Brief History

Many coke works were built with tar distillation facilities enabling them to produce their own benzole absorbing oil (creosote) used for removing crude benzole from the gas stream. South Wales was no exception, with small tar distilleries located at Tondu, Pontypridd, Bargoed, Llanbradach, Bedwas, Coedely, Blaenavon, Aberaman and so on. By the 1930's tar distillation technology had progressed from batch processing to continuous systems and large scale operations were proving to be more cost effective.

The Powell Duffryn Company owned several sites in the Rhymney Valley, including Windsor, Bargoed and Penallta colleries, the coke works and a power station at Bargoed and a brick works at Wernddu. Infact one of the first private power grids supplying electricity to most of PD’s sites in the Rhymney Valley originated from the Bargoed power station, supplying power at 550v, 3 phase. This supply being different from the normal, the latter being 440v, 3 phase. When the coal industry was nationalised in 1947 the power supply used was at the higher voltage of 550v and this became the norm over much of the South Wales coal field including the tar works.

By the late 1930's Powell Duffryn (PD) and Richard Thomas and Baldwin (RTB) had come to an agreement to jointly build a new large tar distillation works replacing smaller batch plants. (RTB operated the coke overs and steel works site at Ebbw Vale). After much searching a new green field site was eventually found at Caerphilly. This site happened to be adjacent to PD’s Wernddu brickwork's, which provided excellent rail facilities, with an existing rail connection off the Great Western's Rhymney - Caerphilly - Cardiff railway line and right opposite the Great Western Railway's Caerphilly Locomotive & Carriage Works; the former controlled by the Wernddu signal box immediately north west of the Caerphilly tunnel.

Wernddu Private Sidings Railway Agreement

In 1922 the Rhymney Railway and PD had negotiated a private siding agreement to provide point work and signalling to the brickworks and it was a natural extension to amend the agreement in 1938 to include a new connection with associated point work and signalling to the new tar works. For interest, the access to the brick and tar works was from the down line by reversing trains across the up main by a diamond crossing and into the private sidings all controlled by Wernddu Signal Box. The normal route of trains for the brick and tar works (and Caerphilly coal yard) being from Radyr with trains being worked up the Penrhos bank and to Wernddu via Watford where the traffic was propelled back across the up main into the private sidings. Receipts being crude tar from the local coke works, coal and coke as fuel for the furnaces and boilers and outwards, empty tank wagons and solid pitch to the Phurnacite works. Despatches were normally taken directly through Caerphilly tunnel, through Cardiff and around what is now the City Line back to Radyr. Under the private sidings agreement PD had to pay for the maintenance of the signal box and the diamond crossing. This arrangement continued into BR days right up to the closure of the signal box in 1982. Infact it was the massive expense of renewing the signalling and pointwork imposed upon Caerphilly tar works under this agreement by BR that finally forced the closure of rail bourne traffic to and from Caerphilly in March 1982.


A 60 year lease was signed on 1 January 1938 with Plymouth Estates and construction began on building 2 x 75 tons/day continuous tar distillation units using the Wilton principle, plus associated tankage, pumps, services etc and also a by product plant manufacturing proprietary tar based products. Some equipment was transferred from other tar works but otherwise most items were new. An interesting legal clause required the NCB to give five years' notice to Plymouth Estates when they wished to quit the site.

Moving specifically on to steam pumps the tar distillation unit circulating, feed and reflux pumps, along with crude tar, daily products, cooling water and effluent pumps were all manufactured by Joseph Evans Ltd of Wolverhampton, although there were a few non-Evans pumps, details as follows:-

Note: In the list below, those pumps that were saved following closure and demolition of Caerphilly tar works have been marked with an asterix *, however, their current condition and whether on display is not known in every case. It must be assumed that all other pumps were scrapped

Tar Distillation No.1 and No.2 Unit Pumps

  • Circulating Pump-No.1 unit 6x5/4½x9 Twin Reliable Jacketted No.31308
  • Circulating Pump-No.1 unit Stothert & Pitt Jacketted No.17696
  • Circulating Pump-No.2 unit 6x5/4½x9 Twin Reliable Jacketted *No.31312
  • Circulating Pump-No.2 unit Stothert & Pitt Jacketted No.17698
  • Feed Pumps - No.1 unit 4x3x4 Reliable *No.30938 & *No.30940
  • Feed Pumps - No.2 unit 4x3x4 Reliable *No.30937 & *No.30939
  • Reflux Pump - No.1 unit 4x3/2½x4 Reliable *No.30933
  • Reflux Pump - No.2 unit 4x3/2½x4 Reliable *No.30934
  • Effluent Pump 5x3x6 Reliable *No.19473 (Ex Llanbradach)
  • Water Pump 5x5x5 Duplex No.30954
  • Water Pump Tangye No.25182
  • Air compressor 8/6½ F Westinghouse *No.61799
  • Air compressor 8/6½ F Westinghouse *No.64752
  • Crude Tar Pumps

