1 saw 1.1 \documentclass{chowto}
2
3 \title{Drift Chamber Gas System Operation}
4 \howtotype{expert} % ``expert'', ``user'', ``reference''
5 %\experiment{Name of experiment} % Optional
6 \author{H. Fenker}
7 \category{general} % Subject area of this document
8
|
9 saw 1.5 \maintainer{H. Fenker} % Optional
10 \date{December 18, 2007} % Can use \today as the argument
|
11 saw 1.1
|
12 saw 1.5 %To attempt to make pretty-looking pdf files...(not standard howto)
13 \usepackage[T1]{fontenc}
14 \usepackage{pslatex}
|
15 saw 1.1
16 \begin{document}
17 \providecommand{\degg}{\ensuremath{^{\circ}\ }}
18
19 \begin{abstract}
|
20 saw 1.5 This document provides detailed setup information for the drift
21 chamber gas mixing system, as well as the correct procedure for
22 refilling the alcohol supply and changing gas bottles. This
23 information is intended for use by {\bf gas system experts only.} For
24 day-to-day shift worker instructions, refer to the corresponding {\it
25 user} howto document.
26
27 {\bf Please Note:} The Hall-C Drift Chamber Gas System was
28 significantly changed in early 2007. It is now a {\it pressure-driven
29 system} whereas it had been flow-controlled. Long-time Hall-C staff
30 and users will find that the system operates quite differently now.
|
31 saw 1.1 \end{abstract}
32
|
33 saw 1.5 %=====================================================================
34 %=====================================================================
|
35 saw 1.1 \section{Overview}
36
|
37 saw 1.5 The drift chamber gas is composed of 50\% Argon and 50\% Ethane (by
38 volume), bubbled through isopropanol maintained at a temperature such
39 that the gas mixture contains approximately 1\% alcohol vapor. The
40 mixing system that produces this gas is housed in the Hall-C gas shed
41 (Bldg. 96c). The bottles supplying the gas to the mixing system are
42 attached to two two-bottle manifolds outside the gas shed, within the
43 fenced-in gas bottle yard.
44
45 A single mixing system provides the gas for both the SOS and the HMS
46 detectors. Gas is delivered to the hall at a pressure of about 9 psi
47 (500~Torr) above atmospheric pressure. Each detector's flow is
48 controlled by its own individual needle-valve with flowmeter, located
49 in the appropriate shield house, near the detector. The job of the
50 mixing system is to simultaneously maintain the delivery pressure and
51 mixing ratio by providing whatever total flow rate of gas (between
52 zero and 5.28 standard liters per minute [SLM]) is demanded by the
53 detectors. This is accomplished by controlling two flow valves (argon
54 and ethane) so that they each flow the same volume of gas while
55 keeping the output pressure nearly constant. The mixing system flow
56 diagram is shown in Fig. \ref{fig:gas_mixer_diagram}.
57 %=====================================================================
58 saw 1.5 %=====================================================================
|
59 saw 1.2 \section{Gas Interlock System}
|
60 saw 1.5 The flow of gas from the supply bottles may be automatically shut off
61 by normally-closed solenoid valves installed in the primary argon and
62 ethane manifolds. Several conditions such as over-temperature, fan
63 failure, gas leak, and fire alarm must all be in the non-alarm state
64 before these valves will open. Alarm conditions are indicated on the
65 gas system alarm panel on the lower-left side of the center
66 counting-house console.
67
68 When any of the required conditions is not satisfied the sounder on
69 the panel in the counting room will make an annoying noise and both
70 solenoid valves will close. The audible alarm may be silenced by a
71 toggle switch on the panel. Be certain to return it to the ``on''
72 position as soon as the fault is cleared.
