PKP Class Pt47 is a Polish 2-8-2 express steam locomotive, built for hauling express trains in Poland. The locomotive was designed in 1947 and was built between 1948 and 1951 by Fablok in Chrzanów, then by H. Cegielski in Poznań, producing in total 180 locomotives (120 by Fablok and 60 by H. Cegielski). Pt47 is an improvement of the successful pre-war PKP class Pt31 class, the main difference is the addition of circular tubes in the fire chamber, thereby significantly increased boiler performance. This class also featured a superheater and many have mechanical stokers to feed coal into the firebox.
History
Before the war
The number of freight and passenger trains was steadily increasing in the 1920s. The passenger steam locomotives of the Ok1, Ok22 and the express Pk1 class, were not able to cope with the weight of heavy transit trains from Berlin to the capital of East Prussia – Königsberg, especially on the demanding Chojnice - Tczew - Malbork route. In the second half of the second decade in the 20th century, the Ministry of Transport decided to build two prototypes of heavy express steam locomotives with four driving axles designated Pu29. The trial run of the Pu29-1 prototype took place on 9 September 1931, and alongside its service in the first few months, it showed very good performance. Despite this, the locomotive was too long and heavy for the needs of Polish railways, and wasn't able to fit into turntables, which led to abandoning the production of the class, and develop a new locomotive design. The second design was to be designated Pt29 and was developed under the direction of the young engineer, Kazimierz Zembrzuski, with supervision from Professor Xiężopolski. On 5 October 1932, Fablok conducted the trial run of PKP class Pt31 locomotive with a train weighing 660 tons on the Strzemieszyce - Skarżysko-Kamienna route. The locomotive, like the Pu29, demonstrated very good performance during subsequent operation. The locomotive's length allowed to fit on most turntables available in the main engine sheds while having less weight and having similar performance, which tipped the decision to choose the design built at Fablok.
Design The situation regarding the number of heavy express locomotives was difficult, most of the locomotives were severely damaged from the war.
On 7 February 1947, in a difficult economic situation, a conference took place at the Mechanical Department of the Ministry of Communication regarding the construction of standardized locomotives for PKP. Professor Xiężopolski supported starting production of the modernized pre-war designs to give time for developing new solutions. Following this idea, on 10 April 1947, professors Albert Czeczott and Antoni Xiężopolski gave a positive opinion on the projects for the Ty45 class locomotives, which was the development of the pre-war Ty37 class, and the Pt47 class locomotive, which was an evolution of the pre-war Pt31 class modernized by the Central Design Office in Poznań. The modernization of the design documentation for the Pt47 class was handled by the Central Design Bureau of the Railway Rolling Stock Industry in Poznań.
In the new locomotive class, many differences were introduced compared to the original Pt31 class, including:
Using the steel firebox instead of a copper firebox, where the side copper stays were replaced with steel stays, and the introduction of the hinged stays, Installing the circulation pipes of the firebox in a quantity of three, on which the arch was supported, Adding two flame tubes, which allowed for the use of 40 elements of the superheater instead of 38. As a result of the changes, the superheater surface area increased by 8 m2, and the boiler increased its heating surface by 5 m2, Increasing the number of cleaning openings of the support, Changine the fittings with valves, including the main steam receiver, Using a shaking grate, Removing the central latch in the form of a knob in the center in the smoke box door, Installing a steam collector on the boiler barrel at the first barrel course, shortening the connecting pipe, where its insulation formed a unified structure together with the sand box, Using a closed cab, Changing the shape and height of the smoke deflectors, and abandoning the characteristic upper edge bevel of the Pt31 on the side facing the front of the locomotive, The locomotive frames being made from a single element, which became a no longer need for manufacturing from two elements and join them under the boiler supports, which was possible in the post-war industry, Changing the construction of the ashpan along with its flaps, Reducing the locomotive's weight by about 2 tons, thanks to the widespread introduction of welding technology and the replacement of riveting, Modifying the construction of the rear bogie of the running gear. A new type of standardized sleeve buffers used on locomotives after the war on the PKP.
Production In the beginning of 1948, the Ministry of Transport placed orders for the delivery of 135 locomotives by 1949, including 100 for Fablok numbered from 1 to 100, and 35 for Cegielski with numbering from 101 onwards. A year later in 1949, both manufacturers were granted additional orders, for 20 and 25 units, in which the total number of locomotives built could reach 180. The delivery date for the first unit, set for May 1948, proved to be too optimistic, as it soon became apparent, and had to be postponed by three months due both to delays in the preparation of construction documentation and to difficulties faced by the subcontractor, Babcock-Zieleniewski Works, which encountered problems in producing the dies and procuring imported firebox plates. The latter issue turned out to be serious enough that the final delivery plan of 35 locomotives from Fablok by the end of the year was achieved with only 28 units.
