At its simplest, differential pressure is a different level of pressure between two different points in a system. For example, the difference between the pressure at a pump inlet and the pressure at the pump outlet. Differential pressure is often written as “DP”.
At first glance, it’s hard to understand how differential pressure could lower emissions, prolong the life of air conditioning filters and provide various other benefits when it comes to dust collection in factories and other environments. So let’s look at this in a little more detail.
What differential pressure tells us
In heating ventilation and air conditioning (HVAC) systems, the pressure difference that we’re interested in is the difference between the pressure on the dirty”side of a filter in a dust collection system and the pressure on the clean side of the same filter. The difference tells us a lot about how much resistance there is to the airflow and how much resistance is being caused by the dust which has already collected on the filter.
In fact, the World Health Organisation uses room pressure differentials as one of its checks on pharmaceutical plants to ensure that air is not being cross-contaminated from one room to another – http://www.who.int/medicines/areas/quality_safety/quality_assurance/SupplementaryGMPHeatingVentilationAirconditioningSystemsNonSterilePharmaceuticalDosageFormsTRS961Annex5.pdf.
If the DP suddenly rises it may tell us that the cleaning system isn’t working or that equipment that is meant to discharge dust is no longer working efficiently. On the other hand, if the DP suddenly drops, we need to investigate whether the filter has ruptured or is leaking.
There are various gauges and digital tools that can be used to measure differential pressure and some of these can be linked to monitoring systems which will then indicate that filter cleaning is necessary. Cleaning the filter may require dismounting and dismantling a ductwork blast gate damper https://www.dustspares.co.uk/Blast-Gate-Damper.html – luckily these are designed to be easy to disassemble.
Other impacts of differential pressure
If the HVAC system also includes fans, these need to be able to cope with the DP and any static build-up in the ductwork, as well as filters that have started to accumulate dust. Blast gate dampers can help to control air volumes in the system as part of DP system design.
Differential pressure is a technical subject but worth getting to grips with because it can make your HVAC system operate far more efficiently.