pnumatic actuator

[lolson]

im working on a da heating valve with sr 2-7 psi and supply pressure is 20psi.

my problem is the valve will not fully close. i have exstended the storke to the max. is there any sujestions? im thinking of some kind of exstension?

actuator: honeywell mp953c 1000 2
valve: (only #) v50 11n1057

[crab master]

You said it yourself "Tinkeritus will cost you $."

Replace the valve. I am not familiar with the valve you are talking about but I suspect you have sediment built up where the valve seats and thus you can't get it to close off.

[orion242]

Stuff stuck in the valve or the valve seats are shot.

If the seats are shot, you can buy rebuild kits for them.

>Extending the shaft...

not likely to help…

Have you put 15-20psi on the valve to see if closes 100% or checked pressure at the valve?

[alpha480v]

Sounds like junk in the valve, not allowing it to seat all the way. Time for a new valve.

[jogas]

One other thing to check:
If you have too high a differential when the valve tries to close, 7 PSI may not be enough to overcome it. Try putting 20 PSI directly to the valve actuator. If it closes, you need to add a pilot positioner to the valve. If not available for that valve, order one that that comes with a positioner.
If it still won't close, you may have a system problem.
I've experienced this exact problem several times.
I've also had valve seats that had missing, broken off pieces. If the above doesn't work, remove the valve, disassemble and inspect.
jogas

[lolson]

thanks everyone i think im going to replace it because i have 6 valves and they all are doing the same thing and also it would be the same assy. that is in most of the building. the other vavs are 4 mixing valves and 6 are electronic. go figure why its not uniform?

[joey791]

The N model valve is the newer model, thats a few failures already(you have to understand most valves I deal with are 20 to 30 years old). I dont know if you do the mechanical side too but if you are having problems with that many valves shutting sounds like its time for a system flush.

[lolson]

The N model valve is the newer model, thats a few failures already(you have to understand most valves I deal with are 20 to 30 years old). I dont know if you do the mechanical side too but if you are having problems with that many valves shutting sounds like its time for a system flush.

im not the boiler mechanic, im mostly there refrigeration tec. but i do heating to systems to, so i will ask if the boiler mechanics about flushing the system out. thanks

[DEC920]

Something more basic here might also be looked at. Has something at the system level changed. I presume the application is heating, system pressure changed at the circulating loop possibly? You have six valves acting in the same manner all at once? The earlier posting on close off pressure was on the right track, look a little deeper.

[shifferbrains]

If these are two way valves and with that many doing the same thing... I concure... I would suspect a system problem. I think it would be a good idea to take a better look at the system differential pressure. I high differential can lift valves off thier seats causing leak through.

[crab master]

With this being on multiple valves there is another issue(s) I going on such as what the others have stated. Get some data from your system - pressures and then get some data on your valves and actuators - see if they have the close off capability needed for your system before you go to replacing valves.

[tlp261]

If you have it fully stroked, the problem is either a physical one like a bad seat or disc, or excessive differential pressure.

For reference, this valve/actutor combo needs 8.5 psi to get above 0 psi close-off, but with 20 psi control signal it will close-off against 200 psi.

[wen-sar]

i have a building full of these pneumatic actuators and water valves driven by KMC reset controllers and using 20 psi supply air..

first a question.. did you put a gauge and verify your supply air pressure at 20 or did you just assume.. cause it would be very unlikely 6 would fail at the same time..

if you have 20 psi at the valve.. replace the valve..
if they are the same new ones i use (Honeywell) you'll have a green spring installed and an orange spring in a bag.. pull the plastic pin on the round cap and twist off and replace the green spring with the orange spring.. the return spring pressure is stronger on the orange and will be needed to open the valve fully..

remember DA (Direct Acting works by that spring opening the valve when pressure drops below the 8 pound psi) so that if the air fails you get heat..
in RA (in Reverse Acting, air pressure above 8 pounds is needed to open the water valve)..
DA = default open water valve.. RA = default closed water valve..

finally an IMPORTANT note.. when replacing these water valves.. direction of water flow does matter.. it usually is intended to enter at the top of the coil and leave from the bottom of the coil.. sometimes someone will screw up the supply lines and hook them up backwards.. DON'T panic.. you'll know quickly because the water valve will began to hammer.. when it does.. don't re-plumb the lines.. JUST remove the water valve and TURN IT AROUND.. the valve will still work perfectly..

good luck.. hope i helped..


:D

[lolson]

due to the cost of flushing the boiler that is a glycol filled system, and in the cold season, but i think that the company didnt want to pay for it, and the cost of new valves and actuators to make the system more uniform, this is what i had to do.

first i disassembled a valve and the glycol was not dirty.
so i hacked away and made an exstion to shorten the stroke on the valve and now they are working ok.

the actuators was properly set and sercured on the valves.

so why did i have a problem? maybe a mismatch of the actuator and valve?

[Control Man]

Had a call last week about a heating valve failing to close off, got to the site was told there were 10 not working properly.

Building operator said he checked everything , asked what his AIR PRESSURE was at the control cabinet , was told 20 PSI , went to check it out , gauge on PRV read 20 PSI going into the control panel , output gauges inside all reading 5 PSI , turns out the gauge on the PRV was faulty and had been reading 40 PSI and they kept turning it down to what was indicating 20 PSI but ended up being 5 PSI.

Never chance the AIR PRESSURE if your getting more than 1 pneumatic device acting up , verify the correct pressures with your own gauges.

[lolson]

yes i did measure 20 psi at the stat and then i bypassed the stat and measured 20 psi at the actuator to see if i had any pressure loss. i had just replaced my gage prior to this call due to a cracked lens and when i diconnected the supply air the sound and feel of it im comfident it is correct

it is a good thing when you keep asking or pointing out are you sure you had 20 psi because there are techs that will only look at the gages that are at the prv and to them it must be true.