S100-2MT3-1 Freezing Rain Sensor SOW 06-30-2021.pdf

Statement of Work Repair and Recondition of the Automated Surface Observing System (ASOS)

Freezing Rain Sensor (FRS)

ASN: S100-2MT3-1, NSN: 6660-01-441-1830

Version: June 30, 2021

Description: This Statement of Work (SOW) provides instructions for the repair, reconditioning and operational testing of the S100-2MT3-1, Freezing Rain Sensor (FRS) to “Like New” condition. The FRS is contained in a special enclosure case measuring approximately 9 inches X 8 inches x 4 ½ inches with a large finned aluminum heat sink with a probe tip assembly attached to the ‘top’ side of case. Weight is approximately 7 lbs. Case color is white. The repair and reconditioning process consists of two procedures and shall be performed in the following order.

1. Pre-cleaning preparations. 2. Cleaning and painting with labeling and marking as required.

The operational testing shall be performed last.

Definition: “Like New” Condition means reconditioned to the listed specification to meet all applicable electrical, mechanical, and cosmetic specifications and Engineering documentation, including the replacement of damaged or missing non-functioning parts.

Government Furnished Equipment: Fiber optic transmitters will be supplied upon request.

Special items supplied by NRC: (a.) Protective dust caps for fiber optic modem ports. (b.) Cap for case access hole: CAPLUGS size 13X, red color. (c.) Protective cover for probe tip:

CAPLUGS P/N SC-1/4-16, red color. (d.) Cylindrical split protective polyethylene sleeve for probe tip and heat sink flange approximately 2.5 inches diameter by 4 inches long, red color with Caution label. (Supplied by NRC on Request). (e.) Case ground studs as required. (f.) Yellow Warning/Caution labels. (g.) Door ID labels (h.) door seals as required

Vendor Furnished Equipment: Vendor shall provide all needed parts and supplies identified in the recommend equipment and supplies section of this SOW to complete repairs and refurbishment of the Freezing Rain Sensors. If there is something that the vendor cannot supply, please contact the NRC for help or direction.

Recommended Equipment and Supplies:

Special Equipment Recommended: (a.) Laptop or PC with RS-232 Comm port and ProComm or equivalent communications program. (b.) Fiber Optic modem interface/power distribution assembly with switches, fuses and analog current meter. (See Attach # 1) (c.) Label maker for serial numbers. Must be capable of producing waterproof labels with self-adhesive backing.

Label colors shall be white with black lettering or black with white lettering as specified below.

All lettering shall be ‘Times New Roman’ style with font size as specified below. (d.) Multi-meter for DC voltage measurements (FLUKE 87 or equivalent). (e.) Compressed air source capable of providing pressure of approximately 30 PSI. (f.) Fiber optic cable 20 feet in length (supplied by NRC on request).

Supplies Recommended: (a.) Anti-seize, THREAD-EZE ULTRA (CHEMSEARCH). (b.)

Penetrating fluid. (c.) Cleaning solution to remove gum from stickers and tape (GOO GONE or equivalent). (d.) Heavy duty cleaning solution to remove surface dirt and grease. (e.) Nylon fiber scouring pads, a combination of light, medium and heavy duty abrasive levels. (f.)

Sandpaper of various grit sizes from fine to course. (g.) WD-40. (h.) Wire brush approx ½ inch wide with stiff wire bristles. (i.) Small brush approx ½ inch wide with stiff non-metallic bristles.

(j.) Cotton tipped swabs. (k.) Cleaning alcohol. (l.) Cleaning cloths for general purpose use.

(m.) Two inch wide blue tape Scotch-Blue # 2090 or equivalent. (n.) Masking tape 2 inches wide. (o.) Compressed air source. (p.) Safety glasses, hearing and breathing protection equipment as appropriate. (q.) Probe tip Warning and Caution label for door of FRS (supplied by NRC). (r.) ID Label for door of FRS (supplied by NRC) (s.) Gasket material for door seal (supplied by NRC) (t.) “WARNING HIGH VOLTAGE” label for terminal strip cover TB1 red color with white lettering (supplied by NRC). (u.) White acrylic spray paint similar to Sherwin- Williams F8W2030 (WAEM-511 GMC White) with primer as required.

