In New Zealand over 5 million cows produce 3% of the world’s milk. 25 million litres of milk are processed per day. 95% is exported. Given our remote location, milk powders are best for transport, accounting for 47% of dairy exports.

New Zealand processing plants lead the world when it comes to drying milk products. Our industry has an international reputation for innovation, excellent hygiene and quality technology.

Keeping that technology running at its best is where we excel. Stewart & Cavalier is proud to work with the dairy industry. We specialize in high pressure valve maintenance for spray dryers.


years life expectancy for well maintained valves


new components fitted as standard


percent of valves fail pre-service test*


percent customer satisfaction rating

* based on our service records over the last 3 years


Stewart and Cavalier is a family firm, based in Te Awamutu, the heart of New Zealand’s dairying country. A major player in our engineering industry for over 60 years, the spray dryer valve business is a successful niche for our specialist team who are are fast making a name for themselves as the go-to supplier for the industry.

We employ over 40 staff in our engineering workshop. Our spray dryer valve service team are all qualified tradesmen, Australasian certified and trained installers of Swagelok components. Our sales engineer, Ross Burrell, is an ex Swagelok employee with over 10 years’ experience with Swagelok products, specializing in spray dryer valves.

In 2014 we obtained exclusive use of the original engineering drawings and parts lists from Swagelok for the modified OEM valve configurations. We’re in a unique position to keep these crucial valves functioning reliably and and to ensure they stand the test of time.

Although we specialise in modified OEM Swagelok valves, Stewart & Cavalier is equipped to provide a full maintenance service for all types of high pressure spray dryer valves.

We also supply complete new units where full replacement is required, including turnkey projects to provide the necessary certified high pressure product distribution header associated with these valves. It would be beneficial if a planned preventative maintenance schedule was incorporated within the engineering and maintenance department to ensure all electrical, mechanical and pneumatic plant and machinery is maintained to design specification.

Excerpt from the Approved Code of Practice for the Prevention, Protection and Control of Fire and Explosion in New Zealand Dairy Industry Spray Drying Plant.


We recommend annual scheduled maintenance. It is rare for new or serviced valves to fail within one year of service. A mid-season shut down is to be avoided at all costs. Valves should never jeopardize the smooth running of your dryers.

Avoid Risk

Fire in the drying chamber due to poor valve operation would be catastrophic. Not only endangering life, it could destroy the dryer and surrounding assets, devastating the milk powder market.

  • Disengaged actuator lines -> valve actuation failure
  • Product leaks within the valve assemblies -> increased risk of fire.

Prevent Loss

Maximising efficiency of your dryers and preventing downtime due to parts failure is essential in the efficient running of your plant.

  • Air leaks -> poor valve actuation.
  • Poor valve shutoff -> droplet formation in your dryer

Reduce Costs

  • Replacing all serviceable valve parts with the designed specification spare parts, should ensure trouble free operation for next season.
  • We build a complete service history for each valve, ensuring no unnecessary work is undertaken.

5.5.1 Equipment must be regularly tested to ensure fitness for use. The testing procedures applied must be appropriate for this purpose but should take into account the conditions of use and the recommendations of the equipment manufacturer, supplier and installer

Excerpt from the Approved Code of Practice for the Prevention, Protection and Control of Fire and Explosion in New Zealand Dairy Industry Spray Drying Plant.


Pre-Service Test

We test the valve prior to service to determine the extent of leak rate (if any). Our custom designed workshop test rig complies with industry best practice. Our service database shows 75% of valves fail this initial test. It is an important part of the process, allowing our engineers to provide useful facts and figures to our clients.


4 new components are fitted as a standard procedure:

  • stem
  • packing bush
  • packing bolt
  • stem seal kit

A detailed history of each client’s numbered asset is kept so we know which parts were replaced on which valves during the last service.

Post Service Test

  • A pass indicates the valve service is complete. We compile a detailed service and test report and arrange delivery and or installation.
  • Failures are not uncommon and are part of the normal process. Our clients are kept fully informed throughout. If the valve fails testing at this point, approval to fit a new body is sought.
  • The life expectancy of a well maintained valve body is approximately 3 years in our experience.

