What is the Trouble with Penstock Valves? (Transcript)
Hello, my name’s David Cole and I’m Technical Director of Penstock Solutions and I’m here to talk to you today about the trouble with Penstock Valves.
What is a Penstock Valve?
What is a Penstock Valve, well, that’s a difficult question to answer. Penstock Valve is an interesting term, it’s a generic term. You’ll find it in the Oxford English Dictionary as a device that’s used to control flow. What’s happened now is that these valves are being used for stopping a flow when they are actually designed for controlling a large flow capacity or large volumes of water.
Why are Penstock Valves Used in water pollution containment?
Penstock Valve is a generic term that’s been used for many years as, and indeed become synonymous with, a pollution containment device and a lot of civil engineers are specifying Penstock Valves for that purpose. It’s a little bit like Hoover. If you mention the word Hoover everyone thinks of a vacuum cleaner but the word Hoover is just a brand name that overtook the actual name, vacuum cleaner. Its the same with the phrase Penstock Valve. Penstock Valve is the term for a device that’s used in situations where you need to control a flow. When water pollution containment became a priority for the regulators the response was we’ll stick a Penstock in there. The real danger is when you use the words Penstock Valve you are actually referring to a whole range of devices. When you place the words Penstock Valve into a building schedule design the builder can go out and buy the simplest, cheapest Penstock Valve when actually what’s required is a pollution containment device.
Why shouldn’t Penstock Valves be used for water pollution containment?
We have established that Penstock Valve to me is too generic a term, and there is such a huge number of different types of Penstock products available. We actually used the word Penstock in the name of our business because that’s what our product is, it can be used as a Penstock type device, a flow control device and that’s the problem. People take a Penstock Valve which is a generic term and think it is a pollution containment device, but actually, a Penstock Valve has a leak rate and they are actually quite slow moving devices, even when you put mains power to them to turn it up and down, open or closed, when the valves get quite large they take several minutes to operate, and it isn’t always a very easy thing to do. So lots of companies have taken the Penstock Valve and they’ve used it for pollution containment and it’s actually the wrong product.
There are quite a few different challenges with a Penstock Valve that we need to go back on. One of the major ones is that ultimately a Penstock Valve is a simple manual, wheel device. Whilst we can fit actuators to them, that requires four fifteen to thirty-volt power units, which means you have to get mains power to them. When you’re looking at a pollution containment system, I think it’s really important to look at what you’re actually trying to achieve.
A pollution containment system is likely to be called into action at the time of an emergency. There’s a lot of sites that have installed a Penstock system, a simple Penstock system with a wheel on it that somebody goes and operates. Then you’ve got to ask yourself the question, so this factory is on fire, and my Penstock valve is across the road, down the riverbank at the end of the site; who goes to operate a valve in the case of an emergency? This factory is on fire and you need someone to be able to go and operate a valve when really you should be evacuating staff and knowing where people are. It’s the last thing you’re really thinking about in an emergency. So, when we look at these devices, when we look at the way they are operated and the way they work we have to start looking at the appropriateness of the functionality of this equipment.
So, the biggest fundamental issue is that they leak. Penstock Valves that were designed to hold back huge volumes of flow. Massive volumes in the water industry where we’ve got a continuous flow of water through a drain pipe, through a sewer. Whereas when we are dealing with firewater containment, pollution containment devices where a Penstock is normally used in an emergency, there might be no flow whatsoever through that drain at the time we need to activate the valve. Once we activate the valve it might just be a small trickle of cyanide or some other really nasty chemical that’s just flowing through and the Penstock Valve you’ve installed can’t actually contain that small flow. Quite often, when these products are installed, there’s no actual way of actually getting to them in an emergency. They’re completely forgotten about and they can’t’ be activated until several minutes or maybe hours after an incident has taken place.