Tools Recommended: (a.) ‘T’ handle and straight handle tap holders, with 1 each M6 x 1.0 metric tap and 1 each ¼ - 20 SAE tap. (b.) Exacto knife with ½ inch straight flat blade. (c.) Drill press and/or 3/8 inch Electric drill with bits ranging from approximately 1/8 to 5/16 inch. (d.)

Vice Grips. (e.) No 1 and No 2 flat blade and Phillips screwdrivers. (f.) Crescent wrench. (g.)

Appropriate tools necessary to remove and install press-in case ground studs.

Recommended Miscellaneous Hardware Supplied to be by the Vendor: (a.) Washers sizes: ¼ inch flat washer approx 0.6 inches in diameter; ¼ inch star washer type 316 stainless steel; ¼ inch nylon washer a minimum of 1.5 mm thick. (b.) Nut sizes: ¼ - 20 type 316 stainless steel; 8- 32 type 18-8 stainless steel. (c.) Screw sizes: Binding head slotted 6-32 x ¼ inch type 18-8 stainless steel; Pan Head Phillips M6-1 X 10mm type 18-8 stainless steel; Pan head slotted nylon M6- 1 X10mm.

First Article: Please check the Purchase Order (SF1449) for any First Article requirements. If First Articles are required, they must pass inspection by the NRC’s Inspection Branch before you are given the “Notice to Proceed” from the Contracting Officer for the remaining units.

Description of Work – Work Procedures:

1.0. Precleaning Preparations:

1.1. Precleaning preparations shall be accomplished as follows:

Caution:

Use extreme care not to bump, scratch, nick or otherwise damage the probe tip assembly. Keep probe tip protective devices on at all times except when performing cleaning or testing.

a.) Position FRS enclosure on a flat surface with the ID label facing down and the probe tip pointing away from the technician. Using a ¼ - 20 tap on a straight handle holder, clean out the screw threads on the top two screw holes and on the left bottom screw hole to a depth of approx 1 inch. The bottom right screw hole is not used and need not be cleaned. Next, using cotton tipped swab, apply anti-seize to threads in the three screw holes cleaned above.

b.) Reposition FRS enclosure with the ID label facing up and probe tip pointing away from the technician. Remove the large split red protective sleeve and small red probe tip covers. Save these items to reuse later. The front panel should contain only two decals, a small 1 ¾ inch x 1 ¼ inch label with Warning/Caution message adjacent to the heater assembly and a larger ID decal 2 ¼ inches x 3 ¼ inches which contains the serial number. No other labels should be on the unit including sides or back. Remove any labels, decals or markings other than the two identified above.

c.) Loosen the four large screws on the FRS door. On some FRS units, it may be necessary to remove seized screws before the door can be opened. Use appropriate shop practices to accomplish this task.

Note:

The FRS uses extended hinges on the door. Grasp the door on both sides and raise it straight up for about 1 ½ inches before attempting to swing it open.

d.) Remove the warning cover on TB1 if installed. Save the warning cover for TB1 for later use. Inspect inside unit and remove any objects that may be loosely floating inside the case.

Inspect TB1 for damage. If TB1 is damaged, please contact the NRC for further guidance. Be aware that sometimes loose screws or other items get lodged between the bottom side of the CCA and case. Insure that protective dust caps are placed over the two fiber optic modem ports.