73
74 The most confusing, but most common alarm condition is ``Low
75 Pressure''. The solenoid valves will not remain open unless there is
76 already ample pressure on the output side of both valves. This
77 prevents, for example, the flow of pure ethane to the drift chambers
78 when the argon bottle is empty. The way to clear this condition is to
79 make sure there are no other faults and that both argon and ethane
80 manifolds are properly pressurized and fitted with non-empty bottles;
81 saw 1.5 then press and hold the ``override'' button on the alarm panel for
82 several minutes. This button forces the solenoid valves to open even
83 if there are fault conditions present. If all is well, gas will flow
84 through the valves and clear the ``low pressure'' condition so that
85 the button may be released.
|
86 saw 1.2
|
87 jones 1.3 \begin{figure}[hbt]
|
88 saw 1.5 \psfig{figure=drift_gas_system-gasmixer2007.eps,width=\textwidth,bbllx=12,bblly=12,bburx=750,bbury=590}
|
89 saw 1.1 \caption{Diagram of Hall~C Gas Mixing System\label{fig:gas_mixer_diagram}}
|
90 jones 1.3 \vspace{0.5cm}
|
91 saw 1.1 \end{figure}
|
92 saw 1.5 %=====================================================================
93 %=====================================================================
|
94 jones 1.3 \section{Operating the Mass Flow Controller.}
|
95 saw 1.1
|
96 jones 1.3 The gas flow is controlled by a MKS~647 controller and mass flow
|
97 saw 1.5 control valves. Delivery pressure is sensed at the mixer output by a
98 {\it Baratron} pressure transducer. The 647 is menu driven from a
99 display on the front panel using a keypad with numeric and cursor
100 controls for input. It features a non-volatile memory so that most of
101 its settings are retained even if the unit is unpowered. The
102 pressure-regulation parameters do need to be reset if power is lost,
103 however, so the controller is powered through an uninterruptible power
104 supply (UPS).
105
106 The temperature of the control
107 system must be maintained within the
108 operating range of the MKS~647 (15\degg C - 40\degg C), the pressure
109 transducer (0\degg C - 50\degg C), and the mass-flow meters and valves
110 (0\degg C - 50\degg C). Therefore,
111 the heating and cooling systems in the gas shed must be maintained in
112 working order. The temperature is indicated by the
113 red LED display labeled \emph{Controller Temperature},
114 located in the right-hand rack of the gas shed.
|
115 jones 1.3
|
116 saw 1.5 %=====================================================================
117 %=====================================================================
|
118 jones 1.3 \subsection{Settings for Normal Operation}
119
|
120 saw 1.5 A summary of all of the settings required to make the controller
121 function properly is given in Table~\ref{tab:mixer_nominals}. The
122 table also shows which screen contains each parameter. Instructions
123 for setting parameters are given below. Detailed instructions for
124 configuring and operating the MKS~647 can be found in the
125 manufacturer's instruction manual\cite{647C_EN_0504A1}.
126
|
127 jones 1.3 \begin{table}[hbt]
128 \begin{minipage}[h!]{\textwidth}
129 {\scriptsize
|
130 saw 1.5 \begin{center}
|
131 jones 1.3 \begin{tabular}{|l|c|l|}
132 \hline
133 Parameter & Set To & {\it Controller Screen}/Comments\\ \hline
134 \multicolumn{2}{|c|}{\bf Manual Valves } & Valves are labeled \\
135 Valves 1, 2, 4, 8 & OPEN & \\
136 Valves 3, 5, 6, 7 & CLOSED & \\ \hline
|
137 saw 1.5 \multicolumn{2}{|c|}{\bf Pressure PID Loop Settings } & {\it Pressure Control} (Fig. \ref{fig:pressure_control}) \\
|
138 jones 1.3 Pressure & 500 Torr & \\
139 PID Mode & AUTO & \\
140 PID GAIN & 4.0 & \\
141 PID INTEG & 10.0 & \\
142 PID LEAD & 0.000 & \\ \hline
|
143 saw 1.5 \bf Mixture & 1 & {\it User} (Fig. \ref{fig:user_display})/ Lower-right corner\\ \hline
144 \multicolumn{2}{|c|}{\bf Gas Composition for Mixture 1} & {\it Gas Composition} (Fig. \ref{fig:gas_composition})\\
