Sound & Vibration Commissioning STUART MCGREGOR, PE ENGINEERING DYNAMICS, INC.

Transcription

1 Sound & Vibration Commissioning 1 STUART MCGREGOR, PE ENGINEERING DYNAMICS, INC.

2 2 Sound and Vibration: Maintaining Tenants Spaces and Building Mechanical Systems 22 August 2018

3 Speaker 3 Stuart McGregor, P.E. Stuart is president and senior acoustical engineer at Engineering Dynamics, Inc. He has experience analyzing, designing and measuring noise and vibration from building mechanical systems on projects ranging from residential condominium buildings to commercial and industrial spaces. Stuart has successfully completed over 1000 projects, testified as an expert witness in noise and vibration related cases, and teaches sound and vibration training seminars for NEBB certified professionals and technicians. Professional affiliations include, Acoustical Society of America, Institute of Noise Control Engineering, American Society of Heating, Refrigerating, and Air Conditioning Engineers, and NEBB.

4 A Proper Building 4 Building owners and design professionals are very familiar with design requirements for Temperature, Humidity, Odor, Fresh Air (Make-up air) and Lighting To have a building that will serve human comfort needs and lead to a productive work environment the Acoustic (Sound) and Vibration environments of the building must also be addressed. Note: We have all been in building where noise from system diffusers is too high, or the spaces echo too much.

5 Why Should the Building Owner consider Sound & Vibration Commissioning 5 Cost - the cost to fix sound and vibration related issues can easily be ten or more times the cost to initially install noise mitigation. Verification - that building design goals and specifications have been achieved have been accomplished and that a quality project has been completed. Satisfaction of building occupants. Help to Minimize - construction delays and costly issues during building initial occupancy.

6 When Should the Sound & Vibration Commissioning Begin 6 Ideally during the Schematic and Design Phases of a project. During the Schematic Phase non-compatible adjacent spaces can be relocated or other building parameters such as floor thickness or wall thickness can be adjusted. This will minimize design changes during CD Phase and minimize change orders during construction. Less than Ideal (however still valuable) during the CD Phase or Bidding Phase. May result in change orders. During Construction or Post-Construction much more costly; delays and change orders. Bottom line is cost - considering the impacts sound and vibration on building occupants and processes, commissioning during the SD and CD Phases can result in significant cost savings.

7 What Subtasks are Involved in Commissioning for Sound and Vibration? Vibration define maximum allowable vibration levels for building mechanical equipment and building structure in vibration sensitive areas. Then verify with measurements. 7 Sound define the appropriate maximum building equipment sound levels for the various space usages within a building. Then verify with measurements. Building Acoustics - Defining appropriate demising walls, floor / ceiling assemblies and acoustical treatments. NOTE: This task is outside the expertise of a typical NEBB Professional or M&P Design Professional.

8 Defining Appropriate Maximum Sound Levels from Building Mechanical Systems (1) 8 The appropriate sound levels in various spaces inside a building depends completely on the usage of the space. Maximum sound levels are typically defined in terms of the Room Criteria (RC) or Noise Criteria (NC). ASHRAE recommends RC as preferable to NC. ASHRAE Applications Handbook Chapter 48, Table 1 provides design guidelines for HVAC related background sound in rooms, in terms of RC and NC. For Example: Conference Rooms NC / RC = 30 / 30(N) Open Offices NC / RC = 40 / 40(N)

9 Defining Appropriate Maximum Sound Levels from Building Mechanical Systems (2) It is critically important to identify noise sensitive spaces within a building during the Schematic Phase of a project when the cost impacts of treating the space or moving that usage to another part of the building can be accomplished with minimal impact. 9 Example #1: About 25-years ago I worked on a large office complex which had a gymnasium, which was initially supposed to be used as a recreation / basketball area. During the initial construction phase the use was changed to a presentation / recording studio. Two very different acoustical requirements.

10 Defining Appropriate Maximum Sound Levels from Building Mechanical Systems (3) 10 Example #2: Another example an architect and mechanical engineer located a large air handler on the roof (directly in the center) of the sanctuary / worship space at a large church (with a lightweight roof structure). Vibration from the HVAC unit coupled into the roof structure and resulted in low frequency noise in the sanctuary. Mitigation: The roof structure was not designed to handle additional weight needed to attenuate vibration. Cost: In 1995 dollars over $100,000 to relocate.

11 Defining Appropriate Maximum Sound Levels from Building Mechanical Systems (4) The solution is to define the space usages for all areas of the building and use ASHRAE criteria to specify NC / RC design goals for each space. 11 Then (Most Importantly) review these design goals with the project owner and design team. Then have these design goals put down in writing in the project documents. This tasks protects the Owner, the Design Team and the Contractor.

12 Defining Appropriate Maximum Sound Levels from Building Mechanical Systems (5) Back to Example #1: Gymnasium NC / RC rating is 50 / 50(N) Speech Recording Rooms NC / RC rating is 25 / 25(N) 12 The NC / RC criteria for acceptability had not been defined and there was a lot of finger pointing. However, in the end Contract Documents which the Design Team relied on clearly showed the space as a gymnasium. So, in this case the owner had to absorb the costs.

