Schroeder Valves · pump protection
Schroeder ARC valve
A series by series guide to the Schroeder ARC valve line, and how to choose the right combination for your pump.
The Schroeder ARC valve line: one principle, several answers
A Schroeder ARC valve always follows the same principle, yet the line contains several series, because a small process pump and a feed water pump at very high pressure do not face the same problem. Every Schroeder ARC valve combines a check valve in the main line with a mechanically coupled bypass that returns the minimum flow when process demand drops. What differs between the series is the pressure level they are built for, the share of the flow they can recirculate, the way they respond to changing loads and the way they deal with large pressure differences.
At Dutch Valve Vision, official and exclusive agent of Schroeder Valves for the Benelux, we are often asked for a side by side comparison of the series. Specifications from engineering firms sometimes mention a series by name, sometimes only describe the duty and leave the choice to us. This page is the comparison we would give you across the table: series by series, with the reasoning behind each choice and the situations in which several series work together.
For the general working principle and the reasons to protect a pump at all, see our ARC valve and minimum flow valve pages. Here we focus on the product line itself.
Four questions that decide which series fits
Before looking at the series, it helps to know the questions we ask. They explain why the line is built the way it is.
The first is pressure. How high is the pump discharge pressure, and how high is the pressure at the point where the bypass returns? That difference is what the bypass has to reduce, and it drives the choice between standard, medium-high and very high pressure designs.
The second is the minimum flow ratio. How large is the minimum flow required by the pump manufacturer compared to the normal process flow? For most pumps that share is modest. For sensitive or heavily loaded pumps it can be large, and that calls for a different design.
The third is the load pattern. Does the process flow change slowly, or does it fluctuate strongly and frequently? Pumps in feed water systems and in plants with fast changing demand put different requirements on the valve than a pump in a steady transfer duty.
The fourth is the condition of the liquid. Is it close to its boiling point, volatile or prone to flashing? Is the pressure drop so large that erosion and noise become a concern? Those questions bring the supporting devices, SDV and SSD, into the discussion.
Schroeder ARC series at a glance
The Schroeder ARC valve line consists of the SSV series for general use, the SSV with control disc for minimum flows up to about 70 percent of the main flow, the SIP series for pressures up to about 250 bar, the SHP series for high and very high pressure and the pilot operated SMA ON/OFF system. SDV back pressure devices and SSD multi-stage throttle valves complete the range. Dutch Valve Vision, exclusive Schroeder agent for the Benelux, helps select the right series.
| Series | Application |
|---|---|
| SSV | Standard, compact all-in-one design |
| SSV with control disc | High minimum flow, up to about 70% of main flow |
| SIP | Medium pressure, up to about 250 bar |
| SHP | High and very high pressure |
| SMA | ON/OFF, pilot operated |
| SDV | Back pressure device with check function |
| SSD | Multi-stage throttle for high differential pressure |
The core Schroeder ARC valve series
The core of the line consists of five executions. Each Schroeder ARC valve in this group integrates the check function and the minimum flow bypass, and each works automatically, without external measurement or control systems.
SSV series: the standard all-in-one design
The SSV series is the standard Schroeder ARC valve. It is a compact, all-in-one design for general industrial applications, and it is broadly applied in power plants and process installations. When the pressure level is moderate, the minimum flow is a normal share of the duty flow and the load changes are not extreme, the SSV is where we start. Its compactness makes it attractive in skids and in existing plants where space on the pump discharge is limited.
SSV series with control disc: for high minimum flow
Some pumps need a minimum flow that is a large part of their normal flow. For those pumps Schroeder offers the SSV with control disc, intended for high recirculation requirements, with a minimum flow of up to about 70 percent of the main flow. It is ideal for sensitive or heavily loaded pumps. In practice this version comes into view when the pump data sheet shows a minimum flow that the standard bypass simply cannot handle. Because the bypass then carries a substantial flow, we also look closely at the return line and the heat returned to the suction vessel.
SIP series: medium-high pressure up to about 250 bar
The SIP series is developed for pressures up to about 250 bar. It is widely used in boiler feed water and utility systems, where pumps combine high pressure with hot water close to its boiling point. When we receive an enquiry for a feed water pump in a power plant or an industrial boiler house, the SIP series is usually the first option on the table. The combination of pressure capability and a proven track record in feed water makes it a natural fit.
SHP series: high and very high pressure
Above the range where the SIP is comfortable, the SHP series takes over. It is a robust design for extreme process conditions at high and very high pressure, and it is developed for strongly fluctuating loads. Think of high pressure pumps in processes where the demand swings from near zero to full load several times a day. The SHP is built for that combination of high pressure and dynamic operation.
SMA series: ON/OFF, pilot operated
The SMA series in the ARC line works differently from the modulating designs. It is an ON/OFF system with pilot operated automatic minimum flow control. Instead of continuously adjusting the bypass opening, the system switches the recirculation on or off, which gives fast and reliable operation at very high pressure. It is a solution for applications where a clear open or closed bypass is preferred over a modulating one, typically at pressure levels where the other series reach their limits. Note that Schroeder also uses the SMA name for its standard automatic recirculation valves for general pump protection, so we always confirm which execution a specification refers to.
