Last updated: 2026-11-04
Short answer: A pneumatic steam valve package for PLC on/off control is six items. The valve is a normally closed pneumatic angle seat valve rated for the steam temperature at the valve. It takes a 3/2-way solenoid valve and clean dry pilot air (4 to 8 bar on our 2000Y). Just ahead of it go a drip leg with a steam trap and a Y strainer. Position feedback is the sixth item, if the PLC must confirm the stroke.
If you have been asked to make the steam to a tank, a kettle or a heating coil open and close on a PLC signal, the valve is the quick part to choose. What takes the time is everything around it: which solenoid valve, what air supply, where the condensate goes while the valve is shut, and what the PLC should expect to see back.
Below is the whole package for an automated steam on/off point in the 1/2″ to 2″ range: the valve, the solenoid valve, the pilot air, the position feedback, the piping on both sides of the valve, and the PLC side. We make the angle seat valve at the centre of it, so where the 2000Y sets a limit, the number is stated.
What a pneumatic steam valve package actually needs
An automated steam on/off point is six items. The valve does the switching, the solenoid valve turns the PLC signal into air, the air supply drives the valve, the feedback tells the PLC what happened, and the piping on each side of the valve deals with the condensate that every steam line produces. Leave out the drain or the strainer and the valve gets blamed for a problem that belongs somewhere else.
| Artículo | Para qué sirve | What you have to decide | Where it comes from |
|---|---|---|---|
| 1. Normally closed pneumatic angle seat valve | Opens on air, closes on the spring; shuts the steam off | Size, end connection, steam temperature and line pressure, actuator head material | Valve manufacturer (our 2000Y) |
| 2. 3/2-way solenoid valve | Turns the PLC output into pilot air to the actuator, and vents it to close | Coil voltage; whether we mount it on the valve | Ordered with the valve and mounted before shipping |
| 3. Pilot air supply | Lifts the plug against the spring and the line pressure | 4 to 8 bar at the valve, filtered and dry; regulator and filter in the line | Your compressed air system |
| 4. Position feedback (optional) | Tells the PLC whether the valve is open or closed | Whether the PLC needs confirmation; sensor input type | Option on the 2000Y |
| 5. Upstream piping | Keeps condensate and debris away from the seat | Isolation valve, drip leg with steam trap, Y strainer | Steam trap supplier; our Y strainer |
| 6. Downstream piping | Drains the condensate that forms while the valve is shut | Drain point where the equipment side is a dead leg | Steam trap supplier |
Why an angle seat valve rather than a pneumatic ball valve? An angle seat valve is a valve whose plug lifts straight off a seat set at an angle to the pipe, driven by a piston actuator on top. The 2000Y has its spring return built into that piston and is made for frequent open/close on automated lines. A spring return pneumatic ball valve with a 3/2 solenoid valve also fails closed, and it suits isolation duty, where the valve stays in one position for long periods. Our guide to ball valves on steam covers what to check, and there is a short section on that choice near the end of this article.
Step 1. The pneumatic steam valve: a normally closed angle seat valve
Use a normally closed angle seat valve with a single acting, spring return piston actuator. Air opens it, the spring closes it, and if the air or the signal fails it closes on its own. Spirax Sarco’s guidance on control valve actuators notes that it makes sense for steam valves to close on air failure. Confirm that in your own safety review, but for a steam supply to process equipment it is the normal choice.
Nuestra 2000Y pneumatic angle seat valve is that valve. The body is cast 316 stainless steel (CF8M) with a PTFE seat (PTFE is the fluoropolymer the plug seals against), in sizes from 1/2″ to 2″ (DN15 to DN50). It is rated for a working pressure of 200 psi (13.8 bar) on water, and for steam and hot water from −20 °C to +150 °C. The PN40 rating is the body pressure class, not a steam rating.
On saturated steam the two ratings are linked, and the temperature is the one you reach first. Saturated steam at 150 °C sits at about 4.76 bar absolute according to the water vapour saturation table at The Engineering ToolBox. Taking off atmospheric pressure, that is 3.75 bar gauge, or 54 psig (gauge pressure, measured above atmospheric). So for saturated steam the 2000Y covers low-pressure process steam up to 3.75 bar g. If the steam at your valve is hotter than 150 °C, the 2000Y is outside its rating.
