PKP class Pt47
Polish express steam locomotive
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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 were 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.[1]
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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.[1][2] 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.[2][3]
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.[1]
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.[4]
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.[4]
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.[4]
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.[4]
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.[5]
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.[5]
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 90 mm (3.5 in). 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 20 mm (0.79 in) 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.
The leading wheel set had guidance through a Krauss-Helmholtz rolling half-bogie with a lateral displacement of the set of 120 mm (4.7 in) to each side, which allowed it to navigate curves with a radius of 150 m (492 ft 2 in). The half-bogie construction is complex, with its main component being a 2,495 mm (98.2 in) long drawbar. One end of it was connected to the first driving wheel at its middle section, and the other to the leading wheel. The half-bogie had two independent return devices. The first, located about halfway along the drawbar, operated using two springs mounted longitudinally on both sides of the drawbar, which exerted pressure on a ⌀120 mm (4.7 in) pin pressed into the lower part of the frame cross-member between the steam cylinders. The second return device was located right at the axle of the trailing wheel, and its design was based on a spring that pressed against the frame beams.
The rear trailing wheel featured guidance through a Bissel pony truck with a lateral swing of 120 mm (4.7 in) to each side, whose construction is decidedly simpler than that of the front pony truck. The adjustment of the pony truck was ensured by a return device installed on the pony truck's drawbar in front of the wheel. It was equipped with a spring, which generated pressure on the frame beams and forced its realignment along the axis of the locomotive.
Wheelsets
The wheel arrangement of the Pt47 locomotive is 1-4-1, known as Mikado. The locomotive had four driving wheels with a rolling circle diameter of ⌀1,850 mm (6 ft 1 in). The second, third, and fourth driving wheels had no lateral play. The first wheel had axial play in the journal boxes that allowed the axles to move 20 mm (0.79 in) to each side, which, together with the design of the trucks, enabled the locomotive to negotiate curves with a radius of 150 m (492 ft 2 in). The driving wheels had cast wheels with 20 spokes, whose counterweights were located on the opposite side of the drive journal; however, they were not symmetrical, but rotated 7°15'57" to the right when viewed from the side of the wheel, resulting in a displacement of 107.2 mm (4.22 in) on the wheel rim. Counterweights were made initially with a lead-filled mass, and in later stages of production, the counterweights were solid without lead. Axles were also produced in two versions. In the first phase of production, being hollow, they had a hole along the entire length with a diameter of 100 mm (3.9 in), and later they were solid. The hollow axles were intended to lower the temperature through additional ventilation and reduce the unsprung mass of the wheelset. Wheels were positioned relative to each other so that, in the direction of travel, the right crank leads the left by 90°. The wheels were pressed onto the axles using a press, where the proper pressing force should be within the range of 127.5 to 178.7 tonnes (281,000 to 394,000 lb) for oil lubrication. The bare wheels were fitted with rims by mounting the rims hot, with a shrinkage allowance of 1 mm per 1 m (39 in) of diameter, and secured with a clamping ring by rolling the rim immediately after it was mounted on the wheel.
All wheel tires of the wheelset had bolted slides on the inside, which worked directly with the journal flange. This allowed for the replacement of a slide in case the spacing of the slides exceeded the repair dimension without the need to replace the wheel tires. After being pressed onto the axle, the wheels were secured with round and square wedges. The leading wheel had wheel tires with 10 spokes and a rolling circle diameter of ⌀1,000 mm (39 in). The trailing wheel had wheel tires with 12 spokes and a rolling circle diameter of ⌀1,200 mm (47 in). Both sets had hollow axles with a hole along the entire length of the axle with a diameter of ⌀70 mm (2.8 in).
Each wheel assembly had two internal lubrication blocks, which were mounted on the axles using bearings cast with so-called white metal – a bearing alloy. Plain bearings were used in practically all class of locomotives operated on PKP. Serial solutions used on other railways, such as in Czechoslovakia or the GDR, where locomotives with rolling bearings operated, were not applied. Lubrication of the lubrication block was carried out through the top oiler and lubrication channels in the bearing. From below, lubrication was provided by the bottom of the lubrication block and oil pads made of wool, pressed against the axle by springs. Water accumulating in the bottoms was drained through a special drain hole. In addition to lubrication from the oilers, the supply of axial oil was ensured by the central Friedmann oiler.
Train collision components
The drawbar and buffer devices for the front and rear of the locomotive, i.e., the connections with the tender, were executed in two structural solutions functioning as conceptually similar on most PKP steam locomotives. At the front, the buffer beam houses a towing device with a hook, which since 1951 has been produced in a version with a reinforced hook head. A standard screw coupling was attached to the hook. On the buffer beam, 75 mm (3.0 in) stroke sleeve buffers of a new type were located, later widely used on PKP.
