A hydraulic turbine flow meter measures the rate of oil flowing through a hydraulic circuit by using a precision turbine positioned inside a flow block. As fluid passes through the meter, the turbine rotates at a speed related to the flow rate.

The Webtec CT and CTR Series use a magnetic reluctance transducer to detect turbine rotation. Electronic signal conditioning converts this information into an output that can be displayed, recorded or transmitted to a monitoring system.

Turbine flow meters are commonly used for hydraulic system testing, commissioning, maintenance, production testing and monitoring the performance of pumps, motors and valves.

Measuring hydraulic flow under different operating conditions can help identify changes in pump or motor performance that may indicate wear, internal leakage or other hydraulic system problems.

For example, a reduction in pump output flow as system pressure increases may indicate a loss of volumetric efficiency. Comparing measurements taken under similar operating conditions can also help identify developing problems before they cause equipment failure.

The Webtec CT Series provides flow measurements for monitoring and diagnostics, while the CTR Series incorporates a loading valve that allows controlled pressure loading during hydraulic system testing.

The main difference is that the Webtec CTR Series includes a built-in loading valve, while the CT Series is designed primarily for flow measurement.

The CT Series measures hydraulic flow and provides an electronic output for connection to compatible displays, data loggers, PLCs or data acquisition systems.

The CTR Series combines the same turbine flow measurement principle with an adjustable loading valve. This allows an operator to progressively increase hydraulic pressure while monitoring flow, making it particularly useful for testing pumps, motors and other hydraulic components.

Both series are capable of bi-directional flow measurement, and versions are available for different electrical interfaces and measurement systems.

A hydraulic pump can be load-tested using a flow meter with an integrated loading valve, such as the Webtec CTR Series.

The loading valve progressively restricts flow to increase the pressure against which the pump operates. By monitoring flow as the pressure increases, an engineer can assess pump performance under conditions that more closely represent normal operation.

The CTR also allows pressure loading in either flow direction, which is useful when testing reversible hydraulic circuits.

For the conditioned-output CT600R and CT800R models, pressure control is limited below 86 L/min (23 US gpm). The maximum controllable pressure in this region depends on the flow rate, so the specific model's performance limits must be checked before testing.
 

Yes. The Webtec CT and CTR Series are designed for bi-directional flow measurement, allowing flow to be measured when the direction of oil movement is reversed.

The CTR Series also permits pressure loading in either direction through its integrated loading valve. A shuttle valve ensures that the pressure connection measures the higher-pressure side of the loading valve.

However, the CTR's specified flow accuracy is achieved in the preferred flow direction, with oil passing through the turbine before the loading valve.

Bi-directional measurement capability should not automatically be confused with an output that identifies the direction of flow. If electronic flow-direction indication is required, this should be confirmed when selecting the measurement system.

The Webtec CT and CTR Series cover a wide range of hydraulic flow rates, but the maximum capability depends on the model and output version.

For conditioned analogue-output versions:

• CT Series: Calibrated flow ranges from 1 to 1,500 L/min, with the highest-flow models covering approximately 396 US gpm.
• CTR Series: Calibrated flow ranges from 8 to 800 L/min (2 to 210 US gpm).
• Maximum rated pressure: Up to 480 bar (approximately 7,000 psi) on selected configurations.

The HPM-compatible sensor ranges differ. CT-SR models are available up to 750 L/min (200 US gpm), whereas CT-CAN models extend to 1,500 L/min (400 US gpm). The CTR-SR and CTR-CAN ranges extend to 750 L/min (200 US gpm).

Not every model has the same pressure rating. Some port and flange configurations have significantly lower limits, so the exact pressure rating must always be checked against the selected model.

The correct turbine flow meter should be selected according to the minimum and maximum flow rates expected during testing, rather than simply the maximum rated flow of the hydraulic pump.

Each Webtec CT or CTR model has a specified calibrated flow range. Selecting a meter that operates within this range helps ensure useful measurements across normal working conditions.

For the CT and CTR ranges, signal conditioning provides turndown ratios between approximately 15:1 and 40:1, depending on the model. Accuracy specifications also differ at low flow rates, so this should be considered where small flows are important.

The selected meter must also have suitable pressure ratings, connection sizes, fluid compatibility and acceptable pressure drop for the hydraulic circuit. The datasheets include pressure-drop curves to assist selection.