  • No. 1 8x6½x9 Horizontal Reliable - Jacketed No.30917
  • No. 2 8x6½x9 Horizontal Reliable - Jacketed No.30893
  • No. 3 5x4x6 Horizontal Reliable *No.13812 (Ex Bargoed)
  • Boiler Feed Pumps - Weir

  • No. 1 6x8½x13 Weir Vertical No.B19533 1938
  • No. 2 6x8½x13 Weir Vertical *No.B19534 1938
  • Babcock & Wilcox Donkey Engine No. 159
  • Daily Product Pumps

  • No. 1 8x6½x9 Hor Reliable *No.30897
  • No. 2 8x6½x9 Hor Reliable No.30898
  • No. 3 8x6½x9 Hor Reliable *No.30905
  • No. 4 8x6½x9 Hor Reliable - Jacketed No.30916
  • No. 5 8x6½x9 Hor Reliable - Jacketed No.30892
  • No. 6 6x5x9 Hor Reliable - Jacketed *No.30810
  • No. 7 6x5x9 Hor Reliable - Jacketed No.30839
  • No. 8 6x5x9 Hor Reliable - Jacketed *No.30809
  • No. 9 6x5x9 Hor Reliable - Jacketed *No.30838
  • No.10 6x5x9 Hor Reliable - Jacketed *No.30808
  • A few years later 2 more pumps were installed

  • Tar Mixing Plant 6x5/4½x9 Hor Reliable - Jacketed No.34679
  • Pitch/Creosote Plant 6x5/4½x9 Hor Reliable - Jacketed No.34680
  • In addition there were other non-Evans pumps

  • Tank 14 5x6x12 Lee Howl Tipton Jacketted *No.45634
  • Road Tar 12x14x24 Lee Howl Tipton No.41161
  • Tar Mixing plant 7½x6x10 Worthington-Simpson Jacketted No.5111111 Ex-Bristol
  • Tar Mixing plant 7½x6x10 Worthington-Simpson Jacketted No.5262643 Ex-Bristol
  • Boiler feed water 6x8½x13 Weir vertical *No.B39713 1951
  • In 1947 following the Nationalisation of the mining industry the Tar Works came under the umbrella of the National Coal Board, Carbonisation Division, later to become Coal Products Division, then Coal Products Ltd and finally Thomas Ness Ltd.

    Expansion of the tar works

    In 1955 the tar plant capacity was doubled by the addition of a third tar distillation unit rated at 50,000 tons / year or 150 tons / day. The site now had the potential of distilling over 100,000 tons per annum of coal tar. At the same time a new tar works was being built at Avenue Coke works near Chesterfield. Both plants were very similar and both used Evans pumps.

    No.3 Tar Distillation Unit Pumps

  • No. 1 Circulating Pump 6x5½/5x9 Twin Reliable J No.53/33951C
  • No. 2 Circulating Pump 6x5½/5x9 Twin Reliable J No.53/33952A
  • No. 3 Circulating Pump 6x5½/5x9 Twin Reliable J No.53/33951A
  • No. 4 Circulating Pump 6x5½/5x9 Twin Reliable J *No.53/33951B
  • No. 1 Feed Pump 6x6/4x6 Duplex J No.53/33618A
  • No. 2 Feed Pump 6x6/4x6 Duplex J No.53/33618B
  • Reflux Pump 5x4/3x6 Reliable *No.53/33619
  • Crude Tar Pump 8x8x12 Duplex J No.53/33617
  • Crash Tank Pump 5x5/4x5 Duplex J *No.54/39275 - note: J = jacketted
  • The original naphthalene plant used the open tray/hot press method for the crystalisation of high grade naphthalene. Once the crystalline product had been formed the final product was elevated to a handling section for bagging for sale. In November 1958 a major fire destroyed this Naphthalene plant; although no one was injured, extensive damage was caused to the works. A new plant was designed to be built on a new area of works at the west end of the site comprising a re-distillation still, furnace and fractionating column with 72 plates, a purification plant using centifuges rather than hot presses to produce the high grade naphthalene along with bulk liquid storage and associated plant.