Next locate the serial number on the front ID sticker; verify that it matches the one written on the inside of the door. If not, change the number on the door to match the ID decal. Verify the serial number with shipping documentation. This is important later when the unit serial number must be placed on the new ID decal.

e.) Next clean the ‘top’ side edge of the door using a light or medium nylon cleaning pad with heavy duty cleaning solution, rub just hard enough to remove the dirt and grime. Dry this section with a clean cloth. (This area is not accessible for cleaning when the door is closed.)

f.) Using the ‘T’ handle holder with the M6 x 1.0 tap, clean out the four door screw inserts to a depth of approx ½ inch. Inspect the four door screw heads; replace any if grooves are excessively worn. Inspect the door screw threads, remove them from the door and clean threads with a small wire brush if needed. Reinstall the four captive door screws. All door screws must be of the same type drive. On some FRS units it may be necessary to remove broken screw shafts from the screw holes. Use appropriate shop practices to accomplish this task.

g.) Inspect door seal. Replace it if damaged. Door seals are pressed fit and may come out of the groove. If this happens, carefully reinsert the seal.

h.) Inspect the CCA assembly. There should be a ¼ - 28 nylon screw attaching the lower right hand part of the CCA to the case (located immediately to the right of TB1). In addition there should be a ¼ inch flat nylon washer between the bottom parts of the CCA and the case. Replace either or both items if missing, broken or of the improper type. Insure the nylon screw is snug but use care not to over tighten it. Inspect the remaining three metal screws for tightness. Clean or replace if corroded or worn.

i.) Inspect the case external ground stud. Remove nuts and washers if installed. Use penetrating fluid to remove nuts and washers if necessary. Discard nuts and washers if corroded.

Some ground studs are not stainless steel and may be corroded. Replace corroded ground studs with stainless steel studs. Use P/N: EFHS-0420-12, press-in captive studs (Available from NRC upon request). If studs are not corroded, thoroughly clean ground stud threads (suggest using a combination of ¼ -20 die and small wire brush with good cleaning solution). Do not replace nuts and washers at this time.

j.) Inspect the internal case ground below CCA TB1. If the nut is missing, replace it with size 8-32 nut. Look for a black decal with white/silver lettering marked ‘E1’ adjacent to this ground stud. If damaged or missing, use label maker to replace it. Font shall be size #14; decal shall be black with white lettering. Cut the decal approx ½ inch square and position it to the right and slightly below the ground stud so that when viewed by the technician it can clearly be identified as ‘E1’.

k.) Inspect the black plastic cover plate on the left side of the CCA below the fiber optic modem. Verify that the bottom half of this cover starting at the line “TERMINAL BLOCK” is as shown in Attach # 2. If not, replace cover plate with one containing the correct markings.

l.) Inspect inside the case and door frame for corrosion and clean as necessary. If excessive corrosion is evident, it may be necessary to remove the CCA and Heat Sink assembly from the case to properly clean it. Normally adequate cleaning of the inside of the case can be accomplished without this process; however, if disassembly becomes necessary, proceed as follows: Otherwise go to paragraph. 2.1.

1. Close FRS door and tighten screws. Clean probe tip and heat sink assembly per paragraph 2.1.

2. Open FRS door. Remove the probe calibration capacitor C7 from the CCA. Remove the two probe cables from the CCA connectors. Remove four screws from CCA and remove the CCA from the case. (There should also be a ¼ inch nylon flat washer in the case, remove it also)

3. Remove the split grommet for the probe cables and remove the four nuts holding the heat sink assembly to the case and carefully remove the heat sink assembly with cables. Use blue tape to secure the calibration capacitor to the heat sink so it does not get lost.

4. Clean case inside using various nylon scouring pads and cleaning solvents as appropriate to remove corrosion. It is not recommended to use sandpaper or metallic scouring pads on the inside of the case surfaces.

Note:

Insure that the probe and final serial numbers marked on the inside of the door are not obliterated during the cleaning process.

5. Before reassembling the probe and heat sink assembly, paint the case per Para 2.1

6. Reinstall the heater assembly in the reverse order in which it was removed.

Insure that the Teflon spacer and ‘O’ ring seals are replaced properly. Install the split grommet on the heater wires. Replace the split grommet if torn or deteriorated.

