How Robolux can reduce wastage and dead volume in the pharmaceutical industry

The problem with traditional diaphragm control valves

A diaphragm valve is the only truly hygienic valve. There are other valves that are listed as being hygienic, which are used in breweries and dairies, but in the ultra-pure biotechnology and pharmaceutical industries they exclusively use diaphragm valves. This is because diaphragm valves are easy to drain; they’re two-way, so have two connections; there are no crevices inside; they provide a smooth flow through them; and you can polish the insides, so they’re very sterile.

The problem arises when you want to divert flow from one pipe into a secondary pipe. That always presents a potential dead leg. Unless you get the valve on the absolute outer edge of that tube there will be a small volume of fluid that can just sit there when that valve is closed. You will still have flow going along the horizontal pipe but then you also have this little pocket of fluid that has the potential for bacteria to grow in it.

The pharmaceutical industry is obsessed with dead legs. There’s a rule in ASME and British Standards that says that the maximum dead leg can be no more than two pipe diameters. If you have a two-inch pipe going one way, and you’ve got a one-inch pipe coming off the bottom of the tube, then the absolute maximum dead leg should be no more than two inches – two diameters of the one-inch pipe.

There are various ways that companies have tried to get around this by combining valves together into a block. Instead of having two individual valves, one horizontal and one vertical, you can then machine a block of stainless steel that has two valve seats in it. Then you put two actuators on it, which reduces the volume and it goes on from there. You can get blocks that maybe have three or four valve seats on them, which can then become massive.

Bürkert Robolux pneumatic diaphragm valve

The problem with a standard pneumatic diaphragm valve is that it’s just a single seat valve with an inlet, an outlet and an actuator on it. The diaphragm opens and closes to let flow through the valve. With a lot of valves used in industry, you can have a two-way valve and a three-way valve, so you have a third port inside the valve and the actuator closes one port and opens another. You can’t do that with a traditional diaphragm valve because it’s only a two-way valve. Bürkert introduced the Robolux valve, which employs two pistons in one actuator to create a three-way type diaphragm valve.

A conventional diaphragm control valve has a weir across the middle that seals the flow from one side to the other. The Robolux valve has two weirs and a gap in between the two, which is like a third port. The actuator allows you to open one weir, so the flow comes in and then goes out through the middle outlet. You can close that weir and then open the other weir and get flow from the other way and that goes out of the outlets. Conversely, if you have flow coming up from the middle, you can divert it one way or the other. It then becomes a divert or mixing valve. There is no other pneumatic diaphragm control valve that can do that.

The beauty of the Robolux is that we’ve developed a way in which you can put an actuator on either side of the valve. If you take this valve with two weirs on one side and then machine the same on the other side you then have four valves in one small block with two actuators on it. A 4-valve seat block using a conventional pneumatic diaphragm valve is quite a big lump of stainless steel. We can get the same functionality with a much smaller lump of stainless steel. As such, a valve block based around Robolux is considerably smaller and lighter than a conventional block, which is an important factor when it comes to installation.

Robolux reduces dead volume by 50%

If you have a diaphragm control valve in a certain orientation and you open it, it will drain itself. When you start to combine these in a block, so that you have multiple seats, you can never get it to drain – there’s always an internal dead volume. That can be a problem, certainly for some parts of the Pharmaceutical industry, where the product they’re manufacturing is very high value. That little volume of product could be worth several thousand pounds.

When you get these big valve blocks, the basic cost is the piece of stainless steel that you’re machining and polishing. It can take weeks to do that and that’s where all the cost is. What we’ve done with the Robolux valve is make that block a lot smaller. Also, because we’ve got this double weir valve, the internal dead volume inside the valve is reduced by 50% or more.

The Robolux valve reduces that internal waste and so reduces the cost of lost product. It also makes it possible to make the valve block more complicated and get more valves into it because each valve in itself is a 3-way valve rather than just a 2-way valve. With Robolux, you can get more diaphragm valves in the same space of valve seats than a conventional one.

For more information about the Robolux valve, or to discuss your application requirements in more detail, please contact our sales team today on +44 (0) 1285 648 720 or email sales.uk@burkert.com.

Robolux multiway diaphragm valve, pneumatically operated

Type 2036

• Extremely compact and space-saving design
• Reduced installation costs
• Reduced number of valves and welds