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Case Study P-CRID DFMA

Jason Beckwith

Jason Beckwith

Technical Sales Manager (Aerospace) Sales



Every night workers maintain and upgrade the London Underground to protect workers the track current is turned off. Only then can trained staff use a handheld device on the track to test that the 630V DC traction current is actually off. To increase safety and efficiency Tube Lines developed a prototype permanent trackside device (P-CRID) to protect engineers from live currents when they are working on the Underground. With a prototype built and successful field trials completed Tube Lines required a contract manufacturer to optimize the design and manufacture 600 units. With a short lead time and installation schedule they went to tender. Drallim won that tender as the most competitive compliant bid.

Piccadilly Line with P-CRID installed
Piccadilly Line with P-CRID installed


With only a prototype and minimal drawings our engineering team worked with an engineer from Tube Lines was based in-house at Drallim’s factory to approve the design and sign off drawings as they were produced so components could be purchased as soon as possible.

Software changes and PCB layout modifications were carried out by Drallim engineers to meet the latest operation and EMC requirements. The final certification required before manufacturing could commence was to ensure the enclosure met the required environmental rating. Again Purpose built manufacturing jigs; tooling and test equipment were also designed and built with an interlocked test area created for the high voltage testing of the completed assemblies.

"Tubelines placed a resident Engineer in our factory to speed up the approval process. We performed the IP testing in-house and with all the documents signed and approved by Tubelines the manufacturing process could commence on a  dedicated production line we set up for the assembly of the P-CRID’s."
Dave Mooney
Managing Director


The project was a superb example of working closely with a customer to achieve a tight deadline while maintaining the highest of quality standards. The units were supplied in batches linked to the install programme and we were readily able to keep them fully supplied to complete the project on time and at a most competitive price. Around 600 P-CRIDS have been installed across the Jubilee, Northern and Piccadilly lines.


Only recently Drallim updated it’s railway design accreditations and is working on several new monitoring projects related to track and signalling issues, including cable theft detection. Our FFC monitoring system can also be applied to oil filled supply cables which are still used in many railway applications. Our Engineers are ready and waiting to engage with you on whatever your railway related issues are. Call our Sales department now.