The connection of the tender to the locomotive was implemented through three links, of which the main link in the middle section was made with a cross-section close to square, measuring 100 mm × 80 mm (3.9 in × 3.1 in). It was mounted on the locomotive through a coupling box, which secured its end with a pin 120 mm (4.7 in) in diameter, fastened with a wedge.
Two buffers were installed on the tender, which rested against the prismatic buffer plates of the locomotive, the surfaces of which were lubricated using wick lubricators with lubrication pipes. The tension generated by the buffers made it difficult to withdraw the main coupling pin. For this purpose, special couplings (a turnbuckle) were used to reduce the distance between the locomotive and the tender. One end was mounted on a pin of the tender specially designed for this purpose and on a special hook on the locomotive’s coupling box. Two sets of couplings were used to compress the buffers and withdraw the coupling pin. Unfortunately, many abandoned and forgotten locomotives, and even monument locomotives, are incompetently uncoupled by burning through the main coupling rod. This makes it impossible to re-couple it, and manufacturing a new part is costly, as in 2020 the part was valued at approximately 5000 PLN
Drive and steam distribution mechanism
The Pt47 locomotives used a twin steam engine with an internal steam inlet, equipped with pressure equalizers of the system designed by engineer Kazimierz Tatara and piston slides. This solution was directly adapted from the Pt31 locomotives, and it was also used in the Pu29 locomotives.
The steam cylinders were suspended on both sides of the frame using 10 M46H8 bolts for each cylinder. A cylinder sleeve with a diameter of ⌀630 mm (25 in) was pressed into the cylinder bore. This solution allowed for the replacement of the sleeve in case of damage to the liner, rather than replacing the entire cylinder. At the top of the cylinder, an engineer Tatara pressure equalizer was installed. This device in the body of the equalizer contained two valves that, during operation without steam, would lift and equalize the pressure in the return spaces of the slide chest. This allowed for the installation of fixed slides on the slide rod guided by a ⌀320H9 slide sleeve sealed with felt. The piston rod was guided through bearings on both cylinder covers, which were sealed with a felt ring and a gland consisting of 4 sets of chamber rings. The piston disk had three sealing rings. After assembly, the piston rod was run in with a single-guide crosshead lubricated using a wick lubricator, with the wick made of cotton-wool yarn 1.2 m (3 ft 11 in) in length. Spring-loaded safety valves were installed on the cylinder covers to protect the cylinders from cover blow-off.
A coupling rod 3,800 mm (12 ft 6 in) in length with an I-beam profile was considered rather long for those used in PKP steam locomotives. The front end of the connecting rod was mounted on a pin with a diameter of ⌀120 mm (4.7 in), featuring a split bearing with wedge-screw adjustment. The rear end also has a split bearing with wedge-screw adjustment mounted on a crankpin with a diameter of ⌀180 mm (7.1 in). The upper space between the half-bearings was filled with a lubrication plate measuring 10 mm × 20 mm × 160 mm (0.39 in × 0.79 in × 6.30 in) made of felt. The coupling rod was secured against falling with a bracket attached to the crosshead beam. Additionally, it was equipped with a step to facilitate the operation of the mechanism. The rods also have split bearings adjustable with a wedge, connected together by a joint. The bearings of the coupling rods and rods were equipped with needle lubricators. Only the front end of the coupling rod has a gravity lubricator.
The general layout of the switch stands is typical for post-war machines with a Heusinger mechanism, a suspended slide rod, and a screw return. The adjustment screw was located on the support of the adjustment device attached to the boiler in the driver's cab. The length of the adjustment rod was determined during assembly on the hot boiler, as its length could vary by over 20 mm (0.79 in) depending on the measurement. This was caused by the boiler's expansion due to the heating and the placement of the adjustment device at the end of the boiler. The bearing of the stand shaft and the yoke were positioned on a beam between the crossbars forming the base for the swinging plates. The moving points of the switches are lubricated using various types of lubricators, such as wick and needle types, whose chambers are opened by threaded plugs or valve mushrooms, as well as open lubricators located at points that do not require intense lubrication. The lubrication of the cylinder and the slide box was carried out using lubricators and central lubrication from a grease pump.
