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The use of Maric Flow Controllers on Slurry Pump Gland
Service Water
Traditionally small Pressure Reducing valves have been used to control the
pressures into the Glands of Slurry Pumps. These pressures are normally
specified by the Pump Manufacturer and in the case of Multi-Stage pumps a
whole range of PRV’s with different setpoints have to be installed. Problems with
these installations are:
Adjustability of the PRV’s can create problems with “tampering” leading
to incorrect settings.
If any gland has a problem leading to increased demand, it could effect the
availability of water for the other glands being fed from the same supply
line, as a PRV will just supply more and more water to meet any demand.
PRV’s are vulnerable to dirty water.
A product which has been developed in Australia (some 30 years ago) and which
has become a popular solution for Gland Service water control is the Maric Flow
Control valve. This valve regulates Flow Rate irrespective of Pressure
fluctuations and will do so within 10% accuracy. This valve has a Rubber
Control ring which flexes to respond to varying Differential pressures across the
valve, thereby controlling the flow. The valve is non-adjustable and also
completely tamperproof. Because the Control Ring flexes continuously, thereby
providing a “self cleaning” action, it is not vulnerable to dirty water.
The following describes the operation of the valve
The Maric flow control valves utilize a flexible rubber control ring, whose orifice
diameter responds instantly to fluctuations in water pressure. As pressure
differential increases, the orifice diameter reduces to maintain the same flow.
Likewise, as pressure reduces, the orifice opens up to maintain the same flow
rate. These valves are particularly suitable for use on poor water quality, because
the flow controlling component is a rubber material, and flexes under normal
operation, which minimizes the risk of blockage, and eliminates scale build-up.
In High Pressure Gland Service Water there is a possibility of damage to the
Control rubber if differential pressure exceeds the maximum recommended of
20bar. It must be mentioned that Maric is extremely robust and can easily
exceed the maximum recommended Differential pressure for short periods.
In these cases some protection mechanisms can be considered ie Pressure
Reducing valve upstream of the Maric and/or a Relief System downstream of the
Maric. In Gland Service Water applications it is recommended to install a Check
Valve downstream of the Maric to ensure that Slurry does not enter the Service
water in the case of some momentary reverse flow situation. Maric also
manufacture a Flow Check Valve which is a combination Flow Control & Check
Valve. The advantage of this is that the Rubber Control ring is the working part
which is self cleaning due to the continuously flexing nature of the rubber, and it
offers a space saving.
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,
Check Valve, Pressure Gauge, Flow Meter or Indicator. Some clients even install
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,
Wafer Pattern (fits between flanges) from 20mm up to 400mm (larger on
Inserts for Flow Meters, Shower heads etc