Emergency stop valve
Emergency stop valve: what matters in practice
Emergency stop valve: the working principle in practice
An emergency stop valve shuts off supply within a defined time when a hazardous condition occurs, which makes closing time a safety parameter rather than a performance figure. The subject of emergency stop valve touches both the construction of the valve and the way the plant is operated. With emergency stop valve the difference between a good and a mediocre solution often sits in details that do not show on a drawing. Condensate carried along in a steam line causes erosion and water hammer, and both attack a valve faster than the steam itself. Steam is a demanding medium because pressure and temperature rise together and the medium can change phase within the same line. In superheated steam the temperature sits above saturation, and soft seats and ordinary packings are then no longer usable. We regularly see that a small change in the execution of emergency stop valve makes a large difference to maintenance frequency. For emergency stop valve this means that construction and operating conditions cannot be judged separately. How emergency stop valve behaves under varying load says more about the quality of the selection than behaviour under steady load. A pressure reducing station brings steam pressure back to the level the consumers require and holds that pressure stable under varying demand. A turbine bypass routes steam around the turbine during start up and on a trip, and that valve has to handle a large duty within seconds. There are assumptions circulating about emergency stop valve that do not hold up under closer examination.
Material, seat and construction on emergency stop valve
The valve normally stays in one position for long periods, which means it must be certain to move when it is finally called on. With emergency stop valve it pays to include phase changes in the medium, because those sharply increase the load on the seal. What weighs heaviest on emergency stop valve in practice is the combination of temperature and differential pressure, not either one alone. A partial stroke test keeps the valve exercised without interrupting the process, and it is often a requirement in a safety loop. On a boiler, blowdown valves control the salt content of the boiler water, with continuous blowdown for fine control and periodic blowdown for sludge at the bottom. A desuperheater injects water into the steam flow to bring temperature back to just above saturation, where atomisation quality determines the result. An emergency stop valve shuts off supply in a hazardous situation, and closing time there is a safety parameter rather than a comfort requirement. The fail position and the actuator energy source both follow directly from the risk analysis of the installation. On commissioning we record set pressure, closing time and test results, so the plant can be shown to run within specification. Insulation around a steam valve should leave the actuator clear, because overheating of the actuator is a common cause of failure. That principle explains why emergency stop valve behaves differently from a standard execution under heavier duty. With emergency stop valve the seat is the component that determines performance, and the body is rarely the limiting factor.
Sectors and applications for emergency stop valve
Emergency stop valves are used on turbines, boilers, fuel supply lines and in any installation with a defined safety function. In power generation these valves sit on the critical paths around boiler and turbine, where downtime costs money immediately. Boiler houses, combined heat and power plants and district heating together form the largest application area for these valves. In an existing plant emergency stop valve is often part of a wider question about availability and maintenance. We supply emergency stop valve both for new build and for replacement within existing installations. Demand for emergency stop valve reaches us mainly from projects where the standard range falls short. On project supply we record per position which execution of emergency stop valve was delivered, including materials and tests. In process industry steam is used for heating, stripping and sterilisation, and each of those duties sets its own requirements. What defines us is that we would rather spend an extra half hour on the specification than ship the wrong valve that comes back two months later. Our customers work in chemicals, petrochemicals, pharmaceuticals, power generation, offshore and in hydrogen and ammonia projects. During turnarounds emergency stop valve is regularly on the critical path, and then predictability matters more than the lowest price. The application range of emergency stop valve runs from simple utility duty to heavy process plant, with a corresponding difference in execution.
Specifying emergency stop valve correctly
Standardising across several positions makes emergency stop valve simpler in maintenance and in spare parts management. Material selection for steam moves towards alloy steel with hardened trim, because erosion and thermal cycling weigh heaviest. A steam test device makes it possible to test the operation of safety valves while the plant stays in service. At large pressure ratios we use multistage or perforated trim to keep noise and erosion within acceptable limits. Where emergency stop valve forms part of a safety function we record the fail position and required stroking time explicitly. We never recommend a heavier execution of emergency stop valve than needed, because over specification only raises price and lead time. For emergency stop valve total cost of ownership weighs more than purchase price, certainly when replacement has to happen during a shutdown. On emergency stop valve we check that the actuator is sized on torque at maximum differential pressure and not on an average value. PRUSS is strongly represented in this segment with valves for steam, boiler, turbine and gas turbine duty. On steam we always advise a condensate drain upstream of the valve, because it is the cheapest life extension available. We come back with a proposal that explains why we recommend a particular execution, including the alternatives we considered. On emergency stop valve we also state what an execution cannot do, because that prevents more problems than a list of advantages. For emergency stop valve we ask as standard for DN, pressure class, medium, temperature and required actuation.
