PERKINS PUMPS UP TEST FACILITIES

The new equipment was fitted as part of a major upgrade to an existing pump test facility, with the principal objective of extending the capabilities of the test rig so that it could be used with pumps of all types, including the most recently developed models.

The pump test rig is used not only to look at the performance of the pumps themselves, but also of the associated fuel injectors and engine control modules (ECMs). As well as allowing new pump designs to be readily evaluated, it is also particularly useful for testing new software versions in the ECM and determining their effects on fuel economy and emissions. Before it was upgraded, the test rig employed a dc motor, arranged for variable speed operation, to drive the pump under test. The motor could, however, provide a maximum output torque of only 50 Nm and, while this was perfectly adequate when the rig was first designed, is nowhere near sufficient for testing the latest pumps, which in some cases require driving torques in excess of 100 Nm.

In addition, the existing dc motor and drive system were becoming unreliable and difficult to maintain, and the test rig’s relay-based control system offered, by modern standards, a poor user interface and it was also limited in its capabilities. Perkins Engines took the decision, therefore, to upgrade the drive and the control system and, in line with company policy, it invited three potential suppliers to submit offers for the work.

“We decided to go with the offer from Softstart UK for several reasons,” said Jason Poole, Component Test Engineer at Perkins Engines. “We liked the company’s proposal, which showed a clear understanding of our requirements, and we also knew from previous experience of working with Softstart that it not only provides excellent equipment but also complements it with equally excellent support. Finally, Softstart’s pricing was very competitive.”

The key to upgrading the capabilities of the test rig was replacing the existing dc motor with a standard ac induction motor – motor control technology having moved on since the rig was first built there was no performance benefit to be gained by retaining dc drive and to do so would have been unnecessarily costly. For the replacement motor, Softstart UK chose a 37 kW four-pole foot-mounted machine which was easily capable of meeting the new torque requirements, and which could be readily accommodated in the available space.

To provide flexible control of the motor, a Hyundai 37 kW N700V inverter drive was used. This model was selected because of its durability, its outstanding speed and torque response, and because of its support for speed sensor feedback, which not only ensures excellent speed accuracy and stability, but also allows high torque to be generated from standstill. The new drive system was complemented by a new control system, which uses a modern Hitachi EH-150 series programmable controller (PLC) to replace the old outmoded and inherently unreliable relay logic. This compact modular PLC combines high operating speed with versatility and large program memory capacity, and will make it easy for modifications to be made to the system should the operational requirements of Perkins Diesel change in the future.

Finally, a new touch-screen operator interface was provided, based on a Hitachi EH-TP45 HMI unit, which has a 10.4-inch colour display. Softstart UK has configured this unit to provide the operator of the test rig with convenient and intuitive control over all of the rig’s functions, and to provide realtime feedback on operating status, as well as alarm indications should a fault condition occur.

At the time of writing the upgraded test rig has been in service for over six months and the component test team at Perkins Engines is very happy with its performance. It is proving totally reliable in operation and the test rig is now much more convenient to use and much more versatile than it was before the upgrade. The new drive system can provide up to 120 Nm of torque continuously, and a peak torque of up to 180 Nm for short periods, which is amply sufficient for testing even the largest of modern fuel pumps.

“We have had excellent service from Softstart UK at every stage of this important project,” said Jason Poole, “from the initial enquiry right through to installation and commissioning. In particular, the work on site was carried out quickly and efficiently, with the minimum of disruption to our operations and, once the new equipment had been installed it was, for all practical purposes, ‘right first time’.” We’ve used Softstart UK in the past and, based on our experience with the test rig upgrade project, I have no hesitation in saying that we’ll be happy to use them again in the future.”