13 Defining Appropriate Maximum Sound Levels from Building Mechanical Systems (6) 13 Some basic design guidelines for HVAC systems to minimize HVAC sound levels and lower NC / RC ratings are; 1. Ductliner this cannot be overstated specially downstream of VAV boxes. 2. Select diffusers with low NC ratings at maximum design air flow. 3. Balancing dampers located far from diffusers; back at main take-offs from trunk lines. 4. AHU / Fan selection for low noise levels. Fan Walls solve many HVAC related noise problems. 5. Vibration isolation of AHU s.

14 Defining Appropriate Maximum Sound Levels from Building Mechanical Systems (7) In our information age there is no shortage of reliable ways to get good design criteria guidelines ASHRAE publications are online. 2. There a many qualified acoustical engineers around. 3. There are also many website were this information can be found. Everyone copies everyone else, who have copied ASHRAE. Acceptable NC / RC ratings for various space usages have not changed in decades.

15 Defining Acoustical Treatments and Partition Designs for Various Spaces(1) 15 As noted above this task should be contracted to an acoustical engineer. It is discussed here because the acoustics of the room / space is as important as noise from building mechanical systems. While, the expertise to analyze and address this issue is or maybe outside the expertise of most M&P Design Professionals, Architects, Commissioning Agents, they should have sufficient knowledge to at least recognize when a noise issue may arise, and bring the issue to light.

16 Defining Acoustical Treatments and Partition Designs for Various Spaces(2) 16 Example #3: A mechanical room located adjacent to private offices or conference rooms. The mechanical equipment may be completely within spec., however, a demising partition between the spaces may not provide sufficient mechanical noise isolation. The problem is not the mechanical engineer s or contractor s, it is the architect s or the Design-Build team. Put the responsibility to remedy a problem on the responsible party.

17 Defining Acoustical Treatments and Partition Designs for Various Spaces(3) 17 The levels of sound isolation between two spaces is defined in terms of the Sound Transmission Class (STC). The higher the STC rating the greater the level of sound attenuation / isolation between the spaces, and the greater the level of speech privacy. The appropriate STC rating is dependent on the adjacent space usage. Sound attenuation between spaces is very important for Speech Privacy, in office / business environments, and Medical Offices Health Insurance Portability and Accountability Act (HIPAA) Privacy Rule

18 Defining Acoustical Treatments and Partition Designs for Various Spaces(4) 18 It is important for all Mechanical Design Professionals and Mechanical Contractors to minimally do the following, 1. Identify if the mechanical equipment room is adjacent to (above, below or beside) a noise sensitive area? This may dictate higher STC walls around mechanical rooms. 2. If it is, in writing, contact the architect, to verify that the demising partitions have been adequately designed. 3. Has ductwork between noise sensitive spaces been designed properly?

19 Defining Acoustical Treatments and Partition Designs for Various Spaces(5) 19 Item c on the previous slide is important for Mechanical Design Professionals and Mechanical Contractors. And the solution is, in concept, easy. 1. Lined ductwork, minimum 1 thick standard ductliner. 2. At least TWO 90 degree elbows, between fan discharge and 1 st take-off to diffuser. 3. Sound boots on return grills. 4. Diffusers selected, to have an NC / RC rating of ~5-points less than the Building Design Goals. 5. And a bit of duct attenuation analysis.

20 Defining Acoustical Treatments and Partition Designs for Various Spaces(6) 20 Example #4: I recently worked on a project, new construction, large corporate office building. Open office area, with cubicles and the new concept of exposed decking and mechanical systems. That is no drop acoustical ceiling. Sometime during the VE process all the ductliner was eliminated. The result was lots of mechanical noise, low frequency air noise and noise from VAVs and FPBs. The cost savings from the VE process was $10k to $20k. The cost to mitigated, after construction was complete and the building occupied, was going to be much higher.

21 Defining Acoustical Treatments and Partition Designs for Various Spaces(7) 21 Acoustical treatments on walls of rooms carpeting and acoustical ceiling tiles. One cannot over state how much benefit carpeting and Acoustical Ceiling Tiles provide. While, open offices and the industrial look are the current architectural trend. These designs do not lead to space with acceptable acoustics, unless significant attenuation is paid to surface treatments and attenuation of HVAC related noise.

22 Defining Maximum Allowable Vibration Limits (1) 22 Vibration commissioning is the process of designing and specifying appropriate vibration isolation of building rotating equipment or vibration isolation of sensitive building areas, and specifying maximum vibration levels (out of balance) for rotating equipment. For Example: Maximum floor vibration limits for a cafeteria are much higher than for an area with Medical Imaging Devices (CAT Scans, MRI s, etc.) The degree of vibration isolation of rotating equipment and maximum out of balance is crucial.

