Flow controls are pretty basic little valves, but like everything else, they are only easy if you already understand how they work. In hydraulics, two general statements could be:

1. Control the flow (gpm, or gallons per minute) and you control the speed of your actuator.

2. Control the pressure (psi, or pounds per square inch) and you control the force of your actuator. (hydraulic cylinder or hydraulic motor)

Flow controls can be as simple as a needle valve, that has two ports and a single adjustable portion (the “needle,”) and the flow will be the same going through this valve from either direction. Then we have what is normally called a flow control valve, which is basically a needle valve with a check valve in one body. The needle portion controls the flow going one direction, and the check valve allows free reverse flow around the needle going in the opposite direction.

At this point, I am sure there are a few people grinding their teeth with the two descriptions that I gave above. More accurately, a “needle” valve has a sharper taper on the control portion for finer control capability, and a “flow control” valve has an adjusting stem that is still tapered, but not to the degree that the needle valve is. However, colloquially speaking, the two descriptions above are how many people think of them.

Here is a question from a meat processing maintenance manager with flow control issues:

How do I keep our hydraulic flow controls operating in a washdown environment? USDA is always on me about rust, so I need stainless steel. But even these have their stems become locked up after just a few weeks of sanitation washing down the production floor, and I am forced to install new ones all the time. And even when the flow controls work, sometimes the conveyor speeds just change on their own. How can I keep a constant conveyor speed?

HS-Innovation Solution:

You asked two good questions above, and I’ll give you the short answer here.
HS Innovations designs speciality and innovative components for the meat processing industry, and we have an all stainless steel washdown flow control that has the adjusting stem completely encapsulated and we fill the cavity with food grade grease. These will stay adjustable in any washdown environment with caustic chemicals in any production area. And they are a cartridge style valve, so in the event that your hydraulic system gets contaminated (I know what you’re going to say, and I’ll just say that it happens to all of us sooner or later), you don’t have to disturb any piping with these valves, just replace the cartridges. You can get them in a single body style, or in a manifold with multiple flow controlled ports with just one supply and return line connection.

As far as keeping your conveyor speeds constant, you need to install “pressure compensated flow controls”, not the regular type of flow control. The cartridge washdown flow controls I mentioned above are pressure compensated. That means if your supply pressure goes up or down, or your conveyor gets full or empty, this flow control automatically adjusts itself internally to “compensate” for these varying conditions, giving the same flow output regardless of the system variables.

The HSI washdown pressure compensated flow control is 100% stainless steel on all the metallic parts, and can be supplied in an in-line body, or in a three station manifold assembly. This pressure compensated flow control is adjustable from 0.05 to 7.5 gpm, and it will remain adjustable for as long as it’s installed, even in a washdown environment. The sealed cover assembly is pre-lubricated with food grade grease, and never needs to be serviced. As with nearly all other hydraulic components, these flow controls will work best with clean fluid passing through them. Because the spring loaded hydrostat has such close tolerances, a contaminated hydraulic system will cause these valves to partially lock up and you will observe a very “herky-jerky” type of actuator travel, rather than a smooth operation.

Please feel free to email me directly about any questions or comments you may have.
kurt.kutz@hs-innovations.com