skip to Main Content
82 Cubic Metres Per Second Of Ventilation On Grosvenor LW101 Face In September 2016 To Dilute Methane Below 2.5%

82 cubic metres per second of ventilation on Grosvenor LW101 Face in September 2016 to dilute methane below 2.5%

The quantity of ventilation across the longwall face between 70 and 80 cubic metres per second was a topic of discussion at the Grosvenor Inquiry.

Principally this was about the increased Oxygen into the goaf from running higher quantities and pressures that heighten the risk of spontaneous combustion in the goaf.

As we also heard at the Inquiry, Grosvenor Management employed between 70 and 80 m3/s in LW 104 to dilute the longwall methane emissions down to less than 2.5% so mining could occur.

However we can see from very early on in LW101 that these sort of quantities are already in place to try and keep methane concentration to less than 2.5%.

Inspector Dobson’s Inspection on the 21st of September conveniently details the ventilation quantities and methane percentages at the back of the Tailgate Drive and at the Ventilation Station in the Tailgate Roadway

21.09.2016 Dobson MRE – Grosvenor Coal Mine –

While Inspector Dobson’s observations are principally about the airborne dust being visibly excessive and this was still the case when operations stopped due to an outbye conveyor issue.

This is a visible comparison to other conventional Longwall operations which have returned compliant personal monitoring samples

I was not surprised by this given the excessive ventilation velocity of 6.1 m/s on the Longwall face. In other operations these velocities are rarely in excess of 3 m/s.

Inspector Dobson identifies that the ventilation velocity and therefore the quantity is about double that on comparable longwall faces.

In the Tailgate Roadway Methane  is 1.75% CH4 in a Ventilation quantity of 82 m3/s

If there was half the quantity, the methane level in the Tailgate would double from the 1.75 % detected by the ERZC to 3.5% CH4.

Just to keep the Methane at below 2.5% would require 57.4 m3/s of ventilation.

We can work out the methane make of LW 101 panel when it is just outbye 19c/t probably after about 400 to 450 metres of retreat.

The longwall methane make 1.23 cubic metres per second.

This from using Inspector Dobson’s MRE from September 2016.

In the Tailgate Roadway Methane  is 1.75% CH4 in a Ventilation quantity of 82 m3/s

We know from Inspector Gouldstone’s MRE from July 2016 that there is a  background methane level of 0.2% CH4 for intake air entering the longwall face.

Therefore the longwall methane make in the longwall face is an additional 1.5% CH4

The longwall methane make is 1.5% of 82 m3/s or 1.23 m3/s.

21.09.2016 Dobson MRE – Grosvenor Coal Mine –

Level 2: > 2.5% CH4 LW Return – spikes shearer in TG.

We further discussed the methane makes for the Longwall tailgate and I was provided with the trends dating back to 17/08/16 as there had been a number of trips at the Tailgate drive in early September that had resulted in delays that were up to 1.25 hours.

Visible dust that was apparent in the general ventilation stream whilst coal cutting activities were being undertaken appeared visibly excessive and this was still the case when operations stopped due to an outbye conveyor issue.

This is a visible comparison to other conventional Longwall operations which have returned compliant personal monitoring samples. I was not surprised by this given the excessive ventilation velocity of 6.1 m/s on the Longwall face. In other operations these velocities are rarely in excess of 3 m/s.

  • Methane – 1.75%
  • Oxygen — 20.1%
  • Ventilation quantity — 82 m3/s
  • Ventilation velocity — 5.5 m/s

I asked if he had inspected the Tailgate which he confirmed and provided his personal gas monitor readings for the Tailgate General body from his earlier inspection which was as follows:

  • Methane – 1.75%
  • Oxygen — 20.1%
  • Carbon Monoxide — Ippm Hydrogen Sulphide — Ippm Nitrogen Dioxide — 0.1 ppm
  • Ventilation quantity — 82 m3/s
  • Ventilation velocity — 5.5 m/s

He then took a reading at the rear of Tailgate drive

  • Methane — 0.2%
  • Oxygen — 20.1%
  • Nil other gases detected

Outbye of the Tailgate drive I asked him to measure the ventilation velocity which was 6.1 m/s.

Visible dust that was apparent in the general ventilation stream whilst coal cutting activities were being undertaken appeared visibly excessive and this was still the case when operations stopped due to an outbye conveyor issue.

This is a visible comparison to other conventional Longwall operations which have returned compliant personal monitoring samples. I was not surprised by this given the excessive ventilation velocity of 6.1 m/s on the Longwall face. In other operations these velocities are rarely in excess of 3 m/s.

This Post Has 0 Comments

Leave a Reply

Your email address will not be published. Required fields are marked *