Supporting devices: SDV and SSD
Around the ARC valves, Schroeder offers two product lines for pressure and flow control. They are not pump protection valves in themselves, but they solve problems that often appear in the same systems.
SDV series: back pressure devices
The SDV series maintains a constant minimum upstream pressure. That protects the installation against cavitation and phase transitions, for example when a liquid close to its boiling point would flash to vapour if the pressure dropped too far. The SDV has an integrated check function. It is used where a stable back pressure is needed, often downstream of a pump or in lines where the pressure must not fall below a certain level.
SSD series: multi-stage throttle valves
The SSD series provides controlled pressure and flow reduction. With multiport and multi-stage designs it handles high pressure differences, and it is suitable for erosion and noise critical applications. In a pump protection system, the SSD typically appears in the bypass line when the pressure difference between pump discharge and return point is so large that a single reduction step would cause erosion, cavitation or excessive noise. Spreading the pressure drop over several stages keeps each step within safe limits.
Combining series in one pump system
In real installations the series are not always used on their own. A few combinations are worth knowing.
A feed water pump with a high discharge pressure and a return to a deaerator at low pressure can be protected with an SIP or SHP valve, with an SSD throttle valve in the bypass to take the large pressure difference in stages. A pump handling a volatile liquid, such as LNG or another hydrocarbon, can benefit from an ARC valve on the discharge and an SDV back pressure device that keeps enough pressure to prevent vaporisation. A pump with a high minimum flow requirement in a plant with frequent start-ups may need the SSV with control disc, sized carefully together with the return line.
These combinations are not fixed recipes. They follow from the four questions above, and the answer depends on your data. What they show is that the Schroeder ARC valve line is designed as a toolbox rather than a list of separate products.
Comparing the series in plain words
If we summarise the line in one paragraph, it sounds like this. Start with the SSV when the duty is general and the pressure moderate. Choose the SSV with control disc when the minimum flow is high relative to the main flow, up to about 70 percent. Move to the SIP for feed water and utility duties up to about 250 bar. Go to the SHP for high and very high pressure combined with strongly fluctuating loads. Consider the SMA ON/OFF system when a pilot operated switching bypass at very high pressure is preferred. Add an SDV where a minimum back pressure is needed against cavitation and phase transitions, and an SSD where the pressure drop in the bypass is too large for one step.
Schroeder ARC valves in all these series are used worldwide in power plants, whether fossil, nuclear or renewable, in chemical and petrochemical installations, in offshore and injection systems, in boiler feed water and auxiliary systems and in heavy industry such as steel and paper. Through us they can be supplied for boiler feed water, ammonia and nitric acid, LNG and hydrocarbons, seawater and fire fighting systems and other special media.
Existing installations: identifying and upgrading an older Schroeder ARC valve
Not every enquiry concerns a new pump. Many enquiries start with a valve that has been in service for many years. The maintenance team knows it is a Schroeder ARC valve, but the original data sheet has disappeared and the only reference is the nameplate. Sometimes the process around the pump has changed since the valve was installed: a different production rate, a new return point or a pump with a different impeller.
The first step is always identification. From the nameplate details and the tag number we can usually trace the series and the original design data. That tells us whether the valve still matches the duty. If the pump and process are unchanged and the valve is simply worn, original spare parts or a repair are the logical route. For older models, Schroeder offers upgrade kits, which can bring a valve closer to current designs without replacing the complete body.
If the duty has changed, the question becomes different. A pump that now runs at part load far more often, or whose minimum flow has gone up after an impeller change, may need another series. A standard SSV might have to make way for the SSV with control disc, or a bypass that now sees a larger pressure difference might need an SSD throttle valve. We work through that comparison with the same four questions we use for a new project.
When a valve is repaired through us, it is rebuilt with original OEM Schroeder parts, receives a flow calibration test and a pressure test on the Schroeder test bench, and is readjusted until it reaches its original settings if deviations are found. It then comes with a full Schroeder factory warranty and can be regarded as new. After repair, upgrade or replacement, the result is a Schroeder ARC valve that fits the pump as it is operated today.
Materials and executions
Schroeder valves are available in different materials, including carbon steel and stainless steel, and the choice is matched to the medium and process conditions. A feed water system, a seawater fire pump and an ammonia or nitric acid duty all lead to different considerations. We discuss the material together with the series, because the pressure level, the temperature and the medium are part of the same selection. Connections are specified according to DIN or ANSI, depending on your installation.
Selecting a Schroeder ARC valve with Dutch Valve Vision
Our selection starts with the data behind the four questions: the pump data sheet with the manufacturer’s minimum flow, the normal and maximum process flow, the pump discharge pressure, the pressure at the return point, the medium and its temperature, and a description of how the pump is operated. We add the connection standard, DIN or ANSI, and the documentation required by your project. From there we propose a series, or a combination of series, and explain why.