7.) Install the CCA in the case. Insure that the flat nylon ¼ inch washer is installed under the CCA on the bottom right hole (adjacent to TB1) and a ¼ - 28 nylon screw is used to secure it. Use care not to over tighten the nylon screw. Use the remaining three metal screws to secure the CCA in the case.

8.) Install the heater cable (yellow wires) to CCA J4; install probe cable to CCA J3.

Install probe calibration capacitor C7 in remaining connector.

m.) Remove the red protective cap in the bottom access hole if installed. Place 2 inch blue tape centered over the hole on the inside of the case. Close Door and snug down the four door screws.

2.0. Cleaning, painting and label markings:

2.1. Cleaning, painting and label marking shall be accomplished as follows:

a.) Position the FRS on a flat surface with the ID decal up and the probe tip pointing towards the technician. Apply WD-40 solvent to the probe tip. Wait for five minutes and then, using a moderately abrasive nylon scouring pad, clean the probe surface. The tip must be thoroughly cleaned from its rounded top to the base (no indications of black residue). Reapply WD-40 if necessary and continue cleaning tip until it is shiny and uniform in appearance. The probe tip is relatively sturdy; however, only use just enough pressure to obtain the desired results. Do not use a metallic scouring pads or anything that would scratch the probe tip.

b.) During the cleaning process in the next two steps use warm water and a heavy duty cleaning agent to thoroughly remove all oily residue. It is especially important that the probe tip be completely free of any residue from the WD-40.

c.) Clean outside of the case as required using sandpaper and scouring pads as appropriate to allow good adhesion of new paint. Use sandpaper to feather any paint that has chipped off so the chips will not be visible when painted.

d.) Clean the heat sink; use the small non-metallic brush to clean between the fins.

Clean thoroughly under the cone shaped flange on the probe tip base. A high pressure stream of water, if available, would be useful for this purpose.

e.) In most cases it will not be required to mask the two door decals. They are often damaged by sun exposure and new replacement labels can be placed over them after painting.

Note:

We have been placing new door decals over the two old ones after painting, at some point in time it may be necessary to remove one or both of these before painting when excessive buildup occurs. No more than 4 labels may be stacked on top of each other.

f.) Mask the four door screw heads with masking tape (some screw heads have been painted, do not paint them again) g.) Install a ¼ inch flat washer approx 0.6 inch diameter on the external ground stud.

Secure with a ¼ - 20 nut. Use masking tape to cover the nut and exposed screw threads.

h.) Mask the heat sink and probe assembly. Place the small red protective cap on the probe tip before masking the heat sink. Do not touch probe tip with fingers at any time after the probe tip has been cleaned as this will contaminate the probe surface.

i.) Paint the entire surface of the case with primer and white acrylic paint. Use only enough paint to make the surface evenly white and uniform. Multiple coats are not required.

j.) After the unit is thoroughly dried, remove all masking tape and the nut and washer on the external ground stud.

k.) Using NRC supplied decals, place a new Caution/Warning decal and a new ID decal directly over the original ones on the door.

l.) Place a ¼ - 20 stainless steel nut on the external ground stud and tighten.

Next, place a ¼ inch stainless steel star washer on the stud and secure it with another nut and tighten just enough to prevent it from coming loose during shipping m.) Open the FRS case and look for the “final serial number” marked on the inside of the door. Using label maker, print the serial number on white tape with black lettering size #14 font.

Leading zeros are required on some serial numbers. Verify serial number with shipping documentation. The serial numbers will not contain any alpha characters. Trim tape to approx ¼” x ¾” and affix to the ID label to the right of and in line with the words ‘SERIAL NO.’

3.0. Perform Operational Testing:

3.1. Operational testing shall be performed as follows:

Warning:

Insure that the probe tip is kept away from any flammable material.

. An occasional FRS failure mode is for the CCA to command the heater on all the time. If this occurs, the heater will cause the probe tip to reach near red hot temperatures in a few seconds with the possibility of igniting a fire. Place a non-flammable material in the area immediately under the probe tip during powered testing.