145 Channel 1 & 1.000 & (Argon) \\
146 Channel 2 & 1.000 & (Ethane) \\
|
147 jones 1.3 Channel 3 & 0.000 & \\
148 Channel 4 & 0.000 & \\ \hline
|
149 saw 1.5 \multicolumn{2}{|c|}{\bf MFC Valve Size } & {\it Range Selection} (Fig. \ref{fig:range_selection}) \\
150 \multicolumn{2}{|c|}{\bf / Gas} & {\it Gas Selection} (Fig. \ref{fig:gas_selection}) \\
151 Channel 1 & 2.0 SLM / Ar & provides 2.78 SLM Argon\\
152 Channel 2 & 5.0 SLM / C$_2$H$_6$ & provides 2.50 SLM Ethane\\
|
153 jones 1.3 Channel 3 & \it unused& \\
154 Channel 4 & \it unused& \\ \hline
|
155 saw 1.5 \multicolumn{2}{|c|}{\bf Channels ON/OFF Settings} & {\it Extended Display} (Fig. \ref{fig:extended_display}) \\
|
156 jones 1.3 Channel 1 & ON & Press ``ON 1'' (\em Argon) \\
157 Channel 2 & ON & Press ``ON 2'' (\em Ethane) \\
158 Channel 3 & OFF & Press ``OFF 3'' (\em not in use) \\
159 Channel 4 & OFF & Press ``OFF 4'' (\em not in use) \\ \hline
|
160 saw 1.5 \multicolumn{2}{|c|}{\bf Pressure Transducer} & {\it Pressure Setup} \\
161 Controller & STD & \\
162 Range F.S. & 1000 Torr& \\ \hline
163 \multicolumn{2}{|c|}{\bf MFC Valve Controls } & {\it Mode Selection} (Fig. \ref{fig:mode_selection}) \\
|
164 jones 1.3 Channel 1 & PID & \\
165 Channel 2 & SLAVE / 1& \\
166 Channel 3 & INDEP & \\
167 Channel 4 & INDEP & \\ \hline
168 \bf Alcohol Temp. & $2^\circ $ C & Electronic Temperature \\
169 & & Control Box \\ \hline
170 \hline
171 \end{tabular}
|
172 saw 1.5 \end{center}
173 }%end of \scriptsize
|
174 jones 1.3 \end{minipage}
175 \caption{Normal Valve and Parameter Settings for the Gas Mixing System.
176 \label{tab:mixer_nominals}}
177 \end{table}
|
178 saw 1.5 %=====================================================================
179 \subsection{General Operation of the Mass Flow Controller}
180 If the controller screen is dark, press {\bf ESC} to awaken the
181 display. Many screens merely provide a menu of other screens you may
182 access: simply press the item number you desire. To go up one level in
183 the menu hierarchy, press {\bf ESC}. The \emph{Menu Tree} for the 647C
184 controller is shown in Fig. \ref{fig:command_tree}.
185
186 In general, to change a parameter displayed on the controller screen
187 use the {\bf left/right} arrow keys to move the cursor to the item you
188 wish to change. Then either use the number keys to enter the value
189 desired for that item (numeric parameter) or use the {\bf ENTER} or
190 {\bf up/down} keys to cycle a parameter through its available settings
191 (configuration parameter). Numeric parameters may be incrementally
192 modified by using the {\bf up/down} arrow keys. To make certain that a
193 new parameter becomes active, move the cursor off of the parameter
194 after you have entered the new value.
195
196 The initial menu upon startup is the {\bf Main Menu}
197 (Fig.~\ref{fig:main_menu}). For normal operation use the {\bf User
198 Display} menu (Fig.~\ref{fig:user_display}). It shows the amount of
199 saw 1.5 each gas currently flowing, the total gas flow, and the current
200 delivery pressure. This display also shows which of several possible
201 pre-defined gas mixtures is selected. These mixtures are configured
202 on the {\bf Gas Composition} screen, Fig. \ref{fig:gas_composition}.
203 For normal operation, we use
204 only mixture {\bf \#1}, (number shown on the lower-right of the
205 display). {\bf Only on this screen can this parameter be changed.}
206 Mixture {\bf \#2} is usually configured to provide 100\% argon for
207 purging flammable gas out of the chambers.
208
209 The {\bf Extended Display} menu (Fig.~\ref{fig:extended_display})
210 shows actual flow, flow set point, units, valve full-scale range, gas
211 calibration factor, whether that channel is enabled, and whether each
212 channel is operating in master, slave, PID, or independent mode. This
213 display is most useful to a system expert wishing to verify the system
214 parameter settings. Most parameters cannot be modified from this
215 screen, however.