In addition to the serious delay in the delivery of locomotives, problems with their quality became apparent, as the first batches deviated from the required technical specifications, and also showed a tendency to delaminate during subsequent operation. In the view of the failure to meet the annual plan, particular importance was attached to the early commissioning of the first unit Pt47-101 by the Cegielski Works in mid-December 1948. This event was given a propagandistic dimension, as an act of the crew to commemorate the Unification Congress of the Workers' Parties, since according to the plan the locomotive was supposed to be ready only by mid-January of the following year. The problems with boiler plates were not the only ones faced in the production process and during the initial period of locomotive operation. For several years, there was an ongoing replacement of cracking driving wheels produced by the Bauerertz Steelworks, which led to prolonged withdrawal from service of several locomotives.
The failure to deliver, or rather not to order on time, the recording speedometers, which were entirely imported from Switzerland, had such effects – the steam locomotives were simply taken from the factories without the equipment.
During the production, no major structural changes were made to the individual batches of locomotives delivered. Minor changes were made to the driver's cab, which was adapted to different types of tenders, and to the use of a three-cylinder compressor (type H11a3) in the later locomotives, which also required reconstructing the smokebox bell. Most of the boilers (140) for the Pt47 locomotives were made by the Babcock-Zieleniewski Works in Sosnowiec, while the rest came from the Cegielski Works. Due to the shortage of spare boilers that gradually made swapping them harder, caused longer repair downtimes, in 1966 the Wrocław ZNTK made two additional welded-design boilers, which differed only slightly in dimensions from the original ones, and these were then installed in the Pt47-93 and Pt47-178 locomotives at ZNTK Bydgoszcz.
Tenders The difficult decisions related to the construction of locomotives after the war were the equipping of new locomotives with tenders. A decision was made to adapt the 34D44 tenders, coupled with German locomotives such as DRG Class 03 and 44 (PKP class Pm2 and Ty4), which had open cabs. For this purpose, the old German tenders were sent for repairs, where they were adjusted to the new locomotives. Coal boxes were raised, adapted to closed cabs, and water inlets were modified, which led to the introduction of the new designation 34D48. Despite this temporary solution, there were ongoing shortages of tenders, and the problem of their lack for systematically repaired locomotives returning to service under the PKP as class Pm2 and Ty4 also emerged. Therefore, there were instances of even using barrel-type tenders 30D43, which were originally used with PKP class Ty2 locomotives. Therefore, in order for new steam locomotives not to remain in factories waiting for tender deliveries, they were paired, as in the case of Pt47-125 at HCP with barrel-type tenders, with the intention that they would eventually be replaced during service. It was only the start of production of 33D48 tenders by Pafawag from 1949 that allowed for pairing new locomotives with brand-new factory tenders.
After the decision to use a mechanical coal feeder, the so-called stoker, on Pt47 class locomotives and its systematic installation during scheduled repairs at ZNTK Bydgoszcz in the 1950s, the capacity of the tender water tank was reduced and its designation changed to 27D48. The Pafawag design wasn't free of flaws, as axle bearing failures happened quite often. Between 1974 and 1976, ZNTK Bydgoszcz carried out a modernization of the 33D48 and 27D48 tender trucks by installing roller bearings.
Design
Locomotive frame
Frame construction The supporting structure of the locomotive consists of a beam frame built from two main beams with a thickness of . The main beams were made as a single element, unlike in the Pt31 class locomotives, where they were composed of two parts. This was due to the technological limitations of the industry at that time, which resulted in the characteristic grouping of bolts connecting the frame plates under the boiler supports of the locomotive. The main beams of the frame, so-called side frames, were connected by vertical crossbars located behind the first driving axle and under the cylinder rollers, to which a swinging plate supporting the boiler was mounted. Between the steam cylinders of the frame, a crossbar known as the smoke box frame was also located, providing a fixed support for the boiler. Crossbars were also positioned over the front and rear carrying axles. Additionally, the main beams featured upper and lower horizontal crossbars, closing the area between the remaining crossbars almost along the entire length of the frame. The front buffer beam, factory-riveted and made of thick sheet metal, and the tender coupling box also constituted a connection of the frame beams.
The suspension is based on a single type of a leaf spring, referred to in the old nomenclature and design documentation as a load-carrying spring. The lower suspension in the area of the drive units was constructed by forming two independent groups. Through spring hangers and a system of simple and knee levers, the first rolling unit was connected with the first and second drive units, forming the first group, and the third and fourth drive units were connected with the rear rolling unit, forming the second group.