PICC valves - don't shoot the messenger
The quicker the industry accepts the shortcomings of the past and embraces new technologies like PICC valves, the quicker our buildings will reach their full potential and deliver what is promised, says Peter Lowther
The results of any accurate test of any type or discipline, or from any industry must provide results that are repeatable. That said, results, when repeatable, do not in themselves necessarily prove accuracy.
When commissioning conventional water systems, water flow rates are quantified and generally set using the same types of testing equipment, usually an orifice plate and manometer box or similar. Once set, and providing the results repeat when witnessed, this is considered sufficient. A tick is put in the box so to speak and everyone is satisfied.
With the introduction of pressure independent control valves, however, another component enters the equation - an 'outsider' effectively, which doesn't always appear to support the flow rate readings from the orifice plates and manometer box. Its presence adds a new dimension to the commissioning process since, whereas previously, a turn or two on the double regulating valve would have done the trick, that option no longer exists.
So which is correct - the PICC (pressure independent characterised control) valve and its pre-set value or the orifice plates and manometer box? Actually, the answer is that both are correct. Despite their shortcomings, the measuring devices are usually not too far off and the commissioning teams usually use them efficiently. Conversely, if the PICC valves have been set correctly and are given the right conditions they will also perform to a close tolerance. So where's the problem? The problem lies in fact in the wording of the proposition, 'given the right conditions'.
PICC valves require three conditions in order to perform to the tolerances claimed by their manufacturers. They need sufficient differential pressure across the valve and the availability of sufficient water of the correct quality. That's all - pressure, quantity, quality.
A sufficient differential pressure is generally around 35kPa minimum across each valve. A sufficient quantity of water means just that, and the requisite quality means de-aerated and reasonably clean.
Most projects that have used PICC valves and hit problems have water issues, not with quality, but more often with quantity and pressure. If a branch regulating valve is left partially closed and/or an isolating valve left shut, the PICC valves will not receive the water they need and the pressure is therefore likely to also be reduced. Under these circumstances, the commissioning team will report that the volumes from the PICC valves are down or variable and suddenly the PICC valve is 'in the dock' and commissioning ceases.
The PICC valve is actually guilty of nothing. Had the system been in commissionable condition the valve would have done what it promised on the box. The problem for the valve manufacturer, however, is that his equipment is, in effect, the new kid on the block and thus any suspicion naturally gravitates in his direction.
Problem never used to happen
The first argument against him is that this problem never happened in the past. Commissioning teams traditionally set the flows with double regulating valve etc and the manometer boxes proved the accuracy of the setting and the flow rate. But they didn't. They proved nothing more than the repeatability of what could have been an inaccurate result. So the apparent inaccuracy of the PICC valve is not a problem of the valve itself but a sign, signal or messenger that something in the system other than the valve, needs to be sorted out.
The real issue is that buildings are often rushed towards handover with insufficient time given to the pre-commissioning and troubleshooting of the hydraulic system. The commissioning team is invariably on a 'read and record' remit, which means that the pre-commissioning and troubleshooting functions disappear between the floorboards.
In the past, the repeatability of potentially inaccurate values still got some buildings over the line whereas these days, PICC valves will identify these projects as deficient. The problem is that in the heat of the moment, the failure of the hydraulic system is often seen as the fault of the PICC valves, rather than hydraulic failure being the real reason the valves fail to work.
So where's the evidence? One factor could be the urgent drive towards soft landings or in other words, the process of a graduated project handover, aftercare and the provision of a forum for client feedback. This initiative has been driven by the recognition that many projects comprise a series of technical steps that are not properly planned or properly linked that contain technology and innovations, which sometimes conflict with each other and which many do not understand.
I admit that in the early days of supplying PICC valves even we did not fully understand what was happening and the struggle was so intense that there were several occasions when we considered giving up on PICC valves altogether.
But three things happened that convinced us to keep going. One: the obvious deficiencies/errors revealed when problem sites were properly investigated. Two: the fact that any building that had sufficient time spent on pre-commissioning worked almost straight out of the box. Three: the recent discussions that have begun regarding the need for 'soft landed' buildings'.
Soft landed projects are those on which the handover of a building to its occupier or owner is planned-for and carried out over a period of time rather than at a point in time. The reason this new approach is seen as necessary is the growing awareness that buildings handed over conventionally are often rushed and, therefore, either need urgent post occupancy attention or, if left alone, never reach the full potential envisaged by their designers.
There is no doubt in my mind that PICC valves represent the future and contrary to some concerns, we do not believe they spell the end of water commissioning. Nevertheless, the quicker the industry begins to accept the shortcomings of the past and embrace new technologies and new methods, the quicker our buildings will reach their full potential and deliver what was promised.
// The author is chairman of Ability Projects //
12 February 2013