We follow a fully documented in-house procedure and are happy to share the details with our clients. Please request the full process diagram when you book your maintenance with us. All components of a pressure nozzle atomisation system including the high pressure pump, feed line, flexible couplings, valves, nozzles and other fittings shall be constructed of appropriate materials with adequate strength to withstand the pressures necessary for effective atomisation. Care must be exercised when selecting combinations and positioning nozzle assemblies in the dryer to ensure that concentrate does not impinge directly on hot surfaces because of inappropriate spray trajectories.

Excerpt from the Approved Code of Practice for the Prevention, Protection and Control of Fire and Explosion in New Zealand Dairy Industry Spray Drying Plant.


Happy with your current supplier and don’t want to change what works? Perhaps your in-house team takes care of dryer valve maintenance? Either way, if you’ve read this far, you want to know if there is a better option. We invite you to the experience the Stewart and Cavalier difference…

Outsourcing is the way forward

You have a qualified team of fitters in-house but do you have a custom built test rig? Do you have access to reports enabling you to forecast future costs? Are your fitters close to maximizing their hours at year-end? Do you need to concentrate on other issues?  We can take ownership of your valve maintenance for you.

Legendary service
Our technical expertise is a given, what makes the difference is the service level we offer. We love what we do but we hate to brag. Best you get an independent review from our clients. Read our testimonials

Experienced engineers and fitters
Valve maintenance is a specialized area, you wouldn’t risk opening up a pressure relief valve for routine maintenance. Overy many years, our team has developed a comprehensive knowledge of how best to maintain high pressure dairy spray dryer valves. Read about our Sales Engineer, Ross Burrell.

Location is not an issue
Concerns around timing and freight are negligible. Our sales team are constantly on the road to provide assessments and talk face to face about your issues. Our fast turnaround guarantees minimal disruption.

We have been servicing spray dryer valves at various sites throughout New Zealand. We are keen to grow this business both nationally and internationally. Talk with our Sales Engineer, Ross Burrell to find out how we can help your plant.



We invite you to experience the Stewart & Cavalier difference. Select one of the buttons below to find out more about what we offer.

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Are your high pressure hoses ready for next season?

You may know Stewart & Cavalier for our HP valve service for spray dryers. But do you know we also service, test and replace dairy spray dryer hoses?

Our service is:

  • Thorough – We remove your hoses from the dryer and transport them to our certified test facility. A visual check for damage is carried out first before mounting the hoses on our test rig. Hoses are hydraulically tested for an agreed time period at an agreed pressure, (typically 1.25 x working pressure).
  • Accurate and fast – Our engineers deliver back to site and reinstall, using a numbering system to position each hose back exactly where it came from. You receive numbered test certificates and we retain a test history. Pre-approved jobs can be turned around in just a week.
  • High quality – We supply only superior brands where replacement stock is required. Our hoses are manufactured in the United States, 6,000 psi rated and compliant with FDA and Council of Europe regulations on the use of colorants in polymers coming into contact with food; giving you complete peace of mind.

Experience the difference – If you haven’t yet booked your HP valve or hose service, now is your chance to experience the Stewart & Cavalier difference.


Spray drying involves atomising the milk concentrate from the evaporator into fine droplets. This is done inside a large drying chamber in a flow of hot air (up to 200C) using either a spinning disk atomiser or a series of high pressure nozzles. The milk droplets are cooled by evaporation and they never reach the temperature of the air. The concentrate may be heated prior to atomisation to reduce its viscosity and to increase the energy available for drying. Much of the remaining water is evaporated in the drying chamber, leaving a fine powder of around 6% moisture content with a mean particle size typically of < 0.1 mm diameter. Final or “secondary” drying takes place in a fluid bed, or in a series of such beds, in which hot air is blown through a layer of fluidised powder removing water to give product with a moisture content of 2-4%.

World's Milk Produced0%


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