Automatic control valves, much like everything else we purchase these days, are not all created equal. Some fall into the high quality bracket with pricing to match, while others hover closer to the lower quality and price sensitive end of the scale. Unfortunately, when evaluating control valve prices, it is not always clear what you are being offered and what standards the valve actually meets. Here are a few questions to consider and ask the supplier to ensure you get years of trouble free operation that lasts longer than it takes the sales person to drive out of your parking lot!

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Q 1 What materials are being used?

Make sure you know what the different components of the valve are made of, as this will certainly affect the life of your valve, specifically:

Body Material ' is the valve body cast iron or ductile iron? Traditionally valves were cast iron but ductile iron has become the new standard due to its superior physical properties that are much better at weathering the elements.

Body Coating ' Most of the world insists on fusion bonded coating of a valve, inside and out. Unfortunately here in North America, that is not always requested. This just makes common sense for valves that are constantly wet and sit in locations that are not always dry and pristine. A valve should last for many years, so insisting on a coated valve is a wise choice.

Seat Material ' bronze is typically the common material for seats but over time, depending on water quality and velocities, bronze wears resulting in the need for replacement. This is time consuming and expensive as seat replacement requires a complete disassembly of the entire valve. Ideally go for stainless steel.

Valve Internals ' Most valve manufacturers utilize stainless steel for their valve stems. Make sure that you ask what grade of stainless you are getting as not all stainless steel is created equal. 316 SS is always the best choice because it is harder and least likely to corrode.

External Fasteners ' Over time valves experience condensation or flooding and this can play havoc with coated studs or bolts. There is nothing worse than trying to remove heavily rusted studs out of an old valve to perform maintenance. Request stainless steel fasteners as this will ensure that bolts will be removable at any age.

Q 2 Does the valve supplier fully understand your application?

Too frequently a specification will be requested and a valve is supplied that is simply the wrong valve for the job. It may also be the case that there is just a better solution. Ensure you give your valve supplier all the necessary pressure and flow details including details of the actual application and what you want this valve to do. Having the wrong valve for the wrong application, at best case will result in a significantly shorter life and worst case, a malfunction that can result in destruction of the valve and other parts of your water distribution system.

Q 3 Will this new valve fit into my existing piping layout?

Don't be tempted to just stay with brand X because that is the valve you may be replacing and has the same lay lengths. Most manufactures can be quite innovative on providing solutions to combat varying lay lengths so explore all of you options rather than just settling because you think it may be easier.

Q 4 Do you need specialty tools for maintenance?

Nobody wants to have to carry around a specific tool that only performs one task. Ensure that your valve can be maintained with everything you would carry in regular tool kit. Some valve manufacturers require specialized seat removal tools, or vice jaws installed with copper jaws to protect valve stems. While these are great ideas, they are certainly not things that the average operator has in his toolkit.

Q 5 Will your personnel receive complimentary factory qualified training?

Control valves are not so difficult to understand and once taught, most operations personnel can easily perform maintenance. Ensure that you will not be reliant on the additional cost of having to bring out a factory person every time your valve requires maintenance. Request that a factory-trained representative is on site when the valve is commissioned. This will allow your operators to be schooled in the regular maintenance needs, know what to look for if things go awry and how to start up a valve in a new system or after service. Simple tricks like removing air out of the pilot system are valuable lessons to see in practice.

Q 6 Does your valve have a solid warranty?

These days having a product with the long term back up of the factory is important. Three years should be the standard to ensure there are no manufacturing faults.

Q 7 Can I make changes to the valve if required

Having a valve 'expansion ready' for the future can save you money and make your decisions a whole lot easier. For example, can you add a limit switch or a position indicator easily? Or, if you need to move the pilot system to the other side of the valve, can you do it, or is it not possible because the valve body does not have the required connections? Things always change and a flexible valve gives you more options to keep your now perfect valve, perfect down the road.

Q 8 Does your valve meet industry standards?

There are third party accreditations that ensure your valve was built to the correct specifications. For example; NSF 61, WRAS, UL/FM, AWWA, ISO et.al. They are important because they ensure that the valve has been built to a given standard so the user can be assured they meet approval for such things as low lead content, bacterial growth tests, functional tests etc.

Q 9 Do you have local and factory support?

Make sure there is someone in the area that is factory trained and available to come out and assist when you have questions or problems. This sounds like a given but it's best to ensure the local agent will in fact be there for you when you need him. When a valve fails, timing is usually of the essence so you should know whom to call prior to such an event.

Q 10 Is the valve solution offered able to handle future needs?

In the world of 'low bid wins', a supplier may be tempted to squeeze as small a valve as possible into the application in order to reduce price. Make sure that the offered solution will supply your needs for the foreseeable future without the burden and additional cost of having to change a valve in a couple of years.

How To: The Top 10 things to consider when selecting industrial valves

So you have been tasked with selecting industrial valves for project or maintenance work and given a list of what valves, sizes and specifications. Great!!

However, how much thought has been given to whether the specification is right, the valves will be suitable, and if they will be right for the job?

There are many assumptions around valve selection, the most common of which are:

• 'this is what we used before'  ' on an entirely different process

• 'contractor x said this is what we need to use' ' based on what? 