The Webtec CT and CTR turbine flow meters have a flow measurement accuracy of ±1% of the indicated reading between 15% and 100% of the full-scale flow range.

Below 15% of full scale, the accuracy becomes a fixed ±0.15% of full scale rather than a percentage of the indicated reading. The CT15 is an exception, with a specified accuracy of ±1% of full scale in this lower region.

Repeatability is better than ±0.2%, making the meters suitable for comparing measurements taken under similar conditions.

When selecting a flow meter, it is important to distinguish between percentage of indicated reading and percentage of full scale, particularly if measurements will frequently be taken towards the lower end of the calibrated range.

Yes. Changes in hydraulic oil viscosity can affect the performance and accuracy of a turbine flow meter.

The Webtec CT and CTR Series are calibrated as standard using ISO32 hydraulic mineral oil to ISO 11158 category HM at a mean viscosity of 21 cSt. This is representative of hydraulic oil operating at approximately 50 °C (122 °F).

As oil temperature changes, its viscosity also changes. This can influence turbine behaviour and introduce additional measurement error, particularly when operating significantly outside the standard calibration conditions.

For applications using substantially different viscosities, Webtec can provide advice on the expected measurement error or discuss calibration at an alternative viscosity.

The Webtec CT and CTR Series are primarily designed for mineral hydraulic oils conforming to ISO 11158.

The CT datasheet also identifies applications involving lubrication oils and fuels. However, compatibility with a particular fluid should be confirmed, especially where different seal materials may be necessary.

The operating temperature range depends on the electrical version:

• Conditioned analogue CT and CTR: Fluid temperature from 5 to 90 °C (41 to 194 °F).
• SR and CAN versions: Fluid temperature from -20 to 90 °C (-4 to 194 °F) for continuous use.

FKM seals are standard, with EPDM options identified for certain CT models. For water-based fluids, alternative oils or other specialised fluids, Webtec should be consulted to confirm suitability.

Correct installation is important because turbulence, restrictions and uneven flow profiles can affect turbine flow measurement accuracy.

The Webtec CT and CTR flow blocks incorporate internal flow straighteners that reduce the effects of turbulence and swirl.

A straight pipe length of approximately 10 pipe diameters is normally recommended, although the built-in flow straighteners allow this to be reduced to 8 diameters where installation space is limited.

Inlet and outlet connections should have a similar bore size to the flow block to avoid unwanted restrictions or venturi effects.

The CT and CTR can be mounted in any orientation and used for intermittent or continuous testing. For applications involving constant operation with repeated pressure spikes, Webtec recommends discussing the installation with its technical sales team.

Clean hydraulic oil is important for maintaining turbine flow meter performance, as contamination can affect the moving turbine and its bearings.

For most Webtec CT and CTR models, the recommended oil cleanliness must be better than ISO 4406: 21/19/16 or NAS 10.

The smaller CT15 requires a higher level of cleanliness, better than ISO 4406: 19/16/13 or NAS 7.

Maintaining the recommended filtration level helps protect the turbine mechanism and supports reliable, repeatable measurements. The required cleanliness should be considered when selecting a meter for a hydraulic maintenance or testing application, particularly where the condition of the hydraulic oil is uncertain.

Yes. Webtec CT and CTR flow blocks have additional connections that allow optional pressure and temperature sensors to be fitted alongside the flow measurement system.

Most models have two additional ports on the top of the flow block, while the CT15 has only one. An M16 x 2 test point is fitted as standard.
Webtec also offers compatible pressure and temperature sensors for its HPM data logging systems. The CT-CAN/SR sensor ranges include temperature measurement within the flow meter, removing the need for a separate temperature sensor.

HPM-compatible pressure transducers are available in ranges up to 1,000 bar (14,500 psi), but the pressure transducer rating must not be confused with the lower maximum operating pressure of the turbine flow block.

The M16 x 2 test point connector also has separate limits: a maximum pressure rating of 630 bar (9,100 psi) and a live connection pressure of 400 bar (5,800 psi) or less.

Yes. The conditioned-output versions of the Webtec CT and CTR Series are designed for direct integration with PLCs, digital displays and data acquisition (DAQ) systems.

These models have built-in electronic signal conditioning that converts turbine rotation into a calibrated analogue output, removing the need for external calibration lookup tables.

Two output options are available:

• 4–20 mA: A three-wire current output, with 4 mA representing zero flow and 20 mA representing full-scale flow.
• 0–5 V: A voltage output, with 0 V representing zero flow and 5 V representing full-scale flow.