Boiler
The locomotive boilers of Pt47 locomotives for Fablok were built by Babcock-Zieleniewski Works in Sosnowiec. For locomotives built by HCP, some of the boilers came from Sosnowiec, and some were built by HCP. In the first phase of production, the boilers were riveted, and only later was welding introduced on a large scale. The working steam pressure was 15 atmospheres, and the hydraulic test pressure was 20 atmospheres. The total length of the boiler without cladding and smoke box doors is 12,302 mm (40 ft 4.3 in), and the highest height from the support point of the stand to the top of the steam collector is 3,196 mm (10 ft 5.8 in). The chimney is not the highest point of the boiler, as its upper edge from the axis of the boiler is at a distance of 1,340 mm (4 ft 5 in), and the steam collector is 1,441 mm (4 ft 8.7 in) without cladding.
Firebox and a boiler stand
The firebox was made of steel rather than copper, as was the case in Pt31 locomotives. The sheets of the firebox were 10 mm (0.39 in) thick, except for the side of the fire tubes, which was 15 mm (0.59 in). The vault of the firebox was constructed with a slope toward the rear of the locomotive of 1:53.1. This allowed the locomotive, when running on significant gradients with a low boiler water level, to maintain a minimum water level height along the entire length of the firebox vault. The firebox opening measured 2,784 mm (9 ft 1.6 in) along the longitudinal axis of the locomotive and 1,616 mm (5 ft 3.6 in) along the transverse axis, resulting in a firebox area of 4.5 m².
The firebox was placed within the boiler stand and connected with a bottom ring at the lower part and a door ring around the door opening, which had a clear dimension of 500 by 360 mm (20 by 14 in), limited by 100 mm (3.9 in) radius at the corners. In addition, the walls of the stand, made of 16 mm (0.63 in) sheet metal, were connected with fixed and movable braces, anchors, and several ties. These, numerous and evenly distributed, were designed to maintain the sheets at equal distances, which, due to temperature changes, worked and led to the breaking of the braces and, consequently, in extreme cases, even to bulging of the firebox sheets. The space between the firebox and the stand formed a water jacket, with a thickness of 100 mm (3.9 in) on the sides and on the side of the door wall, and 120 mm (4.7 in) on the side of the throat wall. According to regulations, the lowest water level from the arch of the firebox was 100 mm (3.9 in).
In order to improve water circulation and enhance boiler efficiency, the firebox was equipped with three seamless circulation pipes ⌀76/64mm, pressed into the firebox walls and welded. For inspection and removal of boiler scale, the stand was equipped with special cleanouts on the door wall, clearly visible in the driver's cab, as well as on the throat wall. Additionally, the pipes served as support for the arch made of fireclay bricks, which was designed to lengthen the flue gas path. In this way, they also protect the connection of the fire tubes to the grate wall from high temperatures and improve the boiler's efficiency.
The firebox was secured with two fusible plugs. Plugs with a 1:8 taper thread were positioned in the ceiling of the firebox. A hole M10 was made along the entire length of the plug, which is filled with an alloy of tin and lead. If the water level falls below the permissible limit due to high temperature, the alloy inside the plug is intended to melt. As a result, the sudden filling of the firebox with water and boiler steam is supposed to extinguish the fire and "inform" the locomotive crew of the situation, preventing further operation of the boiler. Tthis situation is extremely dangerous and, in the case of an incorrect reaction by the locomotive crew, attempting to replenish the boiler water level and start the injector can lead to a boiler explosion.
The total length of the firebox was 2,804 mm (9 ft 2.4 in), and its forward inclination was 1:12.588, which facilitated even feeding of the grate despite its considerable length. The boiler stand was equipped with a single muddrain located at the lowest point of the boiler on the water side, i.e., at the base of the throat wall of the stand. The second muddrain was located on the steam drum.
Steam drum
The steam drum was made from sheets with a thickness of 18 mm (0.71 in), forming two drums with an outer diameter of ⌀1,872 mm (6 ft 1.7 in) for the first and ⌀1,836 mm (6 ft 0.3 in) for the second. The total length of the drum from the sieve wall to the firebox is 6,100 mm (20 ft 0 in), with the thickness of the sieve wall being as much as 26 mm (1.0 in).
The furnace contains 40 flame tubes with a diameter of ⌀143/134.5 mm and 113 small flame tubes with a diameter of ⌀55/50 mm. The number of flame tubes was greater by 2 units compared to the Pt31 boiler, which allowed for an increase in the heating surface of the boiler by 5 m² and the introduction of additional superheater elements with a surface area of 8 m². At the bottom of the first drum, a depression was located for the accumulation of boiler sediment and a sludge trap at its base.
