Evolution of Steam Sub-metering at Penn State University

Transcription

1 Evolution of Steam Sub-metering at Penn State University Big 10 & Friends Utility Conference May 9, 2017 Presenters: Bill Serencsits Penn State University Scott Hunt Emerson Automation Solutions

2 Agenda Back-end metering (measuring the condensate) Flow Technologies Used Issues with back-end metering Trials with various flow technologies for front-end metering BIF Shunt Flow Vortex Shedding Technology DP Flow Technologies Averaging Pitot Tubes (APT s) Orifice plates V-cones and Conditioning plates limited straight run meters Compensation Selecting the right flow meter for the application Summary & Questions

3 Steam Distribution Approx steam meters

4 Back end metering Agenda In other words measuring the condensate and using it to calculate the amount of steam being used Flow meter Technologies used on condensate flows Cadillac meter Turbine meters Magnetic flow meters Issues with back-end metering

5 Condensate flow meters Cadillac Meter Similar to water wheel design where a chamber fills with condensate, once full would rotate and release condensate to the condensate return system, and register a click that would represent x volume of condensate. Worked well Was thought to be accurate Over time were getting costly to install and repair Condensate measurement is perhaps not the best indication of actual steam usage

6 Turbine Flow Meters Rotor (6-24 inch) Inlet Diffuser and Support Fins Rotor (3-4 inch) Body Still have some on condensate flows Had some issues with air in liquid use air powered pumps..air in the flow stream will over spin, and over register Questioned the accuracy Expensive to repair and maintain

7 Issues with measuring condensate.. Measuring Condensate does NOT truly represent Steam Usage. Assumes all the steam is being returned as condensate and no other contaminant streams adding water (ie. Leaks thru heat exchangers) Does not capture steam flashing when condensate drops to atm. Pressure if not returned to flash tank... (loss up to 4%) Does not capture leaking through faulty steam traps or relief valves that are stuck open Does not capture condensate going to drain Condensate flows are intermittent, might be horizontal partially filled lines difficult for any flow meter. Modifying the condensate system, adding condensate pumps, and re-piping enables some newer technologies to be used Magnetic flow meters can be used (if sufficient conductivity) Universities- most condensate from campus is approx. 5 to 15 micromhos Still have the issues with condensate not truly representing steam usage

8 Trials of flow technologies for front- end metering (Steam) Started in approx s Important considerations : Performance vs turndown ( range-ability) Accuracy & repeatability need reliable measurements for billing for determining bldg energy use, and finding system issues, leaks, etc. Permanent Pressure Loss (PPL) Pipe straight runs required Installation Cost includes Purch. Price, Design & Engrg., Procurement Costs, Installation Labor and Commissioning Maintenance remaining part of the Cost of Ownership Frequency & Ease of Calibration in-line, in-house, or send out? Repairs Required? In house or send out? Cost?

9 First Front- end metering trials... BIF Shunt flow Meters Open Flow Path Rotor Assembly Orifice Plate

10 Shut-off valve 2 Meter By-pass Line 10 Main Steam Line For line sizes 5 inch and over, a by-pass assembly is used, including a 2 inch meter, flanged elbows, main line orifice plate, and 2 inch fittings required to make up the by-pass assembly. Shut-off valves are required. Main Line Orifice Plate

11 Issues and Concerns with Shunt Flow Meters Accuracy was questioned No compensation for Variations in Pressure Reliability -Required being sent out for Calibration and Maintenance Did not produce the desired results

12 2 nd step steam metering with Vortex shedding (mid 1990 s) Some of the issues and concerns with Vortex shedding technology Do NOT measure to zero; have minimum measurable flow rate which varies based on steam pressure and density A 6 vortex in a 6 line is most likely oversized; typically require 1 or 2 line size reductions Even though vortex has decent meter range-ability, can get caught between 2 meter sizes, neither size providing full flow coverage Most designs traditionally have required D s of upstream piping

13 Next steam metering with APT s (approx. 2000) Averaging Pitot Tubes (APT s) - (ie. Annubar ) Advantages: Lower installed cost- drill hole, weld weldulet, insert Linear flow coefficients Very low Permanent Pressure Loss (PPL) All these advantages make it a good candidate for the power house, BUT perhaps NOT on steam flows requiring large seasonal turndowns Pipes that are oversized to reduce pressure loss and generate lower dp s make turndowns of even 10:1 difficult for any APT At low dps can be noisy due to wet-leg variations (condensate flashing) Typical variations of 0.1 H2O or more.are a large % at 1-2 H2O dp and under!) Low flow cut-off on most dp flow meters applied on steam should be set to approx. 0.1 to 0.2 H2O due to noise with the wet-legs Since APT s were not all that good for large turndowns, and oversized piping systems..the search continued.

14 Next Orifice plates... Orifice plate technology Proven technology - Approved and used for custody transfer for many years 1 st units added had just dp- no P or T, no compensation Worked fairly well, if sized properly The turndown was usable turndown Pressure drop and Perm. Press. Loss (PPL) balanced with performance and turndown Can be zeroed and calibrated fairly easily in-line or in the shop Little maintenance required if installed properly flow meter should go upstream of the regulator..many times high pressure steam will go through a regulator to drop pressure before going into the building.. Difficulty is when you are a distance out on campus and there is very little steam pressure, and range-ability is required, but can NOT tolerate the Pressure loss.supply pressure drops at higher demands, and that s when a dp device drops max Pressure!

