Fans, hubs, belt and gear drives, motors, speed control and louvres for new coolers and for upgrading old ones. Supplied by Spiro-Gills Thermal Products, including D-series and E-series axial fans and Howden-matched fan casings, and supported in the GCC by Petromarsh.
Tap a part to see what it does. The blue lines are the air moved up through the fan ring.
Fan ring. The close-fitting ring the fan turns in, with a rounded inlet. A small, even tip clearance is what makes the fan efficient.
Blades and pitch. Aluminium or FRP aerofoil blades. Their pitch angle sets how much air the fan moves at a given speed.
Hub. Holds the blades. On a manual hub the pitch is set by hand with the fan stopped. On an auto-variable pitch hub an air-operated actuator changes it while running.
Shaft and bearing housing. Carries the fan weight and thrust. Bearings are greased from a point that can be reached safely.
Belt and sheaves. V-belts or HTD toothed belts reduce motor speed to fan speed. Larger fans use a right-angle gearbox instead.
Motor. Usually a TEFC induction motor, rated for the hazardous area and the high Gulf ambient. A VFD can drive it at variable speed.
Vibration switch. Trips the motor if a blade fails or the fan goes out of balance, before damage spreads to the structure.
An axial fan pushes air along its shaft, through the bundle. It must move a large volume at low pressure, because the finned bundle resists air flow only a little. How much air it moves depends on its diameter, speed and blade pitch.
Large fans at slow speed are quieter and use less power. API 661 limits tip speed, typically to 60 m/s, and asks for the fan to cover at least 40% of the bundle face it serves.
V-belts are simple and common on smaller fans. HTD toothed belts do not slip or stretch as much. Right-angle gearboxes take larger powers, and direct drive removes the belt altogether.
In cool weather or at low throughput the cooler needs less air. Fans can be switched off in steps, slowed with a VFD, re-pitched by an auto-variable hub, or throttled by louvres.
Fans, hubs, drives and controls can be mixed to suit the duty, the noise limit and the maintenance team. Tap one to see when to use it.
Spiro-Gills supplies D-series and E-series axial fans, with fan casings matched to Howden fans. Blade count, diameter and profile are chosen for air volume, pressure and noise.
Blade angle is set during commissioning and can be reset in shutdowns. Simple, reliable and the most common hub.
An air-operated actuator in the hub changes the blade angle in service, under a signal from the control system. It controls air flow closely without changing speed.
Matched V-belts between motor and fan sheaves. Easy to change and cheap, but they stretch and need re-tensioning. API 661 limits the motor power for each belt type.
A toothed belt that does not slip, stretches little and needs less re-tensioning. Often fitted as an upgrade from V-belts to cut maintenance.
A right-angle gearbox takes high power with the motor horizontal. Direct drive uses a low-speed motor on the fan shaft, with no belt at all, often with a VFD.
VFDs vary fan speed to save power and control temperature. Louvres above the bundle throttle air and shade the tubes. A vibration switch on each fan trips the motor on imbalance.
Fan parts work in hot, dusty and sometimes salty air. Blade, hub and drive materials are chosen for temperature and for the site.
| Part | Standard | Upgrade | Notes |
|---|---|---|---|
| Blades | Aluminium aerofoilcast or extruded | FRP (glass reinforced plastic)lighter, quieter profiles | Check blade temperature limit on induced draft |
| Hub | Cast aluminium or steelmanual pitch | Auto-variable pitch hubair-operated | Hub size matched to blade count and load |
| Drive | V-belts and cast iron sheavesmatched sets | HTD belt, gearbox or direct driveless maintenance | Belt guards on every drive |
| Fan ring and casing | Galvanised steel ring with a rounded inlet, or a Howden-matched fan casing for replacement fanshot-dip galvanised to ISO 1461 | ||
API 661 covers fans, hubs, drives and protection for process air coolers. Other standards cover the motor, gearbox and noise.
Fan tip speed, fan coverage of the bundle, hubs, belt and gear drives, guards and vibration switches.
General-purpose gear units for refinery service, used for right-angle fan drives.
Rating and performance of electric motors, including efficiency classes.
Explosion-protected motors, switches and instruments for zoned areas.
Laboratory testing of fan performance using standardised airways.
Sound power found from sound pressure (3744) or sound intensity (9614) measurements. Used to check the noise guarantee.
Measuring and judging machine vibration on fans and drives.
Balance quality of rotating parts such as fan wheels and sheaves.
Fan selection and air flow are checked against the bundle design.
Your engineers red-line our drawings, you approve the design twice before production starts, and you can witness the tests. Tap a step to see what happens and which documents you receive.
Spiro-Gills Thermal Products has designed and built bespoke air-cooled heat exchangers and finned tube in Stafford since 1946, and has supplied them to more than 100 countries. Thermal design is done in HTRI, welding is to ASTM code, and the company holds ISO 9001:2015. Petromarsh is their exclusive representative in the GCC.
For a replacement or upgrade, the old fan and motor details are enough to match it. For new fans, send the air flow and pressure.