Smokebox
The smokebox were made from a single bell with an external diameter of ⌀1,980 mm (6 ft 6 in), made of 15 mm thick sheet metal. The length from the smoke box door ring to the sieve wall of the boiler barrel is 2,875 mm (9 ft 5.2 in). Along the longitudinal axis of the boiler, on top of the smokebox, there is a chimney with an internal diameter of ⌀595 mm (1 ft 11.4 in) and a height of 350 mm (1 ft 2 in). The opening of the door had a diameter of ⌀1,662 mm (5 ft 5.4 in) and was closed with a door hung on two hinges. The door, following the Pt31 model, did not have a central bolt, but had 8 bolts placed around its perimeter. In the initial phase of operation, the smoke box doors had a stamping, which disappeared over years of operation and locomotive repairs at ZNTK Bydgoszcz. This was due to reducing production costs by decreasing labor intensity. As a result of these actions, rationalizers received awards and joined the ranks of the proud PPR work leaders generating savings.
Inside the smokebox, a steam exhaust cone was located, generating draft during the operation of the steam engine. In the event of the locomotive being stationary, an air blower was supposed to improve the steam production by the boiler. The device, being a pipe surrounding the steam cone and having a dozen or so openings, caused the flow of steam and an artificial draft that carried the exhaust gases through the fire tubes from the firebox to the chimney when the steam supply was opened. The capture of hot pieces of coal and other impurities produced during coal combustion was to be reduced by spark-arresting screens. The soot accumulated in the smokebox was sprayed with water using a dropper.
Deep inside the smokebox, on the blast plate, a Schmidt superheater was installed, whose task was to overheat the saturated steam to a temperature of approximately 400°C (752°F) and improve the efficiency of the locomotive. It is also worth mentioning the steam splitter (also called the knife), which was located directly above the steam nozzle cone, with the purpose of directing the steam in a way that directly affects the draught and boiler efficiency. In addition, the smokebox had to be sealed to ensure proper draught. Incorrect adjustment of the splitter and leaks in the smokebox significantly affect the steam production of the boiler. On the left side of the smokebox bell, a recess was provided, creating a space for hanging the air compressor of the locomotive's braking system.
Throttle
The throttle valve of Pt47 locomotives was located in the steam collector on the first boiler shell, unlike in the Pt31, where the throttle valve was placed on the second shell. This arrangement significantly shortened the length of the communication pipe connecting the throttle valve to the screen wall. The valve was constructed from two discs - a small one and a large one. The two discs allowed for a reduction in the force required to open the valve, which was operated by a lever from the driver's cab; the lever's motion caused the shaft to rotate and further, through another lever, lifted the small disc, followed by the large disc. This ensured that the steam flow regulation, especially during start-up, was smooth and under greater control, which was particularly important when starting with heavy trains.
Superheater
All post-war construction steam locomotives operated on PKP were already machines using superheated steam. The use of a superheater, in simple terms, allowed for an increase in the power of the steam engine while simultaneously saving fuel – both water and coal. The superheater consists of a superheater box, which is located in the smokebox and installed on its ceiling on the tube sheet wall. It has two chambers for superheated and saturated steam. Saturated steam enters through the throttle valve and a connecting pipe into the saturated steam chamber, from where it passes through the superheater elements into the superheated steam chamber. The superheater elements are pipes routed inside the fire tubes, where the steam is directed through their interior four times, which, depending on the pressure, allows its temperature to be raised twice and the moisture content of the steam to be reduced. The superheated steam from the superheater chamber then travels through two steam inlet pipes to the slide boxes of the steam cylinders. By adding two fire-tubes relative to the locomotive boiler Pt31, the number of superheater elements increased to 40.
Central steam receiver
The central steam receiver is a set of valves housed within a single body, allowing control of the steam supply to various devices. The receiver was installed in a cab at the top of the stand, and its operation was carried out using knobs. Access for maintenance work was facilitated by an additional hatch in the roof. The central receiver also included a built-in additional shut-off valve, which allowed operation without the need to extinguish the boiler in case the valve gland needed repairs. Each of the valves were served in order from left to right: blower, lighting, grease heater, air pump, and grease sprayer.
Safety valve
The main element protecting a steam locomotive boiler from an increase in steam pressure above the permissible level is the safety valve. Steam boilers were equipped with two safety valves calibrated to slightly different pressure values. In the event of a sudden pressure increase caused, for example, by closing the throttle after intensive locomotive operation on a gradient with heavily fed grates, or by a locomotive standing idle in the roundhouse, one valve would open. Opening the safety valve causes boiler steam to be released into the atmosphere, and if the pressure continues to rise, the second valve opens. Pt47 locomotives were equipped with two Pop-Coale type safety valves installed one behind the other along the longitudinal axis of the locomotive on the boiler stand.