15 Then Compensation was added.. Multi-variable Dp based mass flow meters Include Pressure and Temperature measurement for density correction FLOW

16 Then Compensation was added.. Multi-variable Dp based mass flow meters Can be included on any dp flow primary element & fluid Include Pressure and/or Temperature measurement for density correction Include the flow coefficient curves for compensation Compensate for thermal expansion and contraction of the piping and flow meter Can be calibrated as 3 transmitters in one.dp, Pressure & Temperature All NIST traceable and all in-line or in-house Accurate and repeatable

17 But what about when there is no straight run?? Dp flow meters not requiring much straight runs V-cone (McCrometer) up to 3D Up & 1 D down..plus the lay length of the the meter Conditioning Plate flow meters (Rosemount) - 2D Up and 2D down. Plus the lay length of the meter

18 Cone-style.3D Upstream and 1 D Down.... Initially 17+ years ago or more V-cone was perhaps the only limited straight run meter choice..but today there are additional choices. Can be sized like a plate to get the turndown If sized equivalently with an Orifice Plate has the same dp and Permanent Pressure Loss (PPL) Considerations: Flow meter Size and Weight Cost Flow meter and the Installation Cost

19 Next came the Conditioning plate 2D Upstream and 2 D down (approx. 12 years ago) Now have more than one choice when straight run is limited Can be sized to get the performance over turndown If sized equivalently with a standard O-plate has the same dp and same PPL Considerations with any flow meter: Flow meter Size and Weight shorter lay length, lighter and easier to install Cost: Flow meter Cost & the Installation Cost are generally less 1595 plate style C Compact Conditioning plate Integral style 2-12

20 Conditioning Plate trial at University

21 The test data behind the Conditioning Plates.

22 When considering various flow meter technologies Performance versus Turndown (range-ability): Improve turndown by: Balancing primary element sizing ( acc. vs turndown) with PPL Measure P &/or T compensate for variations in steam density Compensate for variations in flow coefficients (Cd, Y, etc ) Calibrate a flow meter like a flow meter, not a pressure transmitter..more time calibrating at the low dp s improves flow meter performance at the low flow rates ( Ultra for Flow ) Improves performance over larger turndowns Eliminates stacking of dp transmitters

23 Flow Turn Down.. From FTA - Flow Technology Advisor Both the RED & BLUE lines represent a 1495 Orifice plate with a Beta Ratio of 0.7 The Red line represents an older tier 3095MV multi-variable transmitter The Blue line is a 3051SMV high performance tier multi-variable transmitter notice the higher performance at larger turn downs. Both the MAGENTA and GREEN lines represent a 1495 Orifice plate with a smaller bore and a Beta Ratio of 0.56 notice a smaller Beta ratio will improve performance at larger turndowns, but will also result in higher Permanent Pressure Loss (PPL) refer to energy loss calculations. The Magenta line is an older tier 3095MV multi-variable transmitter. The Green line is a 3051SMV high performance tier multi-variable transmitter notice the larger turndown and the improved performance over larger turndown.

24 5 % of nothing. is almost nothing!

25 Flow Sizing & Selection Tools Helps Determine Best Fit & Economics 1. Enter Flow Selection Criteria 2. Input Process Parameters, Choose Meters 3. Compare Results Total System Performance

26 Steam on top!? Testing various installations..still an engineered solution Steam on top: - no wet leg variation - lower dp s and lower flows? - no heat trace required outdoors? Saves $$ (Minimizes freeze protection and damage) If using Wireless: - no wiring - no conduits..

27 Flow meter technologies should also consider PPL - Permanent Pressure Loss Not necessarily the % of generated dp, but the actual pressure loss How much straight run is required? How is performance affected if I do not have the required straight run? Installation Ease & Cost: Purchase price is not a very good indicator of installed cost. Installed cost includes Purchase Price, Design & Engrg., Procurement costs, and Installation, Start-up & Commissioning Cost of Ownership includes Installation Cost above plus.... Calibration - frequency and ease of calibration In-line, in shop, or send it out! Cost of Maintenance Energy loss if I can reduce pressure loss can I save money? Increase capacity? or both?

28 Flow metering technologies.. have evolved and improved Talk to your peers as you are doing here.. They can not only help you with what has worked well, but also what has not worked well Use your Vendors & Specialists To assist in flow meter technology sizing and selection based on the important criteria we just discussed To guarantee the solution To assist with start-up and troubleshooting

29 Flow metering technologies.. If at all possible consider purchasing the flow meters directly from your vendors - don t leave it up to a contractor.. know what you are getting! If you can not install it yourself, then go out for bids on the actual installation portion Otherwise you will have to live with what you get! And like Daniel Bernouli said. You can not manage, what you do not measure!

30 Evolution of Steam Sub-metering at Penn State University QUESTIONS? COMMENTS? Presenters: Bill Serencsits Penn State University Scott Hunt Emerson Automation Solutions

31 THANK YOU!