    New Naphthalene Plant

    By 1962 the new replacement plant had been constructed. This new plant and two new circulating pumps for Nos.1 & 2 tar units (replacing a pair of original 1938 Stothert & Pitt pumps), specified Evans pumps, however Evans, already part of the Pulsometer Group had recently been sold in 1962 to G J Weirs of Glasgow and hence the new pumps, although obviously of Evans design, had Weir serial numbers.

    Naphthalene Plant Pumps

  • Residues Duplex 5x5/4x5 No.J40401
  • Tank 62 Duplex Jacketed 6x6/5x6 No.J40400
  • Water Duplex 4x3/2½x4 No.J40402
  • Main Water Duplex 6x6/5x6 No.322469
  • Tar Distillaton Pumps

  • No 1 Unit Circulating Pump 6x5½/5x9 Twin Reliable Jacketted No.322135 1962
  • No 2 Unit Circulating Pump 6x5½/5x9 Twin Reliable Jacketted No.322134 1962
  • Changes in the late 1960’s and early 1970's

    New CTF fired boilers were purchased allowing the old coal fired Babcock & Wilcox boilers to be scrapped and the third boiler converted to CTF. Similarly the coke fired furnaces for the two small tar units, Nos. 1 & 2 were also modified to burn CTF. New stainless steel pitch cooling belts were installed replacing pitch cooling trays all greatly reducing pollution and site odours. In the early 1970’s towns gas made from coal in coke works was being rapidly replaced by natural gas meaning that the former supplies from the local coke works were not now required by Wales Gas Board for their customers. In the mid 1970’s a new pipe line was constructed from nearby Bedwas coke works to Caerphilly tar plant to supply crude coke oven gas for the tar pipe still furnaces and the boiler plant.

    Various pumps were acquired and/or transferred, as replacements/spares from the many tar/coke works that were now closing. In the 1980's Caerphilly also became a storage site for redundant equipment within the Wales and Ness Groups of Coal Product sites. Some pumps were used, others were stripped for spares, some not used as indicated below, most were J Evans.

    Acquired Pumps

  • Tar Feed Pump Installed 4x4x4 Duplex *No.29798 Ex Greenwich
  • Tar Feed Pump Installed 4x4x4 Duplex *No.31417 Ex Greenwich
  • Reflux Tank Pump Installed 5x4/3x6 Reliable *No.40202 Ex Greenwich
  • Oil Transfer Pump Spares 5x4/3x6 Reliable No.57/64261A Ex Rainham
  • Oil Transfer Pump Installed 5x4/3x6 Reliable *No.57/64261B Ex Rainham
  • Daily Product Pump Spares 6x6/4½x9 Reliable No.37672 Ex Pontypool
  • Daily Product Pump Installed 6x6/4½x9 Reliable *No.37673 Ex Pontypool
  • Circulating Pump Installed 6x5/4½x9 Twin Reliable J No.57/62309A Ex Rainham
  • Circulating Pump Spares 6x5/4½x9 Twin Reliable J No.57/62309B Ex Rainham
  • Circulating Pump Not used 6x5/4½x9 Twin Reliable J *No.57/62309C Ex Rainham
  • Circulating Pump Not used 6x5/4½x9 Twin Reliable J *No.35098 Ex St Anthony's
  • Reflux Pump Not used 4x4/3½x4 Reliable *No.24453 Ex St Anthony's
  • Tar Pump Not used 5x3½x6 Reliable *No.33415 Ex St Anthony's
  • Tar Pump Not used 5x6x5 Duplex *No.29112 Ex St Anthony's
  • Tar Transfer Pump Not used 12x10x12 Reliable *No.35292 Ex Greenwich
  • Tar Transfer Pump Not used 12x10x12 Reliable *No.35466 Ex Greenwich
  • In addition there were also 6 Worthington Simpson Duplex and 6 Lee Howl pumps.

  • W-S Reflux pump Not used 3x2x3 Duplex *No.not known Ex St Anthony's
  • W-S Reflux pump Not used 3x2x3 Duplex *No.D18K Ex St Anthony's
  • W-S Tar pump Not used 4½x3.75x4 Duplex *No.5027835 Ex Greenwich
  • W-S Tar pump Not used 4½x3.75x4 Duplex *No.5027836 Ex Greenwich
  • W-S Tar pump Not used 6x4x6 Duplex No.5110284 Ex Greenwick
  • W-S Tar pump Installed 6x4x6 Duplex *No.D107H Ex St Anthony's
  • L-H Tar pump Installed 6x6x12 Tipton *No.30004 Ex Bexley Gas Works
  • L-H Tar pump Installed 6x5x12 Tipton *No.28695 Ex Norwood TP
  • L-H Tar pump Not used 4x5x9 Tipton *No.65525 Ex Coedely
  • L-H Tar pump Installed 5x4 fig 1167 Electric No.68137 Ex Norwood TP
  • L-H Pitch pump Installed 8x8x10 Duplex-Jacketted No.72346 Ex St Anthony's
  • L-H Pitch pump Installed 8x8x10 Duplex-Jacketted *No.72347 Ex St Anthony's
  • The Final Years to 1985

