Turning to the safety issue

In collaboration with AstraZeneca and Hosokawa, RotaVal has produced a new range of Hypergienic rotary valves

With a global business comes global responsibility – environmental, social and economic. AstraZeneca (AZ) has stated its commitment to meet or exceed legal requirements and to provide a safe and healthy work environment for all its employees. The company constantly evaluates the manufacturing systems installed, while new processes are subjected to intense scrutiny at every stage.

'If you have a very low Occupational Exposure Level (OEL), then the equipment should be designed so that the operators should not have to wear respiratory protective equipment at all times when using that equipment,' said John Sherwood, associate principal scientist, product development, at AZ's Macclesfield facility. 'There are good reasons to return to basic principles before specifying machinery. We do not simply accept what is available off the shelf, but consider how to improve the overall process.'

This philosophy was brought into focus when AstraZeneca began to consider equipment for new production facilities at Bristol, Macclesfield and in Puerto Rico.

Essentially these facilities would be based on fully enclosed mills with rotary valves either side to control pneumatic feeding through the system. The products handled range from sticky, glassy particulates to fine powders. Bulk density is typically around 150kg/m³, and some products are susceptible to flood feeding. The fine powders test the containment capabilities of any system. Even the best Clean In Place (CIP) valves then available had to be fitted outside the high containment isolation boxes, meaning that workers would have to wear full suits when cleaning.

totally enclosed

The new facilities were conceived as totally enclosed, working to OELs between 0.01g/m³ and 0.001g/m³. 'We knew that if we could achieve complete enclosure of the rotary valves, there would be economic and environmental benefits, such as reduced waste of very expensive pure chemicals, lower disposal costs, better containment with a consequent improvement in working conditions, a reduction in downtime and enhanced productivity,' commented Sherwood.

'To meet this requirement two problems had to be covered. The first was that the rotary valve had to be redesigned so that it would fit inside a glove box and could be disassembled and cleaned within this glove box. The second problem was that existing design of valves used castings, which often have small inclusions. Although not important in most applications, the surface finish was unsuitable for enclosure in an isolator box. We needed to totally redesign the valve to achieve complete freedom from pinhole porosity and inclusion defects. This would allow the valves to meet higher standards and gain full validation.'

AZ joined up with Hosokawa Micron and RotaVal to form a small development team to work on the project. Among Hosokawa's responsibilities was the production of a new rotary valve containment system based on the company's proven range of Stott Isolators. An early decision was made to place the drive motor outside the isolator box, introducing the need for a new approach to the contradictory requirements for secure motion transfer through the box wall to the valve, and a system to allow easy removal of the drive shaft during CIP procedures.

'There were so many new features envisaged in this installation,' said Hosokawa sales manager Andy McLeish, 'that the team decided to build a full-size wooden mock-up of the whole isolator and valve assembly using early working drawings of the valve supplied by the RotaVal design team. By asking operators to simulate normal running and clean down routines, we were able to fine-tune to eliminate any problems before building actual equipment.'

Ian Blackmore, managing director of Chippenham-based RotaVal, described the challenge: 'This project meant a complete rethink of valve design techniques, the creation of a number of new manufacturing processes, and a very steep learning curve at the leading edge of current technology.'

hygienic containment

Now available to the food, chemical and pharmaceutical industries, Hypergienic Rotary Valves are offered as standard in sizes from 100 to 300mm, fully tested and certified against 10 barg internal explosion and flame containment (hydrostatic testing is used to 13 barg). Valves are fabricated from 316L stainless steel with a 0.5Ra polished finish internal and external as standard with 0.2Ra finish as an option, using a completely crack and crevice free design. All surfaces are self-draining to avoid fluid retention after washdown, and special features permit cleaning fluid injection or air blast for drying.

The new valves incorporate hygienic quick-release anti-galling end cover fixings, fixed lower rails to aid easy opening of the valve assembly with minimal operator effort, a remote geared motor mounting with removable drive shaft, and full safety interlocks. Bearings are filled with FDA-approved grease and sealed from cleaning fluid by lip seals. The end covers are equipped with inert gas purge and leakage monitor ports. Position indicators provide operators with the essential information to check rotor pockets are empty before the valve is opened. Dummy end covers can be provided, incorporating a spray ball.

AstraZeneca was delighted with the outcome. 'We have improved our containment capability, made the working environment easier and safer and met a demanding set of specifications under tight timescales,' said Sherwood.