Small pressure reducing valves have long been used to control the pressures into the glands of slurry pumps. Multi-stage pumps need several pressure reducing valves, each set differently.
We bump into problems with this approach:
- Pressure reducing valves can be adjusted – people set them incorrectly.
- Increased demand from one gland (perhaps because of a problem) can mean less water available to the other glands. The pressure reducing valve supplies as much water as needed. It doesn’t restrict the demand.
- Pressure reducing valves are vulnerable to dirty water.
The Maric flow control valve solves these prolems.
- It regulates the flow rate accurately regardless of pressure changes.
- It can’t be adjusted and is tamperproof.
- It cleans itself. That means it works fine even in dirty water.
Here’s how it works
The Maric flow control valve has a flexible rubber control ring. It’s orifice diameter responds instantly to changes in water pressure. As the pressure differential goes up, the orifice gets smaller. As it goes down, the orifice gets bigger. That means that the flow rate stays the same. The flexing of the rubber reduces the risk of blockage and gets rid of scale. It’s a good choice for poor quality water.
The Maric valve is robust. It can withstand the maximum recommended differential pressure for short periods. If the long term differential pressure is likely to be more than 20bar it needs some help, perhaps a pressure reducing valve upstream or a relief system downstream.
We recommended that you install a check valve downstream of the Maric valve if you’re using it for slurry pump service water control. This will keep slurry out in case of momentary reverse flow. Maric make a combined flow control and check valve. It fits into a smaller space than 2 separate valves and again the rubber control ring keeps itself clean.
Due to the critical and expensive nature of the equipment being protected, some clients install a complete “train” which includes an isolating valve, the Maric valve, check valve, pressure gauge, flow meter or indicator. I’ve even seen pressure and flow transmitters to monitor in their control room.
The Maric Valve is available in various configurations as follows:
- Screwed ends from 6mm up to 50mm and in various material (Stainless, Brass, PVC)
- Wafer Pattern (fits between flanges) from 20mm up to 400mm (larger on request)
- Inserts for Flow Meters, Shower heads etc
A more complete version of this article is available here: The use of Maric Flow Controllers on Slurry Pump Gland Service Water