Firebox doors
Firebox doors are an extremely important component of the boiler. In Pt47 steam locomotives, factory-installed doors that opened inward to the firebox, based on the Marcotti system, were used. Additionally, they featured air channels, the clearances of which were adjusted with small levers visible on the front wall. In Figure 17, the aforementioned doors are shown, which were nowhere to be found on over 100 locomotives. This was due to the modernization of Pt47 boilers to a mechanical coal feeder, which was installed along with a new door system consisting of double-leaf doors opening to the side.
Ashpan
The ashpan is located directly under the grate and is connected to the stand. Its construction was reconstructed based on the solution known from Pt31. It was equipped with side air flaps that could be opened from the cab. Often, by opening them while stationary, the remaining slag would be washed out from the interior of the ashpan, which facilitated its emptying. The discharge flaps and their operating levers, were operated from outside the locomotive during servicing on the cleaning pit.
Boiler components
Thanks to the components that allow maintaining the required water level and verifying its level, as well as a functioning steam whistle without which the locomotive cannot take to the track, the boiler is a fully functional component.
Boiler power supply components
As a result of the operation of the steam engine, the steam produced by the boiler is consumed, which consequently leads to a decrease in the water level in the boiler. In order to maintain the required water level in locomotive boilers, two types of components were used: piston pumps and injectors. On the Polish State Railways (PKP), the latter became common, with injectors of various designs, divided into two groups, namely for live steam and exhaust steam. The injector, thanks to the nozzle system through which the boiler steam passed, caused the water to move and raised its pressure above the boiler pressure, allowing it to be pumped into the boiler. Factory locomotives Pt47 were equipped with a Metcalf-Friedmann exhaust steam injector on the left side and a Strube live steam suction injector on the right side, which over time was replaced by a Nathan system suction injector.
Supply valves
The component that directly worked with the injectors was the boiler valve. Each injector had one boiler valve, which in a single casing contained two valves, i.e., a check valve and a shut-off valve. The check valve was closed at all times and would open automatically when fresh water was supplied to the boiler, the pressure of which was higher than the boiler pressure. This pressure difference caused the check valve to open and automatically close when the injector stopped operating. Both the check valves and the injectors were subject to damage; therefore, each supply valve had the ability to cut off the valve, allowing for its safe repair. The Pt47 locomotive boilers had two injectors, each of which had its own boiler valve located on the first ring of the boiler barrel in its upper part.
Water level measuring instruments
Every boiler approved for operation on PKP had to have two independent water gauge components. The most widespread and least liked were the test cocks, which were quite problematic in operation. Along with them, a tube water gauge was used as the second device. Factory-produced Pt47 locomotives had precisely these two devices: one tube water gauge on the assistant's side, and three test cocks on the driver's side, as was the case with Pt31 locomotives. Over time, all locomotives were equipped with two tube water glasses, which provided greater operational convenience and reliability of the indicated water level. The third component was the most modern Klinger water gauges, but they were never used on boilers installed on Pt47 locomotives.
Steam whistle
Factory-produced Pt47 locomotives were equipped with a steam whistle typical for locomotives built in Poland, The whistle, mounted on a stand on the boiler directly in front of the front wall of the driver's cab, was operated via a system of levers activated by the locomotive driver. During operation, there were instances of installing multi-ton sirens from locomotives of other series, such as Ty51, where sirens were mounted from number 61 onwards. This measure was implemented by the trained crews to enhance the prestige of their machines. The procedure was not straightforward, as the height of the siren was significantly greater than that of the whistle and required installation along the horizontal axis of the boiler. Additionally, a new lever system had to be constructed, since the original whistle lever system did not generate enough force to open the siren's mushroom valve, whose surface area acting on the boiler steam was larger.
Sandbox
The sand tank was mounted on the locomotive's main casing just behind the steam collector in a single common housing. It was pneumatically operated from the driver's cab. Pipes supplied sand from the front to the direction of travel for all four drive units. Sand pipes for reverse travel were not installed, as the lower design speed for reverse travel did not allow operation at full speed when handling express trains.
