2 s
Typical Response
1 million
Valve Cycle Life
100 bar, IP67
Flow Switch Rating
2
Instruments in Package
DEFINITION & OVERVIEW
What is a Shaft Seal Water System?
A slurry pump shaft seal is flushed with clean water, called gland seal water, on most plant floors. That water keeps abrasive slurry out of the seal and carries heat away from it. When the seal water flow drops or the pressure falls too low, slurry reaches the seal faces and the seal fails mechanically. When the pressure is too high, the running resistance of the seal rises instead. The seal water has to stay inside a correct band, and this system defends the low end of it.
The trouble is that seal water problems are quiet. A choked line, an empty tank or a closed valve will not trip anything until the seal is already damaged, and a failed seal means a leaking pump, a stopped circuit and a maintenance job in a wet and dirty place.
Our Shaft Seal Water System, System 08 in our instrumentation range, watches the seal water line and keeps it supplied. An electronic flow switch confirms water is moving, and a solenoid valve opens to refill from the tank when the flow falls. It is a small packaged system for one of the plant's most common pump failures, and it sits beside our larger control schemes such as the Dense Medium Control System (S1).
Watches the Flow
A thermal flow switch with no moving parts confirms seal water is actually moving.
Refills Automatically
A solenoid valve opens to refill when the flow falls.
Guards Against Low Flow
A falling supply is caught and corrected before it starves the seal, which is the failure that does the damage.
Parameter | Value |
|---|---|
Flow Detection | Electronic flow switch, thermal principle |
Refill Control | Solenoid valve opens the tank to refill when flow falls |
Flow Switch Rating | 100 bar, IP67 |
Flow Switch Response | 1 to 13 s, typically 2 s |
Valve Cycle Life | 1 million cycles |
Valve Execution Options | Waterproof, Exd IIC T5, anti-corrosive |
KEY FEATURES
Key Features & Performance Highlights of Shaft Seal Water System
What the system does for pumps running abrasive slurry.
Protects the Seal, Not Just the Pump
Too little flow or too low a pressure and the seal fails mechanically. Watching the seal water gives you the warning while the pump is still sounding.
Automatic Refill
When the flow falls, the solenoid valve opens the tank to refill, so a dropping supply is corrected without anyone walking the line.
No Moving Parts to Watch
The flow switch uses a heater and a reference resistance in a sealed probe. It has no moving parts and needs no maintenance, so it does not become another thing to repair.
Built for Long Cycling
The valve has stainless steel piston construction and a life of one million cycles, with unrestricted mounting orientation, so it can be fitted where space allows.
Clear Local Indication
LEDs show the flow trend and the switch status, so a fitter can read the state of the line at the instrument. The switch gives a PNP, NPN or SPDT relay output to the control system.
WORKING PRINCIPLE
How the Shaft Seal Water System Works
Detect, then refill.
Seal Water Flows to the Pump
Clean water is supplied to the pump shaft seal through the seal water line.
The Flow Switch Watches It
A thermal flow switch in the line reads the flow. A heated resistance loses heat to the moving water, and the difference from a reference resistance gives the flow.
The Switch Signals a Fall
If the flow drops below the set point, the switch changes state, and its LEDs show it. The output goes to the control system.
The Valve Refills
When the flow falls, the solenoid valve opens the tank to refill the line.
The Control System and the Operator See It
The flow switch output goes to the control system, so a low-flow state raises an alarm, and once the refill has restored the flow, the switch confirms it.
TECHNICAL SPECIFICATIONS
Shaft Seal Water System | Full Specification
Parameter | Specification |
|---|---|
SOLENOID VALVE | |
Function | Opens the tank to refill when flow falls |
Construction | Stainless steel piston; unrestricted mounting orientation |
Cycle Life | 1 million cycles |
Body Material | Cast steel, stainless steel or 316L |
Executions | Waterproof, Exd IIC T5, anti-corrosive |
ELECTRONIC FLOW SWITCH | |
Principle | Thermal, with a heated and a reference resistance in a sealed probe |
Moving Parts / Maintenance | None / none |
Setting Range, Water | 1 to 150 cm/s |
Other Media | The same probe also reads oil and air |
Output | PNP, NPN or SPDT relay |
Supply | 24 V DC or 230 V AC |
COMPARISON
Shaft Seal Water System
Unmonitored Seal Water
Applications of the Shaft Seal Water System
Wherever a pump seal depends on a clean water supply.
Slurry Pump Shaft Seals
Keeps flushing water supplied to the seals of pumps handling abrasive coal slurry.
Circuits That Cannot Stop
Protects pumps whose failure would stop the circuit around them.
Remote or Unattended Pumps
Pumps that are rarely visited get automatic refill and a flow signal to the control room.
Planned Seal Maintenance
Turns a sudden seal failure into a scheduled job.
Temperature and Mixed Signals
The universal input version handles temperature, current, voltage and resistance with one module type.
About John Finlay
Packaged Systems from John Finlay
Why John Finlay?
2
Instruments in the Package
A solenoid valve to refill and a thermal flow switch to watch, working as one small system.
130+
Coal Washery Projects
Completed EPC projects worldwide, including Asia’s largest coking coal washery at 30 MTPA.
EPC
Full Circuit Supply
Supplied as part of a complete instrumentation and automation offering across the coal preparation flowsheet.
IN
India-Based Support
Manufactured at Hefei John Finlay Mining Equipment Co., Ltd. and supported locally in India for installation, commissioning, spares and service.
Shaft Seal Water System | Frequently Asked Questions
Common questions from maintenance engineers looking after pump seals.
Seal water keeps abrasive slurry away from the seal faces. With too little flow or too low a pressure the seal fails mechanically. With too much pressure the running resistance rises.
A thermal flow switch confirms the seal water is moving, and a solenoid valve opens the tank to refill the line when flow falls.
It uses a heated resistance and a reference resistance in a sealed probe. Moving water carries heat away from the heated one, and the difference gives the flow. It has no moving parts and needs no maintenance.
PNP, NPN or SPDT relay output, on 24 V DC or 230 V AC, rated to 100 bar and IP67, with a response of 1 to 13 s, typically 2 s.
One million cycles, with a stainless steel piston and unrestricted mounting orientation. The body is cast steel, stainless steel or 316L.
The valve is offered in an Exd IIC T5 execution.Â
No. The package is a thermal flow switch and a solenoid valve, so it monitors flow. A falling supply is the failure that starves a seal, and flow is where it shows first.Â
Want to stop seal failures before they stop the pump?
Our engineers can help you fit seal water monitoring and automatic refill to your pumps.
Talk to an ExpertRelated Equipment
Dense Medium Control System (S1)
The larger packaged control scheme in the instrumentation range.
Centrifuge Effluent Monitoring (S5)
Sister system that catches basket failures early.
Screen Underflow Anti-Blockage Detection (S4)
Sister system that guards against blockage under the screens.
Flotation Reagent Dosing System (S3)
Packaged dosing control for the flotation circuit.
Instrumentation Overview
All instruments, including the General Instrumentation section.