Serviceability of piping systems
In addition, it is possible to have a piping configuration that is functionally correct, but it’s configured in such a manner that servicing the equipment is difficult, and in some instances, impossible.
Never install lines in a position where they will block equipment access panels. Never install piping systems containing liquids where condensation or leaks could occur directly over electrical panels or electrical equipment without proper protection. Electrical access panels must have at least 36 in. of clearance.
Piping should be installed to provide clear access for servicing equipment. Piping systems should be properly cleaned and flushed to avoid original-installation debris from accumulating in the system or in connected equipment.
The position of the equipment to be installed should be given initial consideration. The position selected should make the installation less complicated, while creating a safe and workable atmosphere for future service and maintenance work.
To address the serviceability of piping, it is necessary to address the types of equipment and pipe accessories that are available.
Space requirements, service accessibilityValves should be installed in a position that allows servicing of units. Consideration should be given to the removal of bonnets and internal operating parts, and to the ability to pack units.
Isolation valves should be installed in a position that will permit the removal of the piping system or equipment.
Isolation valves should be rated at a pressure differential high enough to accommodate full shutoff, with one side open to atmospheric pressure.
Drain valves should be installed at the bottom of the piping system risers in a practical and serviceable area.
Strainers should be installed in the piping system in locations that allow the removal of screens for cleaning.
Strainers should be used on the inlet side of system components to protect critical operating parts from foreign particles and debris.
Flexible connections are installed in the piping system to prevent the transmission of vibrations from equipment to piping in other parts of the building.
Piping system components should be supported independently on each side of a flexible connection so that the connector can be easily removed when a piping system is disconnected.
Piping system components must be properly aligned to prevent any strain on flexible connectors.
Air vents should be installed in the high points of any piping system where air could accumulate, and they should be installed wherever the water stream reduces velocity, changes direction, or is heated. Any such areas should have either a manual or automatic air vent installed.
Automatic air vents should not be installed on the suction side of pumps.
If the vent port of an automatic air vent discharges in an area where there is danger of water damage, it should be piped to a drain. Automatic air vents should be installed with a manual isolation valve so that the air vent can be replaced or repaired.
If automatic air vents are going to be left open to the system, it is necessary to install an automatic makeup water system to compensate for the leakage of the air vent.
Finally, the air vent should be installed in an accessible area for use and service.
Thermometers or thermometer wells should be installed on the inlet and outlet of each heat transfer device. Consideration should be given to locations that will permit easy reading of the thermometer.
Thermometers should be installed in the piping system at points that prevent damage from normal service activities around equipment.
Pressure gauges: Gauge ports with shut-off valves should be installed on the inlet and outlet of each piece of equipment that reflects pressure differential in a piping system. One water pressure gauge can be used for connection between the inlet and outlet of a component by manifolding so an accurate pressure-differential reading can be obtained.
Pressure gauges permanently installed in a piping system should have a pigtail, or where applicable a snubbing device, between the gauge and system shut-off valve. The shut-off valve can be used as a snubber while reading system pressure, and should be shut off when not reading system pressure.
Flow switches: When pressure-differential flow switches are required, they should be installed in the piping system with a minimum of 10 pipe diameters of straight pipe on each side of the pressure-sensing point.
Pressure-differential flow switches have proven to be a service problem due to the small pressure drop across the system components.
If the piping-system line size is less than 1 in., a piston-type flow switch should be used.
If the piping-system line size is greater than 1 in., a paddle-type flow switch should be used. Paddle-type flow switches require at least a 1-in. pipe diameter spacing and operate best with 10 gpm or more of water flow.
Chemical feeders should be installed for the purpose of adding chemical treatment to the piping system.
The pot-type chemical feeder should be piped across the suction and discharge of the pump, and have a drain at the bottom with a hose bib adapter installed so that the pot feeder can be drained by hose to a safe location.
An isolation valve should be installed on each side of a chemical feeder.
The power-driven type chemical feeder, if used, should normally inject chemical treatment into the suction side of the pump.
Connected EquipmentBoilers shall be positioned in the equipment room to provide free access to the burner for servicing, and to provide ample room for cleaning or replacing the boiler tubes. Manufacturers should provide the installer with required clearances for these activities.
Boiler piping should be installed so that it neither obstructs nor prevents servicing, cleaning, or replacing activities.
Boiler shut-off valves and blowdown valves shall be installed in accordance with required boiler codes.
The proper boiler location in the equipment room requires adequate combustion air and ventilation.
Chillers and condensers: When placing chillers and condensers in an equipment room, there should be adequate room for flushing condenser tubes or chiller tubes, and for retubing the barrels.
The piping should be configured so that piping can be removed through the use of unions, flanges, or mechanical-type couplings, and so that clear access to the barrels can be obtained.
There should be adequate room for placing rigging equipment for compressor rebuilding or replacement.
The piping system should be self-supporting to provide ready access to the equipment when unions or flanges are disconnected.
Pumps: In a pump installation, consideration should be given for the future removal of the pump to accomplish motor or seal repairs. Installation should be on a base that will allow the pump to slide out of position without lifting or moving the piping.
The piping system should be self-supporting, with no piping load or piping strain transmitted to the pump. Manufacturers’ mounting instructions should be followed for in-line pumps.
Heating-cooling coils: Coils in air-handling systems or in duct systems should be installed with consideration to accessibility for cleaning and servicing.
The piping system should include isolation valves, control valves with inlet strainers, access for pressure readings, access for temperature readings, and proper drains. Steam-piping systems should be pitched properly (1/4 in. every 10 ft) and steam traps should be accessible.
Expansion tanks should be installed on all closed-loop systems where a water temperature change is present. Chilled-water-system expansion takes place during the “off” cycle.
The two most common types of expansion tanks are the air-cushion, compression-type tank and the diaphragm-type tank. The air-cushion-type tank requires installation with an air-collecting fitting, sight-glass kit, and drain to allow for monitoring and adjusting of the air charge.
The diaphragm-type tank requires an air-exhaust valve for the purpose of checking the air chamber for a leaking diaphragm.
Cooling towers should be oriented to direct discharge air away from the fresh air intakes of the building.
The piping system should be self-supporting to permit removal of the cooling tower when piping is disconnected.
The bleed piping from the tower piping system should be piped to a permanent drain location.
Depressurization: Special caution must be taken to relieve pressure from any piping system before service or removal.
Excerpted from “Guideline for Quality Piping Installation,” a publication of the Mechanical Contracting Foundation, Inc. For more information, contact the Mechanical Contractors Association of America, Inc., at 301-869-5800.