Flow over the seat, and no arrow on the body
For steam service the 2000Y is built for flow over the seat: steam enters above the plug and presses down on it, so the line pressure helps the spring hold the valve shut. The trade-off is that the actuator has to lift the plug against that pressure to open. That is why both the line pressure and the pilot air pressure go on the RFQ, and why the 1″ size comes with a choice of two actuator sizes, the larger one for higher pressure differentials across the valve. There is no flow arrow cast on the body, so if it is not obvious which end is the inlet, ask us before you install it.
Size by flow, then confirm the ends
Choose the valve size from the steam flow the equipment needs rather than from the pipe you happen to have. A valve of the same nominal size as the pipe can pass a different flow, so compare flow coefficients (Kv or Cv, the flow a valve passes at a set pressure drop) with the flow the machine draws at full load.
End connections: PT (BSPT taper) threads are in stock; NPT, PF (BSPP parallel) and socket weld ends are made to order. If you are not sure which thread is on your pipe, our pipe thread chart compares the three. Write the thread standard on the RFQ rather than “1 inch threaded”.
Step 2. The solenoid valve: 3/2-way, in your control voltage
A single acting actuator takes a 3/2-way solenoid valve. The 3/2 has one port to the actuator: energised, it feeds pilot air in and the valve opens; de-energised, it vents the actuator to atmosphere and the spring closes the valve. A 5/2-way valve is for double acting actuators with two air ports. Ordering a 5/2 for a spring return actuator is a common mistake in pneumatic valve packages; our retorno por resorte frente a doble efecto guide explains the difference.
The PLC output drives the coil, through a relay if the output cannot carry the coil current. Loss of control power has the same effect as a close command: the coil drops out, the actuator vents and the spring shuts the steam off. The coil on the valve in the photo is 24 V DC, rated for continuous duty (100% ED) and IP65. State your control voltage on the RFQ.
Mounted on the valve, or in the cabinet
When the solenoid valve is ordered with the valve, we mount it on the actuator before shipping, so the pilot connection between the two is already made and tested. The alternative is a solenoid manifold of your own in the control cabinet with a tube run out to each valve. Mounting on the valve keeps the tube short and the response quick. It also puts the coil next to a hot pipe, so keep the actuator and the solenoid clear of the pipe insulation, leave air around the coil, and check the coil’s ambient temperature rating against the surroundings. If the valve sits inside a hot enclosure, the cabinet-mounted solenoid is the safer layout. Either way, fit a silencer on the exhaust port, like the brass silencer next to the solenoid in the photo.
One safety note for both layouts: the body and the actuator get hot in service and stay hot for a while after shutdown. Route cables and tubing clear of them, and keep hands off until the line has cooled.
Step 3. Pilot air: 4 to 8 bar, filtered and dry
The 2000Y opens on pilot air between 4 and 8 bar, measured at the actuator. It is separate from the steam pressure, but the two are linked: the actuator has to lift the plug against the line pressure, so the air pressure needed rises with line pressure and depends on the actuator size. That is why we ask for both numbers when you request a quote. Run a filter-regulator on the pilot line, set it inside that range, and make sure the pressure is available at the valve rather than only at the compressor.
Water in the pilot air ends up in the solenoid and the actuator, so if your compressed air carries condensate, dry it before it reaches the valve. Keep the air clean, and if the air has ever been lubricated, keep it lubricated. One angle seat valve maker’s steam-service manual specifies nylon tube and metal fittings for the pilot line.
Step 4. Position feedback, if the PLC needs to know
A normally closed valve with a 3/2 solenoid will open and close without any feedback. Add feedback when the PLC has to confirm that the valve moved before the next step, or when a valve that fails to move must raise an alarm instead of letting a batch run cold. On the 2000Y, position feedback is an option ordered with the valve: a stem extension carries a target past two proximity sensors (switches that detect the target without touching it) mounted above the actuator, one for open and one for closed, as in the photo. Each sensor goes to a PLC input.
Use two sensors. With only an open sensor, a valve stuck half-way reads as closed. With both, the PLC can check that exactly one is on, and flag the valve if neither is on once the stroke time has passed. State your PLC input type on the RFQ.
Step 5. Pipe it so it does not bang
Put a drip leg (a short vertical pocket off the bottom of the pipe that collects condensate) with a steam trap (the automatic valve that discharges that condensate) and a Y strainer immediately ahead of the valve, and warm cold lines slowly through a manual isolation valve. That keeps condensate from being driven down the pipe when the valve opens. While the valve is shut, steam in the dead leg upstream, the closed-off length of pipe, condenses, and the water collects against the closed seat. When the valve opens, that water is driven into the equipment at steam speed.