Maintenance of Penstock Valves. It’s quite an interesting area because if you look at, a typical six hundred diameter pipe with a Penstock Valve on it, this might be within a chamber itself. As a business we often go to service these pieces of kit and somebody has put the biscuit on top of that manhole chamber! That valve then can’t be removed without a complete removal of the above ground biscuit which involves digging it out. So when you come to maintain that valve, and yes, they’ve got a very long serviceable life, they were designed to control flow for many many years but there’s not actually that much on them that can be removed to be repaired and most often the placement won’t allow you to remove the whole device without major maintenance work.
What are the Alternatives to Penstock Valves?
There are a few alternatives that I’d use for Penstock Valves and one of them is our ToggleBlok device which was actually developed by myself many many years ago to address the need for a pollution containment device which isn’t a flow control device. I need a valve that sits alone, that can be easily fitted into existing infrastructure where I’m not going to need to completely remove a manhole cover to get it into the drain. I can put it in a modular section if it breaks down, I can take it apart and replace each of the component parts. The important processes is it must stop a flow very simply and very quickly. Most of the pollution containment devices that we produce are going to close a drain down within about five seconds of activation. It needs to be remote so that no human being needs to actually physically get there to operate this valve. It needs to be something that can connect simply into the fire alarm system or operate by your mobile phone device. It needs to be something that can be used and you can understand that it has worked and it’s closed and it needs to be a simple device that can be used completely off-grid because I’m afraid, good chance if you’ve had a major incident, you might have lost your mains power.
It’s quite often that pollution events happen at factories when there is a power failure and processes fail, we might get the overfilling of tanks because valves failed to shut and we get overfilling of banks so we get a flow off and that’s when we need a pollution device to work, when we actually have no power. So, the devices we use as an alternative are pollution containment valves that are stand-alone. A pollution containment device can’t be reliant on mains power that comes from your facility. Pollution containment devices need to be easy to operate and must close almost immediately from when you activate it, or trigger it from some sort of safety device so it shuts your drainage down as soon as an incident takes place, not reliant on a human being walking to a site to turn a hand wheel or press a button.
What do you recommend to anyone whose water pollution containment relies on Penstock Valves?
Well, this is quite a difficult subject because there are hundreds if not thousands of industries in the UK that up until 2014 were recommended by the HSE and the regulator to fit Penstock Valves. The problem is that over time we’ve realised that that’s probably the wrong product as it is too generic and what you see now in guidance is they’ve changed the word, the word no longer exists in most of the guidance notes that are there and now they actually ask you to fit a pollution containment device. What that’s done is it’s changed the process of how you should be thinking about it. You may have a Penstock valve and you may have a system in place that says if we have a pollution event, we will close the drainage down using our Penstock valve. But what we really need to be doing is you need to understand does the product that you actually fit, does it work, is it fit for purpose? There isn’t really much point in waiting for an incident to happen, closing a valve, having a pollution event and then returning to the regulator in your defense and saying, well, the valve just leaked because you’re going to fail, you’re going to lose out potentially because guidances moved on. Something you might have fitted 10 years ago may not be fit for purpose in today’s environment and there’s a lot of pressure on businesses now to actually be much more sustainable and really control pollution to very much an nth degree. There is no real sort of tolerance to just a small pollution event it’s really the equivalent you’ve put in needs to work and make the best practice guidance now in place.
So, if anybody wanted to look at this particular subject the first thing is: do our six-point checklist. Understand regulation. Understand how that regulation impacts your particular business. Carry out a full risk assessment. Don’t scrimp on anything. Step four: design the appropriate system. Deliver that appropriate system and install it. Monitor, maintain and document the system that you’ve installed and be prepared to change it and improve it as guidances improve over the years.
So, if you’d like to know more please go to www.penstocksolutions.co.uk.
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David Cole MSEE
David is a pioneer of the spill containment and water pollution prevention industry with 30 years experience. He was instrumental in the development of CIRIA 736 with The Environment Agency and is passionate about preventing water pollution.