Wafer Style Flowmeter

Figure 1

Principle

of

Operation

These threaded and wafer style flow meters measure flow rate by sensing the pressure differential created across a calculated flow nozzle which is machined in the body of the flow meter. A pair of matched, opposed bellows sense the differential pressure and drive a mechanical linkage and gear movement to indicate flow rate directly on the dial. (When fitted with a blind transmitter or digital display readout, the bellows and mechanical linkage are replaced with a solid state differential pressure sensor).

Select a site which is convenient for viewing and which provides service access to the front and rear of the flow meter. Note that the dial can be ordered in any orientation at 90° increments and can be easily reoriented in the field. See "Changing the Dial Orientation" in the installation section. the site selected should provide at least 10 diameters of straight meter size pipe between the flow meter inlet and any upstream fitting such as elbow, tee or valve. There are no special piping requirements for the downstream connections to the flow meter.

Note that the flow meters are calibrated based on schedule 40 pipe connections. Tubing or hoses do not have the same ID as pipe and should be transitioned to pipe at least 10 diameters upstream of the flow meter to achieve rated accuracy.

Installation

Planning and Site Selection

Avoid placing the flow meter where it will be subjected to water hammer, surges and mount the meter rigidly to minimize shock or vibration.

Flow meters installed outdoors or exposed to splashing liquids should be ordered with a gasketed case (option D).

Protect from freezing liquids.

Do not exceed the pressure and temperature limits marked on the nameplate of the flow meter. Although each flow meter is pressure tested to 150% of nameplate rating, overpressure may cause injury, leaking or flow meter damage.

3.2    Changing the Dial Orientation

Note the flow direction arrow on the body. If necessary, change the dial facing direction by removing the four screws holding the body to the housing. Do not remove the two screws holding the housing to the cell block assembly.

Position the housing at any 90° position. Replace the four screws taking care not the pinch the o-ring seals. See figure 3 for seal location.

O-Ring Installation

Figure 3

3.3    Changing from Horizontal to Vertical or Vertical to Horizontal

Remove the lens by rotating counter-clockwise by hand. Do not remove the pointer. Move the dial to forward by prying with a small knife at 12:00 o'clock position. Rotate the dial to the desired viewing position and push the dial back into position using the 4 locating indents on the housing.

Using a small screwdriver blade to lift the end of the retainer ring up and out of the housing recess, remove the retainer ring and the dial crystal. Do not remove the pointer. Remove the two screws holding the dial and rotate the dial to the desired viewing position.

ABS

Housing

Aluminum

Housing

3.4    Threaded Bodies

Make up thread joint using suitable thread sealant. Be sure threads are clean and free of burrs before making up joints. Apply wrench torque only to the flow meter body. DO NOT exert any wrenching force to the flow meter housing.

3.5    Wafer Style Bodies

Install the flow meter between mating flanges. Take care to center the gaskets so that they do not protrude at all into the pipeline. Gasket protrusion will cause significant calibration errors.

The flow meter does not require routine lubrication or service of any kind. Keep the indicator of the flow meter housing clean and free of dust, moisture, oils or corrosive materials. Protect the flow meter from dripping or splashing corrosives or solvents which may attack flow meter exterior and eventually damage the internal mechanism.

4.2    Checking Zero

Zero Mark

 

Water hammer or pressure surges can displace the bellows and cause the zero to shift. If the pointer does not return to the reference point when flow through the flow meter is zero, or if the pointer does not move away from the zero reference mark at 12-15% of full scale flow, then check the zero adjustment as follows:

• Stop flow.

• Remove the lens.

• Observe the position taken by the pointer. When properly adjusted, the pointer should point to the zero reference mark as shown in Figure 4.

• If the pointer is positioned within 1/2" (12mm) of the zero reference mark, then follow the FINE ADJUSTMENT procedure to re-zero the flow meter.

• If the pointer is positioned more than 1/2" (12mm) from the zero reference mark, then follow the COARSE ADJUSTMENT procedure.

  4.3    Checking the Pointer Preload

  If the fine adjustment has been performed repeatedly, the pointer return spring preload should be checked. Manually rotate the pointer CCW toward full scale. The pointer should stop at full scale. If the pointer goes beyond full scale, make adjustments by following the COARSE ADJUSTMENT procedure. Otherwise, go to the FINE ADJUSTMENT procedure. FINE ADJUSTMENT is made by placing a blade screwdriver in the pointer slot hub. Grip the pointer close to the hub on both sides of the hub and rotate the screwdriver in small increments and release each time to check position, repeat if necessary or until the pointer rests at the zero reference mark.

  4.4    Coarse Zero Adjustment

  If necessary, restore spring preload first before Proceeding with the COARSE ADJUSTMENT procedure.

  Zero Reference Point

  Figure 4

Operation

and

Maintenance

Operation

and

Maintenance

(Continued)

IMPORTANT: The stop nut must stop the center shaft movement before the bellows hits the cell cap. If the bellows hit the cell cap, the bellow or cap can be damaged causing leaking or meter errors.

After completing the preload and stop nut adjustment, adjust the cam nut until the pointer points at the zero reference mark. Gently tap the flow meter to overcome residual friction while making adjustments. Instrumentation Loctite is used to secure the cam and stop nut. Use a small pair of channel locks or pliers to make adjustments, be sure the center shaft assembly does not rotate when making adjustments damage may result.

