Kawaki SA-MA Flow Switch and SA-M Flow Meter for Small Flows

A small-flow drag-plate switch with a proximity contact

The Kawaki SA-MA flow switch and SA-M flow meter are for comparatively small flows of high-temperature, high-pressure, unclear fluids such as oil. The English page gives the range as equivalent to water at 0 to 15 L per minute, while the Japanese manual speaks of small flow measurement from 0 to 20 L per minute, so confirm the scale you need. Versions listed are the SA-M indicator, the SA-MA with a lower or upper limit contact and the SA-MA(A).

The manual lists four features. Small flows can be measured because artificial sapphire bearings keep friction low. The mechanical construction has high breaking strength. The magnetic coupling between sensing part and indicator gives no leakage and allows high-pressure fluid, and the manual states a maximum pressure of 30 MPa as an option. The contact is a proximity switch, adjustable over the full scale.

Technical specifications

Contact function and a point to check

The proximity switch is a self-holding type rated 50 W, 0.5 A at 125 VAC. The manual notes that the contact construction differs for lower-limit and upper-limit use, so an upper-limit unit cannot be used as lower limit and the other way round: state the alarm direction when ordering. Like the other Kawaki flow switches, the sensing principle is a resistance plate in the stream whose movement is carried by magnets to the pointer.

The English page lists 1.0 MPa as the standard pressure and 300 degrees C as a special-order temperature, while the manual cites 30 MPa as an option for the magnetic coupling. Treat the high-pressure figure as special order and confirm the actual limit with the manufacturer for your size and material.

Selection and installation

Specify bore (3/8B to 1B flange or RC3/8 to RC1 screw), fluid, temperature, pressure, the flow range for the scale, upper or lower limit contact and materials. For frequent vibration Kawaki recommends an earthquake-resistant type. As with the other types, install in the direction of the flow arrow, flush the pipework, check the pointer and contact by hand before fitting and open valves slowly.

Key features at a glance

• Drag-plate (resistance plate) sensing that works with opaque or dark liquids where a glass-tube rotameter cannot be read.
• Sapphire bearings that reduce friction, allowing the pointer to respond to small flow rates.
• Magnetic coupling between the wetted part and the indicator, so there is no shaft seal that could leak.
• Local pointer indication on every type, with the SA-MA adding a contact for alarm or interlock duty.
• Flange or screwed connections and a broad choice of body and wetted materials, from cast iron and bronze to SUS316L.

SA-M or SA-MA: which version?

For most protection duties the lower limit contact is used: it signals when lubricating oil, seal flush or cooling water to a machine falls below the safe value. An upper limit contact is used less often, for example to warn of a broken line or an open bypass.

Material choice

The main unit can be supplied in FC250 cast iron, CAC406 bronze, SS400 carbon steel or stainless steels such as SUS304, SUS316 and SUS316L, and the main section in C3604B brass or the same stainless grades. Cast iron and carbon steel suit clean mineral oils; bronze and brass are traditional for water and many oils; stainless steel is preferred for corrosive fluids, seawater-cooled systems and high temperatures. State the fluid when asking for a quotation so the combination can be checked.

Installation and maintenance notes

• Mount the instrument so that the flow arrow on the body follows the actual flow direction, and in the orientation shown in the manual.
• Flush welding slag, scale and debris out of the line before installation; a small strainer upstream protects the drag plate in dirty oil systems.
• Avoid sudden valve openings and water hammer, which can strike the plate against its stop.
• Wire the proximity contact within its rating of 0.5 A at 125 VAC; use an interposing relay for larger loads.
• During maintenance, check that the pointer returns to zero at no flow and that the contact operates at the set point.

Uses in Oman and GCC plants

Small-flow switches of this kind protect bearing lubrication on pumps, compressors and turbines in power and desalination plants, monitor seal flush flow on process pumps in refineries and petrochemical units, and confirm cooling flow to hydraulic power units. In hot climates, oil viscosity changes with temperature, which affects the reading of a drag-plate instrument; give the operating temperature and viscosity so the scale can be set for real conditions.

What to include in an RFQ

• Type (SA-M, SA-MA or SA-MA(A)) and quantity.
• Fluid, viscosity or specific gravity, operating temperature and pressure.
• Flow scale required and the alarm set point.
• Contact direction: lower limit or upper limit.
• Bore and connection (flange 3/8B to 1B or screwed RC3/8 to RC1), and the body and wetted materials.

Documents and quotation

The Kawaki instruction manual is attached; it is in Japanese. Seven Star LLC is an independent supplier in Muscat, and we will request a quotation when you send the model, bore, connection, fluid, temperature, pressure, flow range and contact direction. Related items are listed under Flow Indicators and Switches.