Case study

Challenge

• Our customer was designing a battery powered handheld instrument, which used a new and patented technique to analyse levels of airborne hydrocarbons.
• With the main market in the petrochemical industry, the instrument was expected to be used in a highly hazardous environment, requiring stringent ATEX certification.
• The application required two small air sampling piston pumps to be driven at exactly the same speed but slightly out of phase.

Solution

• Unaware that motors could be manufactured with dual shafts, our customer was initially considering two separate motors with a complex controller to deliver a velocity and phase locked motion control.
• To us this sounded overly complicated, being experienced of course in the design and manufacture of dual shaft motors.
• We designed a dual shaft brushless motor onto which a small pump could be secured at either end. The necessary phase difference would be set by grinding d-flats with appropriate offset into the shaft before the motor was assembled.
• The motor assembly contained an integrated encoder to enable precision motion control, and an enclosure which could be grounded to aid ATEX certification.

Results

• The 12mm brushless ‘in-runner’ motor was a good choice for this application because of it’s lower inductance and lack of brushes and commutator.
• Both of these features enabled ATEX certification to be made far simpler than it would have otherwise have been.
• The motor underwent extensive validation and testing using our in house equipment, and was then further validated by external labs with specific ATEX experience.
• The customer was able to simplify their motion controller significantly, and order a single part number from us with all the features necessary to ensure reliable, safe and long-life operation.

STAGE 1

Initial spec

• Naturally these instruments are used in highly hazardous environments, in particular, environments such as landfills, mines and refineries may contain concentrations of explosive gasses.
• To remove risks of ignition all equipment must be ATEX certified.
• The customer approached us with an initial specification of two motors per unit, synchronised by an complex controller.
• Since motors are a major source of ATEX concern a single motor would make certification easier, and control significantly cheaper.

STAGE 2

Reliable design solutions

• Our design team suggested a way to drive both pumps with a single motor sandwiched in the middle.
• A specific type of brushless motor technology, optimised for low inductance helped significantly with getting ATEX certification for the whole device.
• We had to tweak the winding to comply with maximum inductance limits whilst maintaining enough motor torque for the dual pumps.
• We also designed an encoder sealed within a grounded metal enclosure, and adopted a ground-plane flex PCB to carry the encoder signals separately from the motor drive signals.

STAGE 3

Validating and manufacturing

• The motor underwent extensive validation in order to meet their quality criteria using our bespoke in-house testing equipment.
• Further specific ATEX testing was performed out of house as needed.
• We utilised processes to ensure ultimate quality control, and product traceability. 
• We supported the customer with their final device ATEX application, which they were successful in achieving.
• Detailed planning, lifecycle management and statistical control processes, enabled us to manage their risk, and deliver on time and to spec.