Test for freedom of pointer movement by moving the lever assembly from left to right then release, the pointer should return quickly to the zero reference point. Clean and reinstall the lens.

4.5    Fine Zero Adjustment

Note: If fitted with 4-wire transmitter or reed switches, do not use this procedure. Do all adjustment with the coarse zero adjustment. Adjustment of the fine zero using this method will require recalibration of the reed switches and transmitter.

Grip the pointer with your thumb and index finger close to the hub and both sides of the hub and place a flat blade screwdriver in the hub slot and rotate the screwdriver in small increments while holding the pointer close to the hub with your fingers, CCW to move the pointer position upscale and CW to move the pointer position downscale.

The pointer should point at the zero reference point on the dial shown in figure 4.

Gently tap the flow meter to overcome residual friction after making the adjustment. Test for freedom of pointer movement by moving the lever assembly from left to right with your finger then release. Pointer should return quickly to the zero reference mark. Click here to access video clip instruction.

Cam Nut and Stop Nut

(Rear View)

Figure 6

Check the position of the stop nut by manually moving the center shaft assembly from left to right (as seen from the rear) the pointer will rotate around the dial until the stop nut makes contact with cell block. Proper stop nut adjustment is when the pointer stops at or near 6 o'clock position or the "U" in "USA" on the dial.

Increase

Indication

Decrease

Indication

Check flow meter indication at 50% of full scale. The flow meter should indicate actual flow rate within 3% of full scale. If the flow meter does not indicate actual flow, contact the factory.

4.7    Cleaning of Pressure Ports

Remove the flow meter housing from the body by removing 4 screws. Remove the pulsation snubbers from the body by inserting a wood screw and gently pulling upward. Clean the passages in the body and snubbers. If you are unable to clean without further disassembly, the flow meter should be returned to the factory for service. Click here to access video clip.

Reassemble the flow meter housing in the desired viewing position. Take care to properly seat inner and outer o-ring seals before tightening screws.

4.8    Adjustment of Reed Switches

Check the flow meter zero and correct if necessary using the coarse or fine procedure before proceeding.

Cam Follower Adjustment

Figure 7

The orifice has been factory adjusted to provide the proper differential pressure for accurate flow meter operation. Contact the factory for NIST traceable calibration certificates.

Check the zero adjustment of the pointer. Cycle the flow rate from zero to full scale three to four times and observe the pointer motion. The pointer should return to zero smoothly.

Establish a known flow rate through the flow meter corresponding to approximately 90% of full scale and observe the flow meter indication. Move the cam follower up to decrease the pointer indication or down to increase the pointer indication.

To move the cam follower up, rest a screwdriver on cell block with the blade between the cell block and center shaft. Gently pry up on the cam follower. to move the cam follower down, place the screwdriver on the top of the cam follower and gently press down. Take care not to put excessive forward pressure on the lever to prevent the "C" clip on the pivot shaft from coming off. Re-zero using the cam nut.

Operation

and

Maintenance

(Continued)

5.

Mechanical fluctuation of the pointer is usually a symptom of excessive turbulence in the pipeline. This is frequently caused by valves or fittings installed too close to the flow meter inlet. if moving the flow meter is not practical, snubbers with smaller holes can be installed to increase the mechanical damping of the flow meter. (Pulsation snubbers are installed standard on all gas and liquid flow meters unless ordered with viscosity correction).

5.2    Zero Shift

The need to frequently re-zero the flow meter is an indication of excessive water hammer or surge. Piping or operating procedures should be changed to reduce water hammer in order to prolong the life of the flow meter.

5.3    Sluggish Meter Response

Sluggish flow meter response can be caused by inadequate pointer return spring preload or by clogging of the pressure ports with debris. To check spring preload, see "Checking the Pointer Preload". To clean the pressure ports, see "CLEANING OF PRESSURE PORTS".

6.1    Liquid Service

If the specific gravity of the liquid being metered differs from the value marked on the flow meter dial, a correction factor, J, must be applied to the flow meter reading to obtain the actual flow rate. Click here to access calculator.

Actual flow rate = J x flow meter reading

where:     

    Sc = Specific Gravity for which the flow meter is calibrated

    Sa = Actual specific gravity of the fluid being metered.

Example:

Flow meter, calibrated for water (specific gravity = 1.0) reads 12.5 GPM for a lubricating oil with a specific gravity of 0.85. What is the actual flow rate?

Therefore, actual flow = 1.085 x 12.5 = 13.56 GPM

6.

6.

If the gas pressure or temperature varies from the value marked on the flow meter dial, then a correction factor, K, must be applied to the meter reading to obtain the actual flow rate. Click here to access calculator.

Actual flow rate = K x flow meter reading

where:     

                    K =  

    Pa = Actual gas pressure at inlet to flow meter, psig

    Pc = Calibrated gas pressure marked on the flow meter dial, psig

    Ta = Actual gas temperature at inlet to flow meter, °F

    Tc = Calibrated gas temperature marker on the flow meter dial, °F

Example:

Flow meter calibrated for compressed gas air at 100°F and 80 psig, reads 100 SCFM at an actual temperature of 70°F and pressure of 85 psig. What is the actual flow rate?

                K =   

                K =   

Therefore, actual flow rate = 1.05 x 100 = 105 SCFM

Cutaway View From Front Dial Removed

Figure 9

7.