Kawaki KY-MA Flow Switch and KY-M Flow Meter, Mechanical Seal Type

A mechanical-seal flow switch that works in any flow direction

The Kawaki KY-MA flow switch and the KY-M flow meter suit unclear liquid because the indicator section is separated from the process by a mechanical seal. Kawaki states that the flow direction is not restricted and that the contact position is variable. The manual describes the KY-M as giving an approximate flow measurement of any liquid and the KY-MA as detecting an increase or decrease in flow by opening or closing an electrical contact, so it is used for approximate measurement and warning on lubricating oil or cooling water systems.

Five features are listed in the manual: a simple, sturdy construction with high breaking strength; no restriction on mounting direction; suitability for lubricating oil and other opaque fluids and relatively good resistance to slurry and dirty water; use with fluids containing iron powder, since there are no magnets in the wetted section; and little spring deterioration because the spring lies outside the fluid.

Technical specifications

Working principle

A resistance plate in the stream experiences a positive pressure on its front face and a lower pressure behind it, and the difference moves the plate. The manual quotes the Reck Nagel empirical relation in which the pressure difference is about 1.372 times the density times velocity squared divided by twice gravity. The movement of the plate is carried out of the fluid through the mechanical seal and shown by a pointer. Kawaki gives the minimum scale range as 0 to 30 L per minute of water or 0 to 20 L per minute of oil.

Selection and installation

Specify the bore and connection (flange up to 5B or RC screw up to 1-1/2), the fluid, temperature, pressure, flow range for the scale, the contact rating and material. The accuracy of this type is plus or minus 5 percent of each scale, lower than the SF and FY types, which is acceptable for lubrication monitoring and warning but not for accurate metering. For frequent vibration or at 1.0 MPa and above Kawaki recommends the SF type. Because the unit can be made for any flow direction, state the actual direction when ordering.

Flush the line before fitting and open valves gradually. Contacts can age and drift, so check the operating point periodically and adjust it through the switch mounting plate as described in the manual.

How the Kawaki KY-MA works

The KY-MA is a flow switch built around a resistance plate placed in the liquid stream. The moving liquid pushes on the plate, and the plate moves farther as the flow rises. A mechanical seal carries this movement out of the process fluid to a pointer and to a contact. The contact opens or closes at a set flow, and a warning or a pump stop can follow. Because the electrical parts are separated from the liquid, the switch can be used with opaque and dirty fluids.

Where the Kawaki KY-MA is used

• Lubricating oil lines
• Cooling water circuits
• Dirty or opaque liquids
• Slurry and dirty water duties
• Fluids carrying iron powder

Selection checklist for the Kawaki KY-MA

• Switch KY-MA or indicator KY-M
• Fluid: water or oil
• Flow range on the scale
• Bore from 3/8B to 5B
• Flange or screw connection
• Pressure up to 1.0 MPa
• Temperature up to 80 degrees C
• Contact rating needed

Installation, commissioning and maintenance notes for the KY-MA

The flow direction is not restricted, so the switch can be fitted in a horizontal or vertical line. Fit it in a straight pipe run, wire the contact to the alarm or starter, and set the contact position at the flow limit. Check the contact from time to time and clean the plate if deposits build up.

Requesting a quotation for the Kawaki KY-MA

Please send the fluid, the flow range, the bore, the connection and the quantity. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

KY-MA contact rating

The contact is rated 15 A at 125, 250 or 480 VAC and 0.5 A at 125 VDC.

KY-MA accuracy

Accuracy is plus or minus 5 percent of each indication scale.

KY-MA materials

The main unit uses FC250, CAC406 and SUS304, with C3604B and SUS304 in the main section.

KY-MA minimum scale

The smallest scale reads 0 to 30 L/min for water and 0 to 20 L/min for oil.

KY-MA spring and magnets

The spring lies outside the fluid, so it wears little. No magnets sit in the wetted section.

Switch records for the KY-MA

Record the set point, the fluid and the date of each contact check.

Choosing the right KY-MA scale

Choose a scale where the normal flow sits near the middle.

Documents and quotation

The Kawaki instruction manual is attached; it is in Japanese. Seven Star LLC is an independent supplier in Muscat; send the model, bore, connection, fluid, temperature, flow range and flow direction and we will request a quotation. See Flow Indicators and Switches for related items.