Dutch Valve Vision works with an ISO 9001 certified quality management system, certified by KIWA, and offers advice, technical support and reliable supply chain management. After installation we supply original Schroeder spare parts, including upgrade kits for older models, and repair valves with OEM parts, a flow calibration test and a pressure test on the Schroeder test bench, backed by a full Schroeder factory warranty.
Want a series comparison for your own pump? Contact us at +31 (0)70-2210560 or sales@dutchvalvevision.com, Monday to Friday from 09:00 to 17:00. We will help you find the Schroeder ARC valve that fits your pressure, flow and process.
What is a Schroeder ARC valve?
A Schroeder ARC valve is an automatic recirculation control valve made by Schroeder Valves. It protects a centrifugal pump by keeping a minimum flow through it at all times. In the main line it works as a check valve that prevents reverse flow. A mechanically coupled bypass opens when process demand drops and returns the minimum flow. The valve works without external energy, sensors or control systems. The line includes the SSV, SSV with control disc, SIP, SHP and SMA series. SDV back pressure devices and SSD throttle valves complete the range. Dutch Valve Vision is the exclusive Schroeder agent for the Benelux.
What is the difference between the SSV and the SSV with control disc?
The standard SSV is a compact, all-in-one valve for general industrial applications. It suits pumps whose minimum flow is a normal share of the duty flow. The SSV with control disc is designed for high recirculation requirements. It handles a minimum flow of up to about 70 percent of the main flow. That makes it suitable for sensitive or heavily loaded pumps. Because the bypass then carries a large flow, the return line needs extra attention. The heat returned to the suction vessel also becomes more significant. We check both points when we select this version.
Which Schroeder ARC valve is used for boiler feed water?
The SIP series is the usual choice for boiler feed water. It is developed for pressures up to about 250 bar. It is widely applied in boiler feed water and utility systems. Feed water pumps combine high pressure with hot water close to its boiling point. That makes reliable minimum flow protection essential. For higher pressures or strongly fluctuating loads, the SHP series can be the better option. An SSD throttle valve can be added when the pressure drop to the deaerator is large. We select the combination based on your pump data.
When do I need the SHP series?
The SHP series is intended for high and very high pressure. It is a robust design for extreme process conditions. It is also developed for strongly fluctuating loads. You typically consider it when the pressure exceeds what the SIP series is designed for. It also fits pumps whose demand changes quickly and often. Pumps with large, frequent load swings at high pressure are a typical example. The choice always depends on your pressures and operating profile. We compare the SHP with the alternatives before we advise.
What does the SMA ON/OFF system do?
The SMA series in the ARC line is a pilot operated ON/OFF system for automatic minimum flow control. Instead of modulating the bypass continuously, it switches the recirculation on or off. This gives fast and reliable operation at very high pressure. It suits applications where a clear open or closed bypass is preferred. Schroeder also uses the SMA name for its standard automatic recirculation valves. That is why we always confirm which execution a specification refers to. The nameplate or original order data usually make this clear. We are happy to check existing documentation for you.
What is an SDV back pressure device used for?
An SDV back pressure device maintains a constant minimum upstream pressure. That protects the installation against cavitation and phase transitions. It is useful when a liquid close to its boiling point would flash if the pressure dropped. The SDV has an integrated check function. It is often used in systems with volatile media or hot liquids. In some installations it works together with an ARC valve on the pump discharge. The need for an SDV follows from the process conditions. We assess this together with you during selection.
When is an SSD multi-stage throttle valve needed?
An SSD valve is needed when a large pressure difference has to be reduced in a controlled way. In pump protection this often concerns the bypass line to a low pressure return point. A single reduction step at a high pressure difference causes erosion, cavitation and noise. The SSD spreads the pressure drop over several stages. Multiport and multi-stage designs handle high pressure differences. That makes the SSD suitable for erosion and noise critical applications. It is common in combination with high pressure ARC valves. We determine whether it is needed based on your pressures.
How does Dutch Valve Vision help choose the right series?
We start with your pump data and the minimum flow required by the pump manufacturer. We also need the process flows, the pressures at discharge and return point, and the medium. Information on how the pump is operated helps us judge the load pattern. From there we compare the series and propose a valve or combination of valves. As exclusive Schroeder agent for the Benelux we handle advice, technical support and supply. We work with an ISO 9001 certified quality management system, certified by KIWA. After installation we support you with original spare parts and repair. You can reach us at sales@dutchvalvevision.com or +31 (0)70-2210560.
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Compare Schroeder ARC valve series
Send us the pump data, minimum flow, pressures at discharge and return point, medium and load pattern. We will propose the series, or combination of series, that fits.
- +31 (0)70-2210560
- sales@dutchvalvevision.com
- Vlotlaan 641, 2681 TZ Monster
- Mon-Fri 09:00-17:00
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