Spirax Sarco’s guidance on the installation of steam controls states that without a condensate drain ahead of the valve, water hammer and potentially serious damage can follow when the valve opens. Water hammer is the pressure shock that comes when a slug of water is driven along the pipe and stopped by a bend, a fitting or a valve. The water comes from the condensate, so the fix starts at the drain rather than at the valve.
A typical arrangement, from the main to the equipment:
| Position | Artículo | Para qué sirve | Practice and source |
|---|---|---|---|
| 1 | Branch taken from the top of the steam main | Draws the driest steam into the branch | Spirax Sarco recommends taking branch lines from the top of the main, with the on/off valve as close to the take-off as possible. On the main itself, TLV gives a drip leg about 700 mm (28 in) deep for automatic start-up on mains up to 250 mm |
| 2 | Manual isolation valve | Isolates the branch, and lets an operator warm a cold line up slowly | Open it slowly on a cold line so condensate drains through the traps first (Spirax Sarco) |
| 3 | Separator, where the steam is wet | Throws the water droplets out of the steam before they reach the valve | Spirax Sarco recommends a separator before control valves |
| 4 | Drip leg with steam trap | Collects and drains the condensate that forms while the on/off valve is shut | TLV: a trap immediately before a control valve, and before any valve that stays shut for long periods. Fit a check valve after the trap (Spirax Sarco) |
| 5 | Y strainer, screen pocket on its side | Keeps scale and debris off the seat | A Y strainer has its screen in a pocket that branches off the pipe at an angle; on a horizontal steam line that pocket lies horizontal so it cannot fill with water (Spirax Sarco, TLV). Our Y strainer with blowdown valve lets you clear the screen under pressure |
| 6 | On/off valve, actuator up | The automated shut-off | The 2000Y is installed in one orientation only: actuator pointing up, on a horizontal pipe. Fit a union on each side so the valve can be lifted out for service, and keep the valve off the lowest point of the run |
| 7 | Downstream drain point | Drains the condensate that forms on the equipment side while the valve is shut | Needed where the equipment side is a dead leg; Spirax Sarco applies the same rule downstream of reducing valves that can be shut off |
| 8 | Vacuum breaker and air vent on the jacket (jacketed vessels and kettles) | Lets the jacket breathe and drain once the steam is shut off and what is left in it condenses | Watson McDaniel’s steam design guide shows both on a batch kettle whose steam is switched on and off through a solenoid pilot |
Two of those rows matter most. The drip leg and trap at position 4 are what stop the water hammer, and the Y strainer at position 5 is what stops a piece of scale from scoring the PTFE seat and turning a tight valve into one that drips. Spirax Sarco’s guide to steam mains and drainage puts a strainer and a trap ahead of every control valve, and TLV’s guide to steam line best practices calls for a trap immediately before control valves and before valves that stay shut for long periods. The same applies to an on/off valve that spends most of its time shut. We stock 20, 60 and 100 mesh screens; our mesh to micron chart shows what each one stops.
An automated on/off valve opens quickly and fully. That is fine on a warm line with the drip leg doing its job. It is the wrong way to admit steam to a cold line full of water, and Spirax Sarco lists opening a valve too fast on a cold line among the causes of water hammer. Warm the line through the manual isolation valve first, slowly, and only then hand it over to the automation. If the line still hammers on the first opening of the day, the condensate is not getting out. Look at the drip leg and the trap before you look at the valve, and if needed add a small drain line with its own valve to empty the branch before the on/off valve opens. For water hammer in water systems rather than steam, see our article on golpes de ariete en edificios de gran altura.
Step 6. The PLC side: one output, two inputs, and the start-up order
The control side is small. One digital output drives the solenoid coil. Two digital inputs read the open and closed sensors, if you ordered feedback. The logic that goes with it: energise the output, wait for the open sensor within a stroke timeout you set, and alarm if it does not arrive; on close, do the same with the closed sensor. Because the valve is normally closed and the solenoid vents when de-energised, you need no logic for power failure. The steam shuts off by itself.
One sequencing rule keeps the valve under control: bring the pilot air up and the control power on before you admit steam to the branch, so the valve is already under control when the steam arrives. One angle seat valve maker’s manual gives the same order for restarting after an interruption: air and power first, then the medium.