216
217 Delivery pressure set-point and pressure \emph{PID-loop} control parameters
218 may be configured from the {\bf Pressure Control} screen
219 (Fig.~\ref{fig:pressure_control}).
220 saw 1.5 %
221 \begin{figure}[tb]
222 \begin{center}
223 \framebox{
224 \begin{minipage}{.65\textwidth}
225 \footnotesize
226 \begin{itemize}
227 \item MAIN MENU (Fig. \ref{fig:main_menu})
228 \begin{enumerate}
229 \item [1] USER DISPLAY (Fig.\ref{fig:user_display})
230 \item [2] EXTENDED DISPLAY (Fig.~\ref{fig:extended_display})
231 \item [3] PRESSURE CONTROL (Fig.~\ref{fig:pressure_control})
232 \item [4] DIAGNOSTICS
233 \begin{enumerate}
234 \item [4.1] ERROR LISTING
235 \item [4.2] SIGNALS
236 \end{enumerate}
237 \item [5] INSTRUMENT SETUP
238 \begin{enumerate}
239 \item [5.1] RANGE SELECTION (Fig.~\ref{fig:range_selection})
240 \item [5.2] GAS SELECTION (Fig.~\ref{fig:gas_selection})
241 saw 1.5 \item [5.3] MODE SELECTION (Fig.~\ref{fig:mode_selection})
242 \item [5.4] ZERO ADJUST
243 \item [5.5] TRIP LIMITS
244 \item [5.6] GAS COMPOSITION (Fig.~\ref{fig:gas_composition})
245 \end{enumerate}
246 \item [6] SYSTEM SETUP
247 \item [7] PRESSURE SETUP
248 \item [ ]
249 \item [9] INFORMATION
250 \item [0] POWER OFF
251 \end{enumerate}
252 \end{itemize}
253 \end{minipage}
254 } %%end of \framebox{
255 \caption{Command Tree for the MKS-647C Control Panel}
256 \label{fig:command_tree}
257 \end{center}
258 \end{figure}
259 %
|
260 jones 1.3 \begin{center}
261 \begin{figure}[hbt]
262 \begin{minipage}{2.7in}
|
263 saw 1.5 \psfig{figure=drift_gas_system-main_menu.eps,width=2.6in,height=1.8in}
264 \caption{MKS~647 Main Menu\label{fig:main_menu}}
|
265 jones 1.3 \end{minipage}
266 \begin{minipage}{2.7in}
|
267 saw 1.5 \psfig{figure=drift_gas_system-user_display.eps,width=2.6in,height=1.8in}
268 \caption{MKS~647 User Display\label{fig:user_display}}
|
269 jones 1.3 \end{minipage}
270 \end{figure}
271 \end{center}
|
272 saw 1.5 %
|
273 jones 1.3 \begin{center}
274 \begin{figure}[hbt]
275 \begin{minipage}{2.7in}
|
276 saw 1.5 \psfig{figure=drift_gas_system-extended_display.eps,width=2.6in,height=1.8in}
|
277 jones 1.3 \caption{Extended Display Screen\label{fig:extended_display}}
278 \end{minipage}
279 \begin{minipage}{2.7in}
|
280 saw 1.5 \psfig{figure=drift_gas_system-pressure_control.eps,width=2.6in,height=1.8in}
|
281 jones 1.3 \caption{Pressure Control Screen\label{fig:pressure_control}}
282 \end{minipage}
283 \end{figure}
284 \end{center}
|
285 saw 1.5 %=====================================================================
|
286 jones 1.3 \subsection{Gas Flow Rates}
287 \label{sec:gas_flow_rates}
288 The flow rates are adjusted automatically by the controller in order
289 to maintain a constant delivery pressure at the output. Only the flow
|
290 saw 1.5 {\em ratios} should be set by the operator. We use a 1:1 ratio, set on
291 the {\bf Gas Composition} screen (Fig.~\ref{fig:gas_composition}), as
292 indicated in Table~\ref{tab:mixer_nominals}.
