COSASCO TWO-INCH SYSTEM

Transcription

1 COSASCO TWO-INCH SYSTEM INSTALLATION, OPERATION, & MAINTENANCE MANUAL SAND PROBES Rohrback Cosasco Systems East Smith Ave. Santa Fe Springs, CA Tel: (1) Fax: (1) Web Site: P/N: Rev. -

2 Table of Contents Chapter 1 Introduction...1 Chapter 2 General Chapter 3 Positioning of Sand Probes...3 Chapter 4 Sand Probe Pressure Gauge Assembly, Assembling and Fitting..4 Chapter 5 Sand Probe Remote Alarm/Shut-in Pressure Assembly, Assembling and Fitting.6 Chapter 6 Fitting of Sand Probes 8

3 1 Chapter 1 Introduction Prior to the development of the sand probe, shake-out tests were used to indicate either the presence of, or lack of, sand in the flow stream. This proved to be an after the fact test and could not give any indication of what damage may have been caused, if any. The shake-out test was usually followed up with radiographic (x-rays) or ultrasonic tests to determine the amount of damage that had been done. With the development of Sand Probes, a before the fact test is now possible. Sand Probes are sacrificial tubes, of varying wall thicknesses, used to detect the presence of sand in the flow stream. Their intended harmless sacrificial failure gives an early indication of impending expensive, polluting and potentially disastrous equipment failures or fire hazards, unless appropriate remedial action is taken.

4 2 Chapter 2 General (See Figure 1): Figure 1 illustrates a typical Cosasco Sand Probe. The standard Cosasco Sand Probe (sacrificial tube portion) is 3/8 (9.5 mm) OD and is available in three wall thicknesses:.016 (0.4 mm),.028 (0.7 mm) and.035 (0.9 mm). The tube is closed at one end and connected to a 1/4 MMPT threaded fitting at the other end which enables its mating with a 1/4 FNPT multiple-use Injection/Sampling/Sand Probe Nut. The multiple use nut replaces the solid plug nut of the Solid Plug Assembly and is used in a Cosasco Access Fitting body with Tee. In use, the effect of sand or abrasives eventually erodes through the Sand Probe sacrificial tube portion, exposing the sealed system to the working pressure of the line. The flow stream working pressure is then directed through ports in the Sand Probe Nut to Tee portion of the Access Fitting body --- through a nipple and valve --- to register upon a Pressure Gauge Assembly or a Remote Alarm/Shut-in Pressure Assembly.

5 3 Chapter 3 Positioning of Sand Probes Cosasco s concept of placement within the pipeline is that the midpoint of the Sand Probe sacrificial tube is placed approximately 60% into the pipeline inside diameter (ID). This placement allows for maximum theoretical sand impingement at the center-of-line where product flow velocity is greatest; yet also allows for heavier suspended particles riding slightly lower in the flow stream to a also contact the sacrificial tube. Wall thicknesses offered as standard are in a range allowing an approximate safety factor of ten (10). That is; for the most widely used standard pipe walls:.016 is an approximate of 1/10 th of.154 (standard wall thickness for nominal 2 OD pipes)..028 is an approximate of 1/10 th of.250 (average standard wall thickness for 3, 3-1/2, 4 and 6 nominal OD pipes)..035 is an approximate of 1/10 th of.375 (average standard wall thickness for 8 and 10 nominal OD pipes and standard for 12 and larger nominal OD pipes). Careful consideration should be given to sand probe monitoring locations. Experience has shown that the most erosion occurs immediately downstream of every change of flow direction; and, especially on the outside of a turn. Sand normally returns to the approximate middle of the flow stream about twenty pipe diameters downstream of each turn. Additionally, changes of direction which occur after a long straight run tend to experience more severe erosion rates than do those occurring after shorter runs of straight flow.

6 4 Chapter 4 Sand Probe Pressure Gauge Assembly, Assembling & Fitting (See Figure 2): To obtain a complete, functionable Sand Probe monitoring system, a pressure sending assembly is necessary for transmission of pressure from the Tee connection on the Access Fitting body to a pressure sensing/recording device. A typical Sand Probe Pressure Gauge Assembly is shown in Figure 2. This type of Pressure Gauge Assembly uses a dual dial 5000 PSI (352 kg/sq cm) gage. The Assembly is composed of: Part No. Description Weight English Metric Sand Probe Pressure Gauge Assembly 1 lb-15 oz 880 grams Shut-off Valve, 1/4 NPT 1 lb- 0 oz 454 grams Tee, 1/4 NPT 0 lb- 4 oz 113 grams Pressure Gauge, dual dial 0 lb- 10 oz 284 grams Pipe Plug, 1/4 NPT 0 lb- 1 oz 28 grams

7 Chapter 4 5 In addition, due to various Tee sizes available on Access Fitting bodies, a Tee Reducer or Nipple to Shut-off Valve must be used to make a compatible hook-up. The Reducer or Nipple selection is as follows: Tee size Part No. Description Weight English Metric 1/ Nipple, 1/4 x 1/4 1 oz 28 grams 1/ Reducer, 1/2 x 1/4 2 oz 57 grams 3/ Reducer, 3/4 x 1/4 3 oz 85 grams Reducer, 1 x 1/4 4 oz 113 grams As indicated by the illustration in Figure 2, no special assembly or disassembly instructions are necessary other than using a good grade of thread dope or lubricant on all thread connections to maintain pressure integrity. A thread dope or lubricant containing Teflon has been found to be best for this purpose.