    From the mid 1950's to the early 1970's all 3 distillation units were working with throughput in the 100,000 tons per annum region. In the 1970's Bristol and West Tar Works at Crew's Hole Bristol was purchased by BSC Chemicals and their crude tar to Caerphilly from Port Talbot coke works ceased. At the same time Ebbw Vale coke works closed. (Their tar was still being distilled at Caerphilly under the original RTB & PD agreement). Similarly tar from East Moors coke ovens in Cardiff ceased to be regular. Throughput dropped significantly and therefore, from mid 1970's the works reverted back to a 2 unit works of 75,000 tons per annum maximum with a small unit as stand by. A brief peak occurred in mid 1974 when the third unit was restarted and preparations undertaken to recommission the naphthalene plant, but this was later aborted. Until early 1974 No 2 unit was the stand by unit, but after various coil and instrument failures upon starting up No 1 unit in April 1975 following a routine shut down, No 1 unit never ran again. In fact for the record its last run was prior to the 1974 Christmas shut down. In 1978 the first redundancies occurred as tar availability from the Coal Product’s Coke Works were steadily reducing and economies required. St Anthony's Tar Plant in Newcastle closed in 1978, easing the tar availability for the remaining tar plants. Caerphilly was also boosting its throughput with imports of coal tar and steam cracker residues through Cardiff docks using their own fleet of private tar tank wagons. The final blow to the British Coke and Tar Industry came in 1984/5 - the national NUM strike which lasted for 50 weeks. The works resumed production on 2 units soon after the strike but in June 1985 British Coal announced that tar distillation at Caerphilly would cease by the end of the year. From June until closure, the 2 units worked flat out, No 2 unit finally closing mid November and No 3 on 24 November 1985. Thus ending almost 50 years of tar distillation on this site.

    Post 1986

    By early 1986, No.3 tar distillation unit, the last unit to be built and being very similar to the tar unit at Avenue, was being carefully dismantled and transported to Chesterfield for use as spares. This included the distillation column sections, (but not the fractionating column as this was smaller), heat exchangers and three of the four circulating pumps. Note: circulating pump No.53/33951B was purchased privately and was not included. Also transferred were three circulating pumps from Nos.1 & 2 tar units: Weir 322134/5 installed in 1962 and refurbished pump from the Salamon tar works in Rainham, Essex, No. 57/62309A. These 6 pumps and all the spares were stored in the former pitch bays at the top of the site. As far as I am aware all these pumps and others from Caerphilly were never used and all were subsequently scrapped when the Avenue site closed. Meanwhile, the manufacture of building products, some tar based, including Synthaprufe and Presomet, continued until March 1992 with limited use of pumps for internal transfers only. Many of the remaining steam pumps were purchased by individuals and societies at scrap prices, except for a few retained and used on an 'as required' basis.

    From April 1992 all services were severed and all personnel transferred to the Plas Ness site across the railway line in the old GWR Locomotive Works. The remaining tar based and other building products manufacturing equipment was also transferred over to this site. Site security at the tar plant site was limited to one person from 6.00 pm to 6.00 am with occasional day visits from the other site. Sadly the site became an attraction for vandalism and theft and before long it started to become a major hazardous area. Bronze bearings were stolen along with most of the copper cabling and two large fires, probably started deliberately, forced the Company to commence demolition in May 1993. Unfortunately, with the recession still biting, the demolition company ceased trading in August 1993, with about one quarter of the site still remaining. Demolition resumed in May 1994 with another company and by the November the site had been completely cleared. One further pump was saved, otherwise the remainder were destroyed by the scrap merchants. Those scrapped included a twin circulating pump, 5 Reliable pumps, 4 Duplex pumps - all J Evans; the large Lee Howl Tipton in the crude tar pumphouse and another Lee Howl Duplex. After 56 years of operation, Caerphilly tar plant had finally closed; with the lease finally terminating on 31st December 1997. The site is still vacant with just the outline of the main plant roadways just visible as natural vegetation growth is slowly taking over the site, nevertheless, there are several areas within the boundary of the site that are contaminated with solid coal tar residues.

    S I Smith December 1997

    This section will also contain photos of Caerphilly Tar Plant and Avenue Tar Plant up to just prior to demolition.

    Sorry I'm still updating this section.