The Rotary PICV is selected for a number of reasons, such as:
- The client requires enhanced flexibility for seasonal commissioning, room layouts or programmable flushing routines
- Intrinsic equal percentage control is required
- The BMS controller is Remote® Commissioning capable
- A more engineered solution is required
Some of the great features of this valve include:
- Its design incorporates a characterised ball, with various profiles available to suit the design flow rate, covering high flow, low flow and very low flow requirements
- The ball has equal percentage characteristics, which provide excellent valve authority for control whilst also allowing maximum areas for flow, which reduce any potential problems associated with dirt in the system
- The highly accurate laser cut ball has positive shut-off capability and low operating torque as a result of the unique seat design
- Constant pressure is maintained across the valve by the diaphragm of the differential pressure controller whilst constant flow regulation is achieved through the easily accessible and replaceable stainless steel cartridge
- Cartridges are interchangeable and have low start up pressures with a wide control band to 400kpa (600kpa on request)
- It has an ISO mounting pad for quick and easy installation of actuators
- Accurate valve position can be maintained through the use of BMS actuators.
- The Rotary PICV is suitable for a wide range of actuators as the ISO mounting pad can accommodate actuators with both ISO4 and ISO5 connections. These can be split into three functional types; 3-point floating (Raise/Lower, Drive Open/ Drive Close), 0-10v proportional or programmable multifunction actuators
- The product is maintenance free and uni-directional, suitable for installation in either the flow or return pipework providing the flow direction arrow is correctly observed
- The ball valve position can be adjusted via the actuator to regulate the flow and achieve the desired flow rate
- Test points are included in the design of the PICV for measurement of differential pressure in order to verify that the valve is operating correctly
Rotary PICVs are suitable for maximum flow rates between 0.01l/s and 4.71l/s.
The valve body is manufactured in dezincification resistant brass (DZR) and is currently available in 4 sizes: DN15, DN20, DN25 and DN32. Ductile iron is issued for larger flow rates in sizes DN32 and DN50.
Our Rotary PICV has been designed with an ISO standard mounting arrangement that can accommodate actuators with both ISO4 and ISO5 mounting pads. This means that almost any type of rotary valve actuator may be used with the valve so long as the minimum torque requirements are met.
Installation and Mounting of the Rotary PICV
Marflow Hydronics’ PICVs are maintenance free and uni-directional, suitable for installation in either the flow or return pipework providing the flow direction arrow is correctly observed. Strainers should be installed up-stream of the PICV in order to prevent ingress of dirt. Should the system be designed to accommodate reverse flow then a non-return valve should be installed in the system to prevent reverse flow through the PICVs.
Flow Rate Adjustment
Maximum flow rate is achieved when the ball valve is in the fully open position. The ball valve position can be adjusted via the actuator to regulate the flow and achieve the desired flow rate.
Valve control is achieved in the following ways:
- Use of a factory set pre-programmed multi-functional electro-motive actuator with 0-10v linear control, which ensures that the valve controls to the required design flow rate. If required, the actuator can also be programmed on-site using a hand held tool (Model BEZ-GEN).
- The BMS controller can be set with either the actuator maximum control voltage or run time.
- Programming the design flow rate into the BMS controller and commissioning package, which then allows on-site adjustments as required utilizing the proprietary commissioning software.
Flushing and Media Quality
Systems should be cleaned and flushed as detailed in the BSRIA guide Pre commission cleaning of pipework systems (BG29/2012).
Water quality should also be maintained to the standards referred to in BSRIA guide Water treatment for building services systems (AG2/93).
The compatibility of cleaning agents and water treatments should be checked with Marflow prior to use with the product.
When the PICV is mounted in the flow pipe-work, flushing should be avoided and by-passes used to drain prior to back and then forward flushing the system.
Strainers should be installed up-stream of the PICV in order to prevent ingress of dirt.
For further detailed information or a step-by-step guide to flushing the system, please contact Marflow Hydronics.
Verification of Flow Rates
Test points are included in the design of the PICV for measurement of differential pressure in order to verify that the valve is operating correctly. Providing the measured differential pressure is between the upper and lower differential pressure limits (20kPa and 400kPa), then the valve can be assumed to be working correctly and within its operating range.
It should be noted that the test points cannot be used to measure flow rate across the PICV. Should flow measurement be required, then a separate orifice plate or venturi should be installed downstream of the valve and used to verify this.
CIBSE Commissioning Code W (2010), section W7.7.3, should be referred to for guidance, if verification of flow is required.
Prior to verification the following procedures should be followed:
- Check that the pump has been correctly sized.
- Ensure that the system is clean, has been flushed and is free of air.
- Strainers have been checked and are clean (and have been so for at least 24 hours with the pump in operation).
- Ensure that all actuators are fully open.
Flow can be verified in two ways:
- Calculation of flow at the branch or sub-circuits: All PICVs can be confirmed as working efficiently and correctly if the flow measured independently, at the branches and sub-mains, is within ±10% of design flow rate.
Since the PICV works as a constant flow regulator then the flow at the branch or sub-circuit can be calculated as the sum of all flows downstream of the branch or sub-circuit measuring device. This can be verified further if required by flow measurement at the terminal unit.
- Flow measurement at the terminal unit: For verification it is usual to only sample or batch test flows at a percentage of installed terminal units although it may be preferable to have the facility to check flows at all terminal units should it be required (providing a separate metering station or venturi has been installed).
Optimisation of Energy and Cost Reduction
Once flows have been verified as being within the required tolerances to design flow rate, then pump speed can be reduced in order to optimize energy efficiency. After the “index circuit” has been identified, then the pump speed can be reduced until the pressure drop across the PICV in this circuit is equal to or just above the start up pressure for the valve.
The “index circuit” is generally the one with the lowest differential pressure across the PICV.
The Rotary PICV requires no regular maintenance.
For more information on PICVs, download our Definitive Guide to Pressure Independent Control Valves