293
294 The average total flow should equal the sum of the flows to all of the
295 detectors in the shield house. (Note that the ball-type flowmeters in
296 the shield house are calibrated for nitrogen. The approximate
297 multiplier to convert these readings for 50/50 Argon-Ethane is 0.9 .)
|
298 jones 1.3
299 System configuration parameters specifying the full-scale flow
300 capacity (for nitrogen) of each valve, the types of gases actually
|
301 saw 1.5 flowing through each valve, and the mode of control for the valves are
302 set in the screens pictured in Figs.~\ref{fig:range_selection},
303 \ref{fig:gas_selection}, and \ref{fig:mode_selection}. These figures
304 show the nominal settings for the Hall-C system.
|
305 jones 1.3
306 \begin{center}
307 \begin{figure}[hbt]
308 \begin{minipage}{2.7in}
|
309 saw 1.5 \psfig{figure=drift_gas_system-gas_composition.eps,width=2.6in,height=1.8in}
|
310 jones 1.3 \caption{Gas Composition Screen\label{fig:gas_composition}}
311 \end{minipage}
312 \begin{minipage}{2.7in}
|
313 saw 1.5 \psfig{figure=drift_gas_system-range_selection.eps,width=2.6in,height=1.8in}
|
314 jones 1.3 \caption{Range Selection Screen\label{fig:range_selection}}
315 \end{minipage}
316 \end{figure}
317 \begin{figure}[hbt]
318 \begin{minipage}{2.7in}
|
319 saw 1.5 \psfig{figure=drift_gas_system-gas_selection.eps,width=2.6in,height=1.8in}
|
320 jones 1.3 \caption{Gas Selection Screen\label{fig:gas_selection}}
321 \end{minipage}
322 \begin{minipage}{2.7in}
|
323 saw 1.5 \psfig{figure=drift_gas_system-mode_selection.eps,width=2.6in,height=1.8in}
|
324 jones 1.3 \caption{Mode Selection Screen\label{fig:mode_selection}}
325 \end{minipage}
326 \end{figure}
327 \end{center}
|
328 saw 1.1
|
329 saw 1.5 %=====================================================================
|
330 jones 1.3 \subsection{To set the Delivery Pressure:}
|
331 saw 1.1
|
332 saw 1.5 Navigate to the {\bf Pressure Control} menu. The pressure set-point (in
333 Torr) is indicated at the bottom-center of the screen. This value
334 should be se to 500.0. Note that the system can not respond instantly
335 to a change in requested gas pressure: it has no way to release excess
336 pressure and must wait for the detector systems to consume it
337 \footnote{An \emph{over-pressure relief valve} releases gas through a
338 small oil bubbler in the gas shed if the pressure exceeds about
339 600~Torr.}; it cannot build up pressure any faster than the
340 flow-control valves can supply it. It may take thirty minutes or so
341 for the pressure regulation system to stabilize at a new set-point or
342 stabilize in response to a change in total gas consumption. However,
343 you should be able to observe a change in the gas flow within a few
344 seconds (possibly up to a minute) after a set-point change.
|
345 saw 1.1
|
346 saw 1.5 %=====================================================================
|
347 saw 1.1 \subsection{To turn gas flow on or off:}
348
|
349 saw 1.5 The gas flow can be turned on or off while in any menu. In the
350 Extended Display menu the bottom line displays ``ON'' or ``OFF'', by
351 channel, to show which mass flow valves are enabled. ``ON" must be
352 displayed in the bottom row of the Extended Display menu for gas to be
353 flowing in a particular channel.
|
354 saw 1.1
|
355 saw 1.5 For gas to flow, two conditions must be met:
356 \begin{enumerate}
357 \item Each channel (1 and 2) must be enabled by pressing ``ON" and then
358 the desired channel number.
359 \item The entire system must be enabled by pressing
360 ``ON" and then ``ALL" from the keypad.
361 \end{enumerate}
362 Thus, each valve can be controlled individually using ``ON/OFF~-~\emph{Channel Number}'',
363 or all flow can be controlled using ``ON/OFF~-~ALL''. If the system
364 is enabled, the status line at the bottom of every screen will
365 indicate ``FLOW ON GAS ON''. {\bf Note:} because Valve-2 (ethane) is
366 normally slaved to Valve-1 (argon), when Valve-1 is disabled there will
367 be no flow through Valve-2.
