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Balancing Flow Measurement Devices
Flow measurement devices pair with balancing valves to read circuit flow at a dedicated fitting — a separate measurement point where the regulating valve itself has no fixed orifice, or a combined measure-and-regulate valve where space is tight. The range covers a DZR copper alloy PN25 line in DN15 to DN50 (including an ultra-low-flow DN15-only variant), a stainless steel PN25 line in DN20 to DN600, and a combined flow measurement and regulating valve in DN50 to DN400 at PN16, with taper threaded ends per BS EN 10226-2 (ISO 7-1). Measurement is by square-edged entrance orifice plates with tappings for P84 insertion-style test points at ±5% accuracy: flow follows Q = Kvs × √ΔP / 36 across the fixed orifice, read at the two test points. The D901 suits systems sized for 100 to 400 Pa/m pipe friction loss, while the DN15-only D902 measures ultra-low flows of 0.015 to 0.06 L/s such as fan-coil circuits; D901/D902 literature quotes 6.1 Kv and 4.7 Kvs, with threaded ends rated -10 to +100 °C at 25 bar (derating to 21.8 bar at 120 °C) and WRAS approval to 99 °C per BS 7350. The DM950 combines a double-regulating butterfly valve with a fixed-orifice measurement device over a spool piece — the classic commissioning set. Why balance: in an unbalanced network, excessive water passes through the least restricted circuits (usually nearest the pump) while restricted circuits get too little, and balancing devices adapt to pressure variations in variable-flow systems.
Part of the Balancing Valves family
Last updated: 2026-10
Family specifications
| dzr line | D901 DN15 to DN50 Flow Measurement Device (FMD) – DZR Copper Alloy PN25 |
|---|---|
| ultra low flow variant | D902 DN15 Only Ultra Low Flow Measurement Device (FMD) – DZR Copper Alloy PN25 |
| stainless line | DM900 DN20 to DN600 Flow Measurement Device (FMD) – Stainless Steel PN25 |
| combined regulating valve | DM950G DN50 to DN400 Flow Measurement and Regulating Valve PN16 |
| end connections | D901 - Sizes 1/2" to 2" |
| body materials | DZR Copper Alloy, Stainless Steel |
| size range | DN15-DN50 (D901/D902), DN20-DN600 (DM900), DN50-DN400 (DM950G) |
| pressure class | PN25, PN16 |
| measuring element | Square-edged entrance orifice plates with tappings for P84 insertion-style test points |
| measurement accuracy | ±5% flow measurement accuracy |
| d901 sizing basis | Suitable for systems with pipe frictional losses of 100 to 400 Pa/m |
| d902 ultra low flow band | 0.015 to 0.06 L/sec (DN15 only; e.g. fan coil units) |
| flow capacity d901 d902 | 6.1 Kv / 4.7 Kvs (literature value) |
| temperature pressure rating | Threaded ends -10 to +100 °C at 25 bar, derated to 23.4 bar at 110 °C and 21.8 bar at 120 °C; compression ends 16 bar at -10 to +30 °C; WRAS approval to 99 °C |
| design standards extra | BS 7350: 1990, BS EN 10226, BS EN 1254-2, BS EN 12165, BS EN 12164 |
| approvals | Water Regulations Advisory Scheme (WRAS) |
| dm950g construction | Double-regulating butterfly valve close-coupled to a fixed-orifice flow measurement device via a spool-piece connector; incorporates P84 pressure test valves |
| kv measurement principle | Q = Kvs × √ΔP / 36 (flow in L/s, ΔP in kPa) across the fixed orifice, read at the two test points |
| commissioning set definition | A regulating valve combined with a separate fixed orifice is commonly called a commissioning set; UK practice is proportional balancing of terminal circuits |
| fm1 venturi meter construction | Balancing valve for hydraulic systems. Flow meter with Venturi device. Stainless steel obturator. Complete with quick-fit pressure test ports. |
| fm2 flow meter principle | Balancing valve with flow meter and direct reading of flow rate. Ball valve for flow rate adjustment. Graduated scale flow meter with magnetic movement flow rate indicator. |
| fm2 flow regulation range | 132402 G 1/2" (ISO 228-1) F 2–7 l/min |
| fm2 material rating | Technical data Material : brass Maximum percentage of glycol : 50 % Medium : water, glycol solutions Medium temperature range : -10–110 °C Maximum working pressure : 10 bar |
| fm3 flowmeter bypass design | This particular series of valves is equipped with a flow meter for a direct reading of the regulated flow rate. The flow meter is housed in a by-pass circuit on the valve body and can be shut off during normal functioning, allowing fast and easy balancing of circuits without the need for differential pressure gauges. |
| fm3 flanged size range | 132 series Balancing valve with flow meter, flanged version sizes DN 65, DN 80 and DN 100 |