Do not touch the probe tip during or immediately after powered testing as it may be hot enough to cause burns

Additionally, be aware that 115 VAC is present on the terminals of TB1 during the ‘powered’ portions of this test.

Note:

Testing should be performed under the following conditions

Temperature ----------------------- 25 +/- 5C Relative Humidity ---------------- 10 to 80% UUT Input Power ----------------- 115 +/- 10 VAC a.) Configure the data format on the laptop or PC as follows: N81, 2400 Baud, full duplex, asynchronous. All commands must be issued in “Caps Lock” mode.

b.) Position the FRS and open the door as described in paragraph. 2.1. b. Insure that all switches on interface and power assembly are turned ‘OFF’. Connect heater and electronics power to TB1 on the FRS as follows: (designations are from left to right). All terminal screws in TB1 shall be of the same type drive.

TB1.1 = Hot side of Electronics CCA TB1.2 = Neutral TB1.3 = Blank (if screw or wire present, remove and discard) TB1.4 = Hot side of Heater TB1.5 = Neutral

The probe tip must be clean and have all protective covers removed from the heat sink. Connect interface/power ground wire to case ground on FRS using internal ground stud ‘E1’ or external case ground. Connect fiber optic cables between appropriate ports on the FRS fiber optic modem and interface/power test device.

c.) Apply heater power first and then a few seconds later apply electronics power to the

FRS.

Caution:

Immediately observe the current meter on the interface/power assembly.

The meter should indicate zero amps, if it does not, immediately turn off the heater and electronics power. Failure to do this quickly will severely damage the probe assembly. Note this failure on return documentation to NRC and proceed to step 3.1.i

Additionally, keep a close watch on this current meter during testing when power is applied. The meter should always indicate zero amps, except during the performance of the heater current test in step 3.g.

Otherwise, immediately turn off heater power.

After electronics power is applied, wait approximately 20 seconds to allow the CCA to go through its start-up sequence. At this time, you should hear the heater relay activate/deactivate temporarily (click) and see a slight kick of the current meter needle. Wait one minute before proceeding with the next step.

d.) Measure CCA operating voltage with negative probe at the left side of resistor R2 and positive probe at the right side of R1. Voltage should be 5 VDC +/- 0.25 volts. If power supply section of the unit fails this step, note this failure on return documentation to NRC and proceed to step 3.1.i.

e.) Issue a “Z1” command (Send Routine Data) by typing Z1 on the keyboard. The expected response from the FRS is: ZP XXXXXCC. Where XXXXX is the one minute time averaged probe frequency in hertz and CC represents the checksum of the previous digits in hexadecimal form. The normal output frequency will be approximately ZP 40000XX +/- 40 hertz. Make note of this frequency for later comparison. If unit fails to be within 40 hertz, continue on with the reconditioning and put a note on the unit indicating the FRS may need a field Calibration. If the unit reads greater than 100 hertz out of tolerance the probe is probably defective and may need to be replaced.

In addition, three potential failure response outputs are possible from the FRS (in place of the

ZP):

1.) ZF1 = Probe Failure

2.) ZF2 = Probe Heater Failure

3.) ZF3 = Electronics CCA Failure

If any of the above failure indications are present on this or any subsequent tests, please note this failure on return documentation to NRC and proceed to step 3.1.i f.) Next issue a “Z4” command (Perform Extended Diagnostics) by typing Z4 on the keyboard. After approximately 8 to 10 seconds, the expected output from the FRS is the following: ZP E3, where ZP indicates test pass and E3 is the checksum. There are also three potential failure response outputs possible as defined in paragraph. 3.1.d. If this test fails, replacement components (Fiber Optic Modem, Mother Board) can be supplied by NRC as needed to fix the problem.