Mechanical coal feeder
The operation of heavy long-distance trains, where the gross weight of the consist and the scheduled speed were high, required intensive feeding of coal into the firebox. This led to the use of three-person crews composed of an engineer, an assistant, and a stoker, where the latter two often alternated in tending the firebox. Rapidly, as early as the 1950s, mechanical coal feeders, known as stokers, were introduced on Pt47 locomotives. The device had a small steam engine operated by a steam valve from the driver’s cab. The engine was located in the locomotive's tender and drove a screw, which, situated in a recess in the bottom of the coal-filled tender, moved the coal to ducts installed on a stand by the boiler under the cab. There, delivered to the so-called station using five individually steam-powered jets, the coal was distributed across the firegrates. The firebox doors were replaced from the Marcet type to dual-swing doors, widely used in Ol49 and Ty51 locomotives.
The component required skill in order to evenly "spread" the coal on the grates. It could not be used while stationary, because the amount of steam used for distributing the coal was too great for the blower to draw it through the fire tubes to the chimney. This could cause the fire to back up and burn the crew. It was also necessary to use higher-quality types of coal that would not block the screw conveyor or cause clinker buildup in the firebox. Despite this, operating the steam locomotive became less burdensome.
The installation, followed by the subsequent dismantling and reinstallation of stokers during the initial major repairs, caused a significant rotation of boilers between locomotives. 107 locomotives used stokers in the following numbers: 1, 2, 3, 5, 6, 8, 9, 12, 15, 16, 17, 19, 20, 22, 24, 25, 26, 27, 28, 29, 30, 31, 33, 35, 36, 42, 43, 44, 46, 48, 49, 52, 55, 56, 59, 60, 61, 62, 65, 66, 69, 70, 71, 72, 73, 75, 76, 77, 78, 79, 80, 81, 84, 85, 86, 87, 89, 91, 93, 94, 95, 96, 97, 98, 99, 100, 103, 106, 107, 113, 114, 115, 116, 117, 118, 119, 120, 124, 129, 132, 133, 135, 142, 143, 144, 145, 149, 151, 153, 154, 155, 158, 159, 160, 161, 163, 164, 165, 166, 168, 170, 173, 174, 175, 176, 177, 179.
Locomotive brakes
Pt47 locomotives have brakes that, due to its construction, can be divided into two parts – mechanical, generating friction of the brake pads on the wheel rims through the action of the brake lever system, and pneumatic, which provides air pressure to exert force on the brake cylinder piston and act on the brake lever.
Mechanical part of the brakes
Braking is carried out by brake pads exerting pressure on the rims, increasing friction. The pads are suspended unilaterally at the front of each driving wheel. The hangers at the lower part are connected by a brake triangle, and subsequently, all triangles are connected by brake rods. The last triangle is connected to the brake shaft mounted in the locomotive frame using bushings. Each of them has its own wick lubricator. Above the shaft is a 16" brake cylinder positioned in the vertical axis, which exerts pressure on the shaft lever. The rolling wheel sets are not braked.
The pressure generated by the brake cylinder at 3.5 atmospheres, under normal braking, produces 4,540 kg (10,010 lb). In the case of emergency braking at a pressure of 5 atmospheres, the force increases to 6,475 kg (14,275 lb). As a result, the total pressure on the brake pads during emergency braking amounts to 63.5 t (140,000 lb) for all eight pads. These values pertain to new pads and rims. In the case of worn and already significantly used components, the pressure value increases to 65.3 t (144,000 lb).
In the event of the brake being released and the brake cylinder being purged of air, the retraction of the system is ensured by two brake return springs. It ensures that the brake shaft lever is pulled toward the cylinder, retracting it, and thereby moving the brake pads away from the rim. The handbrake in a screw form is installed on the tender wall regardless of the type of a tender.
Pneumatic part of the brakes
At the heart of the Westinghouse air brake system is the steam-driven air pump, commonly referred to as a compressor, which on the Pt47 was available in two versions – a three-cylinder H11a3 type and a more efficient four-cylinder H11a4 type. In addition to supplying the brake system with compressed air, the compressor provided air to the flame tube blowers from the firebox side and to operate the sanders. The brake system was based on the Knorr-type main driver's valve, an auxiliary valve, a distributor valve, a pump pressure regulator, a safety valve, two main reservoirs with a capacity of 400 liters, an auxiliary reservoir of 100 liters, and a 14-liter equalizing reservoir.
Other components
Driver's cab
Discussions were ongoing at the Ministry of Communications regarding the type of a cab. Ultimately, a closed cab was used, rather than an open one, as was the case in Pt31 locomotives with doors opening inward on both sides. The sliding roof was a solution known on many PKP steam locomotives. Additionally, a hatch was built into the roof to facilitate work at the main steam receiver mounted at the top of the stand. The floor was made of boards and allowed free access to all points within the cab. The recess intended for coal handling was secured with a canvas apron. It limited air turbulence within the cab, and thereby dust, thus improving working conditions in difficult weather conditions.