368
369 %=====================================================================
370 %=====================================================================
|
371 saw 1.1 \section{To Change a Gas Bottle}
372
|
373 saw 1.2 The argon and ethane supply bottles should be replaced by new (full)
|
374 saw 1.5 bottles when the bottle content drops below about 10\% of its
375 capacity. For argon, the bottle content is directly indicated by the
376 bottle pressure: a new bottle usually contains 2000 to
377 3000~psig. Argon bottles should be changed whenever the bottle
378 pressure is found to be below about 200~psig.
379
380 Ethane bottles, on the
381 other hand, contain liquefied ethane. Thus the bottle pressure is just
382 the vapor pressure of ethane at whatever the current temperature
383 happens to be. At 70\degg F this is about 544~psig. The pressure gauge
384 will not tell you how much ethane is left in the bottle until it reads
385 zero! Instead, we measure the ethane content by observing the weight
386 of the bottle and comparing it to the weight when the bottle was
387 full. A standard B-size cylinder contains about 32~pounds of ethane.
388 The ethane cylinders on the manifold sit on scales which have been
389 pre-set to indicate the net weight of ethane in the bottle.
390 Numbers in the green portion of the dial indicate ethane remaining.
391 If the indicator points to the red portion of the dial, the bottle
392 is empty.
393
394 Handling and connecting bottles of compressed gas require special
395 saw 1.5 knowledge. The high pressure gas stored in the cylinders (bottles)
396 constitutes significant stored energy. Mishandling of a gas bottle can
397 pose a lethal hazard! Refer to the JLab ESH\&Q Manual\cite{bi:jlabehs}
398 for safe handling practices. If you do not already know how to safely
399 manipulate compressed gas hardware, have a knowledgeable person train
400 you.
401
402 After attaching a new gas bottle to the supply manifold, check the
403 connection for leaks using \emph{Snoop} or a similar leak detector.
404
405 %=====================================================================
406 %=====================================================================
407 \section{The Alcohol Bubbler}
|
408 saw 1.1
|
409 jones 1.3 To reduce the rate of aging of the wire chambers, the operating gas
410 contains a small quantity of alcohol vapor. The vapor is added by
411 bubbling the argon/ethane mixture through liquid alcohol. The
412 temperature of the alcohol controls the alcohol vapor pressure, which
413 determines the amount of vapor added to the gas. The alcohol content
414 also affects the electron drift velocity in the wire chambers, so it
415 must be held approximately constant.
416
|
417 saw 1.5 Gas is bubbled through the liquid alcohol inside the glass
418 dome vessel in the refrigerator. The dome is covered by a
419 perforated steel cylinder as a precaution against breakage. The
420 alcohol level is controlled by a float valve inside the metal cold
421 reservoir, which is also inside the refrigerator. As long as there is
422 alcohol in the warm reservoir (sitting on top of the refrigerator),
423 the liquid levels inside the refrigerator will remain constant. A
424 drain valve (\#7) inside the refrigerator is available for emptying
425 all liquid from the system. It is for use by experts only and should
426 remain closed during normal operation.
427
428 {\bf The reservoir should be refilled before it becomes empty to
429 maintain a head of liquid over the float valve. This will prevent air
430 from entering the system.}
431 %=====================================================================
432 \subsection{To by-pass the alcohol system}
433
434 Open valve {\bf 3}, then promptly close valves {\bf 1 \& 2}, in that order!
435
436 \noindent To restore flow through the bubbler, open valves {\bf 1 \& 2} then
437 close valve {\bf 3}.
438 saw 1.5
439 %=====================================================================
440 \subsection {Alcohol Temperature Control}
441
442 To keep the alcohol temperature (and thus the vapor pressure) constant,
443 the alcohol bubbler is housed in a refrigerator which is controlled by
444 an electronic temperature regulator having 1~C\degg sensitivity. The
445 controller is located on a shelf in the right-hand rack of the gas mixing
446 system. Normally, the actual temperature in the refrigerator is
447 indicated on the front panel of the controller. The controller should
448 be set to maintain a temperature of 2\degg C.