Stainless steel or plastic actuator head on a steam line
The 2000Y is offered with a stainless steel head or an engineering-plastic head on the same CF8M body and PTFE seat, so the choice does not change the pressure or temperature the valve can take in the line. It changes what the actuator can live with around it. We recommend the stainless steel head for steam service. The plastic head is the lighter, lower-cost option for indoor, dry installations where the surroundings stay cool.
The first reason is heat from below. The actuator sits directly on a body at steam temperature, and some of that heat conducts up into the head. Makers of plastic-headed angle seat valves deal with it by derating the permitted ambient temperature as the medium gets hotter, or by putting a heat sink between the body and the actuator. The material data explains why. Nylon (PA), one of the plastics used for actuator heads, has a long-term service temperature of about 110 °C in Ensinger’s data for glass-filled PA66, and it absorbs moisture, which affects its dimensional stability; a 150 °C body sits right under it. A stainless steel housing has no plastic shell to age under that heat. It is not a licence for a hotter location, though. Stainless steel heads carry an ambient limit too, and on most angle seat valve data sheets it is the same 60 °C range as the plastic ones. The choice is about ageing next to a hot body and about the surroundings rather than about running the actuator hotter.
The second reason is what surrounds a steam valve: condensate drips, hot washdown or a corrosive atmosphere. Stainless steel actuator housings are what angle seat valve makers offer for corrosive atmospheres, cleanability and harsh environments, and a metal housing has no plastic to age outdoors. None of this makes the plastic head wrong on steam. Indoors, dry, with the surroundings cool and nothing dripping on the valve, it does the same job for less money and less weight. Tell us where the valve will be installed and we will recommend the head.
Which steam processes suit on/off control
An on/off package suits batch heating: steam admitted to a jacketed vessel, a tank coil, a sterilizer or a cooker for a cycle, then shut off again. It does not suit a flow-through heat exchanger or a process that has to hold its temperature within a narrow band. Those need a modulating control valve, which opens by degrees, rather than a valve that is either open or shut.
Spirax Sarco’s guidance on preventing stall (stall is the condition where condensate stops draining from heat exchange equipment) states that on/off control is normally only suitable for non-flow or batch heat exchange, such as tanks with robust heating coils and jacketed pans. It should not be used with heat exchangers, because the steam space keeps giving up heat after the valve shuts and the product overshoots. Where the tolerance is tight, the switching band of an on/off valve can be wider than the process allows. For batch heating, the package above is the whole answer.
Within its 150 °C rating, the 2000Y is used for steam on/off to jacketed vessels, heating coils and process equipment, and to the condensate, vent and coolant lines around sterilizers and autoclaves. It also goes to dyeing machines in textile finishing, and to washers and dryers in industrial laundries where the supply to the machine is reduced to 3.75 bar g or less.
Two checks decide whether a given machine falls inside that rating. The first is the line pressure at the machine, which varies more than people expect. A steam-jacketed kettle, for example, is fed at anywhere from 5 to 60 psig according to Oklahoma State University’s fact sheet on kettle installation, and that range straddles the 54 psig (3.75 bar g) line, so the actual setting matters. The second is where the valve sits relative to the pressure reducing valve. The on/off valve sees the line pressure upstream of it rather than the pressure inside the machine. When the plant main runs higher than the valve’s steam rating and a reducing valve drops it for the machine, the on/off valve belongs downstream of the reducing valve, and the steam temperature at the valve should be checked, not only the pressure.
What we do before it ships, and the detail that goes wrong most often
The 2000Y is pressure tested before shipment. If you order the solenoid valve and the position feedback with it, they are fitted and the package is tested as one unit, so on site you connect the air line, the coil wires and the sensor cables and nothing has to be matched up.
The detail that goes wrong most often on orders for this valve is the temperature. An RFQ gives a line pressure, or says “steam” and nothing else, and the temperature at the valve turns out to be higher than the valve is rated for. Write the steam temperature at the valve on the RFQ. If the steam is saturated, write the line pressure as well, so we can check one against the other before we quote.
