The working principle of isolation valves
Isolation valves separate a section of plant so that work can be carried out safely, which makes their tightness a safety issue rather than a performance figure. The term isolation valves is used broadly in the market, which is why it helps to define precisely what it means in your case. We find that questions about isolation valves almost always come back to the same three points: medium, temperature and required tightness. A ball valve closes with a bored ball turning through a quarter turn, which allows fast switching with a full bore. A throttling or control valve is intended to vary flow area rather than to shut off completely, and that difference drives the trim construction. Every valve type has its own working principle, and that principle determines where the type is strong and where it falls short. That principle explains why isolation valves behaves differently from a standard execution under heavier duty. For isolation valves this means that construction and operating conditions cannot be judged separately. What weighs heaviest on isolation valves in practice is the combination of temperature and differential pressure, not either one alone. A butterfly valve closes with a rotating disc in the line, giving the most compact and lightest solution at larger diameters. Directional valves are not about shutting off but about routing flow to one of several outlets. With isolation valves the difference between a good and a mediocre solution often sits in details that do not show on a drawing.
Specifications and executions of isolation valves
Double block and bleed arrangements provide a verifiable isolation, because the vent between the two seats proves it. A correct execution of isolation valves accounts for real operating conditions and not only for design values. How isolation valves behaves under varying load says more about the quality of the selection than behaviour under steady load. An isolation valve is not designed for throttling, and using it that way ruins the seat within a short time. A gate valve closes with a plate moving across the flow, giving an almost unrestricted bore but requiring a long stroke and considerable height. A balancing valve makes it possible to limit and measure flow in a branch, so that a system can be brought into balance. A check valve allows flow in one direction only and works without actuation, purely on the basis of the flow itself. Positive verification of the closed position matters more than speed of operation on this duty. In our advice we also state what a type cannot do, because that prevents more problems than a list of advantages. We regularly replace gate valves with metal seated butterfly valves, gaining on weight, space and operating torque. On isolation valves we always check the full operating envelope, including start up and shutdown. Operating conditions govern the service life of isolation valves far more strongly than the nominal figures on a datasheet.
Isolation valves in demanding installations
They are used for maintenance isolation, tank connections, pipeline sectioning and emergency shutdown. In chemicals the choice is driven mainly by medium compatibility and by the required tightness. In utilities and water treatment butterfly and gate valves dominate through their price at large diameters. We see demand for isolation valves rising in hydrogen and ammonia projects, where tightness requirements are high. Demand for isolation valves reaches us mainly from projects where the standard range falls short. On project supply we record per position which execution of isolation valves was delivered, including materials and tests. In an existing plant isolation valves is often part of a wider question about availability and maintenance. In process industry all types sit alongside each other in the same plant, each where that type is strongest. Alongside QUADAX and PRUSS we represent Pibiviesse, Schroeder, Striko, Malbranque, Daume, FluoroSeal and Guichon, so we can select the right brand for each project. Dutch Valve Vision supplies special valves for special applications from its base in Monster, the Netherlands, with QUADAX and PRUSS as the core brands in the programme. Our customers use isolation valves in positions where a failure has immediate consequences for production. During turnarounds isolation valves is regularly on the critical path, and then predictability matters more than the lowest price.
Selection criteria for isolation valves
For isolation valves we ask as standard for DN, pressure class, medium, temperature and required actuation. The required leakage class drives the choice between a soft and a metal seat more strongly than price does. Face to face length and weight weigh heavily at larger diameters, and there a butterfly valve often beats a gate or ball valve. Where there is doubt we quote two types side by side, with advantages and disadvantages stated explicitly. Where isolation valves forms part of a safety function we record the fail position and required stroking time explicitly. On isolation valves we check that the actuator is sized on torque at maximum differential pressure and not on an average value. If a simpler type will do the job, we say so on isolation valves, even when that means a smaller order. For isolation valves total cost of ownership weighs more than purchase price, certainly when replacement has to happen during a shutdown. Dutch Valve Vision deliberately does not supply every type, but focuses on the specials where the standard market drops out. When standardising across a plant we advise deliberately limiting the number of different types. If you have an existing tag plate or serial number, send it along, because that lets us work directly from the original configuration. The cleaning and flushing procedure counts too on isolation valves, because it can be more aggressive than the process itself. Standardising across several positions makes isolation valves simpler in maintenance and in spare parts management.
Ordering isolation valves from Dutch Valve Vision
We think along on the spare parts strategy for isolation valves, so critical positions stay covered. We work as a technical supplier rather than a catalogue reseller, which means we carry out the selection ourselves on the basis of medium, pressure, temperature and code requirements. For repeat orders of isolation valves we record the configuration, so a follow up delivery is identical to the first. For isolation valves you can come to Dutch Valve Vision for the selection, the delivery and the support afterwards. We quote a realistic lead time rather than an optimistic one, because a missed delivery date costs more than an extra week in the planning. We keep spare parts and overhaul kits mapped per project, so that a breakdown does not start with a search from scratch. Documentation on isolation valves has to be the kind a buyer or inspector accepts without discussion. We work on isolation valves under a KIWA ISO 9001 certified quality system, which safeguards traceability. On isolation valves we make sure the chosen execution demonstrably meets the stated standards rather than merely looking plausible on paper. On isolation valves we come back with a proposal that explains why we recommend a particular execution. Dutch Valve Vision stays available after delivery of isolation valves for technical questions and for parts. Call +31 (0)70-2210560 or send your specification to sales@dutchvalvevision.com and we will pick it up.