g.) Next issue a “Z303” command (Perform Deice Cycle/Heater Current Test) by typing Z303 on the keyboard. After a few seconds delay, you should hear the relay activate and the current meter should indicate approximately 2.4 to 2.9 amps. Also, verify that the heater “ON” time is approximately 3 seconds. (If the heater appears to be staying on longer than three seconds, immediately turn the electronics and heater power switches ‘OFF’. Note this failure on return documentation to NRC and proceed to step 3.1.i ). After the relay deactivates, the FRS should output ZDOK51. Where ZDOK indicates the heaters have been commanded on and 51 is the checksum. Wait for three minutes before proceeding to the next step.

h.) Finally issue another “Z1” after the deice cycle by typing Z1 on the keyboard. Again verify that the unit responds with ZP XXXXXCC and no failure indications. The frequency should be with +/- 4 hertz of that obtained in paragraph. 3.1.e.

i.) Turn the electronics power switch ‘OFF’ and then turn the heater power switch ‘OFF’.

Remove all power and fiber optic cables. Place protective caps on the fiber optic modem ports.

Using a small piece of blue tape, affix the TB1 cover with Warning label to the inside center portion of the door. Functional testing is now competed.

j.) Using compressed air, blow out the inside of case and CCA to remove dust and debris.

k.) Install the small red protective cap on the probe tip and place the large cylindrical split polyethylene sleeve over the heat sink flange. Install the red plug in the case access hole. (These are the red plugs supplied by NRC.) Tighten the four terminal screws on TB1 just enough to prevent them from vibrating loose during shipment.

l.) Close case door and secure the four screws. Only tighten screws just enough to keep door secure, do not over tighten and place unnecessary pressure on the door seals while the unit is in storage.

m.) Before replacing the FRS Assembly in the shipping container, insure the inside of the container is clean and free of any debris.

n.) Process in now complete, unit is ready for return to NRC.

Attach # 1: Suggested schematic of Fiber Optic Modem/power Distribution Interface circuit.

Attach # 2: View of Circuit board cover plate.

Warranty Terms: Vendor will provide a 1-year warranty against material workmanship and against faults occurring during operation. This 1-year warranty will begin after passing the final equipment inspection and acceptance for stock.

NRC Final Acceptance: All repaired units will be inspected for material workmanship and tested for operational performance at the NRC. Units with Probe or Circuit Card Assembly (CCA) failures will be accepted if all other QC inspections pass, including painting and cleaning.

If a Probe or CCA failure should occur; this failure must be annotated as to the type of fails that are present. NRC, ASOS Repair Unit will replace all faulty Probes and CCAs. To meet the material workmanship requirements, the units will need to be in “Like New” condition including external appearance in accordance with the National Weather Service specification drawing or other specification document. The Instrument Inspection Unit verifies these units meet both material and operational requirements. They will test each Freezing Rain Sensor for proper and accurate functionality in the Unit’s environmental chamber. The Freezing Rain Sensor must then perform all normal processing using the ASOS operating and applications software in a live ASOS system with operational sensors. Any inspected item that does not meet the acceptance criteria will be returned to the vendor for rework at no additional cost to the government.

Deliverables: Each repaired and reconditioned Freezing Rain Sensor, by serial number, shall be supplied with a Repair Report documenting the repair, reconditioning, and inspection to include results of all tests and failure analysis.

Shipping Address:

NATIONAL RECONDITIONING CENTER (NRC)

14200 MERRITT RD.

GRANDVIEW, MO. 64030

Transportability: Vendor is responsible for returning repaired products in a shipping container designed to withstand the vibration and shock encountered during transportation by ship, rail, truck, and aircraft. The units shall be packaged to prevent damage to include: physical, electrical, mechanical, cosmetic, and the units shall not be damaged or lose performance capability.

Final Note: When unforeseen problems arise, that may need technical clarification, please contact the Contracting Official who will notify the NRC. If the unit has any problem that prevents a quality repair, do not work on the item until the issue can be resolved.

NRC Reviewed:

WSRB Repair Branch Review: Jerry Forste, Branch Chief, June 30, 2021 TI&MR Branch Review: Gregory Flores, Branch Chief, June 30, 2021