The gas-house centre valve shown in the historical drawing is a distributor for a set of purifier vessels. It routes gas through selected purifiers and cuts one out for servicing. Each purifier has a feed and return connection, allowing a selected series route through the operating vessels.
Centre Valve for a Gas House Interactive Calculator
Choose one purifier to isolate and follow gas through the other three in series. Adjust actual volume flow, connection bore and pressure units.
Equation Used
- One vessel isolated and three connected in a selected clockwise series.
- Each active vessel carries the same volume flow.
- Circular connection pipes with the entered internal diameter.
- Negligible density and volume changes in the ideal continuity calculation.
- No pressure-loss, purification, leakage or water-seal capacity calculation.
- The animation shows a settled valve position, not intermediate switching.
Functional purifier distributor, not a gas-holder shutoff. Three active vessels carry the same flow in series.
A distributor between four purifier vessels
Hiscox figures 1613–1614 show a four-part centre valve arranged to cut out any one of four purifier pans. Barber figure 1684 gives the corresponding sectional and plan views. The drawing has paired vessel connections, a central supply and a surrounding return passage; the lower section shows the water-sealed arrangement.
The plan shows a selected route through three purifiers in series. Each vessel has one inlet and one outlet. Gas enters the first active purifier, returns to the distributor, goes through the second and third, and then reaches the outlet. Both connections of the isolated vessel are capped in the displayed position.
The central supply crosses the annular return at another level. Their crossing in the plan is not a junction. Colored bands identify functional passages, with covers and internal walls simplified to keep the route readable. The small section below the plan distinguishes the central inlet from the annular return.
Changing the active sequence
Newbigging describes the historical arrangement of four purifier vessels with three working and one out for renewal of the purifying material. The interactive plan labels its selected vessels A, B, C and D.
Selecting A as isolated gives B → C → D. Isolating B gives C → D → A; isolating C gives D → A → B; isolating D gives A → B → C. The letters identify vessel positions in the drawing, and the selector sets the illustrated clockwise sequence.
The animation shows flow in one selected settled valve position. Changing the selector redraws the next position; it does not simulate moving a live valve through intermediate connections. The gas markers indicate direction and respond to mean pipe velocity, but their spacing and travel time are schematic.
Flow continuity, pipe velocity and pressure units
For internal pipe diameter D in millimetres, area is A=π(D/1000)²/4 square metres. With actual volume flow Q in m³/h, mean pipe velocity is u=Q/(3600A) metres per second.
Three vessels in series each carry the same flow Q in this ideal model. The flow is not divided by three; that would describe three parallel branches. Negligible volume change through the train is assumed.
For gauge pressure h expressed in millimetres of water column, p=9.80665h pascals, using the conventional conversion. Pressure and volume flow are independent inputs. The calculator does not infer flow from pressure or calculate pressure loss.
At zero Q the velocity is zero and the flow animation stops, while the selected route remains visible. Changing which vessel is isolated changes the routing result without changing the ideal pipe-area or velocity calculation.
Example: 300 m³/h through three purifiers
Select A as isolated, Q=300 m³/h, D=250 mm and h=150 mm water column. The active sequence is B → C → D, with 300 m³/h passing through each vessel.
The connection area is π×0.25²/4=0.04909 m². Mean pipe velocity is 300/(3600×0.04909)=1.70 m/s. The entered pressure converts to 1,471.00 Pa.
Doubling Q doubles velocity. Doubling pipe diameter makes area four times larger and velocity one quarter as large at the same Q. Increasing pressure changes its unit conversion, but does not change entered flow without a separate pressure-loss model.
What the flow model calculates
The eight external connections and selected internal route explain the distributor’s purpose. Vessel bodies, treatment trays, pipe proportions and simplified water-seal section make the installation recognizable; they are not construction dimensions.
The calculator reports continuity and nominal mean velocity in a circular connection. It does not predict purification efficiency, media life, gas density changes, valve leakage, seal depth, operating torque or actuator force. Pipe velocity and pressure-unit conversion do not establish valve lifting loads or actuator requirements.
Flow markers are an explanatory overlay, not a fluid simulation. The displayed valve stays in its selected position and the isolated vessel has no flow. Intermediate switching and maintenance procedures are outside the model.
Centre-valve questions
Is this a gas-holder shutoff?
No. The referenced mechanism distributes gas among purifier vessels.
Why are there eight vessel connections?
Each of the four vessels needs a feed and return connection.
Does each active vessel get a third of the flow?
No. The three active vessels are connected in series, so each carries the same entered volume flow under the stated constant-volume assumption.
Does the inlet connect directly to the return where they cross?
No. They occupy separate levels. The plan shows both for clarity.
Can the pressure input determine seal size?
No. This calculator only converts pressure units. It does not model seal geometry or leakage.
Historical references
Thomas Walter Barber, The Engineer’s Sketch-Book, plate 97, figure 1684: section and plan of the purifier centre valve, with gas-direction arrows.
Thomas Newbigging, Handbook for Gas Engineers and Managers, printed page 140: the four-vessel arrangement with three operating and one out for media renewal.
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