Opportunities for value engineering come in little orange boxes
Visitors to exhibitions may have seen this rig that Belimo uses to demonstrate how pressure-independent characterised control valves (bottom) maintain a constant water flow against differential pressures from 30 to 350 kPa compared with changing flow through simple CCVs (top two valves).
Those distinctive orange Belimo direct-coupled actuators that abound in so many building-services installations and characterised control valves offer the potential for value-engineering opportunities.Belimo’s direct-coupled actuators have become so totally established since their introduction in 1975 that they dominate the market. Those little orange boxes are everywhere! Originally designed for air-control applications such as dampers in ductwork and air-handling units, their scope was extended in 1999 to controlling water flow. New generation
Over the course of 2005, a new generation of actuators has been gradually introduced to market — a mammoth task involving the replacement of a million units a year of the previous design. These new actuators are of modular design, comprising three ‘layers’ — the baseplate with coupling, gearbox and electronics. The electronics box is only a third the size of the previous design and features a new motor that is very much smaller than the old version. The acceptance of the new generation in the OEM market, which is about 30% of Belimo’s total sales, is assured by the new units having the same footprint as those they replace. The inclusion of bus-capable actuators in the new generation and the characterised control valve for water that was introduced in 1999 offer significant and intriguing opportunities for value engineering. Hardware costs and installation costs are both lower than other solutions, so all perceptions of value engineering are satisfied. LonWorks
The potential for value engineering offered by the MP-Bus range of the new-generation actuators arises from the ability to connect up to eight actuators on a single 3-wire bus, which carries both power and data, to a controller. A sensor can also be connected to each actuator and become part of the network. Central controllers can be interfaced with LonWorks or EIB/Konnex. The result is that up to eight actuators and their associated sensors become a single node on a LonWorks network. In LonWorks technology, one channel is restricted to 64 nodes. Using a Belimo UK24LON controller, each of these 64 nodes can be associated with eight actuators, each with its own sensor. That is a total of 1024 devices. Savings
The scale of the savings is demonstrated by the Sälipark multifunctional centre in Olten, Switzerland. Even before commissioning, the application of this bus technology paid for itself, compared with a system based on each actuator and each sensor being connected from the control cabinet with its own separate cable. At Sälipark 244 devices were connected using MP-Bus technology, including fire damper actuators, VAV controllers, damper actuators, valve actuators, MP multi sensors. Additionally, 92 passive and active sensors were connected via actuators; these were standard sensors, not supplied by Belimo. There were four major areas of cost saving. • Number of terminals reduced from 1166 to 113 — a 90% reduction. • Number of cables reduced from 362 to 42 — an 88% reduction. • Cable length shortened from 15 565 m to 3587 m — 77% less. • Number of datapoints cut from 365 to 42 — 88% fewer. Belimo has identified cost savings as follows. • Devices £5100 • Installation £27 200 • Commissioning £2200 • Total £34 500 — amounting to about 16%. Features that simplify installation contribute to cost and time savings. For example, actuator connections cannot be mixed up in the control cabinet since they are automatically identified by software using the MP-Bus address. Balancing
Another aspect of building services addressed by a Belimo innovation is the balancing of water-distribution systems. Basically, Belimo has devised a concept that makes hydraulic balancing unnecessary. Instead of the conventional approach of using globe valves to control the flow of water, Belimo’s approach is based on quarter-turn ball valves with a specially shaped disc inserts to enable them to control flow accurately, rather than just act as on/off devices. These characterised control valves (CCV) have become widely accepted and applied on a wide range of projects. The shape of the opening in the disc causes the water flow to increase slowly when the valve begins to open. An equal percentage flow characteristic is achieved, and the resulting thermal output is linear. Combining a CCV with a differential pressure controller stabilises the flow rate at a particular setting of the CCV over a differential pressure range from 30 to 350 kPa. These devices are known as pressure-independent characterised control valves (PICCV) and provide a means of setting and controlling water flow. Just six sizes of valve from 15 to 50 mm enable water flows to be set from 0.025 l/s (minimum flow with a 15 mm valve) up to 2.5 l/s (maximum flow with a 50 mm valve). Each valve has a substantial flow range; a 15 mm valve, for example, can control flow from 0.09 down to 0.25 l/s. Because the flow is controlled by a ball valve, shut off is ‘bubble tight’, so there is no energy-wasting leakage of hot or chilled water. This feature alone is said to have an 18-month payback. Tested
The performance of these valves has been tested by BSRIA, which has prepared a witness report. Adding an actuator with positioning capability to the ball valve enables flow rate to be controlled over the valve’s range. Despite their clear benefits, PICCVs have only been gradually accepted in Britain. Andy Bartlett, managing director in the UK, believes the reason is the way project responsibilities are traditionally shared. ‘Globe valves are part of the mechanical package, whereas actuators are part of the controls package,’ he explains. ‘It is the systems integrator that is in the best position to perceive and exploit the benefits of PICCV.’ Andy Bartlett further explains that once the concept is explained, there is little resistance to the use of PICCVs and that getting consultants’ specifications changed is the key to exploiting the value-engineering benefits of PICCVs. Belimo Automation UK Ltd is at Shepperton Business Park, Govett Avenue, Shepperton, Middx TW17 8BA