8 6 Chapter 5 Sand Probe Remote Alarm/Shut-In Pressure Assembly, Assembling & Fitting (See Figure 3): As in the pressure gage assembly described in Section 4; when using an automatic remote alarm/shut-in pressure assembly, the flow stream is directed through the Sand Probe Nut ports to the Tee portion of the body --- through the nipple and valve --- then enters a sensor (three-way block and bleed valve). The sensor is piston-actuated by transmitted pressure. The movement of the piston stem closes the control pressure inlet to the control pressure outlet. As this happens, the control pressure in the system is bled off from the outlet port to the exhaust port, which can then trigger a remote alarm or shut-in the system. A manual handle on the sensor may be used to either test, trip, or act as a visual indicator to the system status. The sensor has a vent port to prevent slow pressure build-up and premature tripping due to thermal expansion. Also, the sensor incorporates features allowing it to be directly or remotely connected to the Sand Probe monitoring point on the flow line; or, it can be directly or remotely connected to the control valve which triggers the remote alarm or shuts-in the system.

9 Chapter 5 7 A typical Sand Probe Remote Alarm/Shut-in Pressure Assembly is shown in Figure 3. The assembly is composed of: Part No. Description Weight English Metric Sand Probe Remote Alarm/Shut-in 2 lb-14 oz 1.3 kilogram Pressure Assembly Shut-off Valve, 1/2 FNPT 1 lb-0 oz 454 grams Sensor (Can be connected to customer 1 lb-12 oz 794 grams furnished connections for automatic control) (2 required) Pipe Plug, 1/4 NPT (Closes control pressure inlet/outlet connections until linked with automatic control also keeps inlets/outlets free of debris and contaminants) (2)0 lb-2 oz 57 grams In addition, due to various Tee sizes available on Access Fitting bodies, a Tee Reducer or Nipple to Shut-off Valve must be used to make a compatible hook-up. The Reducer or Nipple selection is as follows: Tee size Part No. Description Weight English Metric 1/ Reducer, ¼ x ½ 2 oz 57 grams 1/ Nipple, ½ 3 oz 85 grams 3/ Reducer, ¾ x ½ 4 oz 113 grams Reducer, 1 x ½ 4 oz 113 grams As indicated by the illustration in Figure 3, no special assembly or disassembly instructions are necessary other than using a good grade of thread dope or lubricant on all thread connections to maintain pressure integrity. A thread dope or lubricant containing Teflon has been found to be best for this purpose.

10 8 Chapter 6 Fitting of Sand Probes First, it is assumed that the Access Fitting body and/or welded end fitting is already in place on the pipeline. If not, Manual , trepanning, Positioning, and Welding should be consulted for proper instructions for its attachment. Additionally, if a Hot Tapping procedure is necessary to gain access to the pressurized pipe, consult Manual , Hot Tap. Second, if the above is already completed, and retrieving or installing Cosasco Solid Plug Assemblies with their attached Sand Probes is necessary while pipelines are under operating pressure, please consult Manual MANUAL, RBS/RBSA Retriever and Service Valve, which describes the considerations, care, and caution that should be used. 1. Loosen the anti-vibration Allen head set screw on the bottom of the solid plug assembly. This will release the securing lock of the set screw on the solid plug nut. The solid plug nut acts as a primary packing retainer in the absence of a corrosion monitoring or preventing device being attached. 2. Remove the solid plug nut from the bottom of the solid plug assembly, ensuring that the primary packing is left in place on the now exposed threaded portion of the solid plug assembly. Please note that this is a left-hand threaded nut. 3. Attach a ¼ NPT multiple-use Injection/Sampling/Sand Probe Nut of a length compatible with the length or height of the Access Fitting body being utilized onto the exposed threaded portion of the solid plug assembly. For convenience the compatible listing is as follows: Access Fitting Body Height Sand Probe Nut & Length Sand Probe Nut Part No ¼ x ¼ x ¼ x ¼ x Again, please remember that this is a left-hand nut. 4. Engage the Sand Probe Nut threads until contact with the primary packing is encountered at its seat location. 5. Compress the primary packing by continued threading of the Sand Probe Nut up to not more than ¼ turn after making initial contact with the packing. 6. Lock the Sand Probe Nut securely to the solid plug assembly by tightening the antivibration Allen head set screw. 7. Lubricate the threads of the ¼ NPT fitting at the one end of the Sand Probe and thread engage to the ¼ FNPT threads at the base of the Injection/Sampling/Sand Probe Nut. A Teflon base thread dope has proven to be the best for this purpose. Make a secure connection to ensure pressure integrity. 8. Install the solid plug assembly into the Access Fitting body.

11 Chapter 6 9 SAND PROBE SIZING FORMULA: (60% of pipeline ID only) NON FLANGE Access Fitting Assemblies (A + Wg + PW + PID x.6) minus ( N) = Sand Probe Length FLANGE Access Fitting Assemblies (Standard weld neck flanges only) (A + Wg + PW + PID x.6 + Fg +MF) minus ( N) = Sand Probe Length A = Access Fitting Assembly height Wg = Weld gap (1/16 or 1.6 mm is normal per ANSI B ) PW = Pipe Wall thickness PID x.6 = pipe inside diameter times.6 N = Injection/Sampling/Sand Probe Nut Length (See Section 1.350A) Fg = Flange face-to-face gap MF = Mating flange dimension from face to root or base HOW TO ORDER 1. Select type of Access Fitting Assembly, Solid Plug Assembly and compatible multiple-use Injection/Sampling/Sand Probe Nut 2. Using the Sand Probe sizing formula, determine the appropriate length, and determine the appropriate wall thickness (reference chapter 3) 3. Determine and select appropriate Sand Probe Pressure Assembly, Figure 2 or 3, and corresponding compatible reducer (s)/nipple (s). 4. The Sand Probe order number is as follows: XXX-L where.xxx = Wall Thickness L = Order Length Example: P/N