| fm3 performance rating | Medium temperature range : -10–110 °C Maximum working pressure : 10 bar |
| fm4 venturi kvs signal | The venturi is able to accelerate the fluid velocity generating a measureable pressure loss or signal from which a flow co-efficient factor Kvs can be calculated. |
| fm4 flow chart reading | From this co-efficient the flow rate passing the valve can be calculated or using the signal the flow rate can be read off the appropriate flow chart |
| fm5 venturi in body | On 130 series threaded valves, the flow rate is measured with a Venturi device, housed inside the valve body. This devices guarantees balancing accuracy and is extremely practical to use during setting. |
| fm5 straight pipe requirement | We recommend keeping the upstream and downstream sections of pipe straight, as shown in the illustrations below, to ensure accurate flow measurement |
| fm5 installation clearance | The balancing valves must be installed in such a way as to ensure free access to the pressure test ports, drain cocks and the adjustment knob. The valves can be fitted on either horizontal or vertical pipes. |
| fm6 venturi valve role | Venturi valves provide balance, ease of commissioning, and shut-off in a wide range of HVAC systems. |
| dzr metering venturi accuracy | Integral venturi orifice for greater accuracy +/- 3%, The venturi orifice design allows for more stable signals without adding system resistance |
| dzr metering flow range | Flow range between 0.008 l/s and 3.2 l/s |
| dzr metering connections | FBSP (M/F ISO 7-1, F side ISO 228-1) for use with threaded pipe |
| dzr metering pressure temp rating | Maximum working pressure: 25 bar, Working range: 25 bar / -10oC to 110oC 20 bar / 110oC to 130oC |
| dzr metering size line | Xtra Low Flow DN15, Ultra Low Flow DN15, Low Flow DN15, Standard Flow DN15, Standard Flow DN20, Standard Flow DN25, Standard Flow DN32, Standard Flow DN40, Standard Flow DN50 |
| dzr metering straight pipe rule | installed on straight pipe of the same nominal size as the valve and of minimum length equal to 5 pipe diameters at the inlet (10 diameters when installed at the outlet of a pump) and 2 pipe diameters at the outlet |
| dzr metering applications | Heating Chilled water Domestic hot and cold water, Not suitable for gas |
| dzr metering fluid scope | Not suitable for steam, oil or aggressive fluids |
| dzr metering approvals | WRAS Approved, Exempt from CE marking |
| dzr metering body materials | Body: DZR brass, Test Points: DZR brass |
| dzr metering nickel leaching control | Self-colour DZR brass body to limit nickel leaching and minimise water contamination |
Ordering & documentation
Documents
Ask for the documentation set with the inquiry — typical items (material certificates, test reports to the listed inspection standard, dimensional drawings) are confirmed and supplied with the quotation.
Quotation
Send the medium, temperature, pressure, size and connection for a quotation-ready inquiry. Lead time, MOQ and price are confirmed at quotation, together with the documents to be supplied with the order.
Sample & supply
Supply terms, order quantities and lead time are agreed per order — state the destination country and required schedule with the inquiry.
Storage & shipping
Store valves with seats and seals protected from UV, ozone and deformation, and keep end-face protectors on until installation; storage limits and shipping arrangements for the selected materials are confirmed at quotation.
Frequently asked questions
What sizes and pressure ratings are available for balancing flow measurement devices?
The published size range is DN15-DN50 (D901/D902), DN20-DN600 (DM900), DN50-DN400 (DM950G), and the published pressure ratings are PN25, PN16. Availability of a specific size and rating is confirmed at quotation.
What materials are balancing flow measurement devices available in?
The published specification lists body materials: DZR Copper Alloy, Stainless Steel. Material availability for a specific size and rating is confirmed at quotation.
What end connections do balancing flow measurement devices support?
The published specification lists D901 - Sizes 1/2" to 2" as the available end connections. The connection for a specific size is confirmed at quotation.
What should a quotation inquiry for balancing flow measurement devices include?
The governing standard and class, nominal size, body and seat materials, the service medium with temperature, and the destination — anything missing is confirmed during quotation.
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