Requesting emergency stop valve from Dutch Valve Vision
On emergency stop valve we come back with a proposal that explains why we recommend a particular execution. 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. Dutch Valve Vision stays available after delivery of emergency stop valve for technical questions and for parts. For emergency stop valve you can come to Dutch Valve Vision for the selection, the delivery and the support afterwards. Our specialists are happy to discuss emergency stop valve on the basis of your P&ID, your datasheet or simply a photograph of the situation. 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. Documentation such as material certificates, test reports and declarations is supplied as standard, matched to what the project requires. Tests around emergency stop valve are carried out by us or on our instruction according to the requirements in the specification. We record which execution of emergency stop valve was delivered, so a follow up delivery or spare part matches exactly later on. We keep the configuration data for emergency stop valve on file, which saves a great deal of searching if a fault occurs later. For repeat orders of emergency stop valve we record the configuration, so a follow up delivery is identical to the first. Even when the specification for emergency stop valve is not yet finalised, you can bring the question to us. You can reach us on +31 (0)70-2210560 and at sales@dutchvalvevision.com, and our office hours are Monday to Friday from 09:00 to 17:00.
Frequently asked questions about emergency stop valve
What exactly does emergency stop valve mean?
An emergency stop valve shuts off supply in a hazardous situation, and closing time there is a safety parameter rather than a comfort requirement. Condensate carried along in a steam line causes erosion and water hammer, and both attack a valve faster than the steam itself. A desuperheater injects water into the steam flow to bring temperature back to just above saturation, where atomisation quality determines the result. On a boiler, blowdown valves control the salt content of the boiler water, with continuous blowdown for fine control and periodic blowdown for sludge at the bottom. If you are unsure about this on emergency stop valve, we are glad to put the question alongside the actual process data. For emergency stop valve a good specification up front is cheaper than a correction afterwards. Anyone looking into emergency stop valve quickly runs into a choice that goes beyond picking a catalogue number. Our market is project driven and international, and we deliver worldwide to installers, EPC contractors and end users.
Which executions of emergency stop valve are available?
Steam is a demanding medium because pressure and temperature rise together and the medium can change phase within the same line. The fail position and the actuator energy source both follow directly from the risk analysis of the installation. Insulation around a steam valve should leave the actuator clear, because overheating of the actuator is a common cause of failure. In superheated steam the temperature sits above saturation, and soft seats and ordinary packings are then no longer usable. We always explain why we arrive at a particular recommendation on emergency stop valve, so you can follow the reasoning yourself. The answer on emergency stop valve depends strongly on operating conditions, which is why we always ask for those first. A correct execution of emergency stop valve accounts for real operating conditions and not only for design values. 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 emergency stop valve?
A pressure reducing station brings steam pressure back to the level the consumers require and holds that pressure stable under varying demand. A partial stroke test keeps the valve exercised without interrupting the process, and it is often a requirement in a safety loop. On commissioning we record set pressure, closing time and test results, so the plant can be shown to run within specification. PRUSS is strongly represented in this segment with valves for steam, boiler, turbine and gas turbine duty. On emergency stop valve we prefer a well founded answer to a fast one that turns out to be wrong later. This is one of the points on emergency stop valve where suppliers differ most clearly from one another. The balance between required tightness and available operating force is a recurring tension on emergency stop valve. 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 emergency stop valve?
What should I watch technically on emergency stop valve?
Which applications call for emergency stop valve?
Boiler houses, combined heat and power plants and district heating together form the largest application area for these valves. In power generation these valves sit on the critical paths around boiler and turbine, where downtime costs money immediately. Emergency stop valves are used on turbines, boilers, fuel supply lines and in any installation with a defined safety function. In process industry steam is used for heating, stripping and sterilisation, and each of those duties sets its own requirements. The answer to this question on emergency stop valve changes as soon as the medium or the temperature changes. In most projects emergency stop valve turns out to be less standard than it first appears. On replacement we always check the existing installation dimensions for emergency stop valve, 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 emergency stop valve?
For an accurate quotation we need the nominal diameter, the pressure class, the medium, the operating temperature and the required actuation. If you have an existing tag plate or serial number, send it along, because that lets us work directly from the original configuration. 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. On repeat orders we record the configuration, so a follow up delivery is identical to the first and installation holds no surprises. That makes emergency stop valve a subject where discussion up front pays for itself in operation. On emergency stop valve we include start up and shutdown, because that is where the heaviest loading occurs. We supply emergency stop valve as a loose product or as a fully assembled unit with actuator and accessories. 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 emergency stop valve?
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. Documentation such as material certificates, test reports and declarations is supplied as standard, matched to what the project requires. 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 keep spare parts and overhaul kits mapped per project, so that a breakdown does not start with a search from scratch. We see this come back regularly in enquiries about emergency stop valve, and the answer is rarely a single sentence. We always explain why we arrive at a particular recommendation on emergency stop valve, so you can follow the reasoning yourself. Material certificates and test reports are supplied with emergency stop valve, matched to what the project requires. 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 emergency stop valve?
A P&ID, a datasheet or even a photograph of the existing installation often helps us faster than a long description. Please also state the connection standard, the required leakage class and any project requirements such as NACE, PED or ATEX. We come back with a proposal that explains why we recommend a particular execution, including the alternatives we considered. 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. This is one of the points on emergency stop valve where suppliers differ most clearly from one another. On emergency stop valve we include start up and shutdown, because that is where the heaviest loading occurs. We handle an enquiry for emergency stop valve on its technical merits rather than as a price request that only produces a number. Bring us your question at sales@dutchvalvevision.com or +31 (0)70-2210560, even when the specification is not finalised yet.