• 'the site standard is x' ' but what if that type of valve wont work on this application

• 'this is what we have always used' ' but have been experiencing downtime and regular failures

Getting your valve selection right from the get go is really important and in this article I will walk you through a simple 10 step process to help you ensure your valve selection is based on facts rather than assumptions.

1. What is the purpose of the valve?

Valves can be used on various different duties and perform a variety of different functions.  The best starting point when selecting any valve for industrial use is to decide what purpose it will serve.  Some things to consider might be:

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• Will it be used to control or isolate media?

• Will it be used many times a minute or every few months for maintenance?

• How critical is it to your process and what would happen if it failed?

• Is it a valve that will need to work in an emergency?

Having this clear in your mind will make it a lot easier to select the right valve for the job!!

2. What is the pressure of the media going through the valve?

In deciding what valve will be most suitable for your application you should always ascertain the pressure. On high pressure applications, specialist valves will be the norm, and these types of valves typically have thick wall diameters to cope with the pressure. They also have specialist sealing arrangements like you would find on Trunnion Mount Ball Valves. On low pressure applications where bubble tight shut off is not imperative, a valve may not be the best solution at all. A good example of this is on low pressure air/exhaust applications where a 'damper' would be more cost efficient and lighter in weight.

3. What is the temperature of the media going through the valve?

Temperature is also a minimum requirement for selecting Valves. Valves that are seeing extremes of temperature will often be 'bespoke' as opposed to 'off the shelf'.  The two main considerations with temperature, are (a) whether the materials of construction will be suitable and (b) whether the valve will seal against the temperature. Your supplier can advise you on the most suitable body material and sealing design. A good reference point here is the use of pressure/temperature charts which show how the temperature limitation of a valve will decrease as the pressure rises. These are available for most types of valves.

4. What media will be going through the valve?

Some things to consider when it comes to media:

• Are you processing something self-lubricating like food oil or engine oil?
• Is it something abrasive like sand or powder?
• Could it be something dry like air or gas?
• Is bubble tight shut off something you definitely need, or can this be sacrificed in order for the valve is used more like a 'barrier' or 'gate'?
• What are your expectations regarding maintenance, and can you invest in a higher specification 'fit and forget' valve which will mean less maintenance down time?

There are a lot of questions around media but ascertaining this at the outset and communicating this to your supplier will mean the right valve is selected and minimise downtime as a result.

5. What are the environmental conditions where the valve will be situated?

Not all valves are going to be situated indoors in an ambient, dry and dust free environment.  Therefore think about where your valve will be fitted.  Could it be on the end of a Jetty in a saline environment? In the middle of a dry, sandy desert in extreme heat for most of the day? Submerged in water? It isn't the end of the world if the valve location is not hospitable.  It just means that the materials and particularly the exterior coatings and internal seals will need to be suitable to withstand the environment. 

6. Is the valve likely to be noisy?

Sometimes valves can be noisy and a good example of this would be a Control Valve on high pressure steam.  This doesn't matter if the valve will be located inside in an area that is well noise insulated, but could be an issue outside when in close proximity to houses and other buildings.  Low noise trims are available on such valves to mitigate some of this noise but its best to get this clarified at design stage as it can be something that catches engineers by surprise.

7. Will the valve be manually operated or automated?

Most modern plants are moving towards automation, but in some instances valves that are rarely used, or just used for maintenance or isolation are kept as manual valves.  Where you are looking to automate a valve, there are a few points worth considering:

• Will you actuate with an Electric or Pneumatic Actuator?
• What will the pressure, temperature and media be (for correct actuator sizing)?
• What is the supply voltage or instrument air pressure available?
• Do you need open/closed feedback indication to your control room?
• Would you like to control the opening and closing 24VDC/110VAC/240VAC?
• Does ATEX apply to the area in which the valve will be situated?

8. Do you need to use the valve for control?

Control is easily achieved in an actuated valve and the easiest way of achieving crude control on a ball or butterfly valve is with a 4-20mA Electro Pneumatic Positioner or a 4-20mA Potentiometer Card (in the case of an Electric Actuator).  Another great option for greater control is a V-Ball or Ball Sector control valve.  Where very accurate control is required, it will be worth considering a rotary control valve, or linear globe style control valve which is sized on a bespoke basis. These will generally be more costly but where control is critical they are generally the best option.

9. Valve dimensions.

Sometimes valves arrive on site for fitting and at that point the fitters realise that there is not enough space. The hand-wheel fouls on adjacent pipework, the valve actuator is hitting a tank, or the lever is hitting some steelwork.  The majority of valves have a dimensional datasheet available, so always get a copy of this and double check that the valve will fit into the space you have available.  There is nothing more disheartening than that call from a frustrated fitter with a hefty quotation for altering pipework.

10. Weight & Supports

Valves by their very nature can be heavy ' very heavy in fact. Large bore valves with actuators and additional controls can weigh over 500kg.  This puts quite a lot of stress on pipework, so always factor this in when you are designing a system that is likely to have large valves installed.  A common place where this can become an issue is ducting and HVAC type installations where the ducting is quite lightweight. As with valve dimensions your supplier should be able to supply you a datasheet with valve weights in kilograms. With actuated assemblies they will calculate for you a weight with actuator, valve, switchboxes and other ancillaries combined.

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