Both conditioned analogue versions operate from a 12–32 V DC supply.
This makes them suitable for hydraulic test benches, production testing, control systems and installations where flow readings need to be displayed or recorded electronically.

Webtec offers CT and CTR turbine flow meters with SR and CAN sensor interfaces for use with compatible HPM hydraulic data loggers.

SR (Sensor Recognition) uses an analogue voltage-based sensor system with automatic sensor recognition. It is compatible with the HPM4000 SR and supported HPM systems designed for SR sensors. The HPM7000 can also support SR sensors using its optional analogue input module.

CAN (Intelligent Digital®) uses the CANopen digital communication standard. These sensors support automatic configuration with compatible HPM equipment, including the HPM4000 CAN, HPM5000 and HPM7000.

The two interfaces use different communication methods and connection arrangements, so the flow meter version must be selected to match the intended data logger.

For further information, see the Webtec HPM Hydraulic Data Logger FAQs.

Yes. Webtec Intelligent Digital® CAN sensors use the CANopen communication standard and can be integrated into compatible third-party CAN bus systems, as well as Webtec HPM data loggers.

The sensors comply with CANopen DS301 and device profile DS404. They can transmit digital measurement information without requiring an external analogue-to-digital converter.

A range of connection cables, Y-splitters and terminating resistors is available. Sensors can be connected along a CAN network using Y-cables, and the datasheet specifies external 120 Ω termination at the final bus node.

CANopen should not be confused with SAE J1939. Although both use CAN communication technology, they are different protocols and compatibility needs to be checked when integrating sensors into an existing machine control system.

The Webtec CTR Series incorporates Webtec’s Interpass® safety protection system as part of its integrated loading valve.

The system uses replaceable safety burst discs that operate if the maximum pressure is exceeded, allowing oil to bypass internally to the return line. This provides protection against over-pressurisation of the loading valve in either flow direction.

Replacement burst discs are stored in a holder machined into the rear of the flow block.

Interpass® is an additional protective feature and should not be regarded as a substitute for correct hydraulic circuit design, suitable system pressure protection or observing the flow meter's rated operating limits.

Webtec CT and CTR turbine flow meters are factory calibrated using ISO32 hydraulic mineral oil at a mean viscosity of 21 cSt.

The turbine flow meters are calibrated against a reference traceable to international measurement standards, with measurements taken across the calibrated flow range.

For the conditioned-output CT and CTR models, calibration certificates are available on request as a chargeable option. Alternative calibration conditions can also be discussed with Webtec.

The CT1500 has a specific qualification: its production calibration is confirmed by testing between 50 and 750 L/min (13.2 to 198.1 US gpm), with performance above 750 L/min (198.1 US gpm) established by design.

The referenced datasheets do not specify a fixed routine recalibration interval. Where periodic traceability is required, the appropriate schedule should be agreed according to the application and measurement requirements.

The electrical supply and ingress protection ratings depend on the type of output selected.

Conditioned analogue versions: Operate from 12–32 V DC and have an IP66 rating with the cable connected. The specified ambient temperature range is 5 to 40 °C (41 to 104 °F).

SR sensor versions: Operate from 7–15 V DC and have an IP54 rating. The specified ambient temperature range is -10 to 50 °C (14 to 122 °F).
CAN sensor versions: Operate from 8–40 V DC and have an IP66 rating with the cable connected. The specified ambient temperature range is -10 to 50 °C (14 to 122 °F).

These differences should be considered when selecting a turbine flow meter for permanent installation, workshop testing, outdoor use or integration into mobile machinery.

The Webtec CT, CTR and CTA Series all use turbine-based flow measurement technology, but they are intended for different system requirements.

The CT Series provides conditioned flow measurement for hydraulic testing and monitoring, with analogue and HPM-compatible sensor versions available.

The CTR Series adds an integrated loading valve and Interpass® safety protection, making it suitable for controlled hydraulic component testing where flow needs to be measured under pressure.

The CTA Series is designed specifically for permanent installation in heavy-duty mobile and industrial machinery. It is available with SAE J1939 CAN-bus communication for flow and temperature or a 4–20 mA flow output, and is designed to meet IP6K9K ingress protection requirements.

The appropriate choice depends on whether the application requires straightforward flow measurement, hydraulic load testing or integration into a heavy-duty machine monitoring system.