Frequently asked questions about isolation valves
What exactly does isolation valves mean?
A butterfly valve closes with a rotating disc in the line, giving the most compact and lightest solution at larger diameters. A throttling or control valve is intended to vary flow area rather than to shut off completely, and that difference drives the trim construction. A balancing valve makes it possible to limit and measure flow in a branch, so that a system can be brought into balance. A ball valve closes with a bored ball turning through a quarter turn, which allows fast switching with a full bore. The answer on isolation valves depends strongly on operating conditions, which is why we always ask for those first. For isolation valves a good specification up front is cheaper than a correction afterwards. The subject of isolation valves touches both the construction of the valve and the way the plant is operated. Our market is project driven and international, and we deliver worldwide to installers, EPC contractors and end users.
Which executions of isolation valves are available?
When standardising across a plant we advise deliberately limiting the number of different types. Double block and bleed arrangements provide a verifiable isolation, because the vent between the two seats proves it. A gate valve closes with a plate moving across the flow, giving an almost unrestricted bore but requiring a long stroke and considerable height. Positive verification of the closed position matters more than speed of operation on this duty. The answer to this question on isolation valves changes as soon as the medium or the temperature changes. If you are unsure about this on isolation valves, we are glad to put the question alongside the actual process data. We regularly see that a small change in the execution of isolation valves makes a large difference to maintenance frequency. Dutch Valve Vision operates under a KIWA ISO 9001 certified quality system, which in the RFQ stage of chemical and offshore projects is usually a hard requirement.
Which materials are used for isolation valves?
Dutch Valve Vision deliberately does not supply every type, but focuses on the specials where the standard market drops out. An isolation valve is not designed for throttling, and using it that way ruins the seat within a short time. A check valve allows flow in one direction only and works without actuation, purely on the basis of the flow itself. In our advice we also state what a type cannot do, because that prevents more problems than a list of advantages. In most projects isolation valves turns out to be less standard than it first appears. Our experience with isolation valves comes from projects in chemicals, power generation, technical gases and offshore. The balance between required tightness and available operating force is a recurring tension on isolation valves. Alongside QUADAX and PRUSS we represent Pibiviesse, Schroeder, Striko, Malbranque, Daume, FluoroSeal and Guichon, so we can select the right brand for each project.
What should I watch technically on isolation valves?
What should I watch technically on isolation valves?
Which applications call for isolation valves?
They are used for maintenance isolation, tank connections, pipeline sectioning and emergency shutdown. In chemicals the choice is driven mainly by medium compatibility and by the required tightness. In process industry all types sit alongside each other in the same plant, each where that type is strongest. In utilities and water treatment butterfly and gate valves dominate through their price at large diameters. This is one of the points on isolation valves where suppliers differ most clearly from one another. On isolation valves we prefer a well founded answer to a fast one that turns out to be wrong later. On replacement we always check the existing installation dimensions for isolation valves, so the pipework can stay untouched. We think along from the basic specification through to the tag plate, and supply documentation that a buyer or inspector accepts without discussion.
What determines the price and lead time of isolation valves?
If you have an existing tag plate or serial number, send it along, because that lets us work directly from the original configuration. We keep spare parts and overhaul kits mapped per project, so that a breakdown does not start with a search from scratch. For shutdowns and turnarounds we look at accelerated routes, and in those cases we are honest up front about what is and is not achievable. We come back with a proposal that explains why we recommend a particular execution, including the alternatives we considered. On isolation valves we include start up and shutdown, because that is where the heaviest loading occurs. That makes isolation valves a subject where discussion up front pays for itself in operation. Even when the specification for isolation valves is not yet finalised, you can bring the question to us. Requests can be submitted by phone on +31 (0)70-2210560, by e-mail at sales@dutchvalvevision.com or through the contact form on our website.
What about maintenance and spare parts on isolation valves?
We quote a realistic lead time rather than an optimistic one, because a missed delivery date costs more than an extra week in the planning. Lead times depend on the execution, because a standard size from a running series behaves very differently from a valve in an exotic alloy with NACE certification. On repeat orders we record the configuration, so a follow up delivery is identical to the first and installation holds no surprises. Documentation such as material certificates, test reports and declarations is supplied as standard, matched to what the project requires. On isolation valves we prefer a well founded answer to a fast one that turns out to be wrong later. We always explain why we arrive at a particular recommendation on isolation valves, so you can follow the reasoning yourself. A tag plate with project data belongs with isolation valves as standard where the project requires it. Dutch Valve Vision supplies special valves for special applications from its base in Monster, the Netherlands, with QUADAX and PRUSS as the core brands in the programme.
How do I request a quotation for isolation valves?
For an accurate quotation we need the nominal diameter, the pressure class, the medium, the operating temperature and the required actuation. Please also state the connection standard, the required leakage class and any project requirements such as NACE, PED or ATEX. A P&ID, a datasheet or even a photograph of the existing installation often helps us faster than a long description. Lead times depend on the execution, because a standard size from a running series behaves very differently from a valve in an exotic alloy with NACE certification. On isolation valves we prefer a well founded answer to a fast one that turns out to be wrong later. The answer on isolation valves depends strongly on operating conditions, which is why we always ask for those first. Our specialists are happy to discuss isolation valves on the basis of your P&ID, your datasheet or simply a photograph of the situation. Bring us your question at sales@dutchvalvevision.com or +31 (0)70-2210560, even when the specification is not finalised yet.