The goal of any HVAC piping installation is to have a system that is designed properly and with the right materials, installed correctly, functions properly, and is readily accessible for maintenance. Proper pressure testing, flushing and cleaning is important to help ensure problem-free system performance.
Before pressure testing a piping system, inline devices that may not be able to withstand test pressure, such as flow meters, pressure sensors, DPTs, etc., should be isolated or removed. Systems should be pressure tested for 2-4 hours at a minimum of 1.5 times the operating pressure. Most hydronic systems (chilled water, reheat, preheat, etc.) are tested using water. Steam and condensate systems are usually tested using clean compressed air. If the piping is subject to freezing, it is important to make sure test water is removed at the completion of testing, or, alternatively, the system can be tested pneumatically. Otherwise, broken or burst coils or piping can be a costly consequence.
After pressure testing has been completed, pipes must be cleaned and flushed. This important step requires that all valves are open and the system operates as a complete loop. In a new system, clean water and a mild detergent such as TSP (trisodium phosphate) should be circulated for a minimum of 4-6 hours. Existing systems with silt, sludge or debris problems need specialized cleaning at higher velocities to remove foreign matter. These issues must be analyzed on a case-by-case basis to determine the severity of the problem.
Once a system has been cleaned and flushed, it must be filled and chemically treated, as good heat transfer requires piping that is properly cleaned and treated, and remains clean. Specifications may call for a particular brand or product such as a rust inhibitor or other treatment. Fluids should be sampled and tested on a yearly basis by a competent testing company and adjusted accordingly. We also recommend periodically inspecting piping systems so that problems can be detected at an early stage fixed with little effort at minimal cost. If these procedures and subsequent maintenance are not properly followed, clogged strainers, coils, control valves and heat exchangers can cause costly problems down the line.
PJM Mechanical Contractors, Inc. is a multi-faceted mechanical contractor providing construction and installation, service and maintenance, and design/build services in a comprehensive range of mechanical disciplines that include HVAC, plumbing, controls, refrigeration, custom metal fabrication, piping, fire protection, and backflow preventer testing. PJM primarily serves clients in pharmaceuticals, manufacturing, healthcare, institutional, and other various commercial and industrial sectors.