What to put on the RFQ
Send these and we can quote the whole package in one pass.
| Artículo | Why we need it | Ejemplo |
|---|---|---|
| Steam temperature at the valve, and the line pressure | The 150 °C rating is what decides whether the 2000Y fits; the line pressure sets the actuator size | Saturated steam, 3 bar g, about 144 °C |
| Size and end connection | 1/2″ to 2″; PT in stock, NPT, PF or socket weld to order | 1″ NPT female |
| Pilot air pressure available at the valve | Must be 4 to 8 bar; with the line pressure it sets the actuator size (1″ has two) | 6 bar, filtered and dried |
| Actuator head | Stainless steel recommended for steam; plastic for indoor, dry, cool installations | Stainless steel head |
| Válvula solenoide | 3/2-way; coil voltage; mounted on the valve | Mounted, 24 V DC |
| Position feedback | Optional; two sensors; your PLC input type | Yes, open and closed |
| Where it will be installed | Outdoor, washdown or hot surroundings change the head and coil choice | Indoor, next to an insulated steam main |
| Quantity and documents | MOQ depends on the product; trial orders welcome; mill certificate on request | 2 pcs trial order, mill certificate required |
If you want the general version of this list for any valve, our guide to writing a precise valve RFQ covers it.
If you were planning to use a ball valve
A pneumatic ball valve can switch steam too, within the steam rating of its seats, and it is the better choice where you need a full, straight bore or a valve that stays in one position for long periods. Our V-2AM and V-3AM pneumatic ball valves can be used on steam; tell us the line pressure and temperature and we will confirm the fit, and specify a spring return actuator with a 3/2 solenoid if the valve must fail closed. The graphite-seated version of our V-2B seal-welded ball valve, rated for steam up to 3 kgf/cm² gauge and 180 °C, is a manual valve and is not offered with an actuator. Whichever ball valve you use on steam, run it fully open or fully closed; a ball valve held part-open on steam erodes its own ball and seats. The full comparison is in our article on ball valves for steam.
Preguntas frecuentes
Does a pneumatic steam valve need a 3/2 or a 5/2 solenoid valve?
A normally closed angle seat valve with a single acting, spring return actuator needs a 3/2-way solenoid valve. One port feeds pilot air to the actuator to open the valve, and the exhaust port vents it so the spring can close the valve. A 5/2-way solenoid valve is for double acting actuators, which have two air ports and no spring. Fitting a 5/2 to a spring return actuator is a common ordering mistake in pneumatic valve packages. If you are unsure which actuator you have, send us the model and we will tell you which solenoid it takes.
What pilot air pressure does a pneumatic angle seat valve need?
Our 2000Y opens on pilot air between 4 and 8 bar, measured at the valve. The pilot pressure is compressed air pressure and is separate from the steam pressure in the line, but the two are linked. The actuator has to lift the plug against the line pressure, so a higher line pressure needs more air or a larger actuator. That is why we ask for both the line pressure and the available pilot pressure on the RFQ. Feed the valve through a filter-regulator, keep the air dry, and make sure the pressure is available at the valve and not only at the compressor.
Can the solenoid valve and position feedback be fitted before delivery?
Yes. Order the 3/2 solenoid valve with the 2000Y and we mount it on the actuator and test the two together before shipping, so the pilot connection is already made. Position feedback is an option on the 2000Y: a stem extension and two proximity sensors above the actuator, one for the open position and one for closed, each wired to a PLC input. State your coil voltage and your PLC input type on the order, and the package arrives ready to connect to air and to the panel.
Why does the steam line bang when the valve opens?
The usual cause is condensate that collected in front of the closed valve or in a low point downstream. When the valve opens, steam drives that water along the pipe and it hits the next bend or fitting. Check four things. There should be a drip leg with a working steam trap just ahead of the valve. The Y strainer pocket should lie on its side so it does not hold water. The branch should not be the lowest point of the run. And cold lines should be warmed up slowly through the manual isolation valve before the automation takes over. Replacing the valve alone is unlikely to stop the noise.
Should the actuator head be stainless steel or plastic on a steam line?
Both heads drive the same CF8M body and PTFE seat, so the steam pressure and temperature limits do not change with the head. For steam service we recommend the stainless steel head. The actuator sits on a body at steam temperature, and heat conducting up from the body is what forces makers of plastic-headed valves to derate or add heat sinks; the surroundings of a steam line are also often wet, washed down or corrosive. The stainless steel head has an ambient temperature limit of its own, so it is not a way to run the actuator hotter. The plastic head is lighter and lower in cost, and suits an indoor, dry installation where the surroundings stay cool.
Summary
Automating a steam on/off point is a package: a normally closed angle seat valve, a 3/2 solenoid valve, 4 to 8 bar of clean dry pilot air, optional position feedback, and a drip leg, trap and strainer ahead of the valve. Specify the steam temperature with the line pressure, and say where the valve will live. Then the quote covers the whole package.
To start, send us the RFQ items above through our quote request form, or read the 2000Y product page for the dimension sheet and the full specification.