues with the valve , partly due to the pilot flow , but mainly due to the piston. The early piston was an extruded type which had labrynth seals (grooves) around the piston to act as a seal. These pistons often were out of round causeing leakage past the piston causing the servo function to mal function. After a few months the steel piston was changed to a cast iron piston with a piston ring plus mods to the pilot system. This solved the problem completely. The only issues after this modification was caused by system debris causing the piston ring to jam in the piston groove , simply cleaning the valve and freeing the piston in the groove gets it working again.
But if the valve is oversized for the duty required it will struggle to go fully open .The EVRA 25 can do approx 1100 kw liquid line capacity on NH3. The coil for this valve is the standard 10 watt 068F6702 coil for 240 volt 50 Hz.
The EVRAT 20 valve as you know is an assisted lift valve with a diaphragm. This valve doesn’t need a pressure drop to keep it open as the assisted lift spring connector does this via the armature. But the EVRAT valves need a bigger coil to open the valve due the the weight of the spring a diaphragm connected to the armature. This valve should have a minimum 12 watt coil fitted to give the coil extra pulling power. The coil code no is 068F6802 for 240 volt 50hz. Often using a weaker coil with these valves causes problems. Always check the diaphragm material ,this should be flat , if the diaphragm has ripples in the diaphragm it must be changed as instead of it simply deflecting open and closed it tends to click open to close which can take a few seconds due to the diaphragm having to overcome the stretched diaphragm material.
In this instance If necessary change the EVRA25 to a EVRAT 20 as it will fit into the same flanges and with its reduced capacity should open without problems

Regards to Tycho,s problem with the PMFL level control system , these level systems were always a pain to set up whether it was an PMFL or PMFH. The main valve was fine but the SV float had to be set correctly via its small throttle valve and then tuned with the feedback springs in the main valve.
The HP system was the biggest problem due to the SV float fitted upside down in the HPmode. This caused the pilot signal to be erratic as it could be either flash gas, saturated or sub cooled liquid in the pilot line. I built “special SV float assemblies” for the HP flooded systems fitted in a well known departmental store in London as the standard SV1 parts just could not control the level. I later found out that the factory made identical SV assemblies to my design and called them the British version which became a Danfoss spare part for the SV1
The LP float system with the PMFL+SV1works quite well but it needs tuning with the pilot flow throttle needle approx 1 turn open , and the feedback springs on the PMFL adjusted to give a proportional flow . Sometimes fitting the SV3 nozzle into the SV1 float as it reduces the PMFL p band .
An even better solution is to use the SV4 float which is the old GRAM float as it has a better float movement and operating P band with the PMFL valve than the SV1 or 3 due to limited float movement

System apparently working, reg valves opened fully, not sure what really happened, information may not be 100% accurate.
Think a lot of air was purged, not sure if that would have effect on solenoids though.
Coil was correct on EVRAT20 as you advised.
Bit of a mystery

[Tycho]

Australian history (if that means much) was to just use SV3 in series with needle valve fully open, no adjustments, just works.
Pilot line to long, diameter to small, or with pockets, no good.
They changed material several times, probably ended up with polymer seat like everything else now.
We have pulled all of them out now, all electronic controlled.

SV1, SV3, same thing just flip the lid around
was the same here, run it in series needle valve full open.

There were some systems I worked on when I were still wearing my baby shoes that had the pilot line laid out in 12 mm pipe and the longest I measured was around 15 meters from the pilot receiver to the PM valve... the line filled with liquid that would take ages to boil of, and keep the valve open much longer than needed.

They were wondering why the pilot tank always emptied before the valve closed... that one took some time to dial in the needle valve.

Was kind of "fun" showing your "can do" when you turned out a needle on the lathe and installed it and said this will last longer than the rest of your plant as a joke (and then it turned out to be true ).

[Tycho]

Tycho,
New solenoid out of the box, buy even that makes me think these days!

indeed, but like I said, if the pressure drop is too high across a diaphragm valve, and you are running liquid, you get the Coanda effect, or like an airplane wing, the flow along the slightly curved diaphragm is to high, it will create a low pressure and pull the diaphragm back down to the closed position.

if it's working now, they have had to have changed some system parameters... no way a solenoid valve is causing problems, and then suddenly starts working perfectly again it either works or it doesn't

In my humble opinion

[Tycho]

System apparently working, reg valves opened fully, not sure what really happened, information may not be 100% accurate.
Think a lot of air was purged, not sure if that would have effect on solenoids though.
Coil was correct on EVRAT20 as you advised.
Bit of a mystery

if they purged a lot of air, maybe the supply pressure was lowered from 1250 kpa to 1000 or 900 kpa, and that was the difference needed to allow the valves to operate?

Just guessing

[mbc]

Hi
How about you put one or two size small solenoid EVRA 15 OR EVRA10 .
you have enough drop pressure to be open

[RANGER1]

Sorry no real feedback except reg valves opened up & for whatever reason now works.
Plant is under more load though I think.

[passandscore]

Hi Ranger,

An oversized solenoid valve of the piloted type may behave strangely at some operating conditions, where there is insufficient pressure differential to open it or maintain it in a stable open condition. In these cases the valve may chug or chatter, or may seem to open just partially, producing a very low flow.