23 Defining Maximum Allowable Vibration Limits (2) 23 Vibration commissioning is the process of designing and specifying appropriate vibration isolation of building rotating equipment or vibration isolation of sensitive building areas, and specifying maximum vibration levels (out of balance) for rotating equipment. Insuring good vibration isolation design is straight forward; 1. Appropriate vibration isolation design 2. Correct installation 3. Post installation conformity

24 Defining Maximum Allowable Vibration Limits (3) 24 Two Important Asides: NEBB s Procedural Standards for Sound and Vibration specify that vibration measurements (Vibration Commissioning) MUST happen before sound measurements (Sound Commissioning). The reason is that poor vibration isolation, improperly adjusted vibration isolation or out-of-balance machines can cause significant sound issues in occupied spaces. As counter intuitive as it is, a small input of vibration to a building structure can cause audible and annoying Sounds.

25 Defining Maximum Allowable Vibration Limits (4) 25 Appropriate vibration isolation design: it may seem obvious, however, it is overlooked more than it should be. This oversight occurs when vibration sensitive areas are not properly defined or during the Value Engineering (VE) process. It is vitally important during the Schematic Design Phase of a project that vibration sensitive areas in a building are identified. For example; Medical Imaging Devices, should typically be located on grade; not on upper floors especially in a lightweight steel pan building. There is no more important place for this than in Hospitals and Electronics and Optical Manufacturing Facilities.

26 Defining Maximum Allowable Vibration Limits (5) 26 What are appropriate vibration limits? Vibration limits for what? The rotating equipment or the building structure. Vibration Severity Ratings for Rotating Equipment are specified in ASHRAE Section 48, Figure 42. Vibration Limits on Building Structures are specified in ASHRAE Section 48, Figure 41.

27 Defining Maximum Allowable Vibration Limits (6) 27 Vibration Severity Ratings for Rotating Equipment are specified in ASHRAE Section 48, Table 46 and Figure 42.

28 Defining Maximum Allowable Vibration Limits (7) 28 Building Structural Vibration Criteria are specified in ASHRAE Section 48, Figure 41.

29 Defining Maximum Allowable Vibration Limits (8) 29 Some basic design guidelines for vibration isolation are presented in ASHRAE Handbook Applications, Section The benefit of spring isolators and inertia bases cannot be overstated. 2. Beyond isolation proper alignment and equipment balancing is a must. 3. For large air handling systems 30,000 CFM, Fan walls will significantly reduce vibration input to building structures.

30 Defining Maximum Allowable Vibration Limits (9) Were is the building located. Is it adjacent to a large roadway or rail line. If so, additional vibration isolation may be required in the actual building foundation or structure. 5. If the building is very close to an airport (Commercial or Military) low frequency noise from for jet noise may impact building occupants or processes. 6. Is the building in an area which sees high wind speeds; etc.

31 Some General Information Regarding Sound and Vibration Commissioning (1) 31 While, there is a cost associated with hiring individuals and firms to do an acoustical (sound and vibration) design review, commissioning, inspection and measurements on a project. Consulting costs are typically, much less than rework or lawyers. The cost savings can be significant. Good mechanical system design, which ASHRAE, SMACNA, NEBB promote can go along way to achieving a successful project, which is in compliance with the project design goals.

32 Some General Information Regarding Sound and Vibration Commissioning (2) Sound levels in occupied spaces are never or almost never loud enough to cause hearing loss or damage. Noise, especially tonal noise, may be very annoying and disrupt the work environment; however it will not damage hearing. 2. Vibration in building structures is almost always insufficient to cause any long term structural fatigue / failure issues. The equipment will self destruct long before structural issues arise.

33 General Information Regarding Sound and Vibration Mitigation Commissioning (1) 33 Mitigation of sound and or vibration exceedances of compliance specifications, may be trivial or significant, depending on the nature of the exceedance. Mitigation of sound problems is typically more expensive than mitigation of vibration problems; unless there were significant. Sound exceedances may be a simple as adjusting diffusers, or may result in rebuilding shaft walls or walls surrounding mechanical rooms. Vibration exceedances are typically easier to address than sound issues; through dynamic balancing or alignment of rotating equipment, or simply adjustment of vibration isolators.

34 Post Commissioning or Continuous Commissioning (1) 34 After commissioning is complete are there any sound or vibration measurements which need to be taken, on a periodic basis? This falls into the realm of Continuous Commissioning, or what is called Predictive Maintenance. Predictive Maintenance deals with taking periodic vibration measurements on mechanical equipment, especially critical equipment, to determine when maintenance or replacement of components is needed. It is a mature industry, with a number of organizations which train people, and has a proven track record of long term cost savings for facility owners.

35 Post Commissioning or Continuous Commissioning (2) 35 Typically, any Post Commissioning sound issues are caused by vibration from failures or beginning of failures in rotating equipment, such as 1. Drive belt wear (should be checked yearly) 2. Drive motor to fan wheel sheave or coupler misalignment. 3. Excessive fan noise due to dirty intake filters (common) 4. Bearing failure (does not occur very often). Bearing failure can occur during initial building commissioning start-up if drive motors or fans have not been rotated periodically after installation and set for an extended period of time (more than a month) 5. Poorly maintained equipment (older equipment)

36 Question and 36 Answers

37 Contact information 37 Stuart McGregor Engineering Dynamics, Inc S. Kalamath St. Englewood, CO

38 38 Thank you for joining the webcast.