There were three doors to the cab. Two side doors allowed direct access from ground level, and one on the fireman’s side provided access to the boiler inspection platform. On the driver’s side, there was no door, only a hinged window. On both sides of the cab, there were also fixed front windows and sliding rear windows. Factory-made Pt47 locomotives had seats more commonly found in tank locomotives, like the TKt48. The round seat, pivotally attached to a bracket on the cab wall, had a built-in spring to absorb shocks during travel. Practically all tenderless steam locomotives of PKP have wooden seats with backrests.
Locomotive lightning
The electric lighting was used, the energy source of which came directly from a turbo generator powered by steam at 5 to 16 atm, with the exhaust steam having a maximum pressure of 1.5 atm. This allowed for a voltage of 25 volts and a power of 0.5 kW. The turbine, mounted on the right side of the boiler on the footplate directly in front of the locomotive cab, was operated by a steam valve from the driver’s cab. The lighting was controlled from a distribution panel installed on the ceiling directly above the locomotive driver. Due to varying steam pressure and power demand, the steam pressure coming from the boiler was regulated using a slide valve. The installation, distributed throughout the locomotive via pipes and junction boxes labeled "Światło" on the cover, supplied power to the ceiling lamps of the locomotive and tender cab, the water gauge and speedometer, the connecting rods, the distributor, and the headlights.
Heating
The train's heating was provided by a switch valve in the driver's cab on the left side of the boiler. The assistant opened the valve and, using a manometer, monitored the steam pressure in the heating system, which reached up to 4 atm. Throughout the entire train, all valves on the buffer beams connecting the locomotive and subsequent cars were open and connected via the heating coupling. On the last car, the valve was set to a half-open position, causing abundant steaming with an intensity dependent on the pressure indicated by the assistant. In low temperatures, when the drain valves of the couplings and cars also produced steam, the entire train could stand on the platforms enveloped in clouds of steam.
SHP system
With the development of railway technology, SHP devices also began to be installed on steam locomotives. Steam locomotives were equipped at a single point with an electromagnet, which was always located on the right side of the locomotive. The system, powered by a turbo generator, was not fully functional and did not resemble the systems known in today’s locomotives. It included a vigilance device and a buzzer, which, in the event that the driver exceeded the required response time, would initiate braking. The solenoid valve released air from the pipe, triggering emergency braking, but did not cut off the steam supply to the steam engine. This function was never implemented on any PKP steam locomotives. It was known on Western steam locomotives of series such as the French 231, or the German 01, or the modernized version 012. Using a pneumatic actuator, in the event the vigilance device was not acknowledged, air was admitted to the actuator, causing the throttle lever to close.
Tenders used by the locomotive
The construction of steam locomotives in post-war Poland progressed relatively quickly. Already in 1948, 29 Pt47 locomotives were put into service by PKP. The new tender design of the Polish-built 33D48 series produced at Pafawag would still not meet the existing demand for a long time. The concept of reconstructing the 32D29 tender used in Pt31 locomotives with Diamond trucks was rejected, and to prevent new locomotives from being idle, a decision was made to adapt the tenders of the former German Pm2 and Ty4 locomotives awaiting repair or reconstruction. The former German tenders were mainly box-type 2'2'T34 constructions, which were designated 34D44 by PKP. However, the design adapted to coupling with locomotives with an open cab required modification, and as a result, the 34D48 tenders were created, which were quite commonly used with Pt47 locomotives. The tenders were obtained from among the Pm2 and Ty4 locomotives that were awaiting repairs. Among them were also locomotives equipped with an older type of tender, namely 2'2'T32, which was an older riveted construction with sliding bearings. These tenders were designated as series 32D2 on the PKP; however, after their adaptation for operation with the Pt47 equipped with a closed cab, they also received the designation 34D48. This led to some confusion and a lack of distinction between tenders through series designation. One of these locomotives is Pt47-38, featured in the cult film "Człowiek na torze" (Man on the Track), which has a 2'2'T32 type tender, but after reconstruction, it was designated as 34D48 with the number 91.
This action was intended to be temporary and required the implementation of a final solution to the problems of turbulence related to the lack of tenders. Therefore, work was simultaneously carried out to adapt the design of the 32D47 series barrel tender for Pt47 locomotives. Operation revealed a number of irregularities, such as unstable running at low water levels, or air turbulence at high speeds caused by the design. The concept was eventually abandoned, and in later years the Pt47 barrel tenders were transferred to other locomotive series.