449
450 %=====================================================================
451 \pagebreak[4]
452 \subsection{Step-by-Step Instructions for Refilling the Alcohol Bubbler}
453 {\em These 13 steps must be individually completed in the order listed!}
454 Refer to Fig.~\ref{fig:gas_mixer_diagram}.\\
455
456 \begin{minipage}{\textwidth}
|
457 saw 1.1 \begin{enumerate}
|
458 saw 1.5 \footnotesize{
|
459 jones 1.3 \item{Remove the three screws securing the cover on the alcohol fill-tank
460 (the top-most metal tank at the rear of the mixer rack. Carefully remove the lid
461 without allowing dust or dirt to fall into the tank.}
462 \item{Fill this tank to about 75\% full from a bottle of 2-propanol.}
463 \item{Replace the lid and retaining screws.}
464 \item{Remove the small brass cap which seals the port on the lid.}
465 \item{Isolate the warm reservoir by {\bf closing valves 4 and 8.}}
466 \item{Release pressure in the warm reservoir by {\bf slowly opening valve 6 fully.}}
467 \item{{\bf Open valve 5 fully} to begin the flow of alcohol from the fill-tank to the warm reservoir.}
468 \item{{\bf Monitor the level} of alcohol in the warm reservoir sight-tube.}
469 \item{When the level is 2~cm from the top of the sight-tube, {\bf close valve 5.}}
470 \item{Replace the brass cap on the lid of the fill-tank.}
471 \item{{\bf Close valve 6, {\it then} slowly open valve 4.}}
472 \item{{\bf Open valve 8.}}
|
473 saw 1.5 \item{Record what you did in both the gas logbook and the electronic logbook.}
474 } %end of scriptsize
|
475 saw 1.1 \end{enumerate}
|
476 saw 1.5 \end{minipage}
|
477 saw 1.1
|
478 saw 1.5 %=====================================================================
479 %=====================================================================
|
480 saw 1.1 \section{Gas Filters Maintenance}
481
482 There are gas filters on the argon and ethane supply lines just inside
483 the gas shed. These filters should be replaced on a regular schedule.
484 See Bill Vulcan for details.
485
|
486 saw 1.5 %=====================================================================
487 %=====================================================================
|
488 saw 1.1 \section{Secure Pressure Regulators}
489
490 The gas mixing system is protected from failure or mis-setting of the
491 primary pressure regulators (the ones mounted on the manifolds on the
492 exterior of the gas shed -- near the bottles) by {\it hidden} regulators
493 mounted just inside the gas shed. It is these regulators which actually
494 set the maximum supply pressure to the mixing valves. These regulators
495 should {\em never} be adjusted by other than a gas system expert! The
496 nominal secondary pressure supplied by both the argon and ethane
|
497 jones 1.3 secure regulators is 30 psig.
498
|
499 saw 1.5 %=====================================================================
500 %=====================================================================
|
501 jones 1.3 \section{Ethane Flow Restrictor}
502
503 A calibrated flow-restricting orifice is installed at the outlet of
504 the main ethane high-pressure manifold outside the gas shed. This
505 orifice passively limits the flow rate of ethane into the gas shed
506 even if there is a catastrophic failure of the flow and pressure-controlling
507 devices inside the shed. It is model {\tt IC-DM4-9-SS} manufactured by
508 {\em O'Keefe Controls Co.}, Trumbull, CT, USA. While it may look like
509 simply a stainless-steel union fitting, it is in fact a precision part,
510 and a necessary component of the gas safety system. It limits the flow
|
511 saw 1.5 of ethane to less than 26.5 SLM, which is a little
|
512 jones 1.3 less than ten times the maximum capacity of the flow-control system.
|
513 saw 1.1
|
514 saw 1.5 %=====================================================================
515 %=====================================================================
516
517 \raggedright %this fixes formatting of bibliography, too.
|
518 saw 1.1
519 \section{Related {\it Howtos}}
520 \begin{itemize}
|
521 jones 1.3 \item MKS~647 Mass Flow Controller Manual \cite{647C_EN_0504A1}
|
522 saw 1.1 \item Base Equipment Shift Checklist Items \cite{howto:base_equip_checklist}
523 \end{itemize}
524
525 \end{document}
526
527 % Revision history:
528 % 1st draft by Howard Fenker 27FEB03 -- taken from existing ops manual.
|
529 jones 1.3 % Rev. 1.1 - added notes on bottle changing, ethane bottle pressure.
530 % $Log$
|
Return to
drift_gas_system.tex
CVS log
Up to [HallC] / Documents / Howtos