Over time, the lack of tenders and the scale of the problem increased. Steam locomotive production outpaced tender deliveries, causing locomotives allocated to their depots to wait in reserve for their tenders. For example, the Pt47-87 and Pt47-88 locomotives, delivered to MD Iława in January 1950, had to wait for their allocations. The first Polish-designed tender, built in November 1949 by Pafawag Wrocław for the Pt47, was the 33D48 series tender. Engine drivers called the tenders coffins and disliked them due to the tenders having bogies with sliding bearings. The introduced design tended to overheat, which occasionally caused the bearings to melt at high speeds.
As a result of equipping steam locomotives with mechanical coal feeders, the so-called stoker, whose steam engine was built into the tender, there was a change in the capacity of the water tank and a change in the designations. German-era tenders 34D48, due to modernization, were designated as series 27D48. The only preserved locomotive with such a tender on its original bogies is Pt47-1 in Łódź, which stands with tender 27D48-1. Unfortunately, Polish tenders 33D48, as a result of being equipped with a mechanical coal feeder, were also designated as series 27D48. This created another confusion with the designation of two different tenders under the same series.
Since 1974, in ZNTK Bydgoszcz, Polish and ex-German tenders have undergone modernization. Polish tenders 33D48 and 27D48, from 1974 to 1976, due to design defects in the bogies and frequent wearing of axle bearings, underwent modernization involving the replacement of the bogies. The new design featured rolling bearings with simultaneous changes in the suspension system. The production of bogies, also carried out by ZNTK Bydgoszcz, proceeded systematically; however, despite modernization, the tenders did not receive a change in designation.
At the same time, the ex-German tenders also underwent modernization. The water tanks, filler openings, coal box, and the tenders themselves received new-type bogies. As a result, in order to distinguish the modernized tenders, their designation was changed from 34D48 to 34D74, tenders without a mechanical coal feeder and from 27D48, which was an ex-German tender with a stoker, to 27D74.
As a result of various situations and upheavals, strange occurrences happened. For example, for a certain period, the 27D48 tenders were labeled with the 26D48 series. This resulted from rounding up the water tank capacity to a full value in meters. Another tender, 26D48-14, was also equipped with a stoker but produced by Pafawag, with the Pt47-25 steam locomotive.
Due to a shortage of tenders, pairing Pt47 locomotives with tenders from other series also occurred, which was already rare. For example, two Pt47 locomotives operated with 26D5 tenders originating from Ty5 series locomotives. In the 21st century, Pt47-65 and Pt47-112 locomotives coupled with a 25D49 series tender originating from an Ol49 locomotive. Pt47 locomotives could not be turned on the turntable at the Wolsztyn engine shed. This procedure enabled it, as well as winter housing in the shed where it served as a heater. The difference in height between the tender and locomotive couplings caused improper cooperation between the two rolling stock and their damage. The extent of subsequent repairs increased, and as a result, the Pt47-65 locomotive rebuilt by the Chabówka museum required greater effort, and after the repair, it received the correct 34D74-42 tender.
| Tender series | 34D48 | 27D48 | 34D74 | 27D74 | 33D48 | 27D48 |
|---|---|---|---|---|---|---|
| Manufacturer | DR | DR | ZNTK Bydgoszcz | ZNTK Bydgoszcz | Pafawag | Pafawag |
| Water capacity | 34m3 | 27m3 | 34m3 | 27m3 | 33m3 | 27m3 |
| Coal capacity | 10 t | 10 t | 10 t | 10 t | 17 t | 17 t |
| Empty mass | 29.9 t | 27.9 t | ||||
| Loaded mass | 74.2 t | 79.2 t | ||||
| Tender length along with the locomotive | 23 835 mm | 23 835 mm | 23 835 mm | 23 835 mm | 24 255 mm | 24 255 mm |
| Tender length | 8 645 mm | 8 645 mm | 8 645 mm | 8 645 mm | 9 130 mm | 9 130 mm |
| Stoker | no | yes | no | yes | no | yes |
Accidents and incidents
- On 3 February 1985, an unknown Pt47 locomotive between Dytmarów and Prudnik, collided with an RSP Jasiona tractor. Two people were killed on the spot, and one was seriously injured (the man fell into a coma and died several years later). The accident was caused by a crossing keeper's mistake near Dytmarów, who despite being aware of the approaching train, raised the barriers at the request of the tractor's passengers so they could pass. Due to the snowstorm, the engine driver did not see the tractor. The locomotive stopped in Prudnik, where blood and a bag of clothes, which had attached to the locomotive after the impact, were noticed on the front of the locomotive.[6]
Nicknames
- Petucha - after the first two letters of the name
